Unity 5 Game Optimization - smactech.in · There are further alternatives that we can explore, such...

http://freepdf-books.com

Unity5GameOptimization


TableofContents


Credits

AbouttheAuthor

Acknowledgments

AbouttheReviewers

www.PacktPub.com

Supportfiles,eBooks,discountoffers,andmore

Whysubscribe?

FreeaccessforPacktaccountholders

Preface

Whatthisbookcovers

Whatyouneedforthisbook

Whothisbookisfor

Conventions

Readerfeedback

Customersupport

Downloadingtheexamplecode

Errata

Piracy

Questions

1.DetectingPerformanceIssues

TheUnityProfiler

LaunchingtheProfiler

Editororstandaloneinstances

Editorprofiling

TheUnityWebplayerconnection

RemoteconnectiontoaniOSdevice

RemoteconnectiontoanAndroiddevice

TheProfilerwindow


Controls

CPUArea

TheGPUArea

TheRenderingArea

TheMemoryArea

TheAudioArea

ThePhysics3D/2DArea

Bestapproachestoperformanceanalysis

Verifyingscriptpresence

Verifyingscriptcount

Minimizingongoingcodechanges

Minimizinginternaldistractions

Minimizingexternaldistractions

Targetedprofilingofcodesegments

Profilerscriptcontrol

CustomCPUProfiling

SavingandloadingProfilerdata

SavingProfilerdata

LoadingProfilerdata

FinalthoughtsonProfilingandAnalysis

UnderstandingtheProfiler

Reducingnoise

Focusingontheissue

Summary

2.ScriptingStrategies

CacheComponentreferences

ObtainingComponentsusingthefastestmethod

Removingemptycallbackdeclarations

AvoidingtheFind()andSendMessage()methodsatruntime

Staticclasses

SingletonComponents


Assigningreferencestopre-existingobjects

Aglobalmessagingsystem

Agloballyaccessibleobject

Registration

Messageprocessing

Implementingthemessagingsystem

Messagequeuingandprocessing

Implementingacustommessage

Messageregistration

Messagesending

Messagecleanup

Wrappingupthemessagingsystem

Disablingunusedscriptsandobjects

Disablingobjectsbyvisibility

Disablingobjectsbydistance

Considerusingdistance-squaredoverdistance

AvoidretrievingstringpropertiesfromGameObjects

Update,Coroutines,andInvokeRepeating

ConsidercachingTransformchanges

FasterGameObjectnullreferencechecks

Summary

3.TheBenefitsofBatching

DrawCalls

MaterialsandShaders

DynamicBatching

Vertexattributes

Uniformscaling

DynamicBatchingsummary

StaticBatching

TheStaticflag

Memoryrequirements


Materialreferences

StaticBatchingcaveats

EditModedebuggingofStaticBatching

Avoidinginstantiatingstaticmeshesatruntime

Visibilityandrendering

StaticBatchingsummary

Summary

4.KickstartYourArt

Audio

Loadingaudiofiles

Profilingaudio

Additionalloadingoptions

Encodingformatsandqualitylevels

Audioperformanceenhancements

MinimizeactiveAudioSourcecount

MinimizeAudioClipreferences

EnableForcetoMonofor3Dsounds

Resampletolowerfrequencies

Considerallencodingformats

Bewareofstreaming

ApplyFiltereffectsthroughMixergroupstoreduceduplication

Use“WWW.audioClip”responsibly

ConsiderAudioModulefilesforbackgroundmusic

Texturefiles

Compressionformats

Textureperformanceenhancements

ReduceTexturefilesize

UseMipMapswisely

Manageresolutiondownscalingexternally

AdjustAnisotropicFilteringlevels

ConsiderAtlasing


Adjustcompressionratesfornon-squareTextures

SparseTextures

ProceduralMaterials

Meshandanimationfiles

Reducingpolygoncount

TweakingMeshCompression

UseRead-WriteEnabledappropriately

Import/calculateonlywhat’sneeded

Considerbakedanimations

LetUnityoptimizemeshes

Combinemeshes

Summary

5.FasterPhysics

PhysicsEngineinternals

Physicsandtime

TheFixedUpdateloop

MaximumAllowedTimestep

Physicsupdatesandruntimechanges

StaticandDynamicColliders

Collisiondetection

Collidertypes

TheCollisionMatrix

Rigidbodyactiveandsleepingstates

Rayandobjectcasting

Physicsperformanceoptimizations

Scenesetup

Scaling

Positioning

Mass

UseStaticCollidersappropriately

OptimizetheCollisionMatrix


Preferdiscretecollisiondetection

ModifytheFixedUpdatefrequency

AdjusttheMaximumAllowedTimestep

Minimizecastandbounding-volumechecks

AvoidcomplexMeshColliders

Usesimplerprimitives

UsesimplerMeshColliders

Avoidcomplexphysicscomponents

Letphysicsobjectssleep

ModifySolverIterationCount

Optimizingragdolls

ReduceJointsandColliders

Avoidinter-ragdollcollisions

Disableorremoveinactiveragdolls

Knowwhentousephysics

ConsiderupgradingtoUnity5

Summary

6.DynamicGraphics

Profilingrenderingissues

GPUprofiling

TheFrameDebugger

Bruteforcetesting

CPU-bound

Multithreadedrendering

GPUSkinning

Frontendbottlenecks

LevelOfDetail

DisableGPUSkinning

Reducetessellation

Backendbottlenecks

Fillrate


Overdraw

OcclusionCulling

Shaderoptimization

ConsiderusingShadersintendedformobileplatforms

Usesmalldatatypes

Avoidchangingprecisionwhileswizzling

UseGPU-optimizedhelperfunctions

Disableunnecessaryfeatures

Removeunnecessaryinputdata

Onlyexposenecessaryvariables

Reducemathematicalcomplexity

Reducetexturelookups

Avoidconditionalstatements

Reducedatadependencies

SurfaceShaders

UseShader-basedLOD

Memorybandwidth

Uselesstexturedata

TestdifferentGPUTextureCompressionformats

Minimizetexturesampling

Organizeassetstoreducetextureswaps

VRAMlimits

Texturepreloading

Texturethrashing

LightingandShadowing

ForwardRendering

DeferredShading

VertexLitShading(legacy)

Real-timeShadows

Lightingoptimization

UsetheappropriateShadingMode


UseCullingMasks

UseBakedLightmaps

OptimizeShadows

Optimizinggraphicsformobile

MinimizeDrawCalls

MinimizetheMaterialcount

MinimizetexturesizeandMaterialcount

Maketexturessquareandpowerof2

UsethelowestpossibleprecisionformatsinShaders

AvoidAlphaTesting

Summary

7.MasterfulMemoryManagement

TheMonoplatform

Thecompilationprocess

ManualJITcompilation

Memoryusageoptimization

Unitymemorydomains

Nativememory

Managedmemory

Garbagecollection

Memoryfragmentation

Garbagecollectionatruntime

Threadedgarbagecollection

Garbagecollectiontactics

ValuetypesandReferencetypes

Passbyvalueandpassbyreference

StructsareValuetypes

ArraysareReferencetypes

StringsareimmutableReferencetypes

Stringconcatenation

Boxing


Theimportanceofdatalayout

TheUnityAPI

Theforeachloops

Coroutines

Closures

.NETlibraryfunctions

Temporaryworkbuffers

Objectpooling

Prefabpooling

PoolableComponents

ThePrefabpoolingsystem

Prefabpools

Objectspawning

Instanceprespawning

Objectdespawning

Prefabpooltesting

PrefabpoolingandSceneloading

Prefabpoolingsummary

ThefutureofMonoandUnity

Summary

8.TacticalTipsandTricks

Editorhotkeytips

GameObjects

SceneView

Arrays

Interface

Other

Editorinterfacetips

General

TheInspectorView

TheProjectView


TheHierarchyView

TheSceneandGameViews

PlayMode

Scriptingtips

General

Attributes

Variableattributes

Classattributes

Logging

Usefullinks

Customeditors/menustips

Externaltips

Othertips

Summary

Index


Unity5GameOptimizationCopyright©2015PacktPublishing

Allrightsreserved.Nopartofthisbookmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformorbyanymeans,withoutthepriorwrittenpermissionofthepublisher,exceptinthecaseofbriefquotationsembeddedincriticalarticlesorreviews.

Everyefforthasbeenmadeinthepreparationofthisbooktoensuretheaccuracyoftheinformationpresented.However,theinformationcontainedinthisbookissoldwithoutwarranty,eitherexpressorimplied.Neithertheauthor,norPacktPublishing,anditsdealersanddistributorswillbeheldliableforanydamagescausedorallegedtobecauseddirectlyorindirectlybythisbook.

PacktPublishinghasendeavoredtoprovidetrademarkinformationaboutallofthecompaniesandproductsmentionedinthisbookbytheappropriateuseofcapitals.However,PacktPublishingcannotguaranteetheaccuracyofthisinformation.

Firstpublished:November2015

Productionreference:1281015

PublishedbyPacktPublishingLtd.

LiveryPlace

35LiveryStreet

BirminghamB32PB,UK.

ISBN978-1-78588-458-0

www.packtpub.com


http://www.packtpub.com

CreditsAuthor

ChrisDickinson

Reviewers

CliffordChampion

Dr.SebastianT.Koenig

AcquisitionEditor

IndrajitDas

ContentDevelopmentEditor

AthiraLaji

TechnicalEditor

PrajaktaMhatre

CopyEditor

CharlotteCarneiro

ProjectCoordinator

BijalPatel

Proofreader

SafisEditing

Indexer

RekhaNair

Graphics

JasonMonteiro

ProductionCoordinator

AparnaBhagat

CoverWork

AparnaBhagat


AbouttheAuthorChrisDickinsongrewupinEnglandwithastrongpassionforscience,mathematics,andvideogames.Hereceivedhismaster’sdegreeinphysicswithelectronicsfromtheUniversityofLeedsin2005,andimmediatelytraveledtoCaliforniatoworkonscientificresearchintheheartofSiliconValley.Findingthatcareerpathunsuitable,hebeganworkinginthesoftwareindustry.

Overthelastdecade,hehasmadeacareerinsoftwaredevelopment,becomingaseniorsoftwaredeveloper.Chrishasprimarilyworkedinsoftwareautomationandinternaltesttooldevelopment,buthispassionforvideogamesneverfullyfaded.In2010,hetookthepathofdiscoveringthesecretsofgamedevelopmentand3Dgraphicsbycompletingaseconddegree—abachelor’sdegreeingameandsimulationprogramming.Heauthoredatutorialbookongamephysics(LearningGamePhysicswithBulletPhysicsandOpenGLbyPacktPublishing).Hecontinuestoworkinsoftwaredevelopment,creatingindependentgameprojectsinhissparetimewithtoolssuchasUnity3D.


AcknowledgmentsI’vemanagedtograspanabsolutelyridiculousamountofknowledgeinjust5years.Noneofthiswouldhavebeenpossiblewithouttheconstantmotivationfrommycoworkers,tutors,friends,andfamily.

ThankstomycomradesinsoftwaredevelopmentforbeingsounderstandingofmyerraticschedulewhileIwaslearninggamedevelopmentatschool.

Thanksalsotomycollegetutorsforhelpingacceleratemepastthecorematerialandlearnsomuchaboutgamedevelopmentsoquickly.

ThankstomyfriendsforalwaysbeingaconstantsourceofharassmentandinquisitivenessaboutwhatI’vebeenworkingon.

Thankstomyfamilyforgivingmetheopportunitytolearn,live,andlovesomuchinsuchashorttime.

Andofcourse,thankstomywonderfulwifeandbestfriend,Jamie,forbeingsocaringandsupportiveofallthelatenightsandhelpingmestaycreative.


AbouttheReviewersCliffordChampionhasabroadbackgroundinsoftwareengineering,withyearsofexperiencespanning3Dgames,Internetapplications,andartificialintelligence.HeholdsdegreesinmathematicsandcomputersciencefromUCLAandUCSD,respectively.Inthepast,CliffordworkedforvideogametechnologycompanyHavok(nowpartofMicrosoft),andinteractivemediaanddesigncompanyPlainJoeStudios.Currently,heleadsasoftwareteamatzSpace(zspace.com),aVRcompanyspecializingin3Dforclassroomsandindustry.

CliffordcanbefoundonTwitterat@duckmaestroandwelcomesdiscussionsonanytopic.

Dr.SebastianT.KoenigreceivedhisPhDinhumaninterfacetechnologyfromtheUniversityofCanterbury,NewZealand,developingaframeworkforindividualizedvirtualrealitycognitiverehabilitation.HeobtainedhisdiplomainpsychologyfromtheUniversityofRegensburg,Germany,intheareasofclinicalneuropsychologyandvirtualrealityrehabilitation.

SebastianisthefounderandCEOofKatanaSimulations,whereheoverseesthedesign,development,andevaluationofcognitiveassessmentandtrainingsimulations.Hisprofessionalexperiencespansover10yearsofclinicalworkincognitiverehabilitationandover8yearsofvirtualrealityresearch,development,andusertesting.Hehasextensiveexperienceasaspeakeratinternationalconferencesandasareviewerofscientificpublicationsintheareasofrehabilitation,cognitivepsychology,neuropsychology,softwareengineering,gamedevelopment,gameuserresearch,andvirtualreality.

Sebastianhasdevelopednumeroussoftwareapplicationsforcognitiveassessmentandtraining.Forhisworkonthevirtualmemorytask,hewasawardedtheprestigiousLavalVirtualAwardin2011,fortheMedicineandHealthcategory.OtherapplicationsofhisincludethevirtualrealityexecutivefunctionassessmentincollaborationwiththeKesslerFoundation,NewJersey,USA,andthepatent-pendingMicrosoftKinect-basedmotorandcognitivetrainingJewelMine/MysticIsleattheUSCInstituteforCreativeTechnologies,California,USA.

Hemaintainsthewebsiteatwww.virtualgamelab.com,whichfeatureshisresearchandhissoftwaredevelopmentprojects.HiswebsitealsocontainsacomprehensivelistoftutorialsfortheUnitygameengine.


http://zspace.com

http://www.virtualgamelab.com

www.PacktPub.com


Supportfiles,eBooks,discountoffers,andmoreForsupportfilesanddownloadsrelatedtoyourbook,pleasevisitwww.PacktPub.com.

DidyouknowthatPacktofferseBookversionsofeverybookpublished,withPDFandePubfilesavailable?YoucanupgradetotheeBookversionatwww.PacktPub.comandasaprintbookcustomer,youareentitledtoadiscountontheeBookcopy.Getintouchwithusat<[email protected]>formoredetails.

Atwww.PacktPub.com,youcanalsoreadacollectionoffreetechnicalarticles,signupforarangeoffreenewslettersandreceiveexclusivediscountsandoffersonPacktbooksandeBooks.

https://www2.packtpub.com/books/subscription/packtlib

DoyouneedinstantsolutionstoyourITquestions?PacktLibisPackt’sonlinedigitalbooklibrary.Here,youcansearch,access,andreadPackt’sentirelibraryofbooks.


http://www.PacktPub.com


mailto:[email protected]


https://www2.packtpub.com/books/subscription/packtlib

Whysubscribe?FullysearchableacrosseverybookpublishedbyPacktCopyandpaste,print,andbookmarkcontentOndemandandaccessibleviaawebbrowser


FreeaccessforPacktaccountholdersIfyouhaveanaccountwithPacktatwww.PacktPub.com,youcanusethistoaccessPacktLibtodayandview9entirelyfreebooks.Simplyuseyourlogincredentialsforimmediateaccess.



PrefaceUserexperienceisacriticalcomponentofanygame.Userexperienceincludesnotonlyourgame’sstoryanditsgameplay,butalsohowsmoothlythegraphicsrun,howreliablyitconnectstomultiplayerservers,howresponsiveitistouserinput,andevenhowlargethefinalapplicationfilesizeisduetotheprevalenceofappstoresandclouddownloads.Thebarriertoenteringgamedevelopmenthasbeenloweredconsiderablythankstothereleaseofcheap,AAA-industry-levelgamedevelopmenttoolssuchasUnity.However,thefeaturesandqualityofthefinalproductthatourplayersexpectustoprovideisincreasingwitheverypassingday.Weshouldexpectthateveryfacetofourgamecanandwillbescrutinizedbyplayersandcriticsalike.

Thegoalsofperformanceoptimizationaredeeplyentwinedwithuserexperience.Poorlyoptimizedgamescanresultinlowframerates,freezes,crashes,inputlag,longloadingtimes,inconsistentandjitteryruntimebehavior,physicsenginebreakdowns,andevenexcessivelyhighbatterypowerconsumption(particularlyimportantinthiseraofmobiledevices).Havingjustoneoftheseissuescanbeagamedeveloper’sworstnightmareasreviewswilltendtofocusontheonethingthatwedidbadly,inspiteofallthethingsthatwedidwell.

Performanceisallaboutmakingthebestuseoftheavailableresources,whichincludestheCPUresourcessuchasCPUcyclesandmainmemoryspace,GraphicsProcessingUnit(GPU)resourcessuchasmemoryspace(VRAM)andmemorybandwidth,andsoon.Butoptimizationalsomeansmakingsurethatnosingleresourcecausesabottleneckataninappropriatetime,andthatthehighestprioritytasksgettakencareoffirst.Evensmall,intermittenthiccupsandsluggishnessinperformancecanpulltheplayeroutoftheexperience,breakingimmersionandlimitingourpotentialtocreatetheexperienceweintended.

Itisalsoimportanttodecidewhentotakeastepbackandstopmakingperformanceenhancements.Inaworldwithinfinitetimeandresources,therewouldalwaysbeanotherwaytomakeitbetter,faster,oreasiertomaintain.Theremustbeapointduringdevelopmentwherewedecidethattheproducthasreachedacceptablelevelsofquality.Ifnot,weriskdoomingourselvestoimplementingfurtherchangesthatresultinlittleornotangiblebenefit.

Thebestwaytodecideifaperformanceissueisworthfixingistoanswerthequestion“willtheusernoticeit?”.Iftheanswertothisquestionsis“no”,thenperformanceoptimizationwouldbeawastedeffort.Thereisanoldsayinginsoftwaredevelopment:

Prematureoptimizationistherootofallevil

Prematureoptimizationisthecardinalsinofreworkingandrefactoringcodetoenhanceperformancewithoutanyproofthatitisnecessary.Thiscouldmeaneithermakingchangeswithoutshowingthataperformanceproblemevenexists(answeringthequestionofwhetherornotitwouldbenoticeabletotheuser),ormakingchangesbecauseweonly


believeaperformanceissuemightstemfromaparticularareabeforeithasbeenproventobetrue.Makingthesemistakeshascostsoftwaredevelopers,asacollectivewhole,adepressingnumberofworkhoursfornothing.

Thisbookintendstogiveusthetools,knowledge,andskillsweneedtobothdetectandfixperformanceissuesinourapplication,nomatterwheretheystemfrom.ThiscouldbehardwarecomponentssuchastheCPU,GPU,orRAM,withinsoftwaresubsystemssuchasPhysics,Rendering,orwithintheUnityEngineitself.Inaddition,themoreresourceswesave,themorewecandowithintheUnityEnginewiththesamehardwaresystem,allowingustogeneratemoreinterestinganddynamicgameplay.

Thiswillgiveourgameabetterchanceofsucceedingandstandingoutfromthecrowdinamarketplacethatisinundatedwithnew,highqualitygameseverysingleday.


WhatthisbookcoversChapter1,DetectingPerformanceIssues,providesanexplorationoftheUnityProfilerandaseriesofmethodstoprofileourapplication,detectperformancebottlenecks,andperformrootcauseanalysis.

Chapter2,ScriptingStrategies,dealswiththebestpracticesforourUnityC#Scriptcode,minimizingComponentoverhead,improvinginter-objectcommunication,andmore.

Chapter3,TheBenefitsofBatching,exploresUnity’sDynamicandStaticBatchingsystemstoeasetheburdenontherenderingsystem.

Chapter4,KickstartYourArt,helpsyouunderstandtheunderlyingtechnologybehindourartassetsandlearnhowtoavoidcommonpitfallswithimporting,compression,andencoding.

Chapter5,FasterPhysics,isaboutinvestigatingthenuancesofUnity’sphysicssystemforboth3Dand2Dgames,andhowtoproperlyorganizeourphysicsobjectsforimprovedperformance.

Chapter6,DynamicGraphics,providesanin-depthexplorationoftherenderingsystem,andhowtoimproveapplicationsthatsufferrenderingbottlenecksintheGPU,orCPU,andspecializedtechniquesformobiledevices.

Chapter7,MasterfulMemoryManagement,examinestheinnerworkingsoftheUnityEngine,theMonoFramework,andhowmemoryismanagedwithinthesecomponentstoprotectourapplicationfromheapallocationsandruntimegarbagecollection.

Chapter8,TacticalTipsandTricks,dealswithamultitudeofusefultechniquesusedbyprofessionalstoimproveprojectworkflowandscenemanagement.


WhatyouneedforthisbookThemajorityofthisbookwillfocusonfeatureswithinthecontextofUnityversion5.x.MostofthetechniquescanbeappliedtoUnity4.xprojects,butmayrequireanupgradetoUnity4ProEditioninordertoaccesssomeofthem(suchasOcclusionCulling,StaticBatching,andeventheProfileritself).


WhothisbookisforThisbookisintendedforintermediateandadvancedUnitydeveloperswhohaveexperiencewithmostofUnity’sfeatureset,andthosewhowanttomaximizetheperformanceoftheirgameorsolveparticularbottlenecks.WhetherthebottleneckiscausedbyCPUoverload,runtimespiking,slowmemoryaccess,fragmentation,garbagecollection,poorGPUfillrate,ormemorybandwidth,thisbookwillteachyouthetechniquesyouneedtoidentifythesourceoftheproblemandhelpexploremultiplewaysofreducingtheirimpactonyourapplication.

FamiliaritywiththeC#languagewillbeneededforsectionsinvolvingscriptingandmemoryusage,andabasicunderstandingofcgwillbeneededforareasinvolvingShaderoptimization.


ConventionsInthisbook,youwillfindanumberoftextstylesthatdistinguishbetweendifferentkindsofinformation.Herearesomeexamplesofthesestylesandanexplanationoftheirmeaning.

Codewordsintext,databasetablenames,foldernames,filenames,fileextensions,pathnames,dummyURLs,userinput,andTwitterhandlesareshownasfollows:“ThemainUnitycallbackforapplicationupdatesistheUpdate()function.”

Ablockofcodeissetasfollows:

publicclassTestComponent:MonoBehaviour{

voidUpdate(){

if(Input.GetKeyDown(KeyCode.Space)){

PerformProfilingTest();

}

}

}

Whenwewishtodrawyourattentiontoaparticularpartofacodeblock,therelevantlinesoritemsaresetinbold:


voidUpdate(){


PerformProfilingTest();

}

}

}

Newtermsandimportantwordsareshowninbold.Wordsthatyouseeonthescreen,forexample,inmenusordialogboxes,appearinthetextlikethis:“ThethresholdvalueforthesleepingstatecanbemodifiedunderEdit|ProjectSettings|Physics|SleepThreshold.”

NoteWarningsorimportantnotesappearinaboxlikethis.

TipTipsandtricksappearlikethis.


ReaderfeedbackFeedbackfromourreadersisalwayswelcome.Letusknowwhatyouthinkaboutthisbook—whatyoulikedordisliked.Readerfeedbackisimportantforusasithelpsusdeveloptitlesthatyouwillreallygetthemostoutof.

Tosendusgeneralfeedback,simplye-mail<[email protected]>,andmentionthebook’stitleinthesubjectofyourmessage.

Ifthereisatopicthatyouhaveexpertiseinandyouareinterestedineitherwritingorcontributingtoabook,seeourauthorguideatwww.packtpub.com/authors.



http://www.packtpub.com/authors

CustomersupportNowthatyouaretheproudownerofaPacktbook,wehaveanumberofthingstohelpyoutogetthemostfromyourpurchase.


DownloadingtheexamplecodeYoucandownloadtheexamplecodefilesfromyouraccountathttp://www.packtpub.comforallthePacktPublishingbooksyouhavepurchased.Ifyoupurchasedthisbookelsewhere,youcanvisithttp://www.packtpub.com/supportandregistertohavethefilese-maileddirectlytoyou.



http://www.packtpub.com/support

ErrataAlthoughwehavetakeneverycaretoensuretheaccuracyofourcontent,mistakesdohappen.Ifyoufindamistakeinoneofourbooks—maybeamistakeinthetextorthecode—wewouldbegratefulifyoucouldreportthistous.Bydoingso,youcansaveotherreadersfromfrustrationandhelpusimprovesubsequentversionsofthisbook.Ifyoufindanyerrata,pleasereportthembyvisitinghttp://www.packtpub.com/submit-errata,selectingyourbook,clickingontheErrataSubmissionFormlink,andenteringthedetailsofyourerrata.Onceyourerrataareverified,yoursubmissionwillbeacceptedandtheerratawillbeuploadedtoourwebsiteoraddedtoanylistofexistingerrataundertheErratasectionofthattitle.

Toviewthepreviouslysubmittederrata,gotohttps://www.packtpub.com/books/content/supportandenterthenameofthebookinthesearchfield.TherequiredinformationwillappearundertheErratasection.


http://www.packtpub.com/submit-errata

https://www.packtpub.com/books/content/support

PiracyPiracyofcopyrightedmaterialontheInternetisanongoingproblemacrossallmedia.AtPackt,wetaketheprotectionofourcopyrightandlicensesveryseriously.IfyoucomeacrossanyillegalcopiesofourworksinanyformontheInternet,pleaseprovideuswiththelocationaddressorwebsitenameimmediatelysothatwecanpursuearemedy.

Pleasecontactusat<[email protected]>withalinktothesuspectedpiratedmaterial.

Weappreciateyourhelpinprotectingourauthorsandourabilitytobringyouvaluablecontent.

QuestionsIfyouhaveaproblemwithanyaspectofthisbook,youcancontactusat<[email protected]>,andwewilldoourbesttoaddresstheproblem.

Chapter1.DetectingPerformanceIssuesPerformanceevaluationformostsoftwareproductsisaveryscientificprocess:determinethemaximumsupportedperformancemetrics(numberofconcurrentusers,maximumallowedmemoryusage,CPUusage,andsoon);performloadtestingagainsttheapplicationinscenariosthattrytosimulatereal-worldbehavior;gatherinstrumentationdatafromtestcases;analyzethedataforperformancebottlenecks;completearoot-causeanalysis;makechangesintheconfigurationorapplicationcodetofixtheissue;andrepeat.

Justbecausegamedevelopmentisaveryartisticprocessdoesnotmeanitshouldnotbetreatedinequallyobjectiveandscientificways.Ourgameshouldhaveatargetaudienceinmind,whocantellusthehardwarelimitationsourgamemightbeunder.Wecanperformruntimetestingofourapplication,gatherdatafrommultiplecomponents(CPU,GPU,memory,physics,rendering,andsoon),andcomparethemagainstthedesiredmetrics.Wecanusethisdatatoidentifybottlenecksinourapplication,performadditionalinstrumentationtodeterminetherootcauseoftheissue,andapproachtheproblemfromavarietyofangles.

Togiveusthetoolsandknowledgetocompletethisprocess,thischapterwillintroduceavarietyofmethodsthatwewillusethroughoutthebooktodeterminewhetherwehaveaperformanceproblem,andwheretherootcauseoftheperformanceissuecanbefound.Theseskillswillgiveusthetechniquesweneedtodetect,analyze,andprovethatperformanceissuesareplaguingourUnityapplication,andwhereweshouldbegintomakechanges.Indoingso,youwillprepareyourselvesfortheremainingchapterswhereyouwilllearnwhatcanbedoneabouttheproblemsyou’refacing.

WewillbeginwithanexplorationoftheUnityProfileranditsmyriadoffeatures.Wewillthenexploreahandfulofscriptingtechniquestonarrow-downoursearchfortheelusivebottleneckandconcludewithsometipsonmakingthemostofbothtechniques.


TheUnityProfilerTheUnityProfilerisbuiltintotheUnityEditoritself,andprovidesanexpedientwayofnarrowingoursearchforperformancebottlenecksbygeneratingusageandstatisticsreportsonamultitudeofUnity3Dcomponentsduringruntime:

CPUusagepercomponentoftheUnity3DEngineRenderingstatisticsGPUusageonseveralprogrammablepipelinestepsandstagesMemoryusageandstatisticsAudiousageandstatisticsPhysicsengineusageandstatistics

NoteWiththereleaseofUnity5.0,UnityTechnologieshasmadetheProfileravailabletoalldevelopersrunningthePersonalEdition(thenewnamefortheFreeEdition).

UsersrunningtheFreeEditionofUnity4musteitherupgradetoUnity5,orpurchasealicenseforUnity4ProEdition.

Thisadditionalreportingcomeswithaprice,however.Additionalinstrumentationflagswillbeenabledwithinthecompiler,generatingruntimeloggingeventsandadifferentlevelofautomatedcodeoptimizationwhiletheProfilerisinuse,whichcausessomeadditionalCPUandmemoryoverheadatruntime.Thisprofilingcostisnotcompletelynegligible,andislikelytocauseinconsistentbehaviorwhentheProfileristoggledonandoff.

Inaddition,weshouldalwaysavoidusingEditorModeforanykindofprofilingandbenchmarkingpurposesduetotheoverheadcostsoftheEditor;itsinterface,andadditionalmemoryconsumptionofvariousobjectsandcomponents.Itisalwaysbettertotestourapplicationinastandaloneformat,onthetargetdevice,inordertogetamoreaccurateandrealisticdatasample.

TipUserswhoarealreadyfamiliarwithconnectingtheUnityProfilertotheirapplicationsshouldskiptothesectiontitledTheProfilerwindow


LaunchingtheProfilerWewillbeginwithabrieftutorialonhowtoconnectourgametotheUnityProfilerwithinavarietyofcontexts:

Localinstancesoftheapplication,eitherthroughtheEditororstandaloneProfilingtheEditoritselfLocalinstancesoftheapplicationinUnityWebplayerRemoteinstancesoftheapplicationonaniOSdevice(theiPadtabletortheiPhonedevice)RemoteinstancesoftheapplicationonanAndroiddevice(atabletorphonedevicerunningAndroidOS)WewillbrieflycovertherequirementsforsettinguptheProfilerineachofthesecontexts.

EditororstandaloneinstancesTheonlywaytoaccesstheProfileristolaunchitthroughtheUnityEditorandconnectittoarunninginstanceofourapplication.Thisisthecasewhetherwe’rerunningourgamewithintheEditor,runningastandaloneapplicationonthelocalorremotedevice,orwhenwewishtoprofiletheEditoritself.

ToopentheProfiler,navigatetoWindow|ProfilerwithintheEditor.IftheEditorisalreadyrunninginPlayMode,thenwemayseereportingdatagatheringintheProfilerWindow:

TipToprofilestandaloneprojects,ensurethattheUseDevelopmentModeandAutoconnectProfilerflagsareenabledwhentheapplicationisbuilt.

SelectingwhethertoprofileanEditor-basedinstance(throughtheEditor’sPlayMode)orastandaloneinstance(separatelybuiltandrunninginthebackground)canbeachievedthroughtheActiveProfileroptionintheProfilerwindow.


TheUnityProfiler

EditorprofilingProfilingtheEditoritself,suchasprofilingcustomEditorScripts,canbeenabledwiththeProfileEditoroptionintheProfilerwindowasshowninthefollowingscreenshot.NotethatthisrequirestheActiveProfileroptiontobeconfiguredtoEditor.

TheUnityWebplayerconnectionTheProfilercanalsoconnecttoaninstanceoftheUnityWebplayerthatiscurrentlyrunninginabrowser.Thisenablesustoprofileourweb-basedapplicationinamorereal-worldscenariothroughthetargetbrowser,andtestmultiplebrowsertypesforinconsistenciesinbehavior.

1. EnsurethattheUseDevelopmentModeflagisenabledwhentheWebplayerapplicationisbuilt.

2. LaunchthecompiledWebplayerapplicationinabrowserand,whileitisactiveinthebrowserwindow,holdtheAltkey(OptionkeyonaMac)andright-clickontheWebplayerobjectwithinthebrowsertoopentheReleaseChannelSelectionmenu.ThenselecttheDevelopmentchannel,asshowninthefollowingscreenshot:

NoteNotethatchangingtheReleaseChanneloptionwillrestarttheWebplayerapplication.


3. Asshowninthefollowingscreenshot,opentheProfilerintheUnityEditorwithintheProfilerwindow,andthennavigatetoActiveProfiler|WindowsWebPlayer(COMPUTERNAME)orActiveProfiler|OSXWebPlayer(COMPUTERNAME),dependingontheOperatingSystem:

YoushouldnowseereportingdatacollectingintheProfilerwindow.

RemoteconnectiontoaniOSdeviceTheProfilercanalsobeconnectedtoanactiveinstanceoftheapplicationrunningremotelyonaniOSdevice,suchasaniPadoriPhone.ThiscanbeachievedthroughasharedWiFiconnection.FollowthegivenstepstoconnecttheProfilertoanAppledevice:

NoteNotethatremoteconnectiontoanAppledeviceisonlypossiblewhentheProfilerisrunningonanAppleMacdevice.

1. EnsurethattheUseDevelopmentModeandAutoconnectProfilerflagsareenabledwhentheapplicationisbuilt.

2. ConnectboththeiOSdeviceandMactoalocalorADHOCWiFinetwork.3. AttachtheiOSdevicetotheMacviatheUSBortheLightningcable.4. BeginbuildingtheapplicationwiththeBuild&Runoptionasnormal.


5. OpentheProfilerwindowintheUnityEditorandselectthedeviceunderActiveProfiler.

YoushouldnowseetheiOSdevice’sprofilingdatagatheringintheProfilerwindow.

TipTheProfilerusesports54998to55511tobroadcastprofilingdata.Makesuretheseportsareavailableforoutboundtrafficifthereisafirewallonthenetwork.

RemoteconnectiontoanAndroiddeviceTherearetwodifferentmethodsforconnectinganAndroiddevicetotheUnityProfiler:eitherthroughaWiFiconnectionorusingtheAndroidDebugBridge(ADB)tool.ADBisasuiteofdebuggingtoolsthatcomesbundledwiththeAndroidSDK.

FollowthegivenstepsforprofilingoveraWiFiconnection:


2. ConnectboththeAndroidanddesktopdevicestoalocalWiFinetwork.3. AttachtheAndroiddevicetothedesktopdeviceviatheUSBcable.4. BeginbuildingtheapplicationwiththeBuild&Runoptionasnormal.5. OpentheProfilerwindowintheUnityEditorandselectthedeviceunderActive

Profiler.

YoushouldnowseetheAndroiddevice’sprofilingdatagatheringintheProfilerWindow.

ForADBprofiling,followthegivensteps:

1. FromtheWindowscommandprompt,runtheadbdevicescommand,whichchecksifthedeviceisrecognizedbyADB(ifnot,thenthespecificdevicedriversforthedevicemayneedtobeinstalledand/orUSBdebuggingneedstobeenabledonthetargetdevice).

NoteNotethat,iftheadbdevicescommandisn’tfoundwhenitisrunfromthecommandprompt,thentheAndroidSDKfoldermayneedtobeappendedontotheEnvironment’sPATHvariable.


3. AttachtheAndroiddevicetothedesktopdeviceviathecable(forexample,USB).4. BeginbuildingtheapplicationwiththeBuild&Runoptionasnormal.5. OpentheProfilerWindowintheUnityEditorandselectthedeviceunderActive

Profiler.

YoushouldnowseetheAndroiddevice’sprofilingdatagatheringintheProfilerwindow.


TheProfilerwindowWewillnowcovertheessentialfeaturesoftheProfilerastheycanbefoundwithintheinterface.

NoteNotethatthissectioncoversfeaturesastheyappearintheUnityProfilerwithinUnity5.AdditionalfeatureswereaddedtotheProfilerwiththereleaseofUnity5;thesemaybedifferent,ornotexist,inUnity4’sProfiler.

TheProfilerwindowissplitintothreemainareas:

ControlsTimelineViewBreakdownView

Theseareasareasshowninthefollowingscreenshot:

ControlsThetopbarcontainsmultiplecontrolswecanusetoaffectwhatisbeingprofiledandhowdeeplyinthesystemdataisgatheredfrom.Theyare:

AddProfiler:Bydefault,theProfilershowsseveralofUnity’senginecomponentsintheTimelineView,buttheAddProfileroptioncanbeusedtoaddadditionalitems.


SeetheTimelineViewsectionforacompletelistofcomponentswecanprofile.Record:EnablingthisoptionwillmaketheProfilercontinuouslyrecordprofilingdata.NotethatdatacanonlyberecordedifPlayModeisenabled(andnotpaused)orifProfileEditorisenabled.DeepProfile:OrdinaryprofilingwillonlyrecordthetimeandmemoryallocationsmadebyanyUnitycallbackmethods,suchasAwake(),Start(),Update(),FixedUpdate(),andsoon.EnablingDeepProfilerecompilesourscriptstomeasureeachandeveryinvokedmethod.Thiscausesanevengreaterinstrumentationcostduringruntimeandusessignificantlymorememorysincedataisbeingcollectedfortheentirecallstackatruntime.Asaconsequence,DeepProfilingmaynotevenbepossibleinlargeprojectsrunningonweakhardware,asUnitymayrunoutofmemorybeforetestingcanevenbegin!

TipNotethatDeepProfilingrequirestheprojecttoberecompiledbeforeprofilingcanbegin,soitisbesttoavoidtogglingtheoptionduringruntime.

Becausethisoptionmeasuresallmethodsacrossourcodebaseinablindfashion,itshouldnotbeenabledduringmostofourprofilingtests.Thisoptionisbestreservedforwhendefaultprofilingisnotprovidingenoughdetail,orinsmalltestScenes,whichareusedtoprofileasmallsubsetofgamefeatures.

IfDeepProfilingisrequiredforlargerprojectsandScenes,buttheDeepProfileoptionistoomuchofahindranceduringruntime,thentherearealternativesthatcanbefoundintheupcomingsectiontitledTargetedProfilingofcodesegments.

ProfileEditor:ThisoptionenablesEditorprofiling—thatis,gatheringprofilingdatafortheUnityEditoritself.ThisisusefulinordertoprofileanycustomEditorScriptswehavedeveloped.

TipNotethatActiveProfilermustbesettotheEditoroptionforthisfeaturetowork.

ActiveProfiler:Thisdrop-downgloballyofferschoicestoselectthetargetinstanceofUnitywewishtoprofile;this,aswe’velearned,canbethecurrentEditorapplication,alocalstandaloneinstanceofourapplication,oraninstanceofourapplicationrunningonaremotedevice.Clear:ThisclearsallprofilingdatafromtheTimelineView.FrameSelection:TheFramecountershowshowmanyframeshavebeenprofiled,andwhichframeiscurrentlyselectedintheTimelineView.Therearetwobuttonstomovethecurrentlyselectedframeforwardorbackwardbyoneframe,andathirdbutton(theCurrentbutton)thatresetstheselectedframetothemostrecentframeandkeepsthatposition.ThiswillcausetheBreakdownViewtoalwaysshowtheprofilingdataforthecurrentframeduringruntimeprofiling.TimelineView:TheTimelineViewrevealsprofilingdatathathasbeencollectedduringruntime,organizedbyareasdependingonwhichcomponentoftheenginewasinvolved.


EachAreahasmultiplecoloredboxesforvarioussubsectionsofthosecomponents.Thesecoloredboxescanbetoggledtoreveal/hidethecorrespondingdatatypeswithintheTimelineView.

EachAreafocusesonprofilingdataforadifferentcomponentoftheUnityengine.WhenanAreaisselectedintheTimelineView,essentialinformationforthatcomponentwillberevealedintheBreakdownViewforthecurrentlyselectedframe.

TheBreakdownViewshowsverydifferentinformation,dependingonwhichAreaiscurrentlyselected.

TipAreascanberemovedfromtheTimelineViewbyclickingonthe‘X‘atthetoprightofanArea.AreascanberestoredtotheTimelineViewthroughtheAddProfileroptionintheControlsbar.

CPUArea

ThisAreashowsCPUUsageformultipleUnitysubsystemsduringruntime,suchasMonoBehaviourcomponents,cameras,somerenderingandphysicsprocesses,userinterfaces(includingtheEditor’sinterface,ifwe’rerunningthroughtheEditor),audioprocessing,theProfileritself,andmore.

TherearethreewaysofdisplayingCPUUsagedataintheBreakdownView:

HierarchyRawHierarchyTimeline

TheHierarchyModegroupssimilardataelementsandglobalUnityfunctioncallstogetherforconvenience—forinstance,renderingdelimiters,suchasBeginGUI()andEndGUI()callsarecombinedtogetherinthisMode.

TheRawHierarchyModewillseparateglobalUnityfunctioncallsintoindividuallines.ThiswilltendtomaketheBreakdownViewmoredifficulttoread,butmaybehelpfulifwe’retryingtocounthowmanytimesaparticularglobalmethodhasbeeninvoked,ordeterminingifoneofthesecallsiscostingmoreCPU/memorythanexpected.Forexample,eachBeginGUI()andEndGUI()callwillbeseparatedintodifferententries,possiblyclutteringtheBreakdownView,makingitdifficulttoread.

Perhaps,themostusefulmodefortheCPUAreaistheTimelineModeoption(nottobeconfusedwiththemainTimelineView).ThisModeorganizesCPUusageduringthecurrentframebyhowthecallstackexpandedandcontractedduringprocessing.BlocksatthetopofthisviewweredirectlycalledbytheUnityEngine(suchastheStart(),Awake(),orUpdate()methods),whileblocksunderneaththemaremethodsthatthosemethodshadcalled,whichcanincludemethodsonotherComponentsorobjects.

Meanwhile,thewidthofagivenCPUTimelineBlockgivesustherelativetimeittooktoprocessthatmethodcomparedtootherblocksaroundit.Inaddition,methodcallsthatconsumerelativelylittleprocessingtime,relativetothemoregreedymethods,areshown


asgrayboxestokeepthemoutofsight.

ThedesignoftheCPUTimelineModeoffersaverycleanandorganizedwayofdeterminingwhichparticularmethodinthecallstackisconsumingthemosttime,andhowthatprocessingtimemeasuresupagainstothermethodsbeingcalledduringthesameframe.Thisallowsustogaugewhichmethodisthebiggestculpritwithminimaleffort.

Forexample,let’sassumethatwearelookingataperformanceprobleminthefollowingscreenshot.Wecantell,withaquickglance,thattherearethreemethodsthatarecausingaproblem,andtheyeachconsumesimilaramountsofprocessingtime,duetohavingsimilarwidths.

Inthisexample,thegoodnewsisthatwehavethreepossiblemethodsthroughwhichtofindperformanceimprovements,whichmeanslotsofopportunitiestofindcodethatcanbeimproved.Thebadnewsisthatincreasingtheperformanceofonemethodwillonlyimproveaboutone-thirdofthetotalprocessingforthatframe.Hence,allthreemethodswillneedtobeexaminedandimprovedinordertominimizetheamountofprocessingtimeduringthisframe.

TheCPUAreawillbemostusefulduringChapter2,ScriptingStrategies.

TheGPUArea

TheGPUAreaissimilartotheCPUArea,exceptthatitshowsmethodcallsandprocessingtimeasitoccursontheGPU.RelevantUnitymethodcallsinthisAreawillrelatetocameras,drawing,opaqueandtransparentgeometry,lightingandshadows,andsoon.

TheGPUAreawillbebeneficialduringChapter6,DynamicGraphics.

TheRenderingArea

TheRenderingAreaprovidesrenderingstatistics,suchasthenumberofSetPasscalls,thetotalnumberofBatchesusedtorenderthescene,thenumberofBatchessavedfromDynamicandStaticBatching,memoryconsumedforTextures,andsoon.

TheRenderingAreawillbeusefulinChapter3,TheBenefitsofBatching.


TheMemoryArea

TheMemoryAreaallowsustoinspectmemoryusageoftheapplicationintheBreakdownViewintwodifferentways:

SimpleModeDetailedMode

TheSimpleModeprovidesonlyahigh-leveloverviewofmemoryconsumptionofcomponentssuchasUnity’slow-levelEngine,theMonoframework(totalheapsizethatwillbegarbage-collected),Graphics,Audio(FMOD),andevenmemoryusedtostoredatacollectedbytheProfiler.

TheDetailedModeshowsmemoryconsumptionofindividualgameobjectsandcomponents,forboththeirnativeandmanagedrepresentations.Italsohasacolumnexplainingthereasonforthatobjectconsumingmemoryandwhenitmightbede-allocated.

TheMemoryAreawillbethemainfocalpointofChapter7,MasterfulMemoryManagement.

TheAudioArea

TheAudioAreagrantsanoverviewofaudiostatisticsandcanbeusedbothtomeasureCPUusagefromtheaudiosystem,aswellastotalmemoryconsumedbyAudioSources(forbothplayingandpausedsources)andAudioClips.

TheAudioAreawillcomeinhandyasweexploreartassetsinChapter4,KickstartYourArt.

TipAudioisoftenoverlookedwhenitcomestoperformanceenhancements,butaudiocanbecomeofthebiggestsourcesofbottlenecksifitisnotmanagedproperly.It’sworthperformingoccasionalchecksontheAudiosystem’smemoryandCPUconsumptionduringdevelopment.

ThePhysics3D/2DArea

TherearetwodifferentPhysicsAreas,onefor3Dphysics(Nvidia’sPhysX)andanotherforthe2Dphysicssystem(Box2D)thatwasintegratedintotheUnityEngineinversion4.5.ThisAreaprovidesvariousphysicsstatisticssuchasRigidbody,Collider,andContactcounts.

WewillbemakinguseofthisAreainChapter5,FasterPhysics.

NoteAsofthepublicationofthistext,withUnityv5.2.2f1asthemostrecentversion,thePhysics3DAreaonlyprovidesahandfulofitems,whilethePhysics2DAreaprovidessignificantlymoreinformation.


BestapproachestoperformanceanalysisGoodcodingpracticesandprojectassetmanagementoftenmakefindingtherootcauseofaperformanceissuerelativelysimple,atwhichpointtheonlyrealproblemisfiguringouthowtoimprovethecode.Forinstance,ifthemethodonlyprocessesasinglegiganticforloop,thenitwillbeaprettysafeassumptionthattheproblemiseitherwiththeiterationofthelooporhowmuchworkisprocessedeachiteration.

Ofcourse,alotofourcode,whetherwe’reworkingindividuallyorinagroupsetting,isnotalwayswritteninthecleanestwaypossible,andweshouldexpecttohavetoprofilesomepoorcodingworkfromtimetotime.Sometimes,hack-ysolutionsareinevitable,andwedon’talwayshavethetimetogobackandrefactoreverythingtokeepupwithourbestcodingpractices.

It’seasytooverlooktheobviouswhenproblemsolvingandperformanceoptimizationisjustanotherformofproblemsolving.ThegoalistouseProfilersanddataanalysistosearchourcodebaseforcluesaboutwhereaproblemoriginates,andhowsignificantitis.It’softenveryeasytogetdistractedbyinvaliddataorjumptoconclusionsbecausewe’rebeingtooimpatientormissedasubtleclue.Manyofushaverunintooccasions,duringsoftwaredebugging,wherewecouldhavefoundtherootcauseoftheproblemmuchfasterifwehadsimplychallengedandverifiedourearlierassumptions.Alwaysapproachingdebuggingunderthebeliefthattheproblemishighlycomplexandtechnicalisagoodwaytowastevaluabletimeandeffort.Performanceanalysisisnodifferent.

Achecklistoftaskswouldbehelpfultokeepusfocusedontheissue,andnotwastetimechasing“ghosts”.Everyprojectisdifferentandhasadifferentsetofconcernsanddesignparadigms,butthefollowingchecklistisgeneralenoughthatitshouldbeabletoapplytoanyUnityproject:

VerifyingthetargetScriptispresentintheSceneVerifyingtheScriptappearsintheScenethecorrectnumberoftimesMinimizingongoingcodechangesMinimizinginternaldistractionsMinimizingexternaldistractions


VerifyingscriptpresenceSometimestherearethingsweexpecttosee,butdon’t.Theseareusuallyeasytonote,becausethehumanbrainisverygoodatpatternrecognition.Ifsomethingdoesn’tmatchtheexpectedpattern,thenittendstobeveryobvious.Meanwhile,therearetimeswhereweassumesomethinghasbeenhappening,butitdidn’t.Thesearegenerallymoredifficulttonotice,becausewe’reoftenscanningforthefirstkindofproblem.Verificationoftheintendedorderofeventsiscritical,orweriskjumpingtoconclusions,wastingvaluabletime.

InthecontextofUnity,thismeansitisessentialtoverifythatthescriptweexpecttoseetheeventcomingfromisactuallypresentintheScene,andthatthemethodcallshappenintheorderweintended.

ScriptpresencecanbequicklyverifiedbytypingthefollowingintotheHierarchywindowtextbox:

t:<monobehaviourname>

Forexample,typingt:mytestmonobehaviour(note:itisnotcase-sensitive)intotheHierarchytextboxwillshowashortlistofallGameObjectsthatcurrentlyhaveaMyTestMonobehaviourscriptattachedasaComponent.

TipNotethatthisshortlistfeaturealsoincludesanyGameObjectswithComponentsthatderivefromthegivenscriptname.

Weshouldalsodouble-checkthattheGameObjectstheyareattachedtoarestillenabled,sincewemayhavedisabledthemduringearliertesting,orsomeone/somethinghasaccidentallydeactivatedtheobject.


VerifyingscriptcountIfweassumethataMonoBehaviour,whichiscausingperformanceproblems,onlyappearsonceinourScene,thenwemayignorethepossibilitythatconflictingmethodinvocationsarecausingabottleneck.Thisisdangerous;whatifsomeonecreatedtheobjecttwiceormoreintheScenefile,orweaccidentallyinstantiatedtheobjectmorethanoncefromcode?WhatweseeintheProfilercanbeaconsequenceofthesameexpensivemethodbeinginvokedmorethanonceatthesametime.Thisissomethingwewillwanttodouble-checkusingthesameshortlistmethodasbefore.

IfweexpectedonlyoneoftheComponentstoappearintheScene,buttheshortlistrevealedmorethanone,thenwemaywishtorethinkourearlierassumptionsaboutwhat’scausingthebottlenecks.Wemaywishtowritesomeinitializationcodethatpreventsthisfromeverhappeningagain,and/orwritesomecustomEditorhelperstodisplaywarningstoanyleveldesignerswhomightbemakingthismistake.

Preventingcasualmistakeslikethisisessentialforgoodproductivity,sinceexperiencetellsusthat,ifwedon’texplicitlydisallowsomething,thensomeone,somewhere,atsomepoint,forwhateverreason,willdoitanyway,andcostusagooddealofanalysiswork.


MinimizingongoingcodechangesMakingcodechangestotheapplicationinordertohuntdownperformanceissuesisnotrecommended,asthechangesareeasytoforgetastimewearson.Addingdebugloggingstatementstoourcodecanbetempting,butrememberthatitcostsustimetointroducethesecalls,recompileourcode,andremovethesecallsonceouranalysisiscomplete.Inaddition,ifweforgettoremovethem,thentheycancostunnecessaryruntimeoverheadinthefinalbuildsinceUnity’sDebugloggingcanbeprohibitivelyexpensiveinbothCPUandmemory.

Onewaytocombatthisproblemistouseasource-controltooltodifferentiatethecontentsofanymodifiedfiles,and/orrevertthembacktotheiroriginalstate.Thisisanexcellentwaytoensurethatunnecessarychangesdon’tmakeitintothefinalversion.

Makinguseofbreakpointsduringruntimedebuggingisthepreferredapproach,aswecantracethefullcallstack,variabledata,andconditionalcodepaths(forexample,if-elseblocks),withoutriskinganycodechangesorwastingtimeonrecompilation.


MinimizinginternaldistractionsTheUnityEditorhasitsownlittlequirksandnuancesthatcanleaveusconfusedbycertainissues.

Firstly,ifasingleframetakesalongtimetoprocess,suchthatourgamenoticeablyfreezes,thentheProfilermaynotbecapableofpickinguptheresultsandrecordingthemintheProfilerwindow.Thiscanbeespeciallyannoyingifwewishtocatchdataduringapplication/Sceneinitialization.Theupcomingsection,CustomCPUProfiling,willoffersomealternativestoexploretosolvethisproblem.

Onecommonmistake(thatIhaveadmittedlyfallenvictimtomultipletimesduringthewritingofthisbook)is:ifwearetryingtoinitiateatestwithakeystrokeandwehavetheProfileropen,weshouldnotforgettoclickbackintotheEditor’sGamewindowbeforetriggeringthekeystroke!IftheProfileristhemostrecentlyclickedwindow,thentheEditorwillsendkeystrokeeventstothat,insteadoftheruntimeapplication,andhencenoGameObjectwillcatchtheeventforthatkeystroke.

VerticalSync(otherwiseknownasVSync)isusedtomatchtheapplication’sframeratetotheframerateofthedeviceitisbeingdisplayedon(forexample,themonitor).ExecutingtheProfilerwiththisfeatureenabledwillgeneratealotofspikesintheCPUusageareaundertheheadingWaitForTargetFPS,astheapplicationintentionallyslowsitselfdowntomatchtheframerateofthedisplay.Thiswillgenerateunnecessaryclutter,makingithardertospottherealissue(s).WeshouldmakesuretodisabletheVSynccoloredboxundertheCPUAreawhenwe’reonthelookoutforCPUspikesduringperformancetests.WecandisabletheVSyncfeatureentirelybynavigatingtoEdit|ProjectSettings|Qualityandthenthesubpageforthecurrentlyselectedbuildplatform.

Weshouldalsoensurethatadropinperformanceisn’tadirectresultofamassivenumberofexceptionsanderrormessagesappearingintheEditorconsole.Unity’sDebug.Log(),andsimilarmethodssuchasDebug.LogError(),Debug.LogWarning(),andsoon,arenotoriouslyexpensiveintermsofCPUusageandheapmemoryconsumption,whichcanthencausegarbagecollectiontooccurandevenmorelostCPUcycles.

ThisoverheadisusuallyunnoticeabletoahumanbeinglookingattheprojectinEditorMode,wheremosterrorscomefromthecompilerormisconfiguredobjects.Buttheycanbeproblematicwhenusedduringanykindofruntimeprocess;especiallyduringprofiling,wherewewishtoobservehowthegamerunsintheabsenceofexternaldisruptions.Forexample,ifwearemissinganobjectreferencethatweweresupposedtoassignthroughtheEditoranditisbeingusedinanUpdate()method,thenasingleMonoBehaviourcouldbethrowingnewexceptionseverysingleupdate.Thisaddslotsofunnecessarynoisetoourprofilingdata.

NotethatwecandisabletheInfoorWarningcheckboxes(showninthefollowingscreenshot)fortheprojectduringPlayModeruntime,butitstillcostsCPUandmemorytoexecutedebugstatements,eventhoughtheyarenotbeingrendered.Itisoftenagoodpracticetokeepalloftheseoptionsenabled,toverifythatwe’renotmissinganythingimportant.


MinimizingexternaldistractionsThisoneissimplebutabsolutelynecessary.Weshoulddouble-checkthattherearenobackgroundprocesseseatingawayCPUcyclesorconsumingvastswathesofmemory.Beinglowonavailablememorywillgenerallyinterferewithourtesting,asitcancausemorecachemisses,hard-driveaccessforvirtualmemorypage-fileswapping,andgenerallyslowresponsivenessoftheapplication.


TargetedprofilingofcodesegmentsIfourperformanceproblemisn’tsolvedbytheabovechecklist,thenweprobablyhavearealissueonourhandsthatdemandsfurtheranalysis.Thetaskoffiguringoutexactlywheretheproblemislocatedstillremains.TheProfilerwindowiseffectiveatshowingusabroadoverviewofperformance;itcanhelpusfindspecificframestoinvestigateandcanquicklyinformuswhichMonoBehaviourand/ormethodmaybecausingissues.However,wemuststilldetermineexactlywheretheproblemexists.Weneedtofigureoutiftheproblemisreproducible,underwhatcircumstancesaperformancebottleneckarises,andwhereexactlywithintheproblematiccodeblocktheissueisoriginatingfrom.

Toaccomplishthese,wewillneedtoperformsomeprofilingoftargetedsectionsofourcode,andthereareahandfulofusefultechniqueswecanemployforthistask.ForUnityprojects,theyessentiallyfitintotwocategories:

ControllingtheProfilerfromscriptcodeCustomtimingandloggingmethods

NoteNotethatthefollowingsectionmostlyfocussesonhowtoinvestigateScriptingbottlenecksthroughC#code.Detectingthesourceofbottlenecksinotherenginecomponentswillbediscussedintheirrelatedchapters.


ProfilerscriptcontrolTheProfilercanbecontrolledinscriptcodethroughthestaticProfilerclass.ThereareseveralusefulmethodsintheProfilerclassthatwecanexplorewithintheUnitydocumentation,butthemostimportantmethodsarethedelimitermethodsthatactivateanddeactivateprofilingatruntime:Profiler.BeginSample()andProfiler.EndSample().

TipNotethatthedelimitermethods,BeginSample()andEndSample(),areonlycompiledindevelopmentbuilds,andassuchtheycausenooverheadinthefinalbuild.Therefore,itissafetoleavetheminourcodebaseifwewishtousethemforprofilingtestsatalaterdate.

TheBeginSample()methodhasanoverloadthatallowsacustomnameforthesampletoappearintheCPUUsageArea’sHierarchyModeview.Forexample,thefollowingcodewillprofileinvocationsofthismethodandmakethedataappearintheBreakdownViewunderacustomheading:

voidDoSomethingCompletelyStupid(){

Profiler.BeginSample("MyProfilerSample");

List<int>listOfInts=newList<int>();

for(inti=0;i<1000000;++i){

listOfInts.Add(i);

}

Profiler.EndSample();

}

TipDownloadingtheexamplecode

Youcandownloadtheexamplecodefilesfromyouraccountathttp://www.packtpub.comforallthePacktPublishingbooksyouhavepurchased.Ifyoupurchasedthisbookelsewhere,youcanvisithttp://www.packtpub.com/supportandregistertohavethefilese-maileddirectlytoyou.

Weshouldexpectthatinvokingthispoorlydesignedmethod(itgeneratesalistcontainingamillionintegers,andthendoesabsolutelynothingwithit)willcauseahugespikeinCPUusage,chewupseveralMegabytesofmemory,andappearintheProfilerBreakdownViewundertheheadingMyProfilerSampleasthefollowingscreenshotshows:



http://www.packtpub.com/support

NotethatthesecustomsamplenamesdonotappearattherootofthehierarchywhenweperformDeepProfiling.ThefollowingscreenshotshowstheBreakdownViewforthesamecodeunderDeepProfiling:

Notehowthecustomnameforthesampledoesnotappearatthetopofthesample,wherewemayexpectitto.It’sunclearwhatcausesthisphenomenon,butthiscancausesomeconfusionwhenexaminingtheDeepProfilingdatawithinHierarchyMode,soitisgoodtobeawareofit.


CustomCPUProfilingTheProfilerisjustonetoolatourdisposal.Sometimes,wemaywanttoperformcustomizedprofilingandloggingofourcode.Maybewe’renotconfidenttheUnityProfilerisgivingustherightanswer,maybeweconsideritsoverheadcosttoogreat,ormaybewejustlikehavingcompletecontrolofeverysingleaspectofourapplication.Whateverourmotivations,knowingsometechniquestoperformanindependentanalysisofourcodeisausefulskilltohave.It’sunlikelywe’llonlybeworkingwithUnityfortheentiretyofourgamedevelopmentcareers,afterall.

Profilingtoolsareverycomplex,soit’sunlikelywewouldbeabletogenerateacomparablesolutiononourownwithinareasonabletimeframe.WhenitcomestotestingCPUusage,allweneedisanaccuratetimingsystem,afast,low-costwayofloggingthatinformation,andsomepieceofcodetotestagainst.Itjustsohappensthatthe.NETlibrary(or,technically,theMonoframework)comeswithaStopwatchclassundertheSystem.Diagnosticsnamespace.WecanstopandstartaStopwatchobjectatanytime,andwecaneasilyacquireameasureofhowmuchtimehaspassedsincetheStopwatchwasstarted.

Unfortunately,thisclassisnotveryaccurate—itisaccurateonlytomilliseconds,ortenthsofamillisecondatbest.Countinghigh-precisionrealtimewithaCPUclockcanbeasurprisinglydifficulttaskwhenwestarttogetintoit;so,inordertoavoidadetaileddiscussionofthetopic,weshouldtrytofindawayfortheStopwatchclasstosatisfyourneeds.

Beforewegetobsessedwiththetopicofhighprecision,weshouldfirstaskourselvesifweevenneedit.Mostgamesexpecttorunat30FPS(frames-per-second)or60FPS,whichmeanstheyonlyhavearound33msor16ms,respectively,tocomputeeverythingfortheentireframe.So,hypothetically,ifweonlyneedtobringtheperformanceofaparticularcodeblockunder10ms,thenrepeatingthetestthousandsoftimestogetmicrosecondprecisionwouldn’treallytellusanythinguseful.

However,ifprecisionisimportant,thenoneeffectivewaytoincreaseitisbyrunningthesametestmultipletimes.Assumingthatthetestcodeblockisbotheasilyrepeatableandnotexceptionallylong,thenweshouldbeabletorunthousands,orevenmillions,oftestswithinareasonabletimeframeandthendividethetotalelapsedtimebythenumberoftestswejustperformedtogetamoreaccuratetimeforasingletest.

ThefollowingisaclassdefinitionforacustomtimerthatusesaStopwatchtocounttimeforagivennumberoftests:

usingUnityEngine;

usingSystem;

usingSystem.Diagnostics;

usingSystem.Collections;

publicclassCustomTimer:IDisposable{

privatestringm_timerName;

privateintm_numTests;


privateStopwatchm_watch;

//givethetimeraname,andacountofthenumberoftestswe're

running

publicCustomTimer(stringtimerName,intnumTests){

m_timerName=timerName;

m_numTests=numTests;

if(m_numTests<=0)

m_numTests=1;

m_watch=Stopwatch.StartNew();

}

//calledwhenthe'using'blockends

publicvoidDispose(){

m_watch.Stop();

floatms=m_watch.ElapsedMilliseconds;

UnityEngine.Debug.Log(string.Format("{0}finished:{1:0.00}mstotal,

{2:0.000000}mspertestfor{3}tests",m_timerName,ms,ms/m_numTests,

m_numTests));

}

}

ThefollowingisanexampleoftheCustomTimerclassusage:

intnumTests=1000;

using(newCustomTimer("MyTest",numTests)){

for(inti=0;i<numTests;++i){

TestFunction();

}

}//thetimer'sDispose()methodisautomaticallycalledhere

Therearethreethingstonotewhenusingthisapproach.Firstly,weareonlymakinganaverageofmultiplemethodinvocations.Ifprocessingtimevariesenormouslybetweeninvocations,thenthatwillnotbewell-representedinthefinalaverage.Secondly,ifmemoryaccessiscommon,thenrepeatedlyrequestingthesameblocksofmemorywillresultinanartificiallyhighercachehitrate,whichwillbringtheaveragetimedownwhencomparedtoatypicalinvocation.Thirdly,theeffectsofJITcompilationwillbeeffectivelyhiddenforsimilarlyartificialreasonsasitonlyaffectsthefirstinvocationofthemethod.JITcompilationissomethingthatwillbecoveredinmoredetailinChapter7,MasterfulMemoryManagement.

Theusingblockistypicallyusedtosafelyensurethatunmanagedresourcesareproperlydestroyedwhentheygooutofscope.Whentheusingblockends,itwillautomaticallyinvoketheobject’sDispose()methodtohandleanycleanupoperations.Inordertoachievethis,theobjectmustimplementtheIDisposableinterface,whichforcesittodefinetheDispose()method.

However,thesamelanguagefeaturecanbeusedtocreateadistinctcodeblock,whichcreatesashort-termobject,whichthenautomaticallyprocessessomethingusefulwhenthecodeblockends.

Note

Notethattheusingblockshouldnotbeconfusedwiththeusingstatement,whichisusedatthestartofascriptfiletopullinadditionalnamespaces.It’sextremelyironicthatthekeywordformanagingnamespacesinC#hasanamingconflictwithanotherkeyword.

Asaresult,theusingblockandtheCustomTimerclassgiveusacleanwayofwrappingourtargettestcodeinawaywhichmakesitobviouswhenandwhereitisbeingused.

Anotherconcerntoworryaboutisapplicationwarmup.UnityhasasignificantstartupcostwhenaScenebegins,giventhenumberofcallstovariousGameObjects’Awake()andStart()methods,aswellasinitializationofothercomponentssuchasthePhysicsandRenderingsystems.Thisearlyoverheadmightonlylastasecond,butthatcanhaveasignificanteffectontheresultsofourtesting.Thismakesitcrucialthatanyruntimetestingbeginsaftertheapplicationhasreachedasteadystate.

Ifpossible,itwouldbewisetowrapthetargetcodeblockinanInput.GetKeyDown()methodcheckinordertohavecontroloverwhenitisinvoked.Forexample,thefollowingcodewillonlyexecuteourtestmethodwhentheSpaceBarispressed:


intnumTests=1000;

using(newCustomTimer("ControlledTest",numTests)){


TestFunction();

}

}

}

TherearethreeimportantdesignfeaturesoftheCustomTimerclass:itonlyprintsasinglelogmessagefortheentiretest,onlyreadsthevaluefromtheStopwatchafterithasbeenstopped,andusesstring.Format()forgeneratingacustomstring.

Asexplainedearlier,Unity’sconsoleloggingmechanismisprohibitivelyexpensive.Asaresult,weshouldneverusetheseloggingmethodsinthemiddleofaprofilingtest(orevengameplay,forthatmatter).Ifwefindourselvesabsolutelyneedingdetailedprofilingdatathatprintsoutlotsofindividualmessages(suchasperformingatimingtestoneachiterationofaloop,tofindwhichiterationiscostingmoretimethantherest),thenitwouldbewisertocachetheloggingdataandprintitallattheend,astheCustomTimerclassdoes.Thiswillreduceruntimeoverhead,atthecostofsomememoryconsumption.ThealternativeisthatmanymillisecondsarelosttoprintingeachDebug.Log()messageinthemiddleofthetest,whichpollutestheresults.

ThesecondfeatureisthattheStopwatchisstoppedbeforethevalueisread.Thisisfairlyobvious;readingthevaluewhileitisstillcountingmightgiveusaslightlydifferentvaluethanstoppingitfirst.UnlesswedivedeepintotheMonoprojectsourcecode(andthespecificversionUnityuses),wemightnotknowtheexactimplementationofhowStopwatchcountstime,atwhatpointsCPUticksarecounted,andatwhatmomentsanyapplicationcontextswitchingistriggeredbytheOS.So,itisoftenbettertoerronthesideofcautionandpreventanymorecountingbeforeweattempttoaccessthevalue.


Finally,there’stheusageofstring.Format().ThiswillbecoveredinmoredetailinChapter7,MasterfulMemoryManagement,buttheshortexplanationisthatthismethodisusedbecausegeneratingcustomstringsusingthe+operatorresultsinasurprisinglylargeamountofmemoryconsumption,whichattractstheattentionofthegarbagecollector.Thiswouldconflictwithourgoalofachievingaccuratetimingandanalysis.


SavingandloadingProfilerdataTheUnityProfilercurrentlyhasafewfairlysignificantpitfallswhenitcomestosavingandloadingProfilerdata:

Only300framesarevisibleintheProfilerwindowatonceThereisnowaytosaveProfilerdatathroughtheuserinterfaceProfilerbinarydatacanbesavedintoafiletheScriptcode,butthereisnobuilt-inwaytoviewthisdata

Theseissuesmakeitverytrickytoperformlarge-scaleorlong-termtestingwiththeUnityProfiler.TheyhavebeenraisedinUnity’sIssueTrackertoolforseveralyears,andtheredoesn’tappeartobeanysalvationinsight.So,wemustrelyonourowningenuitytosolvethisproblem.

Fortunately,theProfilerclassexposesafewmethodsthatwecanusetocontrolhowtheProfilerlogsinformation:

1. TheProfiler.enabledmethodcanbeusedtoenable/disabletheProfiler,whichistheequivalentofclickingontheRecordbuttonintheControlViewoftheProfiler.

NoteNotethatchangingProfiler.enableddoesnotchangethevisiblestateoftheRecordbuttonintheProfiler’sControlsbar.Thiswillcausesomeconfusingconflictsifwe’recontrollingtheProfilerthroughbothcodeandtheuserinterfaceatthesametime.

2. TheProfiler.logFilemethodsetsthecurrentpathofthelogfilethattheProfilerprintsdataoutto.Beawarethatthisfileonlycontainsaprintoutoftheapplication’sframerateovertime,andnoneoftheusefuldatawenormallyfindintheProfiler’sTimelineView.Tosavethatkindofdataasabinaryfile,wemustusetheoptionsthatfollow.

3. TheProfiler.enableBinaryLogmethodwillenable/disableloggingofanadditionalfilefilledwithbinarydata,whichincludesalloftheimportantvalueswewanttosavefromtheTimelineandBreakdownViews.ThefilelocationandnamewillbethesameasthevalueofProfiler.logFile,butwith.dataappendedtotheend.

Withthesemethods,wecangenerateasimpledata-savingtoolthatwillgeneratelargeamountsofProfilerdataseparatedintomultiplefiles.Withthesefiles,wewillbeabletoperusethematalaterdate.


SavingProfilerdataInordertocreateatoolthatcansaveourProfilerdata,wecanmakeuseofaCoroutine.Atypicalmethodwillbeexecutedfrombeginningtoendinonesitting.However,Coroutinesareusefulconstructsthatallowuswritemethodsthatcanpauseexecutionuntilalatertime,oraneventtakesplace.Thisisknownasyielding,andisaccomplishedwiththeyieldstatement.Thetypeofyielddetermineswhenexecutionwillresume,whichcouldbeoneofthefollowingtypes(theobjectthatmustbepassedintotheyieldstatementisalsogiven):

Afteraspecificamountoftime(WaitForSeconds)AfterthenextUpdate(WaitForEndOfFrame)AfterthenextFixedUpdate(WaitForFixedUpdate)JustpriortothenextLateUpdate(null)AfteraWWWobjectcompletesitscurrenttask,suchasdownloadingafile(WWW)AfteranotherCoroutinehasfinished(areferencetoanotherCoroutine)

TheUnityDocumentationonCoroutinesandExecutionOrderprovidesmoreinformationonhowtheseusefultoolsfunctionwithintheUnityEngine:

http://docs.unity3d.com/Manual/Coroutines.htmlhttp://docs.unity3d.com/Manual/ExecutionOrder.html

TipCoroutinesshouldnotbeconfusedwiththreads,whichexecuteindependentlyofthemainUnitythread.Coroutinesalwaysrunonthemainthreadwiththerestofourcode,andsimplypauseandresumeatcertainmoments,dependingontheobjectpassedintotheyieldstatement.

Gettingbacktothetaskathand,thefollowingistheclassdefinitionforourProfilerDataSaverComponent,whichmakesuseofaCoroutinetorepeatanactionevery300frames:

usingUnityEngine;

usingSystem.Text;


publicclassProfilerDataSaverComponent:MonoBehaviour{

int_count=0;

voidStart(){

Profiler.logFile="";

}

voidUpdate(){

if(Input.GetKey(KeyCode.LeftControl)&&Input.GetKeyDown(KeyCode.H))

{

StopAllCoroutines();

_count=0;

StartCoroutine(SaveProfilerData());


http://docs.unity3d.com/Manual/Coroutines.html

http://docs.unity3d.com/Manual/ExecutionOrder.html

}

}

IEnumeratorSaveProfilerData(){

//keepcallingthismethoduntilPlayModestops

while(true){

//generatethefilepath

stringfilepath=Application.persistentDataPath+"/profilerLog"+

_count;

//setthelogfileandenabletheprofiler

Profiler.logFile=filepath;

Profiler.enableBinaryLog=true;

Profiler.enabled=true;

//count300frames

for(inti=0;i<300;++i){

yieldreturnnewWaitForEndOfFrame();

//workaroundtokeeptheProfilerworking

if(!Profiler.enabled)

Profiler.enabled=true;

}

//startagainusingthenextfilename

_count++;

}

}

}

TryattachingthisComponenttoanyGameObjectintheScene,andpressCtrl+H(OSXuserswillwanttoreplacetheKeyCode.LeftControlcodewithsomethingsuchasKeyCode.LeftCommand).TheProfilerwillstartgatheringinformation(whetherornottheProfilerWindowisopen!)and,usingasimpleCoroutine,willpumpthedataoutintoaseriesoffilesunderwhereverApplication.persistantDataPathispointingto.

TipNotethatthelocationofApplication.persistantDataPathvariesdependingontheOperatingSystem.ChecktheUnityDocumentationformoredetailsathttp://docs.unity3d.com/ScriptReference/Application-persistentDataPath.html.

ItwouldbeunwisetosendthefilestoApplication.dataPath,asitwouldputthemwithintheProjectWorkspace.TheProfilerdoesnotreleasethemostrecentlogfilehandleifwestoptheProfilerorevenwhenPlayModeisstopped.Consequently,asfilesaregeneratedandplacedintotheProjectworkspace,therewouldbeaconflictinfileaccessibilitybetweentheUnityEditortryingtoreadandgeneratecomplementarymetadatafiles,andtheProfilerkeepingafilehandletothemostrecentlogfile.Thiswouldresultinsomenastyfileaccesserrors,whichtendtocrashtheUnityEditorandloseanyScenechangeswe’vemade.


http://docs.unity3d.com/ScriptReference/Application-persistentDataPath.html

WhenthisComponentisrecordingdata,therewillbeasmalloverheadinharddiskusageandtheoverheadcostofIEnumeratorcontextswitchingevery300frames,whichwilltendtoappearatthestartofeveryfileandconsumeafewmillisecondsofCPU(dependingonhardware).

Eachfilepairshouldcontain300framesworthofProfilerdata,whichskirtsaroundthe300framelimitintheProfilerwindow.AllweneednowisawayofpresentingthedataintheProfilerwindow.

HereisascreenshotofdatafilesthathavebeengeneratedbyProfilerDataSaverComponent:

NoteNotethatthefirstfilemaycontainlessthan300framesifsomeframeswerelostduringProfilerwarmup.


LoadingProfilerdataTheProfiler.AddFramesFromFile()methodwillloadagivenprofilerlogfilepair(thetextandbinaryfiles)andappenditintotheProfilertimeline,pushingexistingdatafurtherbackintime.Sinceeachfilewillcontain300frames,thisisperfectforourneeds,andwejustneedtocreateasimpleEditorWindowclassthatcanprovidealistofbuttonstoloadthefilesintotheProfiler.

TipNotethatAddFramesFromFile()onlyrequiresthenameoftheoriginallogfile.Itwillautomaticallyfindthecomplimentarybinary.datafileonitsown.

ThefollowingistheclassdefinitionforourProfilerDataLoaderWindow:

usingUnityEngine;

usingUnityEditor;

usingSystem.IO;


usingSystem.Collections.Generic;

usingSystem.Text.RegularExpressions;

publicclassProfilerDataLoaderWindow:EditorWindow{

staticList<string>s_cachedFilePaths;

staticints_chosenIndex=-1;

[MenuItem("Window/ProfilerDataLoader")]

staticvoidInit(){

ProfilerDataLoaderWindowwindow=

(ProfilerDataLoaderWindow)EditorWindow.GetWindow

(typeof(ProfilerDataLoaderWindow));

window.Show();

ReadProfilerDataFiles();

}

staticvoidReadProfilerDataFiles(){

//makesuretheprofilerreleasesthefilehandle

//toanyofthefileswe'reabouttoloadin

Profiler.logFile="";

string[]filePaths=Directory.GetFiles

(Application.persistentDataPath,"profilerLog*");

s_cachedFilePaths=newList<string>();

//wewanttoignoreallofthebinary

//filesthatendin.data.TheProfiler

//willfigurethatpartout

Regextest=newRegex(".data$");

for(inti=0;i<filePaths.Length;i++){

stringthisPath=filePaths[i];

Matchmatch=test.Match(thisPath);

if(!match.Success){

//notabinaryfile,addittothelist

Debug.Log("Foundfile:"+thisPath);

s_cachedFilePaths.Add(thisPath);

}

}

s_chosenIndex=-1;

}

voidOnGUI(){

if(GUILayout.Button("FindFiles")){

ReadProfilerDataFiles();

}

if(s_cachedFilePaths==null)

return;

EditorGUILayout.Space();

EditorGUILayout.LabelField("Files");

EditorGUILayout.BeginHorizontal();

//createsomestylestoorganizethebuttons,andshow

//themostrecently-selectedbuttonwithredtext

GUIStyledefaultStyle=newGUIStyle(GUI.skin.button);

defaultStyle.fixedWidth=40f;

GUIStylehighlightedStyle=newGUIStyle(defaultStyle);

highlightedStyle.normal.textColor=Color.red;

for(inti=0;i<s_cachedFilePaths.Count;++i){

//list5itemsperrow

if(i%5==0){

EditorGUILayout.EndHorizontal();

EditorGUILayout.BeginHorizontal();

}

GUIStylethisStyle=null;

if(s_chosenIndex==i){

thisStyle=highlightedStyle;

}else{

thisStyle=defaultStyle;

}

if(GUILayout.Button(""+i,thisStyle)){

Profiler.AddFramesFromFile(s_cachedFilePaths[i]);

s_chosenIndex=i;

}

}

EditorGUILayout.EndHorizontal();

}

}

ThefirststepincreatinganycustomEditorWindowiscreatingamenuentrypointwitha[MenuItem]attributeandthencreatinganinstanceofaWindowobjecttocontrol.BothoftheseoccurwithintheInit()method.

We’realsocallingtheReadProfilerDataFiles()methodduringinitialization.ThismethodreadsallfilesfoundwithintheApplication.persistantDataPathfolder(thesamelocationourProfilerDataSaverComponentsavesdatafilesto)andaddsthemtoacacheoffilenamestouselater.

Finally,thereistheOnGUI()method.Thismethoddoesthebulkofthework.Itprovidesabuttontoreloadthefilesifneeded,verifiesthatthecachedfilenameshavebeenread,andprovidesaseriesofbuttonstoloadeachfileintotheProfiler.ItalsohighlightsthemostrecentlyclickedbuttonwithredtextusingacustomGUIStyle,makingiteasytoseewhichfile’scontentsarevisibleintheProfileratthecurrentmoment.

TheProfilerDataLoaderWindowcanbeaccessedbynavigatingtoWindow|ProfilerDataLoaderintheEditorinterface,asshowinthefollowingscreenshot:

Hereisascreenshotofthedisplaywithmultiplefilesavailabletobeloaded.ClickingonanyofthenumberedbuttonswillpushtheProfilerdatacontentsofthatfileintotheProfiler.


TheProfilerDataSaverComponentandProfilerDataLoaderWindowdonotpretendtobeexhaustiveorfeature-rich.Theysimplyserveasaspringboardtogetusstartedifwewishtotakethesubjectfurther.Formostteamsandprojects,300framesworthofshort-termdataisenoughfordeveloperstoacquirewhattheyneedtobeginmakingcodechangestofixtheproblem.


FinalthoughtsonProfilingandAnalysisOnewayofdescribingperformanceoptimizationis“theactofstrippingawayunnecessarytasksthatspendvaluableresources”.Wecandothesameandmaximizeourownproductivitythroughminimizingwastedeffort.Effectiveuseofthetoolswehaveatourdisposalisofparamountimportance.Itwouldserveuswelltooptimizeourownworkflowbykeepingawareofsomebestpracticesandtechniques.

Most,ifnotall,adviceforusinganykindofdata-gatheringtoolproperlycanbesummarizedintothreedifferentstrategies:

UnderstandingthetoolReducingnoiseFocusingontheissue


UnderstandingtheProfilerTheProfilerisanarguablywell-designedandintuitivetool,sounderstandingthemajorityofitsfeaturesetcanbegainedbysimplyspendinganhourortwoexploringitsoptionswithatestprojectandreadingitsdocumentation.Themoreweknowaboutourtoolintermsofitsbenefits,pitfalls,features,andlimitations,themoresensewecanmakeoftheinformationitisgivingus,soitisworthspendingthetimetouseitinaplaygroundsetting.Wedon’twanttobetwoweeksawayfromrelease,withahundredperformancedefectstofix,withnoideahowtodoperformanceanalysisefficiently!

Forexample,alwaysremainawareoftherelativenatureoftheTimelineView’sgraphicaldisplay.JustbecauseaspikeorrestingstateintheTimelineseemslargeandthreatening,doesnotnecessarilymeanthereisaperformanceissue.BecausetheTimelineViewdoesnotprovidevaluesonitsverticalaxis,andautomaticallyreadjuststhisaxisbasedonthecontentofthelast300frames,itcanmakesmallspikesappeartobeabiggerproblemthantheyreallyare.SeveralareasintheTimelineprovidehelpfulbenchmarkbars,givingaglimpseofhowtheapplicationwasperformingatthatmoment.Theseshouldbeusedtodeterminethemagnitudeoftheproblem.Don’tlettheProfilertrickusintothinkingthatbigspikesarealwaysbad.Asalways,it’sonlyimportantiftheuserwillnoticeit!

Asanexample,ifalargeCPUusagespikedoesnotexceedthe60FPSor30FPSbenchmarkbars(dependingontheapplication’stargetframerate),thenitwouldbewisetoignoreitandsearchelsewhereforCPUperformanceissues,asnomatterhowmuchweimprovetheoffendingpieceofcodeitwillprobablyneverbenoticedbytheenduser,andisn’tacriticalissuethataffectsproductquality.


ReducingnoiseTheclassicaldefinitionofnoiseincomputerscienceismeaninglessdata,andabatchofprofilingdatathatwasblindlycapturedwithnospecifictargetinmindisalwaysfullofdatawhichwon’tinterestus.Moredatatakesmoretimetomentallyprocessandfilter,whichcanbeverydistracting.Oneofthebestmethodstoavoidthisittosimplyreducetheamountofdataweneedtoprocess,bystrippingawayanydatadeemednonvitaltothecurrentsituation.

ReducingclutterintheProfiler’sgraphicalinterfacewillmakeiteasiertodeterminewhichcomponentiscausingaspikeinresourceusage.RemembertousethecoloredboxesineachTimelineareatonarrowthesearch.However,thesesettingsareautosavedintheEditor,sobesuretore-enablethemforthenextprofilingsessionasthismightcauseustomisssomethingimportantnexttime!

Also,GameObjectscanbedeactivatedtopreventthemfromgeneratingprofilingdata,whichwillalsohelpreduceclutterinourprofilingdata.Thiswillnaturallycauseaslightperformanceboostforeachobjectwedeactivate.But,ifwe’regraduallydeactivatingobjectsandperformancesuddenlybecomessignificantlymoreacceptablewhenaspecificobjectisdeactivated,thenclearlythatobjectisrelatedtotherootcauseoftheproblem.


FocusingontheissueThiscategorymayseemredundant,giventhatwe’vealreadycoveredreducingnoise.Allweshouldhaveleftistheissueathand,right?Notexactly.Focusistheskillofnotlettingourselvesbecomedistractedbyinconsequentialtasksandwildgoosechases.

RecallthatprofilingwiththeUnityProfilercomeswithaminorperformancecost.ThiscostisevenmoreseverewhenusingtheDeepProfilingoption.Wemightevenintroducemoreminorperformancecostsintoourapplicationwithadditionalloggingandsoon.It’seasytoforgetwhenandwhereweintroducedprofilingcodeifthehuntcontinuesforseveralhours.

Weareeffectivelychangingtheresultbymeasuringit.Anychangesweimplementduringdatasamplingcansometimesleadustochaseafternonexistentbugsintheapplication,whenwecouldhavesavedourselvesalotoftimebyattemptingtoreplicatethescenarioundernon-profilingconditions.Ifthebottleneckisreproducibleandnoticeablewithoutprofiling,thenit’sacandidatetobeginaninvestigation.Butifnewbottleneckskeepappearinginthemiddleofanexistinginvestigation,thenkeepinmindthattheycouldsimplybebottleneckswerecentlyintroducedwithtestcode,andnotsomethingthat’sbeennewlyexposed.

Finally,whenwehavefinishedprofiling,havecompletedourfixes,andarenowreadytomoveontothenextinvestigation,weshouldmakesuretoprofiletheapplicationonelasttimetoverifythatthechangeshavehadtheintendedeffect.


SummaryYoulearnedagreatdealthroughoutthischapteronhowtodetectperformanceissueswithinyourapplication.YoulearnedaboutmanyoftheProfiler’sfeaturesandsecrets,youexploredavarietyoftacticstoinvestigateperformanceissueswithamorehands-on-approach,andyou’vebeenintroducedtoavarietyofdifferenttipsandstrategiestofollow.Youcanusethesetoimproveyourproductivityimmensely,solongasyouappreciatethewisdombehindthemandremembertoexploitthemwhenthesituationmakesitpossible.

Thischapterhasintroducedustothetips,tactics,andstrategiesweneedfindaperformanceproblemthatneedsimprovement.Duringtheremainingchapters,wewillexploremethodsonhowtofixissues,andimproveperformancewheneverpossible.So,giveyourselfapatonthebackforgettingthroughtheboringpartfirst,andlet’smoveontolearningsomestrategiestoimproveourC#scriptingpractices.


Chapter2.ScriptingStrategiesSincescriptingwillconsumeagreatdealofourdevelopmenttime,itwillbeenormouslybeneficialtolearnsomebestpractices.Scriptingisaverybroadterm,sowewilltrytolimitourexposureinthischaptertosituationsthatareveryUnityspecific,focusingonproblemsarisingfromwithintheUnityAPIsandenginedesign.WewilldiscussthenuancesandadvancedtopicsoftheC#language,.NETlibrary,andMonoFramework,inChapter7,MasterfulMemoryManagement.

Whetheryouhavesomespecificproblemsinmindthatyouwishtosolveoryoujustwanttolearnsometechniquesforfuturereference,thischapterwillintroduceyoutoanarrayofmethodsthatyoucanusetoimproveyourscriptingeffortsnowandinthefuture.Ineachcase,wewillexplorehowandwhytheperformanceissuearises,anexamplesituationinwhichtheproblemisoccurring,andoneormoresolutionstocombattheissue.


CacheComponentreferencesAcommonmistakewhenscriptinginUnityistooverusetheGetComponent()method.Forexample,thefollowingscriptcodeistryingtocheckacreature’shealthvalue,andifitshealthgoesbelow0,disableaseriesofComponentstoprepareitforadeathanimation:

voidTakeDamage(){

if(GetComponent<HealthComponent>().health<0){

GetComponent<Rigidbody>().enabled=false;

GetComponent<Collider>().enabled=false;

GetComponent<AIControllerComponent>().enabled=false;

GetComponent<Animator>().SetTrigger("death");

}

}

Eachtimethismethodexecutes,itwillreacquirefivedifferentComponentreferences.Thisisgoodintermsofheapmemoryconsumption(inthatitdoesn’tcostany),butitisnotveryfriendlyonCPUusage.ThisisparticularlyproblematicifthemainmethodwerecalledduringUpdate().Evenifitisnot,itstillmightcoincidewithotherimportantevents,suchascreatingparticleeffects,replacinganobjectwitharagdoll(thusinvokingvariousactivityinthephysicsengine),andsoon.Thiscodingstylecanseemharmless,butitcancausealotoflong-termproblemsandruntimeworkforverylittlebenefit.

Itcostsusverylittlememoryspace(only32or64bitseachtime;Unityversion,platform,andfragmentationpermitting)tocachethesereferencesforfutureuse.So,unlessyou’reextremelybottleneckedonmemory,abetterapproachwouldbetoacquirethereferencesduringinitializationandkeepthemuntiltheyareneeded:

privateHealthComponent_healthComponent;

privateRigidbody_rigidbody;

privateCollider_collider;

privateAIControllerComponent_aiController;

privateAnimator_animator;

voidAwake(){

_healthComponent=GetComponent<HealthComponent>();

_rigidbody=GetComponent<Rigidbody>();

_collider=GetComponent<Collider>();

_aiController=GetComponent<AIControllerComponent>();

_animator=GetComponent<Animator>();

}

voidTakeDamage(){

if(_healthComponent.health<0){

_rigidbody.detectCollisions=false;

_collider.enabled=false;

_aiController.enabled=false;

_animator.SetTrigger("death");

}

}

CachingtheComponentreferencesinthiswaysparesusfromreacquiringthemeachtime

they’reneeded,savingussomeCPUoverheadeachtime,attheexpenseofsomeadditionalmemoryconsumption.


ObtainingComponentsusingthefastestmethodThereareseveralvariationsoftheGetComponent()method,anditbecomesprudenttocallthefastestpossibleversionofthismethod.ThethreeoverloadsavailableareGetComponent(string),GetComponent<T>(),andGetComponent(typeof(T)).ItturnsoutthatthefastestversiondependsonwhichversionofUnitywearerunning.

InUnity4,theGetComponent(typeof(T))methodisthefastestoftheavailableoptionsbyareasonablemargin.Let’sprovethiswithsomesimpletesting:

intnumTests=1000000;

TestComponenttest;

using(newCustomTimer("GetComponent(string)",numTests)){

for(vari=0;i<numTests;++i){

test=(TestComponent)GetComponent("TestComponent");

}

}

using(newCustomTimer("GetComponent<ComponentName>",numTests)){


test=GetComponent<TestComponent>();

}

}

using(newCustomTimer("GetComponent(typeof(ComponentName))",numTests)){


test=(TestComponent)GetComponent(typeof(TestComponent));

}

}

ThiscodetestseachoftheGetComponent()overloadsamilliontimes.Thisisfarmoreteststhanwouldbesensibleforatypicalproject,butitisenoughteststoprovethepoint.

Hereistheresultwegetwhenthetestscomplete:

Asyoucansee,GetComponent(typeof(T))issignificantlyfasterthanGetComponent<T>(),whichisaroundfivetimesfasterthanGetComponent(string).ThistestwasperformedagainstUnity4.5.5,butthebehaviorshouldbeequivalentallthewaybacktoUnity3.x.

Note

GetComponent(string)shouldnotbeused,sinceitisnotoriouslyslowandisonlyincludedforcompleteness.

TheseresultschangewhenweruntheexactsametestinUnity5.UnityTechnologiesmadesomeperformanceenhancementstohowSystem.TypereferencesarepassedaroundinUnity5.0,and,asaresult,GetComponent<T>()andGetComponent(typeof(T))becomeessentiallyequivalent:

Asyoucansee,theGetComponent<T>()methodisonlyatinyfractionfasterthanGetComponent(typeof(T)),whileGetComponent(string)isnowaround30timesslowerthanthealternatives(interestingly,itbecameevenslowerthanitwasinUnity4).Multipletestswillprobablyyieldsmallvariationsintheseresults,butultimatelywecanfavoreitherofthetype-basedversionsofGetComponent()whenwe’reworkinginUnity5,andtheoutcomewillbeaboutthesame.

Thereisonecaveat,however.Ifwe’rerunningUnity4,thenwestillhaveaccesstoavarietyofquickaccessorpropertiessuchascollider,rigidbody,camera,andsoon.ThesepropertiesbehavelikeprecachedComponentmembervariables,whicharesignificantlyfasterthanallofthetraditionalGetComponent()methods:


Rigidbodytest;

using(newCustomTimer("Cachedreference",numTests))

{


test=gameObject.rigidbody;

}

}

NoteNotethatthiscodeisintendedforUnity4,andwillnotcompileinUnity5duetotheremovaloftherigidbodyproperty.

RunningthistestinUnity4givesusthefollowingresult:

Inanefforttoreducedependenciesandimprovecodemodularizationintheengine’sbackend,UnityTechnologieshasdeprecatedallofthesequickaccessorvariablesinUnity5.Onlythetransformpropertyremains.

TipUnity4usersconsideringanupgradetoUnity5shouldknowthatupgradingwillautomaticallymodifyanyofthesepropertiestousetheGetComponent<T>()method.However,thiswillresultinuncachedGetComponent<T>()callsscatteredthroughoutyourcode,possiblyrequiringyoutorevisitthetechniquesintroducedintheearliersection,entitledCacheComponentReferences.

ThemoralofthestoryisthatifwearerunningUnity4,andtherequiredComponentisoneofGameObject’sbuilt-inaccessorproperties,thenweshouldusethatversion.Ifnot,thenweshouldfavorGetComponent(typeof(T)).Meanwhile,ifwe’rerunningUnity5,thenwecanfavoreitherofthetype-basedversions:GetComponent<T>()orGetComponent(typeof(T)).

RemovingemptycallbackdeclarationsWhenwecreatenewMonoBehaviourscriptfilesinUnity,whetherwe’reusingUnity4orUnity5,itcreatestwoboilerplatemethodsforus:

//Usethisforinitialization

voidStart(){

}

//Updateiscalledonceperframe

voidUpdate(){

}

TheUnityenginehooksintothesemethodsduringinitializationandaddsthemtoalistofmethodstocallbackatkeymoments.However,ifweleavetheseasemptydeclarationsinourcodebase,thentheywillcostusasmalloverheadwhenevertheengineinvokesthem.

TheStart()methodisonlycalledwhentheGameObjectisinstantiatedforthefirsttime,whichcanbewheneverthesceneisloadedoranewGameObjectisinstantiatedfromaPrefab.Therefore,leavingtheemptyStart()declarationmaynotbeparticularlynoticeableunlessthere’salotofGameObjectsinthesceneinvokingthematstartuptime.However,italsoaddsunnecessaryoverheadtoanyGameObject.Instantiate()call,whichtypicallyhappensduringkeyevents,sotheycanpotentiallycontributeto,andexacerbate,alreadypoorperformancessituationwhenlotsofeventsarehappeningsimultaneously.

Meanwhile,theUpdate()methodiscalledeverytimethesceneisrendered.IfourscenecontainsthousandsofGameObjectsowningcomponentswiththeseemptyUpdate()declarations,thenwecanbewastingalotofCPUcyclesandcausinghavoconourframerate.

Let’sprovethiswithasimpletest.OurtestsceneshouldhaveGameObjectswithtwotypesofComponent,onetypewithanemptyUpdate()declaration,andanotherwithnomethodsdefined:

publicclassCallbackTestComponent:MonoBehaviour{

voidUpdate(){}

}

publicclassEmptyTestComponent:MonoBehaviour{

}

Herearethetestresultsfor32,768Componentsofeachtype.Ifweenableallobjectswithnostubmethodsduringruntime,thennothinginterestinghappenswithCPUusageintheProfiler.WemaynoticesomememoryconsumptionchangesandsomeslightlydifferentVSyncactivity,butnothingveryconcerning.However,assoonasweenablealltheobjectswithemptyUnitycallbackdeclarations,wewillobserveahugeincreaseinCPUusage:


Thefixforthisissimple;deletetheemptydeclarations.Unitywillhavenothingtohookinto,andnothingwillbecalled.Sometimes,findingsuchemptydeclarationsinanexpansivecodebasecanbedifficult,butusingsomebasicregularexpressions(regex),weshouldbeabletofindwhatwe’relookingforrelativelyeasily.

TipAllcommoncode-editingtoolsforUnity,suchasMonoDevelop,VisualStudio,andevenNotepad++,provideawaytoperformaregex-basedsearchontheentirecodebase.Checkthetool’sdocumentationformoreinformation,sincethemethodcanvarygreatlydependingonthetoolanditsversion.

ThefollowingregexsearchshouldfindanyemptyUpdate()declarationsinourcode:

void\s*Update\s*?$\s*?$\s*?\n*?\{\n*?\s*?\}

ThisregexchecksforastandardmethoddefinitionoftheUpdate()method,whileincludinganysurpluswhitespaceandnewlinecharactersthatcanbedistributedthroughoutthemethoddeclaration.

Naturally,alloftheaboveisalsotrueforthenon-boilerplateUnitycallbacks,suchasOnGUI(),OnEnable(),OnDestroy(),FixedUpdate(),andsoon.ChecktheMonoBehaviourUnityDocumentationpageforacompletelistofthesecallbacksathttp://docs.unity3d.com/ScriptReference/MonoBehaviour.html.

Itmightseemunlikelythatsomeonegeneratedemptyversionsofthesecallbacksinourcodebase,butneversaynever.Forexample,ifweuseacommonbaseclassMonoBehaviourthroughoutallofourcustomcomponents,thenasingleemptycallbackdeclarationinthatbaseclasswillpermeatetheentiregame,whichcancostusdearly.BeparticularlycarefuloftheOnGUI()method,asitcanbeinvokedmultipletimeswithinthesameframeoruserinterface(UI)event.


http://docs.unity3d.com/ScriptReference/MonoBehaviour.html

AvoidingtheFind()andSendMessage()methodsatruntimeTheSendMessage()methodandfamilyofGameObject.Find()methodsarenotoriouslyexpensive,andshouldbeavoidedatallcosts.TheSendMessage()methodisabout2,000timesslowerthanasimplefunctioncall,andthecostoftheFind()methodscalesverypoorlywithScenecomplexitysinceitmustiteratethrougheveryGameObjectintheScene.ItissometimesreasonabletocallFind()duringinitializationofaScene,suchasAwake()andStart(),onlyforobjectsthatalreadyexistsintheScene.However,usingeithermethodforinter-objectcommunicationatruntimeislikelytogenerateaverynoticeableoverhead.

RelyingonFind()andSendMessage()typemethodsistypicallysymptomaticofpoordesign,inexperienceinprogrammingwithC#andUnity,orjustplainlazinessduringprototyping.Theirusagehasbecomesomethingofanepidemicamongbeginner-andintermediate-levelprojects,suchthatUnityTechnologiesfeelstheneedtokeepremindinguserstoavoidusingtheminarealgame,overandoveragainintheirdocumentationandattheirconferences.Theyonlyexistasalessprogrammer-ywaytointroducenewuserstointer-objectcommunication,andforsomespecialcaseswheretheycanbeusedinalazy,butresponsible,way.

Tobefair,Unitytargetsawidedemographicofusers,fromindividualhobbyists,students,andthosewithdelusionsofgrandeur,tosmall,mid-sized,andlargedevelopmentteams.Thisresultsinanincrediblywiderangeofsoftwaredevelopmentability.Whenyou’restartingoutwithUnity,itcanbedifficulttofigureoutonyourownwhatyoushouldbedoingdifferently,especiallygivenhowtheUnityenginedoesnotadheretothedesignparadigmsofmanyothergameengines.Ithassomeforeignandquirkyconceptssurroundingscenesandprefabs,aswellasnogodclassentrypoints,noranyobviousraw-datastoragesystemstoworkwith.

Sincewe’retalkingaboutscriptingoptimizationinthissection,let’sexplorethesubjectinsomedetail,discussingsomealternativemethodsforinter-objectcommunication.

Let’sstartbyexaminingaworst-caseexample,whichusesbothFind()andSendMessage()methods,anddiscoversomewaystoimproveuponit.Thefollowingexamplemethodattemptstoinstantiateagivennumberofenemiesfromaprefab,andthennotifiesanEnemyManagerobjectoftheirexistence:

publicvoidSpawnEnemies(intnumEnemies){

for(inti=0;i<numEnemies;++i){

GameObjectenemy=(GameObject)GameObject.Instantiate(_enemyPrefab,

Vector3.zero,Quaternion.identity);

GameObjectenemyManagerObj=GameObject.Find("EnemyManager");

enemyManagerObj.SendMessage("AddEnemy",enemy,

SendMessageOptions.DontRequireReceiver);

}

}

Puttingmethodcallsinsidealoop,whichalwaysoutputtothesameresult,isabigredflagforpoorperformance,andwhenwe’redealingwithexpensivemethodssuchasFind(),weshouldalwayslookforwaystocallthemasfewtimesaspossible.Ergo,oneimprovementwecanmakeistomovetheFind()calloutsideoftheforloopandcachetheresultinalocalvariabletobeusedwithintheloop.

WecanalsooptimizeourusageoftheSendMessage()methodbyreplacingitwithaGetComponent()call.Thisreplacesaverycostlymethodwithamuchgentlervariation,achievingeffectivelythesameresult.

Thisgivesusthefollowing:

publicvoidSpawnEnemies(intnumEnemies){

GameObjectenemyManagerObj=GameObject.Find("EnemyManager");

EnemyManagerComponentenemyMgr=

enemyManagerObj.GetComponent<EnemyManagerComponent>();

for(inti=0;i<numEnemies;++i){

GameObjectenemyIcon=(GameObject)GameObject.Instantiate(_enemyPrefab,


enemyMgr.AddEnemy(enemy);

}

}

IfthismethodiscalledduringtheinitializationoftheScene,andwe’renotoverlyconcernedwithloadingtime,thenwecanprobablyconsiderourselvesfinishedwithouroptimizationwork.

However,weoftenneednewobjectsthatareinstantiatedatruntimetofindanexistingobjecttocommunicatewith.Inthisexample,wewantnewenemyobjectstoregisterwithourEnemyManagerComponentsothatitcandowhateveritneedstodotocontroltheenemyobjectsinourScene.WewouldlikeareliableandfastwayfornewobjectstofindexistingobjectswithoutunnecessaryusageoftheFind()method,duetotheoverheadinvolved.

Therearemultipleapproacheswecantaketosolvingthisproblem,eachwiththeirownbenefitsandpitfalls:

StaticclassesSingletonComponentsAssignreferencestopre-existingobjectsAglobalmessagingsystem

StaticclassesThisapproachinvolvescreatingaclassthatisgloballyaccessibletotheentirecodebaseatanytime.Theobjectstaysalivefromthemomenttheapplicationstarts,tothemomentitisclosed.Globalmanagerclassesareoftenfrownedupon,sincethenamedoesn’tsaymuchaboutwhatit’smeanttodo,andtheycanbedifficulttodebugsincechangescanoccurfromanywhere,atanypointduringruntime.Inaddition,itisprobablytheleastrobustapproachwhenitcomestochangingorreplacingitatafuturedate.Despiteallofthesedrawbacks,itisbyfartheeasiestsolutiontoimplement,andsowewillcoveritfirst.

TheSingletondesignpatternisacommonwayofensuringthatwehaveaglobally-accessibleobject,andthatonlyoneinstanceeverexistsinmemory.However,thewaythatSingletonsareprimarilyused(notethequalifier)inUnityprojects,canbeeasilyreplacedwithasimpleC#Staticclasswithouttheneedtoimplementprivateconstructors,andtheunnecessarypropertyaccessofanInstancevariable.Essentially,implementingatypicalSingletondesignpatterninC#justtakesmorecode,andtime,toachievethesameresultasastaticclass.

AstaticclassthatfunctionsinmuchthesamewayasourEnemyManagerComponentisusedinthepreviousexamplecanbedefinedasfollows:


publicstaticclassEnemyManager{

staticList<GameObject>_enemies;

publicstaticvoidAddEnemy(GameObjectenemy){

_enemies.Add(enemy);

}

publicstaticvoidRollCall(){

for(inti=0;i<_enemies.Count;++i){

Debug.Log(string.Format("Enemy\"{0}\"reportingin…",

_enemies[i].name));

}

}

}

Notethateverymemberandmethodhasthestatickeywordattached,whichimpliesthatonlyoneinstanceofthisobjectwilleverresideinmemory.Staticclasses,bydefinition,donotallowanynonstaticinstancememberstobedefined,asthatwouldimplythatwecouldsomehowduplicatetheobject.

Staticclassescanbegivenastaticconstructor,whichcanbeusedtoinitializememberdata.Astaticconstructorcanbedefinedlikeso,anditiscalledthemomenttheclassisfirstaccessed(eitherthroughamembervariableoramemberfunction):

staticEnemyManager(){

_enemies=newList<GameObject>();

}

Thistypeofglobalclassisgenerallyconsideredtobeacleanerandeasier-to-useversion

ofthetypicalSingletondesignpatternintheworldofC#development.


SingletonComponentsThedisadvantageofthestaticclassapproachisthattheymustinheritfromthelowestformofclass—Object.ThismeansthatstaticclassescannotinheritfromMonoBehaviourandthereforewecannotmakeuseofanyofitsUnity-relatedfunctionality,includingtheall-importanteventcallbacks,aswellasCoroutines.Also,sincethere’snoobjecttoselect,welosetheabilitytoinspecttheobject’sdataatruntimethroughtheInspector.ThesearefeaturesthatwemaywishtomakeuseofinourglobalSingletonclasses.

Acommonsolutiontothisproblemistoimplementa“SingletonasaComponent”classthatspawnsaGameObjectcontainingitself,andprovidingstaticmethodstograntglobalaccess.Notethat,inthiscase,wemustessentiallyimplementthetypicalSingletondesignpattern,withprivatestaticinstancevariables,andaglobalInstancemethodforglobalaccess.

HereisthedefinitionforaSingletonAsComponentclass:

publicclassSingletonAsComponent<T>:MonoBehaviourwhereT:

SingletonAsComponent<T>{

privatestaticT__Instance;

protectedstaticSingletonAsComponent<T>_Instance{

get{

if(!__Instance){

T[]managers=

GameObject.FindObjectsOfType(typeof(T))asT[];

if(managers!=null){

if(managers.Length==1){

__Instance=managers[0];

return__Instance;

}elseif(managers.Length>1){

Debug.LogError("Youhavemorethanone"+

typeof(T).Name+"inthescene.Youonly

need1,it'sasingleton!");

for(inti=0;i<managers.Length;++i){

Tmanager=managers[i];

Destroy(manager.gameObject);

}

}

}

GameObjectgo=newGameObject(typeof(T).Name,

typeof(T));

__Instance=go.GetComponent<T>();

DontDestroyOnLoad(__Instance.gameObject);

}

return__Instance;

}

set{

__Instance=valueasT;

}

}

}

Sincewewishthistobeaglobalandpersistentobject,weneedtocallDontDestroyOnLoad()shortlyaftertheGameObjectiscreated.ThisisaspecialfunctionthattellsUnitythatwewishtheobjecttopersistbetweenScenesforaslongastheapplicationisrunning.Fromthatpointonward,whenanewsceneisloaded,theobjectwillnotbedestroyedandwillretainallofitsdata.

Thisclassdefinitionassumestwothings.Firstly,becauseitisusinggenericstodefineitsbehavior,itmustbederivedfrominordertocreateaconcreteclass.Secondly,amethodwillbedefinedtoassignthe_Instancevariableandcastitto/fromthecorrectType.

Forexample,thefollowingisallthatisneededtosuccessfullygenerateanewSingletonAsComponentderivedclasscalledMySingletonComponent:

publicclassMySingletonComponent:

SingletonAsComponent<MySingletonComponent>{

publicstaticMySingletonComponentInstance{

get{return((MySingletonComponent)_Instance);}

set{_Instance=value;}

}

}

ThisclasscanbeusedatruntimebyhavinganyotherobjectaccesstheInstancepropertyatanytime.IftheComponentdoesnotalreadyexistinourScene,thentheSingletonAsComponentbaseclasswillinstantiateitsownGameObjectandattachaninstanceofthederivedclasstoitasaComponent.Fromthatpointforward,accessthroughtheInstancepropertywillreferencetheComponentthatwascreated.

TipWhileitispossible,weshouldnotplaceourSingletonAsComponentderivedclassinaSceneHierarchy.ThisisbecausetheDontDestroyOnLoad()methodwillneverbecalled!ThiswouldpreventtheSingletonComponent’sGameObjectfrompersistingwhenthenextSceneisloaded.

PropercleanupofaSingletonComponentcanbealittleconvolutedbecauseofhowUnitytearsdownScenes.Anobject’sOnDestroy()methodiscalledwheneveritisdestroyedduringruntime.Thesamemethodiscalledduringapplicationshutdown,wherebyeveryComponentoneveryGameObjecthasitsOnDestroy()methodcalledbyUnity.ApplicationshutdownalsotakesplacewhenweendPlayModeintheEditorandreturntoEditMode.However,destructionofobjectsoccursinarandomorder,andwecannotassumethattheSingletonComponentwillbethelastobjectdestroyed.

Consequently,ifanyobjectattemptstodoanythingwiththeSingletoninthemiddleoftheirOnDestroy()method,thentheywillbecallingtheInstanceproperty.IftheSingletonhasalreadybeendestroyedpriortothismoment,thencallingInstanceduringanotherobject’sdestructionwouldcreateanewinstanceoftheSingletonComponentinthemiddleofapplicationshutdown!ThiscancorruptourScenefiles,asinstancesofourSingletonComponentswillbeleftbehindintheScene.Ifthishappens,thenUnitywillthrowthefollowingerrormessageatus:

ThereasonsomeobjectsmaywishtocallintoourSingletonduringdestructionisthatSingletonsoftenmakeuseoftheObserverpattern.Thisdesignpatternallowsotherobjectstoregister/deregisterwiththemforcertaintasks,similartohowUnitylatchesontocallbackmethods,butinalessautomatedfashion.WewillseeanexampleofthisintheupcomingsectionAglobalmessagingsystem.Objectsthatareregisteredwiththesystemduringconstructionwillwanttoderegisterwiththesystemduringtheirownshutdown,andthemostconvenientplacetodothisiswithinitsOnDestroy()method.Consequently,suchobjectsarelikelytorunintotheaforementionedproblem,whereSingletonsareaccidentallycreatedduringapplicationshutdown.

Tosolvethisproblem,weneedtomakethreechanges.Firstly,weneedtoaddanadditionalflagtotheSingletonComponent,whichkeepstrackofitsactivestate,anddisableitattheappropriatetimes.ThisincludestheSingleton’sowndestruction,aswellasapplicationshutdown(OnApplicationQuit()isanotherusefulUnitycallbackforMonoBehaviours,whichiscalledduringthistime):

privatebool_alive=true;

voidOnDestroy(){_alive=false;}

voidOnApplicationQuit(){_alive=false;}

Secondly,weshouldimplementawayforexternalobjectstoverifytheSingleton’scurrentstate:

publicstaticboolIsAlive{

get{

if(__Instance==null)

returnfalse;

return__Instance._alive;

}

}

Finally,anyobjectthatattemptstocallintotheSingletonduringitsownOnDestroy()method,mustfirstverifythestateusingtheIsAlivepropertybeforecallingInstance.Forexample:

publicclassSomeComponent:MonoBehaviour{

voidOnDestroy(){

if(MySingletonComponent.IsAlive){

MySingletonComponent.Instance.SomeMethod();

}

}

}

ThiswillensurethatnobodyattemptstoaccessInstanceduringdestruction.Ifwedon’tfollowthisrule,thenwewillrunintoproblemswhereinstancesofourSingletonobjectwillbeleftbehindintheSceneafterreturningtoEditMode.

TheironyoftheSingletonComponentapproachisthatweareusingoneofUnity’s


Find()methodstodeterminewhetherornotoneoftheseSingletonComponentsalreadyexistsintheScenebeforeweattempttoassignthe__Instancereferencevariable.Fortunately,thiswillonlyhappenwhentheSingletonComponentisfirstaccessed,butit’spossiblethattheinitializationoftheSingletonwouldnotnecessarilyoccurduringSceneinitializationandcanthereforecostusaperformancespikeatabadmomentduringgameplay,whenthisobjectisfirstinstantiatedandFind()getscalled.TheworkaroundforthisistohavesomegodclassconfirmthattheimportantSingletonsareinstantiatedduringSceneinitializationbysimplycallingInstanceoneachone.

Thedownsidetothisapproachisthatifwelaterdecidethatwewantmorethanoneofthesemanagerclassesexecutingatonce,orwewishtoseparateitsbehaviortobemoremodular,thentherewouldbealotofcodethatneedstochange.

Therearefurtheralternativesthatwecanexplore,suchasmakinguseofUnity’sbuilt-inbridgebetweenscriptcodeandtheInspectorinterface.


Assigningreferencestopre-existingobjectsAnotherapproachtotheproblemofinter-objectcommunicationistouseUnity’sbuilt-inserializationsystems.Softwaredesignpuriststendtogetalittlecombativeaboutthisfeature,sinceitbreaksencapsulation;itmakesvariablesmarkedprivateactinawaythattreatsthemaspublic.EventhoughthevalueonlybecomespublicwithrespecttotheUnityInspectorandnothingelse,thisisstillenoughtowavesomeredflags.

However,itisaveryeffectivetoolforimprovingdevelopmentworkflow.Thisisparticularlytruewhenartists,designers,andprogrammersarealltinkeringwiththesameproduct,whereeachhaswildlyvaryinglevelsofcomputerscienceandsoftwareprogrammingknowledge.Sometimesit’sworthbendingafewrulesinthenameofproductivity.

Wheneverwecreateapublicvariable,UnityautomaticallyserializesandexposesthevalueintheInspectorinterfacewhentheComponentisselected.However,publicvariablesaredangerousfromasoftwaredesignperspective—thesevariablescanbechangedthroughcodeatanytime,whichcanmakeithardtokeeptrackofthevariable,andintroducealotofunexpectedbugs.

Asanalternative,wecantakeanyprivateorprotectedmembervariableofaclassandexposeittotheUnityEditorInspectorinterfacewiththe[SerializeField]attribute.Thisapproachispreferredoverpublicvariables,asitgivesusmorecontrolofthesituation.Thisway,atleastweknowthevariablescannotbechangedatruntimeviacodeoutsidetheclass(orderivedclass),andthereforemaintainencapsulationfromtheperspectiveofscriptcode.

Forexample,thefollowingclassexposesthreeprivatevariablestotheInspector:

publicclassEnemySpawnerComponent:MonoBehaviour{

[SerializeField]privateint_numEnemies;

[SerializeField]privateGameObject_enemyPrefab;

[SerializeField]privateEnemyManagerComponent_enemyManager;

voidStart(){

SpawnEnemies(_numEnemies);

}

voidSpawnEnemies(int_numEnemies){

for(inti=0;i<_numEnemies;++i){

GameObjectenemy=(GameObject)GameObject.Instantiate(_enemyPrefab,


_enemyManager.AddEnemy(enemy);

}

}

}

TipNotethattheprivateaccessspecifiersshownintheprecedingcodeareredundantkeywordsinC#,asmembervariablesarealwaysprivateunlessspecifiedotherwise,but

theseaccessspecifiersareincludedforcompleteness.

LookingatthisComponentintheInspectorviewrevealsthreevalues,initiallygivendefaultvaluesof0,ornull,whichcanbemodifiedthroughtheInspectorinterface:

WecandraganddropaPrefabreferencefromtheProjectswindowintotheEnemyPrefabfield,or,ifwefeltsoinclined,evenareferencetoanotherGameObjectthatispresentintheScene.Although,giventhatit’sbeingusedlikeaPrefabinthecode,itwouldbeunwisetodothis,sincewewouldbecloningaGameObjectthatmighthavealreadyundergonechangesintheScene.PrefabsservethepurposeofablueprintfromwhichtoinstantiatenewGameObjectsandshouldbeusedassuch.

TheEnemyManagerfieldisinterestingbecauseitisaComponentreferenceandnotaGameObjectreference.IfaGameObjectisdroppedintothisfield,thenitwillrefertotheComponentonthegivenobject,asopposedtotheGameObjectthatwedraggedanddroppedintothefield.IfthegivenobjectdoesnothavetheexpectedComponent,thennothingwillbeassigned.

TipAcommonusageoftheComponentreferencetechniqueistoobtainreferencestoComponentsattachedtothesameGameObjectitisattachedto.ThisisanalternativeapproachtothetopicdiscussedinthesectionentitledCacheComponentReferences,earlierinthischapter.

ThedangerhereisthatsincePrefabsareessentiallyGameObjects,PrefabswiththerequiredComponentcanbeassignedtothesefields,eventhoughwemightnotwishthemtobe.UnityloadsPrefabsintomemorymuchlikeGameObjects,andassumesthey’llbeusedinPrefab-likeways;thatis,treatedasnothingmorethanblueprintstobeinstantiatedfromonanas-neededbasis.However,theystillcountasdatastoredinmemoryandcanthereforebeeditedonawhim,makingthemsusceptibletochangesthatdirectlyaffectallfutureGameObjectsinstantiatedfromthem.

Tomakemattersworse,thesechangesbecomepermanenteveniftheyaremadeduringPlayMode,sincePrefabsoccupythesamememoryspacewhetherPlayModeisactiveornot.ThismeansthatwecanaccidentallycorruptourPrefabs,ifweassignthemtothewrongfields.Consequently,thisapproachisamoreteam-friendlywayofsolvingtheoriginalproblemofinter-objectcommunication,butitisnotidealduetoalloftherisksinvolvedwithteammembersaccidentallybreakingthingsorleavingnullreferencesinplace.

ItisalsoimportanttonotethatnotallobjectscanbeserializedbytheInspectorview.


Unitycanserializeallprimitivedatatypes(ints,floats,strings,andbools),variousbuilt-intypessuchas(Vector3,Quaternion,andsoon)enums,classes,andstructs,aswellasarraysandlistsofotherserializabletypes.However,itisunabletoserializestaticfields,read-onlyvalues,properties,anddictionaries.

TipSomeUnitydevelopersliketoimplementpseudo-serializationofdictionariesviatwoseparatelistsforkeysandvalues,alongwithaCustomEditorscript,orviaasinglelistofobjects,whichcontainbothkeysandvalues.Bothofthesesolutionsarealittleclumsy,butperfectlyvalid.

Thelastsolutionwewilllookatwillprovideawaytohopefullygetthebestofbothworldsbycombiningeaseofimplementation,easeofextension,andstrictusagethatavoidstoomuchhumanerror.


AglobalmessagingsystemThefinalsuggestedapproachtotheproblemofinter-objectcommunicationistoimplementaglobalmessagingsystemthatanyobjectcanaccessandsendmessagesthroughtoanyobjectthatmaybeinterestedinlisteningtothatspecifictypeofmessage.Objectseithersendmessagesorlistenforthem,andtheresponsibilityisonthelistenertodecidewhatmessagesitisinterestedin.Themessagesendercanbroadcastthemessagewithoutcaringatallwhoislistening.Thisapproachisexcellentforkeepingourcodemodularanddecoupled.

Thekindsofmessagewewishtosendcantakemanyforms,suchasincludingdatavalues,references,instructionsforlisteners,andmore,buttheyshouldallhaveacommon,basicdeclarationthatourmessagingsystemcanusetodeterminewhatthemessageis,andwhoitisintendedfor.

ThefollowingisasimpleclassdefinitionforaMessageobject:

publicclassBaseMessage{

publicstringname;

publicBaseMessage(){name=this.GetType().Name;}

}

TheBaseMessageclass’sconstructorcachestheTypeinalocalstringpropertytobeusedlaterforcataloguinganddistributionpurposes.CachingthisvalueisimportantaseachcalltoGetType().Namewillresultinanewstringbeingallocatedontheheap,andwewanttominimizethisasmuchaspossible.Ourcustommessagesmustderivefromthisclass,whichallowsthemtoaddwhateversuperfluousdatatheywish,whilestillmaintainingtheabilitytobesentthroughourmessagingsystem.Takenotethat,despiteacquiringtheTypenameduringthebaseclassconstructor,thenamepropertywillstillcontainthenameofthederivedclass,notthebaseclass.

MovingontoourMessagingSystemclass,weshoulddefineitsfeaturesbywhatkindofrequirementsweneedittofulfill:

ItshouldbegloballyaccessibleAnyobject(MonoBehaviourornot)shouldbeabletoregister/deregisteraslisteners,toreceivespecificmessagetypes(thatis,theObserverpattern)RegisteringobjectsshouldprovideamethodtocallwhenthegivenmessageisbroadcastThesystemshouldsendthemessagetoalllistenerswithinareasonabletimeframe,butnotchokeontoomanyrequestsatonce

AgloballyaccessibleobjectThefirstrequirementmakesthemessagingsystemanexcellentcandidateforaSingletonobject,sinceweshouldonlyeverneedoneinstanceofthesystem.Although,itiswisetothinklongandhardifthisistrulythecasebeforecommittingtoimplementingaSingleton.Ifwelaterdecidethatwewantmultipleinstancesofthisobjecttoexist,thenitcanbedifficulttorefactorduetoallofthedependencieswewillgraduallyintroduceto


ourcodebaseasweusethesystemmoreandmore.

Forthisexample,wewillassumethatweareabsolutelypositivethatwewillonlyneedoneofthesesystems,anddesignitaccordingly.

RegistrationMeetingthesecondandthirdrequirementscanbeachievedbyofferingsomepublicmethodsthatallowregistrationwiththemessagingsystem.Ifweforcethelisteningobjecttoprovideusadelegatefunctiontocallwhenthemessageisbroadcast,thenthisallowslistenerstocustomizewhichmethodiscalledforwhichmessage.Thiscanmakeourcodebasemucheasiertounderstand,ifwenamethedelegateafterthemessageitisintendedtoprocess.

TipDelegatefunctionsareincrediblyusefulconstructsinC#thatallowsustopasslocalmethodsaroundasargumentstoothermethods,andaretypicallyusedforcallbacks.ChecktheMSDNC#ProgrammingGuideformoreinformationondelegatesathttps://msdn.microsoft.com/en-us/library/ms173171.aspx.

Insomecases,wemightwishtobroadcastageneralnotificationmessageandhavealllistenersdosomethinginresponse,suchasan“EnemySpawned”message.Othertimes,wemightbesendingamessagethatspecificallytargetsasinglelisteneramongstagroup.Forexample,wemightwishtosendan“EnemyHealthValueChanged”messagethatisintendedforaspecifichealthbarobjectthatisattachedtotheenemythatwasdamaged.Ifweimplementawayforlistenerstostopmessageprocessingearly,thenwecansaveasignificantnumberofCPUcycles,iftherearemanylistenerswaitingforthesamemessagetype.

Thedelegatewedefineshouldthereforeprovideawayofretrievingthemessageviaanargument,andreturnaresponsethatdetermineswhetherornotprocessingforthemessageshouldstopwhenthelistenerisdonewithit.ThedecisiononwhethertostopprocessingornotcanbeachievedbyreturningasimpleBoolean,wheretrueimpliesthatthislistenerhashandledthemessage,andprocessingforthemessagemuststop.

Hereisthedefinitionforthedelegate:

publicdelegateboolMessageHandlerDelegate(BaseMessagemessage);

ListenersmustdefineamethodofthisformandpassareferencetoitwhenitregisterswiththeMessagingSystem,thusprovidinganentrypointforthemessagingsystemtocallwhenthemessageisbroadcast.

MessageprocessingThefinalrequirementforourmessagingsystemisthatthisobjecthassomekindoftiming-basedmechanismbuiltintopreventitfromchokingontoomanymessagesatonce.Thismeansthat,somewhereintheprocess,wewillneedtomakeuseofMonoBehavioureventcallbacksinordertoworkduringUnity’sUpdate()andbeabletocounttime.


https://msdn.microsoft.com/en-us/library/ms173171.aspx

Thiscanbeachievedwiththestaticclass-basedSingleton(whichwedefinedearlier),whichwouldrequiresomeotherMonoBehaviour-basedgodclasstocallintoit,informingitthattheScenehasupdated.Alternatively,wecanusetheSingletonAsComponenttoachievethesamething,butdosoindependentlyofanygodclass.Theonlydifferencebetweenthetwoiswhetherornotthesystemisdependentonthecontrolofotherobjects.

TheSingletonAsComponentapproachisprobablythebest,sincetherearen’ttoomanyoccasionswherewewouldn’twantthissystemactingindependently,evenifmuchofourgamelogicdependsuponit.Forexample,evenifthegamewaspaused,wewouldn’twantthegamelogictopauseourmessagingsystem.Westillwantthemessagingsystemtocontinuereceivingandprocessingmessagessothatwecan,forexample,keepUI-relatedComponentscommunicatingwithoneanotherwhilethegameplayisinapausedstate.

ImplementingthemessagingsystemLet’sdefineourmessagingsystembyderivingfromtheSingletonAsComponentclass,andprovideamethodforobjectstoregisterwithit:


publicclassMessagingSystem:SingletonAsComponent<MessagingSystem>{

publicstaticMessagingSystemInstance{

get{return((MessagingSystem)_Instance);}


}

privateDictionary<string,List<MessageHandlerDelegate>>_listenerDict=

newDictionary<string,List<MessageHandlerDelegate>>();

publicboolAttachListener(System.Typetype,MessageHandlerDelegate

handler){

if(type==null){

Debug.Log("MessagingSystem:AttachListenerfailedduetonomessage

typespecified");

returnfalse;

}

stringmsgName=type.Name;

if(!_listenerDict.ContainsKey(msgName)){

_listenerDict.Add(msgName,newList<MessageHandlerDelegate>());

}

List<MessageHandlerDelegate>listenerList=_listenerDict[msgName];

if(listenerList.Contains(handler)){

returnfalse;//listeneralreadyinlist

}

listenerList.Add(handler);

returntrue;

}

}

The_listenerDictvariableisadictionaryofstringsmappedtolistsofMessageHandlerDelegates.Thisdictionaryorganizesourlistenerdelegatesintolistsbywhichmessagetypetheywishtolistento.Thus,ifweknowwhatmessagetypeisbeingsent,thenwecanquicklyretrievealistofalldelegatesthathavebeenregisteredforthatmessagetype.Wecantheniteratethroughthelist,queryingeachlistenertoseeifoneofthemwantstohandleit.

TheAttachListener()methodrequirestwoparameters;amessagetypeintheformofaSystem.Type,andaMessageHandlerDelegatetosendthemessagetowhenitcomesthroughthesystem.

MessagequeuingandprocessingInordertoprocessmessages,ourMessagingSystemshouldmaintainaqueueofincomingmessageobjectssothatwecanprocessthemintheordertheyarebroadcasted:

privateQueue<BaseMessage>_messageQueue=newQueue<BaseMessage>();

publicboolQueueMessage(BaseMessagemsg){

if(!_listenerDict.ContainsKey(msg.name)){

returnfalse;

}

_messageQueue.Enqueue(msg);

returntrue;

}

Themethodsimplychecksifthegivenmessagetypeispresentinourdictionarybeforeaddingittothequeue.Thiseffectivelytestswhetherornotanobjectactuallycarestolistentothemessagebeforewequeueittobeprocessedlater.Wehaveintroducedanewprivatemembervariable,_messageQueue,forthispurpose.

Next,we’lladdadefinitionforUpdate().ThismethodwillbecalledregularlybytheUnityEngine.Itspurposeistoiteratethroughthecurrentcontentsofthemessagequeue,onemessageatime,verifywhetherornottoomuchtimehaspassedsincewebeganprocessing,andifnot,passthemalongtothenextstageintheprocess:

privatefloatmaxQueueProcessingTime=0.16667f;

voidUpdate(){

floattimer=0.0f;

while(_messageQueue.Count>0){

if(maxQueueProcessingTime>0.0f){

if(timer>maxQueueProcessingTime)

return;

}

BaseMessagemsg=_messageQueue.Dequeue();

if(!TriggerMessage(msg))

Debug.Log("Errorwhenprocessingmessage:"+msg.name);

if(maxQueueProcessingTime>0.0f)

timer+=Time.deltaTime;

}

}

Thetime-basedsafeguardisinplacetomakesurethatitdoesnotexceedaprocessingtimelimitthreshold.Thispreventsthemessagingsystemfromfreezingourgameiftoomanymessagesgetpushedthroughthesystemtooquickly.Ifthetotaltimelimitisexceeded,thenallmessageprocessingwillstop,leavinganyremainingmessagestobeprocessedduringthenextframe.

Lastly,weneedtodefinetheTriggerMessage()method,whichdistributesmessagestolisteners:

publicboolTriggerMessage(BaseMessagemsg){

stringmsgName=msg.name;

if(!_listenerDict.ContainsKey(msgName)){

Debug.Log("MessagingSystem:Message\""+msgName+"\"hasno

listeners!");

returnfalse;//nolistenersformessagesoignoreit

}


for(inti=0;i<listenerList.Count;++i){

if(listenerList[i](msg))

returntrue;//messageconsumedbythedelegate

}

returntrue;

}

Thismethodisthemainworkhorseofthemessagingsystem.TheTriggerEvent()‘spurposeistoobtainthelistoflistenersforthegivenmessagetypeandgiveeachofthemanopportunitytoprocessit.Ifoneofthedelegatesreturnstrue,thenprocessingofthecurrentmessageceasesandthemethodexits,allowingtheUpdate()methodtoprocessthenextmessage.

Normally,wewouldwanttouseQueueEvent()tobroadcastmessages,butTriggerEvent()canbecalledinstead.ThismethodallowsmessagesenderstoforcetheirmessagestobeprocessedimmediatelywithoutwaitingforthenextUpdate()event.Thisbypassesthethrottlingmechanism,butthismightbenecessaryformessagesthatneedtobesentduringcriticalmomentsingameplay,wherewaitingoneadditionalframemightresultinstrange-lookingbehavior.

ImplementingacustommessageWe’vecreatedthemessagingsystem,butanexampleofhowtouseitwouldhelpuswrapourheadsaroundtheconcept.Let’sstartbydefiningasimplemessageclass,whichwecanusetotransmitsomedata:

publicclassMyCustomMessage:BaseMessage{

publicreadonlyint_intValue;

publicreadonlyfloat_floatValue;

publicMyCustomMessage(intintVal,floatfloatVal{

_intValue=intVal;

_floatValue=floatVal;

}

}

Goodpracticeformessageobjectsistomaketheirmembervariablesreadonly.Thisensuresthatthedatacannotbechangedaftertheobject’sconstruction.Thissafeguardsthecontentofourmessagesagainstbeingaltered,asthey’repassedbetweenonelistenerandanother.

MessageregistrationHere’sasimpleclassthatregisterswiththemessagingsystem,requestingtohaveitsHandleMyCustomMessage()methodcalledwheneveraMyCustomMessageobjectisbroadcastfromanywhereinourcodebase:

publicclassTestMessageListener:MonoBehaviour{

voidStart(){

MessagingSystem.Instance.AttachListener(typeof(MyCustomMessage),

this.HandleMyCustomMessage);

}

boolHandleMyCustomMessage(BaseMessagemsg){

MyCustomMessagecastMsg=msgasMyCustomMessage;

Debug.Log(string.Format("Gotthemessage!{0},{1}",

castMsg._intValue,castMsg._floatValue));

returntrue;

}

}

WheneveraMyCustomMessageobjectisbroadcast(fromanywhere!),thislistenerwillretrievethemessagethroughitsHandleMyCustomMessage()method.Itcanthentypecastitintotheappropriatederivedmessagetypeandhandlethemessageinitsownuniqueway.Otherclassescanregisterforthesamemessage,andhandleitdifferentlythroughitsowncustomdelegatemethod(assuminganearlierobjectdidn’treturntruefromitsowndelegate).

WeknowwhattypeofmessagewillbeprovidedbythemsgargumentoftheHandleMyCustomMessage()method,becausewedefineditduringregistrationthroughtheAttachListener()call.Duetothis,wecanbecertainthatourtypecastingissafe,andwecansavetimebynothavingtodoanullreferencecheck,although,technically,thereisnothingstoppingususingthesamedelegatetohandlemultiplemessagetypes!Inthesecases,thoughwewouldneedtoimplementawayofdeterminingwhichmessageobjectisbeingpassed,andtreatitaccordingly.Thebestapproachistodefineauniquemethodforeachmessagetypeinordertokeepthingsappropriatelydecoupled.

NotehowtheHandleMyCustomMessagemethoddefinitionmatchesthefunctionsignatureofMessageHandlerDelegate,andthatitisbeingreferencedintheAttachListener()call.Thisishowwetellthemessagingsystemwhatmethodtocallwhenthegivenmessagetypeisbroadcast,andhowdelegatesensuretypesafety.Ifthefunctionsignaturehadadifferentreturnvalueoradifferentlistofarguments,thenitwouldbeaninvaliddelegatefortheAttachListener()method,andwewouldgetcompilererrors.


Thebeautifulpartisthatwe’refreetogivethedelegatemethodwhatevernamewewant.Themostsensibleapproachistonamethemethodafterthemessagewhichithandles.Thismakesitcleartoanyonereadingourcodewhatthemethodisusedforandwhatmessageobjecttypeisrequiredtocallit.

MessagesendingFinally,let’simplementanexampleofsendingamessagesothatwecantestthissystemout!Here’sacomponentthatwillbroadcastaninstanceofourMyCustomMessageclassthroughthemessagingsystemwhentheSpaceBarispressed:

publicclassTestMessageSender:MonoBehaviour{

publicvoidUpdate(){


MessagingSystem.Instance.QueueMessage(newMyCustomMessage(5,

13.355f));

}

}

}

IfweaddboththeTestMessageSenderandTestMessageListenerobjectstoourSceneandpresstheSpacebar,weshouldseealogmessageappearintheconsole,informingusofasuccessfultest:

OurMessagingSystemSingletonobjectwillbecreatedimmediatelyuponSceneinitialization,whentheTestMessageListener‘sStart()methodiscalledanditregisterstheHandleMyCustomMessagedelegate.NoadditionaleffortisrequiredonourparttocreatetheSingletonweneed.

MessagecleanupSincemessageobjectsareclasses,theywillbecreateddynamicallyinheapmemoryandwillbedisposedofshortlyafterwardswhenthemessagehasbeenprocessedanddistributedamongstalllisteners.However,asyouwilllearninChapter7,MasterfulMemoryManagement,thiswilleventuallyresultinagarbagecollectionasheapmemoryaccumulatesovertime.Ifourapplicationrunsforlongenough,itwilleventuallyresultintheoccasionalgarbagecollection.Therefore,itiswisetousethemessagingsystemsparinglyandavoidspammingmessagestoofrequentlyoneveryupdate.

Themoreimportantclean-upoperationtoconsiderisderegistrationofdelegatesifanobjectneedstobedestroyedorde-spawned.Ifwedon’thandlethisproperly,thenthemessagingsystemwillhangontodelegatereferencesthatpreventobjectsfrombeingfullydestroyedandfreedfrommemory.

Essentially,weneedtopaireveryAttachListener()callwithanappropriateDetachListener()methodwhentheobjectisdestroyed,disabled,orweotherwisedecide


thatwenolongerneedittobequeriedwhenmessagesarebeingsent.

ThefollowingmethoddefinitionintheMessagingSystemclasswilldetachalistenerforaspecificevent:

publicboolDetachListener(System.Typetype,MessageHandlerDelegate

handler)

{

if(type==null){

Debug.Log("MessagingSystem:DetachListenerfailedduetonomessage

typespecified");

returnfalse;

}

stringmsgName=type.Name;

if(!_listenerDict.ContainsKey(type.Name)){

returnfalse;

}


if(!listenerList.Contains(handler)){

returnfalse;

}

listenerList.Remove(handler);

returntrue;

}

HereisanexampleusageoftheDetachListener()method,addedtoourTestMessageListenerclass:

voidOnDestroy(){

if(MessagingSystem.IsAlive){

MessagingSystem.Instance.DetachListener(typeof(MyCustomMessage),


}

}

NotehowthisdefinitionmakesuseoftheIsAlivepropertydeclaredintheSingletonAsComponentclass.Thissafeguardsusagainsttheaforementionedproblemsduringapplicationshutdown,wherewecannotguaranteethattheSingletonwasdestroyedlast.

WrappingupthemessagingsystemCongratulationsareinorder,aswehavefinallybuiltafullyfunctionalglobalmessagingsystemthatanyandallobjectscaninterfacewith,tosendmessagesbetweenoneanother!AusefulfeatureofthisapproachisthatitisMonoBehaviour-agnostic,meaningthatthemessagesendersandlistenersdonotevenneedtoderivefromMonoBehaviourtointerfacewiththemessagingsystem;itjustneedstobeaclassthatprovidesamessagetypeandadelegatefunctionofthematchingfunctionsignature.

AsfarasbenchmarkingtheMessagingSystemclassgoes,weshouldfindthatifitis


capableofprocessinghundreds,ifnotthousandsofmessagesinasingleframewithminimalCPUoverhead(dependingontheCPU,ofcourse).TheCPUusageisessentiallythesamewhetheronemessageisbeingdistributedto100differentlisteners,100messagesaredistributedtojustonelistener.Itcostsaboutthesameeitherway.

Evenifwe’repredominantlysendingmessagesduringUIorgameplayevents,thisisprobablyfarmorepowerthanweneed.So,ifitdoesseemtobecausingperformanceproblems,thenit’sfarmorelikelytobecausedbywhatthelistenerdelegatesaredoingwiththemessagethanthemessagingsystem’sabilitytoprocessthosemessages.

Therearemanywaystoenhancethemessagingsystemtoprovidemoreusefulfeatureswemayneedinthefuture,suchas:

Allowmessagesenderstosuggestadelay(intimeorframecount)beforeamessageisprocessedanddistributedAllowmessagelistenerstodefineapriorityforhowurgentlyitshouldreceivemessagescomparedtootherlistenerswaitingforthesamemessagetype—awayofskippingtothefrontofthequeueifitregisteredlaterthanotherlistenersImplementsomesafetycheckstohandlesituationswherealistenergetsaddedtothelistofmessagelistenersforaparticularmessage,whileamessageofthattypeisstillbeingprocessed—C#willthrowanenumerationexceptionatussincethedelegatelistwillbechangedbyAttachListener(),whileitisstillbeingiteratedthroughinTriggerEvent()

Atthispoint,wehaveprobablyexploredmessagingsystemsenough,sothesetaskswillbeleftasanacademicexerciseforyoutoundertake,ifyoubecomecomfortableusingthissolutioninyourgames.

Let’sexploresomefurthertechniquesthatwecanusetoimproveperformancethroughscripting.


DisablingunusedscriptsandobjectsScenescangetprettybusysometimes,especiallywhenwe’rebuildinglarge,openworlds.ThemoreobjectsinvokingcodeinanUpdate()method,theworsethingswillscaleandthesloweryourgamebecomes.However,muchofwhatisbeingprocessedmaybecompletelyunnecessaryifitisoutsideoftheplayer’svieworsimplytoofarawaytomatter.Thismaynotbeapossibilityinlargecity-buildingsimulationgameswheretheentiresimulationmustbeprocessedatalltimes,butitisoftenpossibleinfirstpersonandracinggames,wheretheplayeriswanderingaroundalargeexpansivearea,wherenon-visibleobjectscanbetemporarilydisabledwithouthavinganynoticeableeffectongameplay.


DisablingobjectsbyvisibilitySometimes,wewantComponentsorGameObjectstobedisabledwhenthey’renotvisible.Unitycomeswithbuilt-inrenderingfeaturestoavoidrenderingobjectsthatarenotvisiblebyCameras(FrustumCulling,whichisautomaticinallversions),andtoavoidrenderingobjectsthatarehiddenbehindotherobjects(OcclusionCulling,tobediscussedinChapter6,DynamicGraphics),butthisdoesnotaffectComponentsthatarenon-renderable,suchasAIscripts.Wemustcontrolthatbehaviorourselves.

ThisproblemcanbesolvedeasilybyusingtheOnBecameVisible()andOnBecameInvisible()MonoBehaviourcallbacks.Asthenamesimply,thesecallbackmethodsareinvokedwhenarenderableobjecthasbecomevisibleorinvisiblewithrespecttothegameviewandanyCamerasinourScene.Inaddition,whentherearemultipleCamerasinaScene(forexample,alocalmultiplayergame),thecallbacksareonlyinvokediftheobjectbecomesvisibletoanyoneCamera,andbecomesinvisibletoallCameras.Thismeanstheaforementionedcallbackswillbecalledatexactlytherighttimestoimplementthisfeature.

Sincethevisibilitycallbacksrelatetoandcommunicatewiththerenderingsystem,theGameObjectmusthavearenderableobjectattached,suchasaMeshorSkinnedMesh.WemustensurethattheComponentswewanttoreceivethevisibilitycallbacksfromareattachedtothesameGameObjectastherenderableobjectandnotsomeparentorsub-object,otherwisetheywon’tbeinvoked.

TipNotethatUnityalsocountsthehiddencameraoftheSceneViewtowardstheOnBecameVisible()andOnBecameInvisible()callbacks.IfwefindthatthesemethodsarenotbeinginvokedproperlyduringPlayModetesting,makesuretoturntheSceneViewCameraawayfromeverything.

Toenable/disableindividualcomponentswiththevisibilitycallbacks,wecanaddthefollowingmethods:

voidOnBecameVisible(){enabled=true;}

voidOnBecameInvisible(){enabled=false;}

And,toenable/disabletheentireGameObjecttheComponentisattachedto,wecanimplementthemethodsthiswayinstead:

voidOnBecameVisible(){gameObject.SetActive(true);}

voidOnBecameInvisible(){gameObject.SetActive(false);}


DisablingobjectsbydistanceInothersituations,wewantComponentsorGameObjectstobedisabledaftertheyarefarenoughawayfromtheplayer,suchthattheymaybebarelyvisible,buttoofarawaytomatter.AgoodcandidateforthistypeofactivityisroamingAIcreaturesthatwewanttoseeatadistance,butwherewedon’tneedittoprocessanything.

ThefollowingcodeisasimpleCoroutinethatperiodicallychecksthetotaldistancefromthetargetobjectanddisablesitselfifitstraystoofarawayfromit:

[SerializeField]GameObject_target;

[SerializeField]float_maxDistance;

[SerializeField]int_coroutineFrequency;

voidStart(){

StartCoroutine(DisableAtADistance());

}

IEnumeratorDisableAtADistance(){

while(true){

floatdistSqrd=(Transform.position-

_target.transform.position).sqrMagnitude;

if(distSqrd<_maxDistance*_maxDistance){

enabled=true;

}else{

enabled=false;

}

for(inti=0;i<_coroutineFrequency;++i){

yieldreturnnewWaitForEndOfFrame();

}

}

}

WeshouldassignthePlayerobject(orwhateverobjectwewantittocomparewith)tothe_targetfieldintheInspector,definethemaximumdistancein_maxDistance,andmodifythefrequencywithwhichtheCoroutineisinvokedbyusingthe_coroutineFrequencyproperty.Anytimetheobjectgoesfurtherthan_maxDistancedistanceawayfromtheobjectassignedto_target,itwillbedisabled.Itwillbere-enabledifitreturnswithinthatdistance.

Asubtleperformance-enhancingfeatureofthisimplementationiscomparingagainstdistance-squaredinsteadoftherawdistance.Thisleadsusconvenientlytoournexttip.

Considerusingdistance-squaredoverdistanceItissafetosaythatCPUsarerelativelygoodatmultiplyingfloating-pointnumberstogether,butrelativelydreadfulatcalculatingsquarerootsfromthem.EverytimeweaskaVector3tocalculateadistancewiththemagnitudepropertyorwiththeDistance()method,we’reaskingittoperformasquarerootcalculation(asperthePythagoreantheorem),whichcancostalotofCPUoverheadcomparedtomanyothertypesofvectormathcalculations.

However,theVector3classalsooffersasqrMagnitudeproperty,whichisthesameasdistance,onlysquared.Thisletsusperformessentiallythesamecomparisoncheckwithouttheexpensivesquarerootincluded,solongaswealsosquarethevaluewe’retryingtocompareitagainst;or,todescribethismathematically,ifthemagnitudeofAislessthanthemagnitudeofB,thenA2willbelessthanB2.

Forexample,considercodelikethefollowing:

floatdistance=(transform.position–

other.transform.position).Distance();

if(distance<targetDistance){

//dostuff

}

Thiscanbereplacedwiththefollowingandachieveanearlyidenticalresult:

floatdistanceSqrd=(transform.position–

other.transform.position).sqrMagnitude;

if(distanceSqrd<targetDistance*targetDistance){

//dostuff

}

Thereasontheresultisnearlyidenticalisbecauseoffloating-pointprecision.We’relikelytolosesomeoftheprecisionthatwewouldhavehadfromusingthesquare-rootvalues,sincethevaluewillbeadjustedtoanareawithadifferentdensityofrepresentablenumbers;itcanlandexactlyon,orcloserto,amoreaccuraterepresentablenumber,or,morelikely,itwilllandonanumberwithlessaccuracy.Asaresult,thecomparisonisnotexactlythesame,butinmostcases,itiscloseenoughtobeunnoticeable,andtheperformancegaincanbequitesignificantforeachinstructionwereplaceinthismanner.

Ifthisminorprecisionlossisnotimportanttoyou,thenthisperformancetrickshouldbeconsidered.However,ifprecisionisveryimportanttoyou(suchasrunninganaccuratelarge-scalegalacticspacesimulation),thenyoumightwanttolookelsewhereforperformanceimprovements.

Notethatthistechniquecanbeusedforanysquare-rootcalculations;notjustfordistance.Thisissimplythemostcommonexampleyoumightrunacross,andbringtolighttheimportantsqrMagnitudepropertyoftheVector3class—apropertywhichUnityTechnologiesintentionallyexposedforustomakeuseofinthismanner.

AvoidretrievingstringpropertiesfromGameObjectsOrdinarily,retrievingastringpropertyfromanobjectisthesameasretrievinganyotherreferencetypepropertyinC#;itisacquiredwithnoadditionalmemorycost.However,forwhateverarcanereasonhiddenwithintheUnitysourcecode,retrievingstringpropertiesfromGameObjectsduplicatesthestringinmemoryandresultsinaheapallocation.ThisdrawstheattentionoftheGarbageCollector,which,ifwearenotcareful,cancauseCPUspikesthatwillaffectperformanceduringruntime.

ThetwopropertiesofGameObjectaffectedbythisstrangebehavioraretagandname.Retrievingeitherofthesepropertiesforanyreasonwillcauseunnecessaryheapallocations.Therefore,itisunwisetouseeitherpropertyduringgameplay,andyoushouldonlyusetheminperformance-inconsequentialareassuchasEditorScripts.However,theTagsystemiscommonlyusedforruntimeidentificationpurposes,whichcanmakethisasignificantproblemforsometeams.

Forexample,thefollowingcodewouldcauseanadditionalheapmemoryallocationduringeveryiterationoftheloop:

for(inti=0;i<listOfObjects.Count;++i){

if(listOfObjects[i].tag=="Player"){

//dosomethingwiththisobject

}

}

ItisoftenbetterpracticetoidentifyobjectsbytheirComponents,classtypes,andidentifyingvaluesthatdonotinvolvestrings,butsometimeswe’reforcedintoacorner.Maybewedidn’tknowanybetterwhenwestarted,weinheritedsomeoneelse’scodebase,orwe’reusingitasaworkaroundforsomething.Let’sassumethat,forwhateverreason,we’restuckwiththeTagsystem,andwewanttoavoidtheseheapallocations.

Fortunately,thetagpropertyismostoftenusedincomparisonsituations,andGameObjectprovidesanalternativewaytocomparetagproperties,whichdoesnotcauseaheapallocation—theCompareTag()method.

Let’sperformasimpletesttoprovehowthissimplechangecanmakeallthedifferenceintheworld:

voidUpdate(){


if(Input.GetKeyDown(KeyCode.Alpha1)){


if(gameObject.tag=="Player"){

//dostuff

}

}

}

if(Input.GetKeyDown(KeyCode.Alpha2)){


if(gameObject.CompareTag("Player")){

//dostuff

}

}

}

}

Wecanexecutethesetestsbypressingthe1and2keystotriggertherespectiveforloop.Herearetheresults:

LookingattheBreakdownviewforeachspike,wecanseetwocompletelydifferentsituations:

Retrievingthetagproperty10milliontimesresultsinabout363MBofmemorybeingallocatedjustforstringsalone.Thistakes2435millisecondstoprocess,where488millisecondsarespentongarbagecollection.Meanwhile,usingCompareTag()10milliontimescosts1788millisecondstoprocess,andcausesnoheapmemoryallocations,andhencenoGarbageCollection.Thisshouldmakeitabundantlyclearthatwemustavoidusingthenameandtagproperties.So,ifTagcomparisonbecomesnecessary,thenweshouldmakeuseofCompareTag().

Notethatpassinginastringliterallike"Player"doesnotresultinaruntimeheapallocation,sincetheapplicationtechnicallyallocatesthisvalueduringinitializationandmerelyreferencesitatruntime.However,ifwedynamicallygeneratethecomparisonstring,thenwewillrunintothesameheapmemoryallocationproblems,becausewe’reessentiallycreatinganewstringobjecteachtime.


YouwilllearnmorenuancesabouttheGarbageCollectorandstringusageinChapter7,MasterfulMemoryManagement.


Update,Coroutines,andInvokeRepeatingUpdateiscalledeveryframe,butsometimeswehackinwaysfortheUpdatetobecalledlessfrequentlythannormal,andperhaps,withoutrealizingit,wecreateasituationwhereanemptymethodiscalledmoreoftenthannot:

voidUpdate(){

_timer+=Time.deltaTime;

if(_timer>_aiUpdateFrequency){

ProcessAI();

_timer-=_aiUpdateFrequency;

}

}

Withthisfunctiondefinition,weareessentiallycallinganemptyfunctionalmosteveryframe.Infact,itisworsethanthat;we’realsoperformingaBooleancheckthatalmostalwaysreturnsfalse.Thisisfineifwedon’tabusetheconcept,butasyou’velearned,havingtoomanyoftheseunnecessaryfunctioncallshidinginourScenecanbeasneakyhitonourperformance.

ThisfunctionisaperfectexampleofafunctionwecanconvertintoaCoroutinetomakeuseoftheirdelayed-invocationproperties:

voidStart(){

StartCoroutine(UpdateAI());

}

IEnumeratorUpdateAI(){

while(true){

yieldreturnnewWaitForSeconds(_aiUpdateFrequency);

ProcessAI();

}

}

However,thisapproachhasitsdrawbacks.Forone,aCoroutinecomeswithanadditionaloverheadcostrelativetoastandardfunctioncall(aroundtwiceasslow),aswellassomeheapmemoryallocationstostorethecurrentstateinmemoryuntilthenexttimeitisinvoked.Secondly,onceinitialized,Coroutinesrunindependent,oftheGameObject’sUpdate()processandwillbeinvokedregardlessofwhethertheGameObjecthasbeendisabledornot.Caremustbetakenbeforedecidingtoadoptthisapproach.

However,ifthesituationisappropriate,thebenefitsofcallingnothingduringmostframes,oftenoutweighstheadditionalcostduringtheframeswhereitisinvoked.Indeed,ifwearen’tperformingtoomanycomplexthingswithyieldstatements,thenwecanoftencreateanevensimplerversionofthemethodusingInvokeRepeating(),whichhasaslightlysmalleroverheadcost(about1.5timesslowerthanastandardfunctioncall):

voidStart(){

InvokeRepeating("ProcessAI",0f,_aiUpdateFrequency);

}

NotethatInvokeRepeatingisalsoindependentoftheGameObject’sUpdate()method,


andwillcontinuetobeinvokedeveniftheobjectisdisabled.

Regardlessofwhichapproachwepick,thereisanadditionalrisk—havingtoomanymethodstriggeringinthesameframesimultaneously.ImaginethousandsoftheseobjectsthatinitializedtogetherduringSceneinitialization.Everytime_aiUpdateFrequencysecondsgoby,theywillallinvoketheProcessAI()methodwithinthesameframe,andcauseahugespikeinCPUusage.

Possiblesolutionstothisprobleminclude:

GeneratinganewrandomtimetowaiteachtimethetimerexpiresorCoroutinetriggersSpreadoutCoroutineinitializationsothatonlyahandfulofthemarestartedeachframeDelegatetheresponsibilityofcallingupdatestosomemasterclassthatplacesalimitonthenumberofinvocationsthatoccureachframe

ReducingexcessiveUpdatedefinitionstoasimpleCoroutinecanpotentiallysaveusalotofunnecessaryoverhead,soweshouldconsiderconvertingthemwheneverwefeelitisappropriate.However,wemightalsoconsiderre-evaluatingoursolutiontotheoriginalprobleminordertopreventlotsoftimedeventsalltriggeringatthesamemoment.

AnotherapproachtooptimizingupdatesistonotuseUpdate()atall,ormoreaccurately,toonlyuseitonce.WhenUnitycallsUpdate(),itinvolvesbridgingthegapbetweenaGameObject’snativeandmanagedrepresentationoftheGameObject,whichcanbeacostlytask.Youwilllearnmoreaboutthisnative-managedbridgeinChapter7,MasterfulMemoryManagement,butfornow,justconsiderthateverycallbackwerelyonUnitytoinvokeforuscomeswithahiddenprocessingcostattachedrelativetoastandardfunctioncall.

Wecanthereforeminimizethisoverheadbylimitinghowoftenitneedstocrossthebridge.Wecandothisbyhavingagodclasstakecareofcallingourowncustomupdate-stylemethodacrossallofourcustomComponents,initsowndefinitionofUpdate().Infact,manyUnitydeveloperspreferthisapproachrightfromthestartoftheirprojects,asitgivesthemfinercontroloverwhenandhowupdatespropagatethroughoutthesystem,forthingssuchasmenupausingandcooltimemanipulationeffects.

Allobjectswantingtointegratewithsuchasystemmusthaveacommonentrypoint.Wecanachievethisthroughaninterfaceclass.Interfacesessentiallysetupacontractwherebyanyclassthatimplementstheinterfacemustprovideaspecificseriesofmethods.Inotherwords,ifweknowtheobjectimplementsaninterface,thenwecanbecertainaboutwhatmethodsareavailable.InC#,classescanonlyderivefromasinglebaseclass,buttheycanimplementanynumberofinterfaces(thisavoidsthe“deadlydiamondofdeath”problemthatC++programmersmaybefamiliarwith).

Thefollowinginterfacedefinitionwillsuffice,whichonlyrequirestheimplementingclasstodefineasinglemethod:

publicinterfaceIUpdateable{

voidOnUpdate(floatdt);


}

Next,we’lldefineaMonoBehaviourclass,whichimplementsthisinterface:

publicclassUpdateableMonoBehaviour:MonoBehaviour,IUpdateable

{

publicvirtualvoidOnUpdate(floatdt){}

}

Notethatwe’renamingthemethodOnUpdate()ratherthanUpdate().We’redefiningacustomversionofthesameconcept,butwewanttoavoidnamecollisionswiththestandardUpdate()callback.

TheOnUpdate()methodoftheUpdateableMonoBehaviourclassretrievesthecurrentdeltatime(dt),tospareusfromabunchofunnecessaryTime.deltaTimecalls.We’vealsomadethefunctionvirtual,toallowderivedclassestocustomizeit.However,asyouknow,UnityautomaticallygrabsandinvokesmethodsdefinedwiththenameUpdate(),butsincewe’redefiningourowncustomupdatewithadifferentname,thenweneedtoimplementsomethingthatwillcallthismethodwhenthetimeisappropriate;somekindof“GameLogic”godclass.

DuringtheinitializationofthisComponent,weshoulddosomethingtonotifyourGameLogicobjectofbothitsexistenceanditsdestruction,sothatitknowswhentostartandstopcallingitsOnUpdate()function.

Inthefollowingexample,wewillassumethatourGameLogicclassisaSingletonComponent,asdefinedearlierinthesectionentitledSingletonComponents,andhasappropriatestaticfunctionsdefinedforregistrationandderegistration(althoughbearinmindthatitcanjustaseasilyuseourmessagingsystem!).

ForMonoBehaviourstohookintothissystem,themostappropriateplaceiswithinStart()andOnDestroy():

voidStart(){

GameLogic.Instance.RegisterUpdateableObject(this);

}

voidOnDestroy(){

GameLogic.Instance.DeregisterUpdateableObject(this);

}

ItisbesttousetheStart()methodforthistask,sinceusingStart()meansthatwecanbecertainallotherpre-existingComponentswillhaveatleasthadtheirAwake()methodscalledpriortothismoment.Thisway,anycriticalinitializationworkwillhavealreadybeendoneontheobjectbeforewestartinvokingupdatesonit.

Notethat,becausewe’reusingStart()inaMonoBehaviourbaseclass,ifwedefineaStart()methodinaderivedclass,thenitwilleffectivelyoverridethebase-classdefinitionandUnitywillgrabthederivedStart()methodasacallbackinstead.Itwould,therefore,bewisetoimplementavirtualInitialize()methodsothatderivedclassescanoverrideittocustomizeinitializationbehaviorwithoutinterferingwiththebaseclass’staskofnotifyingtheGameLogicobjectofourcomponent’sexistence.


Forexample:

voidStart(){

GameLogic.Instance.RegisterUpdateableObject(this);

Initialize();

}

protectedvirtualvoidInitialize(){

//derivedclassesshouldoverridethismethodforinitializationcode

}

Weshouldtrytomaketheprocessasautomaticaspossibletospareourselveshavingtore-implementthesetasksforeachnewComponentwedefine.AssoonasaclassinheritsfromourUpdateableMonoBehaviourclass,thenshouldbesecureintheknowledgethatitsOnUpdate()methodwillbecalledwheneveritisappropriate.

Finally,weneedtoimplementtheGameLogicclass.TheimplementationisprettymuchthesamewhetheritisaSingletonComponentorastandaloneComponent,andwhetherornotitusestheMessagingSystem.Eitherway,ourUpdateableMonoBehaviourclassmustregisterandderegisterasIUpdateableObjectobjects,andtheGameLogicclassmustuseitsownUpdate()callbacktoiteratethrougheveryregisteredobjectandcalltheirOnUpdate()function.

HereistheclassdefinitionfortheGameLogicsystem:

publicclassGameLogic:SingletonAsComponent<GameLogic>{

publicstaticGameLogicInstance{

get{return((GameLogic)_Instance);}


}

List<IUpdateableObject>_updateableObjects=newList<IUpdateableObject>();

publicvoidRegisterUpdateableObject(IUpdateableObjectobj){

if(!_Instance._updateableObjects.Contains(obj)){

_Instance._updateableObjects.Add(obj);

}

}

publicvoidDeregisterUpdateableObject(IUpdateableObjectobj){

if(_Instance._updateableObjects.Contains(obj)){

_Instance._updateableObjects.Remove(obj);

}

}

voidUpdate(){

floatdt=Time.deltaTime;

for(inti=0;i<_Instance._updateableObjects.Count;++i){

_Instance._updateableObjects[i].OnUpdate(dt);

}

}

}

IfwemakesureallofourcustomMonoBehavioursinheritfromthe

UpdateableMonoBehaviourclass,thenwe’veeffectivelyreplacedNinvocationsoftheUpdate()callbackwithjustoneUpdate()callback,plusNvirtualfunctioncalls.Thiscansaveusalargeamountofperformanceoverhead,becauseeventhoughwe’recallingvirtualfunctions,we’restillkeepingtheoverwhelmingmajorityofupdatebehaviorinsidemanagedcode,andavoidingthenative-managedbridgeasmuchaspossible.

Dependingonhowdeepyoualreadyareintoyourcurrentproject,suchchangescanbeincrediblydaunting,time-consuming,andlikelytointroducealotofbugsassubsystemsareupdatedtomakeuseofacompletelydifferentsetofdependencies.However,thebenefitscanoutweightherisksiftimeisonyourside.ItwouldbewisetodosometestingonagroupofobjectsinaScenethatissimilarlydesignedtoyourcurrentScenefilestoverifyifthebenefitsoutweighthecosts.


ConsidercachingTransformchangesTheTransformComponentonlystoresdatarelativetoitsownparent.ThismeansthataccessingandmodifyingaTransformComponent’sposition,rotation,andscalepropertiescanresultinalotofunanticipatedmatrixmultiplicationcalculationstogeneratethecorrectTransformrepresentationfortheobjectthroughitsparents’Transforms.ThedeepertheobjectisintheHierarchy,themorecalculationsareneededtodeterminethefinalresult.Tomakemattersworse,changestoaTransformComponentalsosendinternalnotificationstocolliders,rigidbodies,lights,andcameras,whichmustbeprocessed.

However,thisalsomeansthatusinglocalPosition,localRotation,andlocalScalehavearelativelytrivialcostassociatedwiththem,becausethevaluescanberetrievedandwrittenastheyarepassedin.Therefore,theselocalpropertyvaluesshouldbeusedwheneverpossible.However,changingourmathematicalcalculationsfromworldspacetolocalspacecanovercomplicatewhatwereoriginallysimple(andsolved!)problems,somakingsuchchangesrisksbreakingourimplementationandintroducingalotofunexpectedbugs.Sometimesit’sworthabsorbingaminorperformancehitinordertosolveacomplex3Dmathematicalproblemmoreeasily!

Inaddition,itisnotuncommon,duringsomecomplexevent,wereplaceaTransform’spropertiesmultipletimesinthesameframe(althoughthisisprobablyawarningsignofover-engineereddesign).WecanconsiderminimizingthenumberoftimeswemodifytheTransformvaluesbycachingtheminamembervariableandcommittingthemonlyattheendoftheframe,asfollows:

privatebool_positionChanged;

privateVector3_newPosition;

publicvoidSetPosition(Vector3position){

_newPosition=position;

_positionChanged=true;

}

voidFixedUpdate(){

if(_positionChanged){

transform.position=_newPosition;

_positionChanged=false;

}

}

ThiscodewillonlycommitchangestothepositioninthenextFixedUpdate()method.

Notethatthiswillnotresultinsluggish-lookingbehaviorduringgameplay,sinceallphysicscalculationsareperformedimmediatelyafterFixedUpdate().TherewouldnotbeanyframesrenderedbeforethephysicsenginegetsachancetorespondtotheTransformchange.


FasterGameObjectnullreferencechecksItturnsoutthatperforminganullreferencecheckagainstaUnityobjectinvokesamethodontheothersideofthenative-managedbridge(mentionedearlierandexploredinmoredetailinChapter7,MasterfulMemoryManagement),which,asexpected,resultsinsomeunnecessaryperformanceoverhead:

if(gameObject!=null){

//dostuffwithgameObject

}

Thereisasimplealternativethatgeneratesafunctionallyequivalentoutput,butoperatesaroundtwiceasquickly(althoughitdoesobfuscatethepurposeofthecodealittle):

if(!System.Object.ReferenceEquals(gameObject,null)){

//dostuffwithgameObject

}

ThisappliestobothGameObjectsandComponents,aswellasotherUnityobjects,whichhavebothnativeandmanagedrepresentations.However,somerudimentarytestingrevealsthateitherapproachstillconsumesmerenanosecondsonanIntelCorei53570Kprocessor.So,unlessyouareperformingmassiveamountsofnullreferencechecks,thenthegainsmightbemarginalatbest.

However,itisnoteworthyinthesensethattherecanbemanyothersimplealternativesthathaveyettobediscovered,whichcanhelpimproveperformancebycircumventingthenative-managedbridge.


SummaryThischapterintroducedyoutomanymethodsofimprovingyourscriptingpracticesintheUnityEngine,withtheaimofimprovingperformanceif(andonlyif)youhavealreadyproventhemtobethecauseofaperformanceproblem.Someofthesetechniquesdemandsomeforethoughtandprofilinginvestigationbeforebeingimplemented,sincetheyoftencomewithintroducingadditionalrisksorobfuscatingourcodebasefornewdevelopers.Workflowisoftenjustasimportantasperformanceanddesign,sobeforeyoumakeanyperformancechangestothecode,youshouldconsiderwhetherornotyou’resacrificingtoomuchonthealtarofperformanceoptimization.

Wewillinvestigatemoreadvancedscriptingimprovementtechniqueslater,inChapter7,MasterfulMemoryManagement,butlet’stakeabreakfromstaringatcodeandexploresomewaystoimproveapplicationperformanceusingbuilt-inUnityfeaturessuchasStaticandDynamicBatching.


Chapter3.TheBenefitsofBatchingIn3Dgraphicsandgames,batchingisaverygeneraltermdescribingtheprocessofgroupingalargenumberofwaywardpiecesofdataandprocessingthemtogetherasasingle,largeblockofdata.Thegoalofthisprocessistoreducecomputationtime,oftenbyexploitingparallelprocessingorreducingoverheadcosts,iftheentirebatchistreatedasindividualelements.Insomecases,theactofbatchingcentersaroundmeshes,largesetsofvertices,edges,UVcoordinates,andsoon,whichareusedtorepresenta3Dobject.However,thetermcouldjustaseasilyrefertotheactofbatchingaudiofiles,sprites,andtexturefiles(alsoknownasAtlasing),andotherlargedatasets.

So,justtoclearupanyconfusion,whenthetopicofbatchingismentionedinUnity,itisusuallyreferringtothetwoprimarymechanismsitoffersforbatchingmeshfiles:StaticandDynamicBatching.Thesemethodsareessentiallyaformofgeometryinstancing,whereweusethesamemeshdatainmemorytorepeatedlyrenderthesameobjectmultipletimeswithoutneedingtopreparethedatamorethanonce.

Thesebatchingfeaturesofferusopportunitiestoimprovetheperformanceofourapplication,butonlyaslongastheyareusedwisely.Theyarefairlynuancedsystems,andtherehasbeenalotofconfusionsurroundingtheconditionsthattheyaretriggeredunder,andjustasimportantly,underwhatconditionswewouldevenseeaperformanceimprovement.Insomecases,batchingcanactuallydegradeperformanceifbatchesareaskedtoprocessdatasetsunderconditionsthatdon’tfitaveryparticularmold.

ThebatchingsystemsinUnityaremostlyablackbox,inwhichUnitytechnologieshavenotrevealedmuchdetailed,technicalinformationabouttheirinnerworkings.But,basedontheirbehavior,profilerdata,andthelistofrequirementsneededtomakethemwork,wecanstillinferagreatdeal.Thischapterintendstodispelmuchofthemisinformationfloatingaroundaboutbatchingsystems.Wewillobserve,viaexplanation,exploration,andexamples,justhowthesetwobatchingmethodsoperate.Thiswillenableustomakeinformeddecisions,makingthemostofthemtoimproveourapplication’sperformance.


DrawCallsBeforewediscussStaticandDynamicBatchingindependently,let’sfirstunderstandtheproblemsthattheyarebothtryingtosolvewithinthegraphicspipeline.Wewilltrytokeepfairlylightonthetechnicalities.WewillexplorethistopicingreaterdetailinChapter6,DynamicGraphics.

TheprimarygoalofthesebatchingmethodsistoreducethenumberofDrawCallsrequiredtorenderallobjectsinthecurrentview.Atitsmostbasicform,aDrawCallisarequestsentfromtheCPUtotheGPU,askingittodrawanobject.But,beforeaDrawCallcanberequested,severalimportantcriterianeedtobemet.Firstly,meshandtexturedatamustbepushedfromtheCPUmemory(RAM)intoGPUmemory(VRAM),whichtypicallytakesplaceduringinitializationoftheScene.Next,theCPUmustpreparetheGPUbyconfiguringtheoptionsandrenderingfeaturesthatareneededtoprocesstheobjectthatisthetargetoftheDrawCall.

ThesecommunicationtasksbetweentheCPUandGPUtakeplacethroughtheunderlyinggraphicsAPI,whichcouldbeeitherDirectXorOpenGLdependingontheplatformwe’retargetingandcertaingraphicssettings.TheseAPIsfeaturemanycomplexandinterrelatedsettings,statevariables,anddatasetsthatcanbeconfigured,andtheavailablefeatureschangeenormouslybasedonthehardwaredevicewe’reoperatingon.ThemassivearrayofsettingsthatcanbeconfiguredbeforerenderingasingleobjectisoftencondensedintoasingletermknownastheRenderState.UntiltheseRenderStateoptionsarechanged,theGPUwillmaintainthesameRenderStateforallincomingobjectsandrendertheminasimilarfashion.

ChangingtheRenderStatecanbeatime-consumingprocess.Wewon’tgotoodeeplyintotheparticularsofthis,butessentiallytheRenderStateisacollectionofglobalvariablesthataffecttheentiregraphicspipeline.Changingaglobalvariablewithinaparallelsystemismucheasiersaidthandone.AlotofworkmusthappenontheGPUtosynchronizetheoutcomeofthesestatechanges,whichofteninvolveswaitingforthecurrentbatchtofinish.InamassivelyparallelsystemsuchasaGPU,alotofvaluabletimecanbelostwaitingforonebatchtofinishbeforebeginningthenext.ThingsthatcantriggerthissynchronizationmayincludepushinganewtextureintotheGPU,changingaShader,changinglightinginformation,shadows,transparency,andchangingalmostanysettingwecanthinkof.

OncetheRenderStatehasbeenconfigured,theCPUmustdecidewhatmeshtodraw,whatMaterialitshoulduse,andwheretodrawtheobjectbasedonitsposition,rotation,andscale(allrepresentedwithinasingletransformmatrix).InordertokeepthecommunicationbetweenCPUandGPUverydynamic,newrequestsarepushedintoaCommandBuffer.Thisisabufferedlist,whichtheCPUsendsinstructionsto,andwhichtheGPUpullsfromwheneveritfinishesthepreviouscommand.TheCommandBufferbehaveslikeaFirstInFirstOut(FIFO)queue,andeachtimetheGPUfinishesonecommand,itpopstheoldestcommandfromthefrontofthequeue,processesit,andrepeatsuntiltheCommandBufferisempty.


NotethatanewDrawCalldoesnotnecessarilymeanthatanewRenderStatemustbeconfigured.IftwoobjectssharetheexactsameRenderStateinformation,thentheGPUcanimmediatelybeginrenderingthenewobjectsincethesameRenderStateismaintainedafterthelastobjectwasfinished.

Becausetherenderingprocessrequirestwohardwarecomponentstoworkintandem,itisverysensitivetobottlenecks,whichcouldoriginateinoneorbothcomponents.GPUscanrenderindividualobjectsincrediblyquickly,soiftheCPUisspendingtoomuchtimegeneratingDrawCallcommands(orsimplygeneratingtoomanyofthem),thentheGPUwillwaitforinstructionsmoreoftenthanitisworking.Inthiscase,ourapplication’sgraphicswouldbeCPU-bound.We’respendingmoretimewaitingontheCPUtodecidewhattodraw,thantheGPUspendsdrawingit.Conversely,beingGPU-boundmeanstheCommandBufferfillsupwithrequestsastheGPUcannotprocessrequestsfromtheCPUquicklyenough.

NoteYouwilllearnmoreaboutwhatitmeanstohaverenderingbottlenecksineithertheCPUorGPU,andhowtosolvebothcases,inChapter6,DynamicGraphics.

Anothercomponentwhichcanimpedethespeedofgraphicsactivityinthischainofeventsiswithinthehardwaredriver.ThiscomponentmediatescommandscomingthroughthegraphicsAPI,whichcancomefrommultiplesourcessuchasourapplication,otherapplications,andeventheOperatingSystemitself(suchasrenderingthedesktop).Becauseofthis,usingupdateddriverscansometimesresultinafairlysignificantincreaseinperformance!

Next-generationgraphicsAPIs,suchasMicrosoft’sDirectX12,Apple’sMetal,andtheKronosGroup’sVulcan,allaimtoreducetheoverheadonthedriverbysimplifyingandparallelizingcertaintasks;particularly,howinstructionsarepassedintotheCommandBuffer.OncetheseAPIsbecomecommonplace,wemaybeabletogetawaywithusingsignificantlymoreDrawCallscomfortablywithinourapplication.ButuntiltheseAPIsmature,wemusttreatourDrawCallconsumptionwithagooddealofconcern,inordertoavoidbecomingCPU-bound.


MaterialsandShadersShadersareshortprogramswhichdefinehowtheGPUshouldrenderincomingvertexandpixeldata.AShaderonitsowndoesnothavethenecessaryknowledgeofstatetoaccomplishanythingofvalue.Itrequiresinputssuchasdiffusetextures,normalmaps,colors,andsoon,andmustdecidewhatRenderStatevariablesarerequiredinordertocompleteitsintendedtask.

Unity’sMaterialsystemisessentialtoprovidingthisinformationtoourShaders.Ultimately,thisjustmeansaShaderisdependentuponaMaterialinordertobeusedtorenderanobject.EveryShaderneedsaMaterial,andeveryMaterialmusthaveaShader.EvennewlyimportedmeshesthatareintroducedintotheScenewithoutanyassignedMaterialsareautomaticallyassignedadefault(hidden)Material,whichgivesthemabasicdiffuseShaderandawhitecoloration.So,thereisnowayofgettingaroundthisrelationship.

NoteAsingleMaterialcanonlysupportasingleShader.TheuseofmultipleShadersonthesamemeshrequiresseparateMaterialstobeassignedtodifferentpartsofthesamemesh.

ThesetwosystemscapturethemajorityoftheRenderStatevariableswediscussedintheprevioussection.Asaresult,ifwecanminimizethenumberofMaterialsbeingusedtorendertheScene,thenweminimizetheamountofRenderStatechangesrequired,andhencereducetheamountoftimetheCPUspendspreparingtheGPUeachframe.

Let’sbeginwithasimpleSceneinordertovisualizethebehaviorofMaterialsandbatching.But,beforewestart,weshoulddisableseveralglobaloptionsforrenderingfeaturestoavoiddistractingourselveswithadvancedrenderingfeatures:

NavigatetoEdit|ProjectSettings|QualityandsetShadowstoDisableShadows(orselectthedefaultFastestqualitylevel)NavigatetoEdit|ProjectSettings|Player,opentheOtherSettingstab,anddisableStaticBatching,DynamicBatching,andGPUSkinningiftheyareenabled

TipTheStaticBatchingandGPUSkinningoptionsarenotavailableinUnity4FreeEdition,andrequireanupgradetoUnity4ProEdition.

Next,we’llcreateaScenethatcontainsasingleDirectionalLightandeightmeshes;fourcubes,andfourspheres,whereeachobjecthasitsownuniqueMaterial,position,rotation,andscale:


IfweobservetheBatchingvalueintheGameView’sStatspopup,weseeninetotalbatches(notethatthisvaluewillbelabeledDrawCallsintheUnity4Statspopup).UnlesstheCamera’sClearFlagssettingissettoDon’tClear,thenonebatchwillbeconsumeddrawingtheCamerabackground.ThiscouldbetheScene’sSkyboxorasinglequadthatfillsthescreenwithallpixelscoloredaspertheCamera’sBackgroundcolorproperty.

Thenexteightbatchesareusedtodrawoureightobjects.Ineachcase,theDrawCallinvolvespreparingtherenderingsystemusingtheMaterial’spropertiesandaskingtheGPUtorenderthegivenmeshatitscurrentposition,rotation,andscale.TheMaterialalsodefineswhichShaderisused,whichcontrolstheprogrammablepartsofthegraphicspipeline(vertexandfragmentsteps).

NotethatiftheRenderingPathsettingunderthePlayerSettingsissettoForward,thenwecanenableanddisabletheDirectionalLightinourSceneandthenumberofbatchesremainsatnine.ThefirstDirectionalLightinForwardrenderingiseffectivelyfreeatleastintermsofDrawCalls.AssoonasweaddmoreLightstoourScene,whethertheyareDirectional,Point,Spot,orAreaLights,wecauseallobjectstoberenderedwithanadditional“pass”throughtheShaderforeachLight,uptothevalueofthePixelLightCountvalueundertheQualitySettings(lightswithhighbrightnessvaluesareprioritizedfirst).

NoteLightingoptionscanbecomeasignificantsourceofDrawCalls,andyouwilllearnmoreaboutthissysteminChapter6,DynamicGraphics.

Aspreviouslymentioned,wecantheoreticallyminimizethenumberofDrawCallsby


reducinghowoftenwecausethesystemtochangeRenderStateinformation.So,partofthegoalthereforeistoreducetheamountofMaterialsweuse.But,ifwesetallobjectstousethesameMaterial,wedon’tseeanybenefitandthenumberofbatchesremainsatnine:

Thisisbecausewe’renotactuallyreducingthenumberofRenderStatechangesnorefficientlygroupingmeshinformation.Withoutanyformofbatching,therenderingsystemisnotsmartenoughtorealizewe’reoverwritingtheexactsameRenderStatevalues,andthenaskingittorenderthesamemeshes,overandoveragain.Thispresentsanopportunitytohavetherenderingprocessrecognizethesesituations,renderallofthesemeshestogetherasoneobject,andavoidunnecessaryDrawCalls.ThisisbasicallyhowDynamicBatchingworkstoreduceourDrawCalls.


DynamicBatchingThepurposeofDynamicBatchingistobundletogetherlargegroupsofsimplemeshesandpushthemthroughtherenderingsystemasifitwasasinglemesh.OnlymeshesthatarecurrentlyvisibleintheCameraviewarecandidatesforDynamicBatching,whichmeansthatmostofthebatchingworkisaccomplishedatruntime,ratherthanpre-calculated.Thismeansthattheobjectsthatarebatchedtogetherwillvaryfromframetoframe.Hence,thename“Dynamic”Batching.

IfwereturntothePlayerSettingspageandenableDynamicBatching,weshouldseethatthenumberofbatchesdropsfromninedowntosix.DynamicBatchingisautomaticallyrecognizingthatourobjectsshareMaterialandmeshinformationandcancombinethemintoasinglebatchforprocessing.ThisisadecentCPUcost-savingstechniqueandreducesthelikelihoodthatourgamewithbeCPU-bound,sinceitfreesupmoretimeforothertasks,suchasAIandPhysicsprocessing.

Attheriskofsoundingungrateful,weshouldaskourselveswhyweonlysavethreeDrawCalls,andnotsix.Wewouldhopethatthesystemissmartenoughtogroupallofthecubestogetherinonebatchandallofthespheresinanother,takingonlytwoDrawCallstorenderthemall(plusoneDrawCallforthebackground).

ThecompletelistoftherequirementsneededtosuccessfullydynamicallybatchameshcanbefoundintheUnitydocumentationathttp://docs.unity3d.com/Manual/DrawCallBatching.html.

AllmeshinstancesmustusethesameMaterialreferenceOnlyparticlesystemsandmeshrenderersaredynamicallybatched.Skinnedmeshrenderers(foranimatedcharacters)andallotherrenderablecomponenttypescannotbebatchedThetotalnumberofvertexattributesusedbytheShadermustbenogreaterthan900Eitherallmeshinstancesshoulduseauniformscaleorallmeshesshoulduseanonuniformscale,butnotamixtureofthetwoMeshinstancesshouldrefertothesameLightmapfileTheMaterial’sShadershouldnotdependonmultiplepassesMeshinstancesmustnotreceivereal-timeShadows

TherearealsoacoupleofundocumentedrequirementsthathavebeenrevealedduringsomeUniteConferencepanels:

Thereisalimitof300meshesperbatchTheremustbenomorethan32,000meshindicesintheentirebatch

However,acoupleoftheserequirementsarenotcompletelyintuitiveorclearfromthedescription,whichmeritssomeadditionalexplanation.


http://docs.unity3d.com/Manual/DrawCallBatching.html

VertexattributesAvertexattributeisapropertycontainedwithinameshfileonapervertexbasis.Thisincludes,butisnotlimitedto,avertex’sposition,anormalvector(mostoftenusedinlightingcalculations),andUVcoordinates(usedtodefinehowatexturewrapsaroundthemesh).Onlymesheswithlessthan900totalvertexattributesusedbytheShadercanbeincludedinDynamicBatching.

TipNotethatlookingintoamesh’srawdatafilemaycontainlessvertexattributeinformationthanUnityloadsintomemorybecauseofhowtheengineconvertsmeshdatafromoneofseveralrawdataformatsintoaninternalformat.

UsingmoreattributedatapervertexwithintheaccompanyingShaderwillconsumemorefromour900-attributebudgetandhencereducethenumberofverticesthemeshisallowedtohavebeforeitcannolongerbeusedinDynamicBatching.Forexample,asimpleShaderwhichonlyusesthreeattributespervertex,suchassomeofthelegacydiffuseShaders,cansupportDynamicBatchingusingmesheswithupto300vertices.ButamorecomplexShader,requiringfiveattributespervertex,canonlysupportDynamicBatchingwithmeshesupto180vertices.

ThisrestrictioniswhyourSceneonlysavesthreeDrawCallswithDynamicBatchingenabled,despitehavingallobjectssharethesameMaterialreference.ThecubethatisautogeneratedbyUnitycontains8verticeseachwithposition,normal,andUVdata,for24attributesintotal.Thisisfarlessthanthe900-vertexattributelimitwhenallofthisdataisusedbytheShader.However,anautogeneratedspherecontains515vertices,whichclearlycannotbedynamicallybatchedifwecountaposition,normal,andUVcoordinateforeachvertex.ThisexplainsoursixDrawCalls:oneforthebackground,oneforabatchedgroupofcubes,andfourforthespheresthatarenotbeingdynamicallybatched,whichmustberenderedwithseparateDrawCalls.


UniformscalingThedocumentationsuggeststhat,generally,objectsshouldeithershareauniformscaleoreachhaveauniquenonuniformscaleinordertobeincludedindynamicbatching.But,inreality,thebehaviorofthisrestrictionchangesslightlydependingonwhichversionofUnitywearerunningduetosomechangestotheDynamicBatchingsysteminUnity5.

TipAuniformscalemeansthatallthreecomponentsofthescalevector(x,y,andz)areidentical.

InbothversionsofUnity,ifallinstancesofameshhaveauniformscale,thentheycanbegroupedtogetherinthesamedynamicbatch.InUnity5,itwilldynamicallybatchallnonuniformlyscaledinstancesofthemeshwiththeoriginalbatch,nomattertheirscale.However,inUnity4,nonuniformlyscaledobjects,usingthesamemeshandMaterial,willbegroupedtogetherintoseparatebatches.

Thisassumeswe’reworkingwithpositivescales.Thescalerestrictiongetsalittleunintuitivewhenwe’redealingwithnegativescales.InUnity4,negativescalesdonotaffectDynamicBatchingandallofthesamerulesapplyasbefore.But,inUnity5,ifthemeshhasoneorthreenegativevaluesinitsscalevector,thenitwillnotbeincludedinthebatch.Ifitcontainstwonegativevalues,thenitcanbebatchedalongwithalloftheotherinstances.Itdoesnotevenmatterwhichofthethreevaluesarenegative,onlythattherearezeroortwoofthem.

Presumably,thisisabi-productofthealgorithmusedtodetectvalidbatchablegroups,sincemirroringameshintwodimensionsismathematicallyequivalenttorotatingthemeshaboutbothofthesameaxes180degrees.Thus,thebehaviorweobserveisjusttheDynamicBatchingsystemautomaticallytransformingtheobjectforus.

So,itisworthkeepinginmindthatDynamicBatchingisalittlemoreefficientinUnity5,butithassometrade-offs.Ifwewishtousenegativescalesasashortcuttomirroramesh,thenitwillbeincapableofbeingDynamicallyBatched.


DynamicBatchingsummaryTherewereclearlysomesignificantimprovementsmadetotheDynamicBatchingsysteminUnity5,allowingittobemoreversatiletoavarietyofsituations.However,nomatterwhichversionofUnityweareusing,DynamicBatchingisveryusefulwhenwewishtorenderverylargegroupsofsimplemeshes.

Thedesignofthesystemmakesitidealtousewhenallofthemesheswe’reDynamicallyBatchingaresimpleandnearlyidenticalinappearance.PossiblesituationstoapplyDynamicBatchingcouldbeasfollows:

Alargeforestfilledwithrocks,trees,andbushesAbuilding,factory,orspacestationwithmanycommonelements(computers,pipes,andsoon)throughouttheSceneAgamefeaturingmanydynamic,nonanimatedobjectswithsimplegeometryandparticleeffects(agamesuchasGeometryWarsspringstomind)

ThepotentialbenefitsofDynamicBatchingaresignificantenoughtosetasidesometimetoinvestigateifandwherewecanmakeuseofitinourScene.TherearenottoomanyoccasionswhereDynamicBatchingwouldactuallydegradeperformance.

ThemostcommonmistakewithDynamicBatchingistosetupaScenethatgenerateslotsofbatches,whicheachcontainonlyahandfulofmeshes.Inthesecases,theoverheadcostofdetectingandgeneratingthebatchesmightcostmorethanthetimeitsavesjustmakingaseparateDrawCallforeachmesh.

Inaddition,we’refarmorelikelytoinflictperformancelossesonourapplicationbysimplyassumingDynamicBatchingistakingplace,whenwe’veactuallyforgottenoneoftheessentialrequirements.Everysituationisunique,soitisworthexperimentingwithourMaterials,meshes,andShaderstodeterminewhatcanandcannotbedynamicallybatched.


StaticBatchingUnityoffersasecondbatchingmechanismthroughStaticBatching.ThepurposeofthisfeatureistograntusawaytobatchnonidenticalmeshesofanysizeintoasinglebatchwithasimilargoalandmethodologytoDynamicBatching,butsolvingtheproblemforadifferentsetofconditions.TheessentialdifferencebetweenthetwobatchingmethodsisthatStaticBatchingoccursduringapplicationinitialization,whereasDynamicBatchingtakesplaceatruntime.WethereforehavealotmorecontroloverwhenandwhereStaticBatchingtakesplace.

NoteStaticBatchingisavailableinalleditionsofUnity5,butonlyintheProEditionofUnity4.Unity4FreeuserswillneedtoupgradetotheProEditiontomakeuseofthisfeature.

TheStaticBatchingsystemhasitsownsetofrequirements:

Asthenameimplies,themeshesmustbeflaggedasStaticAdditionalmemorymustbesetasideforeachmeshbeingstaticallybatchedThemeshinstancescancomefromanysourcemesh,buttheymustsharethesameMaterial

Let’scovereachoftheserequirementsinmoredetail.


TheStaticflagStaticBatchingcanonlybeappliedtoobjectswiththeStaticflagenabledor,morespecifically,theBatchingStaticsubflag(alsoknownasStaticEditorFlags).ClickingonthedownarrownexttotheStaticoptionforaGameObjectwillrevealadropdownoftheseStaticEditorFlags,whichcanaltertheobject’sbehaviorforvariousStaticprocesses.


MemoryrequirementsTheadditionalmemoryrequirementforStaticBatchingwillvarydependingontheamountofreplicationoccurringwithinthebatchedmeshes.StaticBatchingworksbycombiningallflaggedmeshesintoasingle,largemesh,andpassingitintotherenderingsystemthroughasingleDrawCall.Ifallofthemeshesbeingstaticallybatchedareunique,thenthiswouldcostusnoadditionalmemoryusagecomparedtorenderingtheobjectsnormally,asthesameamountofmemoryspaceisrequiredtostorethemeshes.

However,staticallybatchedduplicatescostusadditionalmemoryequaltothenumberofmeshesmultipliedbythesizeoftheoriginalmesh.Ordinarily,renderingone,ten,oramillionclonesofthesameobjectcostsusthesameamountofmemory,becausethey’reallreferencingthesamemeshdata.Theonlydifferenceisthetransformofeachobject.But,becauseStaticBatchingneedstocopythedataintoalargebuffer,completewithitstransformdata,thisreferencingislost,andanewduplicateoftheoriginalmeshiscopiedintothebufferwithahard-codedtransformposition,regardlessofwhetherthesamemeshhasalreadybeencopiedin.

Therefore,usingStaticBatchingtorender1,000identicaltreeobjectswillcostus1,000timesmorememorythanrenderingthesameobjectsnormally,becauseeachtreemustbecopiedintotheStaticBatchingbufferasauniquesetofvertexdata.ThiscausessomesignificantmemoryconsumptionandperformanceissuesifStaticBatchingisnotusedwisely.


MaterialreferencesFinally,wealreadyknowaboutsharingmaterialreferencesasameansofreducingRenderStatechanges,sothisrequirementisfairlyobvious.However,sometimeswe’restaticallybatchingmeshesthatrequiremultiplematerials.Inwhichcase,allmeshesusingadifferentmaterialwillbegroupedtogetherintheirownstaticbatch,andagainforeachuniquematerialbeingused.

Thedownsidetothisdesignfeatureisthat,atbest,StaticBatchingcanonlyrenderallofthestaticmeshesusinganumberofDrawCallsequaltothenumberofmaterialstheyneed.But,thebenefitisthatwecancontrolwhichmeshesgetbatchedtogetherusingdifferentmaterials,effectivelyforcingittostartanewstaticbatchthroughsomecunningmaterialduplication.ThiswillbecomeclearafterwecoversomeoftheStaticBatchingsystem’scaveats.


StaticBatchingcaveatsTheStaticBatchingsystemisnotwithoutitsdrawbacks.Becauseofhowitapproachesthebatchingsolution,bycombiningmeshesintoasinglegreatermesh,theStaticBatchingsystemhasafewcaveatsthatweneedtobeawareof.TheseconcernsrangefromminorinconveniencestomajordrawbacksdependingontheScene:

DrawCallsavingsarenotimmediatelyvisiblefromtheStatswindowuntilruntimeStaticobjectsshouldnotbeintroducedtotheSceneatruntimeStaticallybatchedmeshescannotbemovedfromtheiroriginalstartingtransformIfanyoneofthestaticallybatchedmeshesisvisible,thentheentiregroupwillberendered

EditModedebuggingofStaticBatchingTryingtodeterminetheoveralleffectthatStaticBatchingishavingonourScenecanbealittletrickysincenothingisbeingStaticallyBatchedwhileinEditMode.AllofthemagichappensduringSceneinitialization,whichcanmakeitdifficulttodeterminewhatbenefitsStaticBatchingisactuallyproviding.Thisisespeciallytrueifweleaveimplementingthisfeatureuntillateintheprojectlifecycle,wherewecanspendalotoftimelaunching,tweaking,andrelaunchingourScenetoensurewe’regettingtheDrawCallsavingswe’reexpecting.Consequently,itisbesttostartworkingonStaticBatchingoptimizationearlyintheprocessofbuildinganewScene.

AvoidinginstantiatingstaticmeshesatruntimeNewstaticobjectsintroducedintotheScenewillnotbeautomaticallycombinedintoanyexistingbatchbytheStaticBatchingsystem.Todosowouldcauseanenormousruntimeoverheadbetweenrecalculatingthemeshandsynchronizingwiththerenderingsystem,soUnitydoesnotevenattempttodoit.Thisrestrictionmeansweshouldnotattempttodynamicallyinstantiatethestaticallybatchedcontent.AllmesheswewishtostaticallybatchshouldbepresentintheoriginalScenefile.

NoteDynamicinstantiationofobjectscanbeacostlyactioninitsownright.WewillcoversolutionstothatprobleminChapter7,MasterfulMemoryManagement.

Aswiththepreviouscaveat,staticallybatchedmeshesshouldnotbemovedaftertheyhavebeenbatched,sincedoingsowouldgenerateatremendousCPUoverhead.TheStaticBatchingsystemhasalreadytakentheoriginaldataandcombineditintoanewmeshobject.MovingtheoriginalmeshesisbothimpossiblewhiletheStaticflagisenabled,andnotevenrecognizedbytheUnitysystemiftheflagisdisabledandtheobject’stransformischanged.

VisibilityandrenderingThefinalcaveatisperhapsthemostimportant.IfevenasinglevertexofaStaticallyBatchedmeshisvisibletotheCamera,thenthewholemeshwillbepushedintothe


renderingsystemandprocessedinitsentirely.WeneedtobesmartabouthowweuseStaticBatchingandoptimizeitsusagetopreventusrenderingagiganticmesheachandeveryframe!

Forexample,ifwehaveaScenewithmanyroomsconnectedtogetherwhichallsharethesameMaterial,thenenablingStaticBatchingforeveryroomobjectwillcauseeverysingleroomtoberenderedevenifonlyasingleroomisvisible,andeveniftheplayerisstaringstraightintoawall.SuchSceneswouldfarebetterusingOcclusionCulling(exploredinChapter6,DynamicGraphics)topreventnonvisibleroomsfrombeingrendered.

Meanwhile,largeoutdoorsceneswillfinditusefultoduplicateMaterials.Thisisausefultricktoforcesimilarobjectstobestaticallybatchedintodifferentgroups.Assigningidentical,butduplicateMaterialstodifferentsectionsoftheworldwillrenderthemthesame;however,theywillbegroupedseparately.ThiswouldincreasethenumberofDrawCalls,butallowustoreusethesameTexture,Material,andShaderfilesfortheentireScene.

DuplicatingMaterialscanbecomeabitofachorefromthemaintenanceperspective,sinceanychangesmadetooneMaterialmustalsobemadetotheothers.Hypothetically,wemightthinkwecanaccomplishthisthroughScriptbyattachingaComponentthatautomaticallyduplicatesaMaterialandassignsittothemeshduringSceneinitialization.Unfortunately,StaticBatchinghappenstooearlyintheinitializationprocessforustointerceptthroughacustomComponentsuchasthis,sothetaskmustbedonethroughtheEditor(agoodopportunitytomakeuseofEditorscripts).


StaticBatchingsummaryStaticBatchingisapowerful,butdangeroustool.Ifwedon’tuseitwisely,wecanveryeasilyinflictperformancelossesviamemoryconsumptionandrenderingcostsonourapplication.Italsotakesagoodamountofmanualtweakingandconfiguration.However,itdoeshaveasignificantadvantage:itcanbeusedonobjectsetsofanysize.ThereisessentiallynolimitasfarasStaticBatchingisconcerned.


SummaryItisclearthattheStaticandDynamicBatchingfeaturesarenosilverbullet.WecannotblindlyapplythemtoanygivenSceneandexpectimprovements.IfourapplicationandScenehappentofitaparticularsetofparameters,thenthesemethodsareveryeffectiveatreducingCPUloadandrenderingbottlenecks.But,ifnot,thensomeadditionalworkisrequiredtoprepareourScenetomatchitsfeaturerequirements.Ultimately,onlyagoodunderstandingofthebatchingsystemsandhowtheyfunctioncanhelpusdeterminewhereandwhenthisfeaturecanbeapplied.

WewillcovermoregraphicsimprovementtechniquesinChapter6,DynamicGraphics.Untilthen,let’smoveontoadifferenttopic,andlookintosomeofthemoresubtleperformanceimprovementsthatwecanachievethroughmanagingourartassetsinintelligentways.


Chapter4.KickstartYourArtArtisaverysubjectivearea,dominatedbypersonalopinionandpreference.Itcanbedifficulttosaywhetheronepieceofartis“better”thantheother,andit’slikelythatwewon’tbeabletofindcompleteconsensusonouropinions.Thetechnicalaspectsbehindartassetsthatsupportagame’sartistrycanalsobeverysubjective.Therearemultipleworkaroundsthatcanbeimplementedtoimproveperformance,butthesetendtoresultinalossofqualityforthesakeofspeed.Ifwe’retryingtoreachpeakperformance,thenit’simportantthatweconsultwithourteammemberswheneverwedecidetomakeanychangestoourartassetsasitisprimarilyabalancingact,whichcanbeanartforminitself.

Whetherwe’retryingtominimizeourruntimememoryfootprint,keepingthesmallestpossibleexecutablesize,maximizingloadingspeed,ormaintainingconsistencyinframerate,thereareplentyofoptionstoexplore.Therearesomemethodsthatareclearlyalwaysideal,andotherswhichmayrequirealittlemorecareandforethoughtbeforebeingadopted,astheymightresultinreducedqualityorincreasethechancesofdevelopingbottlenecksinothercomponents.

Wewillbeginexaminingaudiofiles,followedbyTexturefiles,andfinishupwithmeshesandanimations.Ineachcase,wewillinvestigatehowUnityloads,stores,andmanipulatestheseassetsduringruntime,whatouroptionsare,andwhatwecandotoavoidbehaviorthatmightgenerateperformancebottlenecks.


AudioDependingonthescopeoftheproject,audiofilescanrangeanywherefromthelargestdiskspaceconsumer,tothesmallest.Unity,asaframework,canbeusedtobuildsmallapplicationsthatrequireonlyahandfulofsoundeffectsandasinglebackgroundtrack,ortobuildlargeexpansiveroleplayinggamesthatneedmillionsoflinesofspokendialog,musictracks,andambientsounds.ItwillbeusefultomakesenseofhowaudiofilesaremanagedinUnitytobetterunderstandwhatweshoulddoforthesakeofoptimizationinbothcases.

ManydevelopersaresurprisedtofindthatruntimeaudioprocessingcanturnintoasignificantsourceofCPUandmemoryconsumption.Audioisoftenneglectedonbothsidesofthegamingindustry;developerstendnottocommitmanyresourcestoituntilthelastminute,whileuserswillrarelydrawattentiontoit.Nobodynoticeswhentheaudioisgoodorpassable,butweallknowwhatbadaudiosoundslike;it’sinstantlyrecognizable,jarring,andguaranteedtocatchunwantedattention.Thismakesitcrucialnottosacrificetoomuchaudioclarityinthenameofperformance.

Audiobottleneckscancomefromavarietyofsources.Excessivecompression,toomuchaudiomanipulation,toomanyactiveaudioclips,inefficientmemorystoragemethods,andaccessspeedsareallwaystoinvitepoormemoryandCPUperformance.But,withalittleeffortandunderstanding,allittakesisafewtweakshereandtheretosaveusfromauser-experiencedisaster.

NoteSeveralaudiooptionsarenamedslightlydifferentlybetweenUnity4andUnity5,butthefeaturesareidenticalforallintentsandpurposes.WewillproceedusingtheUnity5nameforeachfeature.


LoadingaudiofilesWhenweselectanimportedAudioClipintheUnityEditor,weseethatthefirstoptionisthefile’sLoadType.Therearethreepossiblesettingsavailable:

DecompressOnLoadCompressedInMemoryStreaming

TheactualmomentwhenthefileisfirstloadedwilldependonotherAudioClipsettingsandhowtheyareusedduringruntime,whichwewillexplorelater.Thisoptionmerelydefinesthemethodofloadingwhenitoccurs.

DecompressOnLoadcompressesthefileondisktosavespace,anddecompressesitintomemorywhenitisfirstloaded.Thisisthestandardmethodofloadinganaudiofile,andshouldbeusedinmostcases.

CompressedInMemoryloadsthecompressedfilestraightintomemorywhenitisloaded,anddecompressesitduringruntimewhenitisbeingplayed.ThiswillsacrificeruntimeCPUwhentheclipisplayed,butimprovesloadingspeedandreducesruntimememoryconsumption.Hence,thisoptionisbestusedforverylargeaudiofilesthatareusedfairlyfrequently,orifwe’reincrediblybottleneckedonmemoryconsumptionandarewillingtosacrificesomeCPUcyclestoplaytheAudioClip.

Finally,theStreamingoptionwillload,decode,andplayfileson-the-flyatruntimebygraduallypushingthefilethroughasmallbuffer.ThismethodusestheleastamountofmemoryforaparticularAudioClipandthelargestamountofruntimeCPU.Thiscomeswiththeunfortunatedrawbackthattheycannotbereferencedmorethanonce.AttemptingtostreammultiplecopiesofthesameAudioClipwillgenerateanewbufferforeachinstance,resultinginasignificantamountofRAMandruntimeCPUcostifusedrecklessly.Consequently,thisoptionisbestreservedforsingle-instanceAudioClipsthatplayregularlyandneverneedtooverlapwithotherinstances.Ergo,thissettingisbestusedwithbackgroundmusicandambientsoundeffectsthatneedtoplayduringthemajorityofaScene’slifetime.

ProfilingaudioWecanconfirmmuchofthisbehaviorbyplayingmultipleinstancesofanygivenAudioClipviamultipleAudioSourcesinaScene,andbenchmarkingusingtheAudioViewoftheProfilertoseehowmuchmemoryandCPUisconsumedusingthevariousLoadTypeoptions.However,beawarethattheProfileroutputforaudiomemoryandCPUconsumptioninEditorModecanbeverymisleading,sinceitperformsaudioloadingdifferentlytohowitwouldoccurinaruntimeapplication.

ThefirsttimeweloadtheEditorandenterPlayMode,theEditorwilldecompressaudiofiles,costingacertainamountofmemoryandCPUcyclesduringinitializationinordertoaccomplishthis.WecanobservethememorycostsofthisprocessintheProfilerundertheAudioArea.However,ifwerestarttheScene,thenwemaynoticethatthememoryspentondecompressingaudiofilessuddenlydropstonearly0KB,sincefileshavealreadybeen


decompressedandtheEditorhasflushedawaydataitnolongerneeds.Thisisnotrepresentativeofarealsituation,asapplicationswouldneedtoperformthisdecompression.

So,ifwewantaccurateaudioprofilinginUnity,weshouldruntheProfileragainstastandalone,orremote,versionofourapplicationontheintendedplatform/device.

AdditionalloadingoptionsThereisanadditionalpairofoptionsthataffectaudiofileloadingbehavior:

LoadInBackgroundPreloadAudioData

Inthetypicalusecase,whereanAudioClipisassignedtoanAudioSourceComponentinaScene,theaudiofilewillbeloadedintomemoryduringSceneinitialization.But,iftheLoadInBackgroundoptionisenabled,thenloadingtheAudioClipwillbedeferredtoabackgroundtaskthatbeginsoncetheScenehasfinishedinitializingandgameplayhasessentiallybegun.So,itstandstoreasonthatwecanimprovetheSceneloadingspeedbyenablingthisoptionforAudioClipsthatwewon’tneeduntillaterintheScene’slifetime,suchassoundeffectsusedinmid-levelcutScenes.

WecanuseanAudioClipobject’sloadStatepropertytoverifyiftheassetisloadedbeforeattemptingtouseit.But,usingtheLoadInBackgroundoptionrisksintroducingjarringbehaviorifwetrytoaccessasoundfilebeforeitisfullyloaded.Inthesecases,thesoundfilewon’tplayuntilthebackgroundloadingtaskhascompleted,inwhichcasethesoundwillprobablyplayataninappropriatemoment.

Thesecondoption,PreloadAudioData,isenabledbydefault,whichtellstheUnityEnginetoautomaticallybeginloadingthefileduringSceneinitialization.DisablingthisoptiondefersloadingtothefirstinstantthattheAudioSourceobject’sPlay()orPlayOneShot()methodsareinvokedatruntime.ThiswillcauseaspikeintheCPU,astheaudiodataisloadedfromthedisk,decompressed(ornot,dependingontheLoadTypesetting),pushedintomemory,andeventuallyplayedonceloaded.

Duetotheamountofplaybackdelay,andtheperformancecost,itisnotrecommendedtorelyonloadingoccurringatthemomentthataudioplaybackisneeded.WeshouldinsteadcontrolloadingourselvesbycallingtheAudioClipobject’sLoadAudioData()atsomeconvenientmomentbeforethefileisneeded.Moderngamestypicallyimplementconvenientstoppingpointsinlevelstoperformtaskssuchasthis,suchasanelevatorbetweenfloorsorlongcorridors,whereverylittleactionistakingplace.NotethatwecanalsomanuallycontrolthefreeingofaudiofilememoryusingtheAudioClipobject’sUnloadAudioData()method.

Solutionsinvolvingcustomloadingandunloadingofaudiodataviathesemethodswouldneedtobetailor-madetotheparticulargame,dependingonwhenAudioClipsareneeded,howlongthey’reneededfor,howScenesareputtogether,andhowplayer(s)traversethem.Thiscanrequireasignificantnumberofspecial-casechanges,testing,andassetmanagementtweakstoachieve.So,itisrecommendedtosavethisapproachasa“Nuclear


Option”tobeusedlateinproduction,intheeventthatallothertechniqueshavenotsucceededaswellaswehoped.


EncodingformatsandqualitylevelsUnitysupportsthreegeneral-caseencodingformatsforaudiofiles,withafewspecificcasesthatareplatform-dependent(suchasHEVAGforthePSVitaandXMAforXBoxOne).Wewillfocusonthethreeoptionalencodingformats:

CompressedPCMADPCM

ThecompressionalgorithmusedwiththeCompressedformatwilldependontheplatformbeingtargeted.Standaloneapplications,WebGL,andothernon-mobileplatformsuseOgg-Vorbisforcompression,whilemobileplatformsuseMPEG-3(MP3).

TheaudiofilesweimportintotheUnityEnginecanbeoneofmanypopularaudiofileformats,buttheactualencodingthatisbundledintotheexecutablewillendupinoneofthepreviouslymentionedformats.StatisticsareprovidedforthecurrentlyselectedformatintheareafollowingtheCompressionFormatoption,providinganideaofhowmuchdiskspaceisbeingsavedbythecompression,andhowmuchmemorytheAudioClipwillconsumeatruntime(notethatthisalsodependsonthecurrentlyselectedLoadType).

Theencoding/compressionformatusedcanhaveadramaticeffectonthequality,filesize,andmemoryconsumptionoftheaudiofileduringruntime,andonlytheCompressedoptiongivesustheabilitytoalterthequalitywithoutaffectingthesamplingrateofthefile.ThePCMandADPCMformatsdonotprovidethisluxury,andwe’restuckwithwhateverfilesizethosecompressionformatsdecidetogiveus,unlesswe’rewillingtoreduceaudioqualityforthesakeoffilesizebyreducingthesamplingrate.

Eachencodingandcompressionformatprovidesdifferentbenefitsandpitfalls,andeachaudiofilemaybeabletosacrificeonemetricforanotherbasedonitspurposeandcontents.Ifwewishtoproperlyoptimizeourapplication’saudiofiles,thenweneedtobewillingtousealloftheavailableformatsinasingleapplicationtomakethemostofouraudiofiles.

ThePCMformatisalosslessanduncompressedaudioformat,providingacloseapproximationofanalogaudio.Ittradeslargefilesizesforhigheraudioquality,andisbestusedforveryshortsoundeffectsthatrequirealotofclaritywhereanycompressionwouldotherwisedistorttheexperience.

Meanwhile,theADPCMformatisfarmoreefficientinbothsizeandCPUconsumptionthanPCM,butcompressionresultsinafairamountofnoise.Thisnoisecanbehiddenifitisreservedforshortsoundeffectswithalotofchaos,suchasexplosions,collisions,andimpactsoundswherewemightnotbeawareofanygeneratedartefacts.

Finally,theCompressedformatwillresultinsmallfilesthathavelowerqualitythanPCM,butsignificantlybetterqualitythanADPCM,attheexpenseofadditionalruntimeCPUusage.Thisformatshouldbeusedinmostcases.Thisoptionallowsuscustomizetheresultantqualitylevelofthecompressionalgorithm,totweakqualityagainstfilesize.BestpracticeswiththeQualityslideraretosearchforaqualitylevelthatisassmallas


possible,butunnoticeabletousers.Someusertestingmayberequiredtofindthe“sweetspot”foreachfile.

TipDonotforgetthatanyadditionalaudioeffectsappliedtothefileatruntimewillnotplaythroughtheEditorinEditMode,soanychangesshouldbefullytestedthroughtheapplicationinPlayMode.


AudioperformanceenhancementsNowthatwehaveabetterunderstandingofaudiofileformats,loadingmethods,andcompressionmodes,let’sexploresomeapproachesthatwecanmaketoimproveperformancethroughtweakingaudiobehavior.

MinimizeactiveAudioSourcecountSinceeachactivelyplayingAudioSourceconsumesaparticularamountofCPU,thenitstandstoreasonthatwecansaveCPUcyclesforeachredundantAudioSourcethatisplayinginourScene.OneapproachistocontrolourAudioSourcesinsuchawaythatweputahardcaponhowmanyinstancesofanAudioClipcanplaysimultaneouslysothatwedon’tattempttoplaytoomanyofthesamesoundeffectssimultaneously.WecandothisbyhavingamanagementobjecttakecontrolofourAudioSources.ItshouldacceptsoundplaybackrequestsandplaysthefilethroughanyAudioSourcesthataren’talreadybusyplayinganexistingsound.

Themanagementobjectcouldalsothrottletherequestssuchthatthereisalimittohowmanyversionsofthesamesoundeffectcanplay,andhowmanytotalsoundeffectsareplayingatanygiventime.Thiswouldbebestusedon2Dsoundeffectsorsingleinstancesof3Dsoundeffects(whichwouldrequiremovingtheAudioSourcetothecorrectlocationatthemomentofplayback).

AlmosteveryAudioManagementAssetavailableintheUnityAssetStoreimplementsanaudio-throttlingfeatureofsomekind(oftenknownas“audiopooling”),andforgoodreason;it’sthebesttrade-offinminimizingexcessiveaudioplaybackwiththesmallestamountofeffortinpreparingaudioassetstomakeuseofit.Forthisreason,andbecausetheseassetsoftenprovidemanymoresubtleperformance-enhancingfeatures,itisrecommendedtouseapre-existingsolution,ratherthanrollingoutourown,asthescriptingprocesscanbeveryinvolved.

Notethatambient3DsoundsstillneedtobeplacedatspecificlocationsintheScenetomakeuseofthelogarithmicvolumeeffect,whichgivesitthepseudo-3Deffect,sotheaudiomanagementsystemwouldprobablynotbeanidealsolution.Limitingplaybackonambientsoundeffectsisbestachievedbyreducingthetotalnumberofsources.Thebestapproachistoeitherremovesomeofthemorreducethemdowntoonelarger,louderAudioSource.Naturally,thisapproachaffectsthequalityoftheuserexperience,sinceitwouldappearthatthesoundiscomingfromasinglesourceandnotmultiplesources,andsoitshouldbeusedwithcare.

MinimizeAudioClipreferencesEachAudioSourceintheScenewithareferencetoanAudioClipwithPreloadAudioDataenabledwillconsumeacertainamountofmemoryfortheAudioClip(compressed,decompressed,orbuffered,dependingonLoadType)throughouttheentirelengthofthegivenScene.TheexceptiontothisruleisiftwoormoreAudioSourcesreferencethesameAudioClip,inwhichcasenoadditionalmemoryisconsumedasalloftheAudioSourcesarereferencingthesamelocationinmemoryandreadingfromitonanas-needed


basis.

AudioClipsareunmanagedresourceswithinUnity,whichmeanstheywillnotbereleasedfrommemorymerelybysettingallreferencestonull.Unityexpectsustoloadandreleasetheseresourcesourselves,creatingandreleasingthemfrommemoryas-needed.Keepingfilesinmemoryforlongperiodsisreasonableforfrequentlyusedsoundeffects,sinceloadingafileintomemoryeverytimeitisrequestedwouldcostussomemeasureofCPUuse.

However,ifwefindthatweareusingtoomuchmemoryfromthesefrequentlyusedsoundeffects,thenwemustmakethedifficultchoiceofeitherreducingtheirqualityorremovingthementirely,tofindmemorysavings.Removingsoundeffectscompletelyisnotnecessarilyabadoption.Wemightbeabletoachieveauniquesoundeffectbyreusingexistingsoundeffectscombinedwithspecialeffectsandfilters.

Ontheotherhand,keepinginfrequentlyusedsoundeffectsinmemoryforthelengthofaScenecanposeasignificantproblem.Wemighthavemanyone-time-onlysoundeffects,suchasdialogclips,wherethereislittlereasontokeeptheminmemoryjustfortheoneuniquemomenttheyareneeded.CreatingAudioSourceswithassignedAudioClips(intheirAudioClipproperty)willgeneratesuchreferences,andcauseexcessmemoryconsumptionevenifweonlyusethemforasinglemomentduringgameplay.

ThesolutionistomakeuseofResources.Load()andResources.UnloadAsset()tokeeptheaudiodatainmemoryonlyforaslongasitisbeingplayed,andthenimmediatelyreleaseitonceitisnolongerneeded.Thefollowingcodesamplewillachievethiseffectinthesimplestmannerpossible(trackingonlyasingleAudioSourceandAudioClip)usingourSingletonAsComponentclass,justtogiveusanideaofwhatsuchasystemmightlooklike:

usingUnityEngine;



publicclassAudioSystem:SingletonAsComponent<AudioSystem>{

[SerializeField]AudioSource_source;

AudioClip_loadedResource;

publicstaticAudioSystemInstance{

get{return((AudioSystem)_Instance);}


}

publicvoidPlaySound(stringresourceName){

_loadedResource=Resources.Load(resourceName)asAudioClip;

_source.PlayOneShot(_loadedResource);

}

voidUpdate(){

if(!_source.isPlaying&&_loadedResource!=null){

Resources.UnloadAsset(_loadedResource);

_loadedResource=null;

}

}

}

ThisclasscanbetestedwiththefollowingComponent,whichloadsasoundfilewhentheAkeyispressed:

publicclassAudioSystemTest:MonoBehaviour{

voidUpdate(){

if(Input.GetKeyDown(KeyCode.A)){

AudioSystem.Instance.PlaySound("TestSound");

}

}

}

TipNotethat,totestthiscode,anaudiofilenamedTestSoundmustbeplacedwithinafoldernamedResourcesinorderforUnitytofinditatruntime.

Usingthisapproachtoplaysoundeffects,weshouldnotethatmemoryforthesoundisonlyallocatedwhenitisplayed,andthenimmediatelyfreedwhenthesoundeffectends.Onceagain,multipleaudiotoolsintheUnityAssetStoreprovidethisfeature,buttheAudioSystemclasscanbeexpandedtohandlemultipleAudioSourcesandAudioClipsfairlyeasilyifwewishtocustomizethesolution.

EnableForcetoMonofor3DsoundsEnablingtheForcetoMonosettingonastereoAudioFilewillmixittogetherwiththechannelsintoasinglechannel,saving50percentofthefile’stotaldiskandmemoryspaceusage.Enablingthisoptionisgenerallynotagoodideaforsome2Dsoundeffectswherethestereoeffectisoftenusedtocreateacertainaudioexperience.Butwecanenablethisoptionforsomegoodspacesavingson3Dsoundeffects,wherebeingastereosourceisgenerallymeaningless,and2Dsoundswherethestereoeffectisn’timportant.

ResampletolowerfrequenciesResamplingimportedaudiofilestolowerfrequencieswillreducethefilesizeandruntimememoryfootprint.ThiscanbeachievedthroughanAudioClip’sSampleRateSettingandSampleRateproperties.Somefilesrequirehighsampleratestosoundreasonable,suchasfileswithhighpitchesandmodernmusicfiles.However,lowersettingscanreducethefile’ssizewithoutmuchnoticeablequalitydegradationinmostcases.22050Hzisacommonvalueforsourcesthatinvolvehumanspeechandclassicalmusic.Somesoundeffectsmaybeabletogetawaywithevenlowerfrequencyvalues.But,eachsoundeffectwillbeaffectedbythissettinginauniqueway,soitwouldbewisetospendsometimedoingsometestingbeforewefinalizeourdecisiononsamplingrate.

ConsiderallencodingformatsIfmemoryandharddiskconsumptionarenotaburdenonourapplication,thentheWAVformatcanbeusedtoreduceCPUcostsatruntime,duetohavingasmalleroverhead


requiredtodecodethedataduringeachplayback.Meanwhile,ifwehaveCPUcyclestospare,wecansavespacewithcompressedencoding.

BewareofstreamingStreamingfilesfromdiskshouldberestrictedtolarge,single-instancefilesonly,asitrequiresruntimeharddiskaccess;oneoftheslowestformsofdataaccessavailabletous.Layeredortransitioningmusicclipsmayrunintomajorhiccupsusingthismethod,atwhichpointitwouldbewisetoconsidertheResources.Load()approach.Weshouldalsoavoidstreamingmorethanonefileatatimeasitlikelytoinflictalotofcachemissesonthediskthatinterruptgameplay.

ApplyFiltereffectsthroughMixergroupstoreduceduplicationFiltereffectsareadditionalComponentsthatwecanattachtoanAudioSourcetomodifysoundplayback.EachindividualFiltereffectwillcostsomeamountofbothmemoryandCPU,andattachingduplicatestomanyAudioSourcesinourScenecanresultindireconsequencesifthey’reusedtoofrequently.AbetterapproachistomakeuseofUnity’sAudioMixerutilitytogeneratecommontemplatesthatmultipleAudioSourcescanreferencetominimizetheamountofmemoryoverhead.

TheofficialtutorialonAudioMixerscoversthetopicinexcellentdetail:

https://unity3d.com/learn/tutorials/modules/beginner/5-pre-order-beta/audiomixer-and-audiomixer-groups

Use“WWW.audioClip”responsiblyUnity’sWWWclasscanbeusedtostreamgamecontentinviatheWeb.But,accessingaWWWobject’saudioClippropertywillallocateawholenewAudioClipresourceeachtimeitisinvoked,andsimilarlywithotherWWWresource-acquiringmethods.ThisresourcemustbefreedwiththeResources.UnloadAsset()methodonceitisnolongerrequired.

Discardingthereference(settingittonull)willnotautomaticallyfreetheresource,soitwillcontinuetoconsumememory.Ergo,weshouldonlyobtaintheAudioClipthroughtheaudioClippropertyoncetoobtaintheresourcereference,useonlythatreferencefromthatpointforward,andreleaseitwhenitisnolongerrequired.

ConsiderAudioModulefilesforbackgroundmusicAudioModulefiles,alsoknownasTrackerModules,areanexcellentmeansofsavingasignificantamountofspacewithoutanynoticeablequalityloss.SupportedfileextensionsinUnityare.it,.s3m,.xm,and.mod.UnlikethecommonPCMaudioformats,whicharereadasbitstreamsofdatathatmustbedecodedatruntimetogenerateaspecificsound,TrackerModulescontainlotsofsmall,high-qualityPCMsamplesandorganizetheentiretracksimilartoamusicsheet;definingwhen,where,howloud,withwhatpitch,andwithwhatspecialeffectseachsampleshouldbeplayedwith.Thiscanprovidesignificantsizesavings,whilemaintaininghigh-qualitysampling.So,iftheopportunityisavailabletoustomakeuseofTrackerModuleversionsofourmusicfiles,thenitisworthexploring.


https://unity3d.com/learn/tutorials/modules/beginner/5-pre-order-beta/audiomixer-and-audiomixer-groups

TexturefilesTheterms“Texture”and“Sprite”oftengetconfusedingamedevelopment,soit’sworthmakingthedistinctionthatinUnity3DaTextureissimplyanimagefile;abiglistofcolordatatellingtheinterpretingprogramwhatcoloreachpixeloftheimageshouldbe.WhereasaSpriteisthe2Dequivalentofamesh,whichjusthappenstobeasinglequadthatrendersflatagainstthecurrentcamera.TherearealsothingscalledSpriteSheets,whicharelargecollectionsofindividualimagescontainedwithinalargerTexturefile,commonlyusedtocontaintheanimationsofa2Dcharacter.ThesefilescanbesplitapartbyUnity’sSpriteBatchtool,toformindividualTexturesfortheanimationframes.

Let’strytoignorealloftheseconfusingnamingconventionoverlaps,andsimplytalkaboutTextures:theimagefileswe’reimportingintoourapplicationthatweregeneratedintoolssuchasAdobePhotoshoporGimp.Atruntime,thesefilesareloadedintomemory,pushedtotheGPU,andrenderedbytheShaderoverthetargetobjectduringagivenDrawCall.


CompressionformatsMuchlikeAudiofiles,UnityprovidesuswithavarietyofcompressiontechniquestostoreourTexturefilesmoreefficiently.WhenaTexturefileisimported,thereareseveralsettingsthatwecanmanipulate.ThefirstisTextureType.Thissettingdoesnotaffectthefileitself,butratherhowUnitywillinterpret,manipulate,andcompressitwithinthefinalexecutablewebuild.

WithmostoftheTextureTypeoptions,theonlythreecompressionoptionsUnityexposestousareCompressed,16-bit,andTrueColor.Alternatively,ifwesettheTextureTypetoAdvanced,thenweexposealargernumberofsettings.ThisgivesusfarmorecontrolovertheinterpretationoftheTexturefile.


Thiswillbeusefulinformationgoingforwardasthereareseveralperformance-enhancingopportunitiestofindthroughthisparticularviewofaTexturefile,whichwouldnotbevisibleordinarily.

ThenumberofcompressionformatsinAdvancedmodearesignificantlymorebroadandvaried,buttheoptionsremainidenticalbetweenUnity4andUnity5.Someformatsallowalphavalues,whereassomedonot,whichrestrictsourchoicesifwewishtomaintainalphatransparencyinourTexture(orafourthfloatdatavaluefromaTexturebeingusedasaHeightmap!).

SomeformatsalsocostdifferentlevelsofperformanceduringSceneinitializationtodecompressandpushintotheGPU,whichcanvaryenormouslydependingontheplatformwe’retargetingandthechosenformat.AdvancedmodeprovidestheAutomaticCompressedoption,whichtriestopickthebestoptionforthegivenplatformanddevice.Wecanusethisoptionifwe’renotcompletelysureaboutthebestformatforourgame,orwecanspendthetimetodosomeperformance-testingwithdifferentformatstoconfirmthebestchoice(s)forthetargetdevice.


NotethatthePreviewWindowatthebottomoftheInspectorViewprovidessomeusefulstatisticstohelpusdeterminehoweffectivelythecurrentlyselectedcompressionmethodisbehaving.


TextureperformanceenhancementsLet’sexploresomechangeswecanmaketoourTexturefiles,whichmighthelpimproveperformance,dependingonthesituationandthecontentofthefileswe’reimporting.Ineachcase,we’llexplorethechangesthatneedtobemade,andtheoveralleffecttheyhave,whetherthisresultsinapositiveornegativeimpactonmemoryorCPU,anincreaseordecreaseintheTexturequality,andunderwhatconditionswecanexpecttomakeuseofthesetechniques.

Also,becausetheUnity5PersonalEditionhasmademultiplefeaturesavailabletousthatwerepreviouslyonlyavailableintheProEdition,someusersmaynotbeawareofsomeadditionaltechniquesthatwecanapplytoourTexturestoimproveapplicationperformance.So,wewillalsocoversomeofthesetechniquestowardtheendofthissection.

ReduceTexturefilesizeThelargeragivenTexturefile,themoreGPUmemorybandwidthwillbeconsumedpushingtheTexturewhenitisneeded.Ifthetotalmemorypushedpersecondexceedsthegraphicscard’stotalmemorybandwidth,thenwewillhaveabottleneckastheGPUwaitsforallTexturestobeloadedbeforethenextrenderingpasscanbegin.SmallerTexturesarenaturallyeasiertopushthroughthepipelinethanlargerTextures,soweneedtofindagoodmiddlegroundbetweenhighqualityandperformance.

Acommontesttofindoutifwe’rebottleneckedinmemorybandwidthistosimplyreducetheresolutionofourgame’smostabundantandlargestTexturefilesandrelaunchtheScene.Iftheframeratesuddenlyimproves,thentheapplicationwasmostlikelyboundbytheTexturethroughput.Iftheframeratedoesnotimproveorimprovesverylittle,theneitherwestillhavesomememorybandwidthtomakeuseof,ortherearebottleneckselsewhereintherenderingpipelinepreventingusfromseeinganyfurtherimprovement.

UseMipMapswiselyTherewouldbenopointrenderingsmall,distantobjectssuchasrocksandtreeswithahigh-detailTextureifthere’snowaytheplayerwouldeverbeabletoseethatdetail,oriftheperformancelossistoogreattowarrantaminordetailincrease.MipMapswereinventedasawaytosolvethisproblem(aswellashelpingeliminatealiasingproblemsthatwereplaguingvideogamesataroundthesametime),bypregeneratinglower-resolutionalternativesofthesameTextureandkeepingthemtogetherinthesamememoryspace.Atruntime,theGPUpickstheappropriateMipMapoptionbasedonhowlargethesurfaceappearswithintheperspectiveview(essentiallybasedonthetexel-to-pixelratiowhentheobjectisrendered),andthenpicksanappropriatelyscaledMipMapoftheTexture.

ByenablingtheGenerateMipMapsoption,Unityautomaticallyhandlesthegenerationoftheselower-resolutioncopiesoftheTexture.Thesealternativesaregeneratedusinghigh-qualityresamplingandfilteringmethodswithintheEditor,ratherthanatruntime.

Thefollowingimageshowshowa1024x1024imagewillbeMipMappedintomultiple


lower-resolutionduplicates:

ThedownsidetoMipMappingisthatithasanegativeimpactonfilesizeandloadingtimeduetothelargercombinedTexturefilesthatarebeingautomaticallygenerated.ThefinalTexturefilewillbearound33percentlargerwhenMipMappingisenabled.TherearealsosomesituationswheretheMipMappingprocessisawasteofeffort,soweshouldexaminesomeofourTexturefilestoseeifMipMapsarebeingappliedwisely.

MipMappingisonlyusefulifwehaveTexturesthatneedtoberenderedatvaryingdistancesfromthecamera.IfwehaveTexturesthatalwaysrenderedatasimilardistancefromthemaincamera,suchthattheMipMappedalternativesareneverused,thenenablingMipMapsisjustwastingspace.Inthesecases,weshoulddisabletheMipMappingfeaturebydisablingtheGenerateMipMapsoptionfortheTexture.

IfonlyasingleMipMapalternativeisused,thenweshouldconsiderdisablingMipMappinganddownscalingtheresolutionoftheoriginalTexturefile.

AdditionalcandidatesfordisablingtheMipMappingfeatureare:

AlmostanyTexturefileusedina2DgameUserInterface(GUI)TexturesTexturesformeshes,Sprites,andParticleEffects,whichalwaysrendernearthecamera—examplesincludetheplayercharactersthemselves,anyobjectstheyholdorcarry,andanyParticleEffectswhichalwayscenteraroundtheplayer

ManageresolutiondownscalingexternallyUnityputsalotofeffortintomakingthingsaseasytouseaspossibleandprovidesuswiththeabilitytoplacetheprojectfilesfromexternaltoolstoourProjectworkspace,suchasPSDandTIFFfiles,whichareoftenlargeandsplitintomultiplelayeredimages.UnityautomaticallygeneratesaTexturefilefromthefile’scontentsfortherestoftheEngineto


makeuseof,whichcanbeveryconvenient,asweonlyneedtomaintainasinglecopyofthefilethroughSourceControlandtheUnitycopyisautomaticallyupdatedwhenanartistmakeschanges.

TheproblemisthatthealiasingintroducedbyUnity’sauto-Texturegenerationandcompressiontechniquesfromthesefilesmaynotbeasrobustandefficientasthetoolsweusetogeneratesuchfiles,suchasAdobePhotoshoporGimp.Unitymaybeintroducingartefactsthroughaliasing,andwemightfindourselvesgettingintothehabitofimportingimagefileswithahigherresolutionthannecessary,justtokeeptheintendedqualitylevel.But,hadwedownscaledtheimagethroughtheexternalapplicationfirst,wemightsuffermuchlessaliasing.Inthesecases,wemayhavebeenabletoachieveanacceptablelevelofqualitywithalowerresolution,whileconsuminglessoveralldiskandmemoryspace.

WecaneitheravoidusingPSDandTIFFfileswithinourUnityprojectasamatterofhabit(storingthemelsewhereandimportingthedownscaledversionintoUnity),orjustperformsomeoccasionaltestingtoensurewe’renotwastingfilesize,memory,andGPUmemorybandwidthusinglargerresolutionfilesthannecessary.Thiscostsussomeconvenienceinprojectfilemanagement,butcanprovidesomesignificantsavingsforsomeTextures,ifwe’rewillingtospendthetimecomparingthedifferentdownscaledversions.

AdjustAnisotropicFilteringlevelsAnisotropicFilteringisafeaturewhichimprovestheimagequalityofTextureswhentheyareviewedatveryshallow(oblique)angles.ThefollowingscreenshotshowstheclassicexampleofpaintedlinesonaroadwithandwithoutAnisotropicFilteringapplied.WithoutAnisotropicFiltering,thepaintedlinesappearblurryanddistortedthefurthertheyareawayfromthecamera,whereastheviewwithAnisotropicFilteringappliedmakestheselinesmorecrispandclear.

ThestrengthofAnisotropicFilteringappliedtotheTexturecanbehand-modifiedonaper-TexturebasiswiththeAnisoLevelsettingaswellasgloballyenabled/disabledusingtheAnisotropicTexturesoptionwithintheQualitySettingsscreen.

MuchlikeMipMapping,thiseffectcanbecostlyandsometimesunnecessary.IfthereareTexturesinourScenewherewearecertainwillneverbeviewedatanobliqueangle(such


asdistantbackgroundspritesandparticle-effectTextures),thenwecansafelydisableAnisotropicFilteringforthemtosavesomeruntimeoverhead.WecanalsoconsideradjustingthestrengthoftheAnisotropicFilteringeffectonaper-Texturebasistofindthemagicspotbetweenqualityandperformance.

ConsiderAtlasingAtlasingisthetechniqueofcombininglotsofsmaller,isolatedTexturestogetherintoasingle-largeTexturefileinordertominimizethenumberofMaterials,andhenceDrawCalls,weneedtoapplybyexploitingDynamicBatching.Conceptually,thistechniqueisverysimilartotheapproachesofminimizingMaterialusageyoulearnedinChapter3,TheBenefitsofBatching.

EachuniqueMaterialwouldrequireanadditionalDrawCall,buteachMaterialonlysupportsasingleprimaryTexture(thisexcludesNormalMaps,EmissionMaps,andothersecondaryTextures).BycombiningallTexturesintoasinglecolossalTexture,wecanminimizethenumberofDrawCallsusedtorenderobjectsthatsharethisTexture:

Thebenefitsareclear;reducingDrawCallsresultsinreducingtheCPUworkloadandimprovingtheframerateifourapplicationisCPU-bound(orsimplyfreesupcyclesforothertasks).Therewillbenolossofquality,andmemoryconsumptionwillbeessentially


identical.Allwe’redoingisexploitingUnity’sDynamicBatchingsystemtoreduceDrawCalls.NotethatAtlasingdoesnotresultinreducedmemorybandwidthconsumption,sincetheamountofdatabeingpushedisidentical.ItjusthappenstobebundledtogetherinonebiggerTexturefile.

TipAtlasingisonlyanoptionwhenallofthegivenTexturesrequirethesameShader.IfsomeoftheTexturesneeduniquegraphicaleffectsappliedthroughShaders,thentheymusteitherbeisolatedintotheirownMaterialsorAtlasedwithotherTextures,whichusethesameShader.

AtlasingisacommontacticappliedtoUserInterfaceelements,andingamesthatfeaturealotof2Dgraphics.AtlasingbecomespracticallyessentialwhendevelopingmobilegameswithUnity,sinceDrawCallstendtobethemostcommonbottleneckonthoseplatforms.But,wewouldnotwanttogeneratetheseatlasfilesmanually.LifewouldbemuchsimplerifwecouldcontinuetoeditourTexturesindividually,andautomatethetaskofcombiningthemintoalargerfile.

ManyGUI-relatedtoolsintheUnityAssetStoreprovideanautomatedTexture-atlasingfeature,therearesomestandaloneprogramsscatteredacrosstheInternet,whichcanhandlethiswork,andUnityitselfprovidedabuilt-inSpritePackertoolwiththenewUIsysteminversion4.6,whichcanbeeasilycustomizedtopackTexturesindifferentways.

ChecktheUnitydocumentationtodiscovermoreaboutthisusefulfeature,ifinterested:

http://docs.unity3d.com/Manual/SpritePacker.html

Eitherway,itisrecommendedtomakeuseofanexistingsolutionforatlasgenerationinordertoavoidreinventingthewheel.

TipNotethatTexturesmustbedefinedastheSpritetypeinordertoberecognizedandpackedbytheSpritePackertool.

Atlasingdoesnotneedtoapplyto2DgraphicsandUIelementseither.Wecanapplythistechniqueto3Dmeshesifwehappentobecreatingalotoflow-resolutionTextures.3DgamesthatfeaturesimpleTextureresolutions,oraflat-shadedlow-polyartstyle,areidealcandidatesforAtlasinginthisway.

However,becauseDynamicBatchingonlyaffectsnon-animatedmeshes(thatis,MeshRenderers,andnotSkinnedMeshRenderers),thereisnoreasontocombineTexturefilesforanimatedcharactersintoanatlas.Sincetheyareanimated,theGPUneedstomultiplyeachobject’sbonesbythetransformofthecurrentanimationstate.Thismeansauniquecalculationisneededforeachcharacter,andtheywillresultinanextraDrawCallregardlessofanyattemptswemaketohavethemshareMaterials.

Asaresult,combiningTexturesforanimatedcharactersshouldonlybedoneasamatterofconvenienceandspace-saving;forexample,inaflat-shadedlow-polyartstylegame,whereeverythinghappenstouseacommoncolorpalette,wecanmakesomesignificant


http://docs.unity3d.com/Manual/SpritePacker.html

spacesavingsbyusingasingleTexturefortheentiregameworld,objects,andcharacters.

ThedisadvantagesofAtlasingaremostlyintermsofdevelopmenttimeandworkflowcosts.ItrequiresalotofefforttooverhaulanexistingprojecttomakeuseofAtlasing,whichcanbealotofworkjusttofigureoutifitisworththeeffortornot.Inaddition,weneedtobewareofgeneratingatlasfiles,whicharetoolargeforthetargetplatform.

Somedevices(specificallymobiledevices)havearelativelylowlimitonthesizeofTexturesthatcanbepulledintothelowestmemorycacheoftheGPU.Iftheatlasistoolarge,thenitmustbebrokenupintosmallerTextures,tofitthetargetmemoryspace.IftherendererhappenstoneedTexturesfromdifferentpiecesoftheatlaseveryotherDrawCall,thennotonlywillweinflictalotofcachemisses,butalsowemightfindthatwechokethememorybandwidthasTexturesareconstantlypulledfromVRAMandthelower-levelcache.

WewouldprobablynothavethisproblemiftheatlaswasleftasindividualTextures.ThesameTextureswappingwouldoccur,butwillresultinmuchsmallerfilesbeingswappedatthecostofadditionalDrawCalls.OurbestoptionsatthisstagewouldbetolowertheatlasresolutionorgeneratemultiplesmalleratlasestohavebettercontroloverhowtheywillbeDynamicallyBatched.

So,Atlasingisclearlynotaperfectsolution.Ifitisnotclearwhetheritwouldresultinaperformancebenefit,thenweshouldbecarefulnottowastetoomuchtimeonimplementation.

Ingeneral,weshouldattempttoapplyAtlasingtomid-range/high-qualityMobilegamesrightfromthestartoftheproject,keepingwithintheTexturelimitforthetargetplatform,makingper-platformandper-deviceadjustmentsasnecessary.Ontheotherhand,thesimplestMobilegameswillmostlikelyfunctionwithoutneedinganyAtlasing.

Meanwhile,weshouldconsiderapplyingAtlasingtohigh-qualityDesktopgames,onlyifourDrawCallcountexceedsreasonablehardwareexpectations,sincewewillwantmanyofourTexturestomaintainhighresolutionsformaximumquality.Low-qualityDesktopgamescanprobablyaffordtoavoidAtlasing,sinceDrawCallsareunlikelytobethebiggestbottleneck.

Ofcourse,nomatterwhattheproductis,ifwe’reeverCPU-boundbyDrawCallsandwe’vealreadyexhaustedmanyofthealternativetechniques,thenAtlasingwouldbethenextbesttechniquetoimplement,asitcanresultinsomeimpressiveDrawCallsavingswhenusedproperly.

Adjustcompressionratesfornon-squareTexturesItisnotrecommendtoimportnon-squareand/ornon-power-of-2Texturesintoourapplication,becauseGPUsoftenrequirethepushedTexturetobesquare,andapower-of-2sizeresultsinunnecessaryworkloaddealingwithmalformedTexturesizes.UnitywillautomaticallyadjusttheTextureandaddadditionalemptyspaceinordertofittheformfactorthattheGPUexpects,whichwillresultinadditionalmemorybandwidthcosts,pushingwhatisessentiallyuselessdatatotheGPU.


So,thefirstrecommendationistoavoidnon-squareand/ornon-power-of-2Texturesaltogether.Iftheimagecanbeplacedwithinasquare,power-of-2Texture,anddoesnotresultintoomuchqualitydegradationduetosqueezing/stretching,thenweshouldapplythosechangesjusttokeeptheCPUandGPUhappy.

However,ifwestillwanttousenon-squareTextures,thereisatrickwecanapplytoachievehigherqualitywithoutcostinganyadditionalspace.Sincethewaynon-squareTexturesarepackedbycompressionalgorithms,wecanoftenincreasethebit-rate(andhencequality)ofthechosencompressionformatforanon-squareTextureandstillachieveanidenticalimportedfilesizeandruntimeoverheadcost.ThisonlycostsusthetimeittakestofindtheseTexturesandtestavarietyofcompressionalgorithmstofindthehighestqualityversion.

SparseTexturesSparseTextures,alsoknownasMega-TexturesorTiled-Textures,provideawayofeffectivelystreamingTexturedatafromdiskatruntime.Relativelyspeaking,iftheCPUperformsoperationsintheorderofseconds,thenthediskwilloperateintheorderofdays.Socommonadviceisthatharddiskaccessduringgameplayshouldbeavoidedatallcosts,sinceanysuchtechniquerisksinflictingmorediskaccessthanavailable,causingourapplicationtogrindtoahalt.

But,SparseTexturingbreaksthisruleandofferssomeinterestingperformancesavingtechniques.TheaimofSparseTexturingistocombinemanyTexturesintoanenormousTexturefile,whichwouldbefartoolargetoloadintographicsmemoryasasingleTexturefile.ThisissimilartotheconceptofAtlasing,exceptthefilecontainingtheTexturesisincrediblylarge(forexample,32,768x32,768resolution)andcontainsconsiderabledetail(32bitsperpixel).Theideaistosavelargeamountsofruntimememoryandmemorybandwidthbyhand-pickingsmallsubsectionsoftheTexturedynamically,andpullthemfromthediskjustbeforetheyareneededinthegame.Themaincostofthistechniqueisthefilesizerequirement(theexampleresolutionfilewouldconsume4GBofdiskspace!).OthercostsforthistechniquecanbeovercomewithagreatdealofScenepreparationwork.

ThegameworldneedstobecreatedinsuchawaythatitminimizestheamountofTextureswappingtakingplace.Inordertoavoidjarring,“texturepopping”problems,Texturesubsectionsmustbepulledfromadiskwithjustenoughtimetosparethattheplayerdoesnotnotice.ThistakesplaceinthedesignoftheTexturefileitself,bykeepingcommonelementsforagivenSceneinthesamegeneralareaoftheTexture,andthedesignoftheScene,bytriggeringnewTexturesubsectionloadingatkeymomentsduringgameplay.Ifitishandledwithgreatcareandattentiontodetail,thenSparseTexturingcanresultinsomeimpressiveScenequalityandequallyimpressivememorysavings.

SparseTexturingwaspreviouslyaProEdition-onlyfeatureinUnity4,butwasmadeavailablewiththePersonalEditionofUnity5.SparseTexturingrequiresspecializedhardwareandplatformsupport,however,sothisoptionisnotavailabletoallgames.Itisahighlyspecializedanduncommontechniquewithinthegamingindustry,whichisreflectedinthelackofdocumentation.TheUnitydocumentationdoesnotprovidemuch


informationonSparseTexturing,butitdoesprovideanexampleSceneshowingtheeffectatwork.ItcanbefoundatthefollowingURL:http://docs.unity3d.com/Manual/SparseTextures.html.

ForUnitydeveloperswhoconsiderthemselvesadvancedenoughtofigureitoutontheirown,itmightbeworthtakingthetimetoperformsomeresearchtoseeifSparseTexturingisrightfortheirprojectandwhethertheyarewillingtomaketheappropriateScenechangesnecessarytogaintheperformancebenefitsthatthisfeaturepresents.

ProceduralMaterialsAlsoknownasSubstances,ProceduralMaterialsareameansofprocedurallygeneratingTexturesatruntimebycombiningsmall,high-qualityTexturesampleswithcustommathematicalformulas.ThegoalofProceduralMaterialsistogreatlyminimizetheapplicationfootprintatthecostofadditionalruntimememoryandCPUprocessingduringinitialization.LikeSparseTexturing,thisfeaturewaspreviouslyonlyavailableintheProEditionofUnity4andisnowavailableinUnity5.

ThisgivesmanyusersanopportunitytoviewtheirMaterialsfromadifferentperspective,asProceduralMaterialsareamoremodernapproachtotheirgames.Texturefilesareoftenthebiggestdiskspaceconsumerofagameproject,andit’sfairlycommonknowledgethatdownloadtimeshaveatremendousnegativeimpactonthecompleteddownloadrateandjustgettingpeopletotryourgame(evenifit’sfree!).ProceduralMaterialsofferustheabilitytosacrificesomeinitializationandruntimeprocessingpowerformuchfasterdownloads.ThisisveryimportantforanupcominggenerationofMobilegamesthataretryingtocompeteviagraphicalfidelity.

TheUnitydocumentationonProceduralMaterialsisfarmoreextensivethanforSparseTexturing,soitisrecommendedtoworkthroughthedocumentationforaclearerpictureofhowSubstancesworkandhowtheycanprovideuswithperformancebenefits:

http://docs.unity3d.com/Manual/ProceduralMaterials.html


http://docs.unity3d.com/Manual/SparseTextures.html

http://docs.unity3d.com/Manual/ProceduralMaterials.html

MeshandanimationfilesFinally,let’scovermeshandanimationfiles.Thesefiletypesareessentiallylargearraysofvertexandskinnedbonedata,andthereareavarietyoftechniqueswecanapplytominimizefilesize,whilekeepingasimilar,ifnotidentical,appearance.Therearealsosometimeswaystolowerthecostofrenderinglargegroupsoftheseobjectsthroughbatchingtechniques.Let’slookintoaseriesofperformance-enhancingtechniqueswecanapplytosuchfiles.


ReducingpolygoncountThisisthemostobviouswaytogainperformance,butweshouldneverdisregardit.Infact,sincewecannotbatchobjectsusingSkinnedMeshRenderers,it’soneoftheonlygoodwaysofreducingCPUandGPUruntimeoverheadforanimatedobjects.

Reducingthepolygoncountissimple,straightforward,andprovidesbothCPUandmemorycostsavingsforthetimerequiredforartiststocleanupthemesh.Muchofanobject’sdetailisprovidedalmostentirelybydetailedTexturingandcomplexShadinginthisdayandage,sowecanoftengetawaywithstrippingawayalotofverticesonmodernmeshesandmostuserswouldbeunabletotellthedifference.

TweakingMeshCompressionUnityoffersfourdifferentMeshCompressionsettingsforimportedmeshfiles:Off,Low,Medium,andHigh.IncreasingthissettingwillstripawaymoreandmorepartsofthemeshthatUnitythinksaren’tneededinordertomakeagoodestimateofthesamemeshwiththeaimofreducingoverallfilesize.Thisisessentiallyanautomatedversionofhavinganartistmanuallyreducingthepolygoncount.

However,automatedmeshoptimizationisaverydifficultproblemtosolvemathematicallyandeventhebestalgorithmstendtogeneratealotofartefactsandirregularities.DifferentlevelsofMeshCompressioncanbeattemptedasaquicksolutiontoreducingpolygoncount,butitwillprobablynevercomparetohavinganartistmakeappropriatepolycountreductionsbyhand.

TipThese3Dtoolsoftenprovidetheirownbuilt-inwaysofautomatedmeshoptimization,andshouldbetestedasameansofoptimizingthemeshbeforeimportingthemintoUnity.

UseRead-WriteEnabledappropriatelyTheRead-WriteEnabledflagallowschangestobemadetothemeshatruntimeeitherviaScriptingorautomaticallybyUnityduringruntime.Internally,thismeansitwillkeeptheoriginalmeshdatainmemoryuntilwewanttoduplicateitandmakechangesdynamically.DisablingthisoptionwillallowUnitytodiscardtheoriginalmeshdatafrommemoryonceithasdeterminedthefinalmeshtouse.

Ifweonlyeveruseauniformlyscaledversionofameshthroughouttheentiregame,thendisablingthisoptionwillsaveruntimememorysincewewillnolongerneedtheoriginalmeshdatatomakefurtherrescaledduplicatesofthemesh(incidentally,thisishowUnityorganizesobjectsbyscalefactorwhenitcomestoDynamicBatching).Unitycan,therefore,discardthisunwanteddataearlysincewewillneverneeditagainuntilthenexttimetheapplicationislaunched.

However,ifthemeshoftenreappearsatruntimewithdifferentscales,thenUnityneedstokeepthisdatainmemorysothatitcanrecalculateanewmeshmorequickly,andsotheRead-WriteEnabledflagshouldbeenabled.DisablingitwillrequireUnitytonotonlyreloadthemeshdata,butalsomaketherescaledduplicateatthesametime,causinga


potentialperformancehiccup.

Unitytriestodetectthecorrectbehaviorforthissettingatinitializationtime,butwhenmeshesareinstantiatedandscaledinadynamicfashionatruntime,thenwemustforcetheissuebyenablingthissetting.Thiswillimproveinstantiationspeedoftheobjects,butcostsomememoryoverheadsincetheoriginalmeshdataiskeptarounduntilit’sneeded.

TipNotethatthisalsoapplieswhenusingtheGenerateCollidersoption.


Import/calculateonlywhat’sneededThisappearstobeanotherobvioussuggestion,butmeshesdonotonlycontainvertexpositionaldata.TherecouldbeunnecessaryNormalsandTangentsinourmeshthattheShaderswon’tneed,orwecouldbeautogeneratingNormalandTangentcoordinatesthatwewon’tuse,particularlywhentheSmoothingAngleisverylow.Inthesecases,eachvertexrequiresmultiplenormalvectorstocreatethefaceted,flat-shadingstylethatresultsfromit.

Double-checkyourmeshimportsettingsandexaminetheresultantfilesizeandin-gameappearance,bytinkeringwiththeimportsettingstoseeifyoucanmakeanysavingsbystrippingawayunwantedandunnecessarydata.


ConsiderbakedanimationsThiswilldependonthe3Driggingandanimationtoolthatweareusing,andtheoverallvertexcountofourmesh;insomecasesbakinganimationscanresultinmuchsmallerfilesizesandmemoryoverheadthanblended/skinnedanimations.Bakedanimationsworkbystoringakeyframedpositionforeachvertexforeachframethatwassampled,andifthemesh’spolygoncountislowenough,thenwemayseesomesignificantsavingsthroughthissimplechange.

Inaddition,howoftenthebakedsampleistakencanusuallybecustomizedbytheexportingapplication.Differentsampleratesshouldbetestedtofindagoodvaluewherethekeymomentsoftheanimationstillshine-throughwhatisessentiallyasimplifiedestimate.


LetUnityoptimizemeshesTheOptimizeMeshesoptioninamesh’simportsettingswillreorganizethevertexdataforquickerreadability,andsometimesregeneratethelow-levelrenderingstyle(downtothelevelofpointsversustrisversusstrips)tooptimizetherenderingspeedofthemesh.Simplyput,thisoptionshouldbeenabledinalmostallcases,asthereisverylittlereasontonotletUnitymaketheseadjustmentsforus,unlesswe’vedonesomeprofilingandwe’repositivethatit’ssomehowgeneratingbottlenecks.

Ifwe’regeneratingmeshesprocedurally,thenwecantellUnitytoinvokethisprocessusingtheOptimize()methodonaMeshFilterComponent.Thisprocesscantakesometime,soitshouldbeusedduringinitializationorotherconvenientstoppingpoint.


CombinemeshesCombiningmeshesintoalarge,singlemeshcanbeconvenienttoreduceDrawCallsifthemeshesaretoolargeforDynamicBatchinganddon’tplaywellwithotherStaticallyBatchedgroups.ThisisessentiallytheequivalentofStaticBatching,butperformedmanually,sosometimesit’swastedeffortifStaticBatchingcouldtakecareoftheprocessforus.

However,ifwe’reusingtheUnity4FreeEditionwhereStaticBatchingisnotavailabletousorwewishthemeshtomovearoundtheScene,thenthisisagoodoptiontominimizeourDrawCalls.BewarethatitcomeswiththesameriskasStaticBatching.IfanysinglevertexofthemeshisvisibleintheScene,thentheentireobjectwillberenderedtogetherasonewhole.Thiscanleadtoalotofwastedprocessingifthemeshisonlypartiallyvisiblemostofthetime.

ThistechniquealsocomeswiththedrawbackthatitgeneratesawholenewmeshassetfilethatwemustdepositintoourScene,whichmeansanychangeswemaketotheoriginalmesheswillnotbereflectedinthecombinedone.Thisresultsinalotoftediousworkflowefforteverytimechangesneedtobemade,soifStaticBatchingisanoption,itshouldbeusedinstead.

Thereareseveraltoolsavailableonline,whichcancombinemeshfilestogetherforusinUnity.TheyareonlyanAssetStoresearch,orGooglesearchaway.


SummaryTherearemanydifferentopportunitiesthatwecanexploretoachieveperformancegainsforourapplicationjustbytinkeringwithourimportedassets.Or,fromanotherperspective,thereareplentyofwaystoruinourapplication’sperformancethroughassetmismanagement.

Almosteverysingleopportunityisatrade-offbetweenoneperformancemetricorworkflowtaskandanother.So,wemustremainvigilantandonlypicktherighttechniquesintherightprojectsfortherightreasons.Theworstthingwecandoisimplementsuchchangeswithoutunderstandingtheimpact.It’sexcitingtostumbleonsomebigperformanceenhancingsuggestionoutinthebig,wideworld,butunlessweunderstandhowitworks,andtheresultingcosts,wecaninvitefurtherperformanceproblemsandbottleneckswithoutrealizingit,costingusmoretimeandeffortdowntheroad.

Thisconcludesourexplorationofimprovingperformancethroughartassetmanipulation.Inthenextchapter,wewillbeinvestigatingtheBox2DandPhysXphysicssolutionsprovidedbyUnity,thechangeswecanmaketoourscriptcode,Scene,andprojecttomakethesecomponentsprocessourdatafaster;andbehaviortoavoidthatmightcausethemtostumble.


Chapter5.FasterPhysicsEachoftheperformance-enhancingsuggestionswe’veexploredthusfarhavebeenprimarilycenteredonreducingsystemrequirementsandavoidingframerateissues.Butatitsmostfundamentallevel,seekingpeakperformancemeansimprovingtheuserexperience.Thisisbecauseeveryframeratehiccup,everycrash,andeverysystemrequirementthatistoocostlyforagivenmarketultimatelydetractsfromthequalityoftheproduct,andleavesuswonderingwhetherweshouldhavetriedhardertotweaksettingsandfixmorebugsbeforerelease.

TherearecertainlyopportunitiestomanipulatePhysicsEnginebehaviorthatimprovealloftheaforementionedissues,butPhysicsEnginesalsofallintoauniquecategoryofhavingadirectimpactongameplayquality.Ifimportantgameplaycollisioneventsgetmissed(suchastheplayerfallingthroughthefloor),orthegamefreezeswhileitcalculatesacomplexsituation,thenthesehaveasignificantimpactongameplayquality.Thisoftenresultsinpullingtheplayeroutoftheexperience,andit’sacoin-tosswhethertheuserfindsitinconvenient,obnoxious,orhilarious.UnlessourgameisspecificallytargetingtheComedyPhysicsgenre(which,incidentally,hasgrowninpopularityinrecentyearswithgameslikeQWOPandGoatSimulator),thesearesituationsweshouldstrivetoavoid.

Forsomegames,thePhysicsEngineisusedtohandleasignificantnumberoftasksduringgameplay,fromcollisiondetectionwithotherobjectsandinvisibletriggerboxestoraycastingandgatheringalistofobjectsinagivenregion.Forexample,itisessentialinplatformerandactiongamestotunethephysicsproperly;howtheplayercharacterreactstoinputandhowtheworldreactstotheplayercharactercanbetwoofthemostimportantaspectsofwhatmakesthegamefeelresponsiveandfun.Othergamesmayonlyusephysicsforsimplegameplayevents,interestingspectacles,andothereye-candy,butthemoreefficientlythePhysicsSystemisused,themoreofaspectaclethatcanbecreated.

Therefore,inthischapter,wewillnotonlycoverwaystoreduceCPUspikes,overhead,andmemoryconsumptionthroughUnity’sPhysicsSystem,butalsoincludewaystoalterphysicsbehaviorwiththeaimofimprovinggameplayquality.Inaddition,becauseUnity’sPhysicsSystemsarea“black-box”,inthatwecan’tdomuchinternaldebugging,itcanbeverytrickytofigureoutexactlywhen,where,andwhycertainphysicsglitchesareplaguingourproject,andwhatweshoulddotopreventthem.Asaresult,themethodscoveredinthischapterwillincludeseveralsuggestionsonhowtoreduceinstabilityandproblematicphysicssituations.


PhysicsEngineinternalsUnitytechnicallyfeaturestwodifferentPhysicsEngines:NvidiaPhysXfor3DphysicsandtheOpenSourceprojectBox2Dfor2Dphysics.However,theirimplementationishighlyabstracted,andfromtheperspectiveoftheUnityAPI,bothenginesoperateinanearlyidenticalfashion.

Ineithercase,themoreweunderstandaboutUnity’sPhysicsSystem,themoresensewecanmakeofpossibleperformanceenhancements.So,firstwe’llcoversometheoryaboutUnity’sPhysicsEngines.


PhysicsandtimePhysicsEnginesgenerallyoperateundertheassumptionthattimeisiteratinginfixedvaluesoftime,andbothofUnity’sPhysicsEnginesoperateinthismanner.ThePhysicsEnginewillonlycalculateusingveryspecificvaluesoftime,independentofhowmuchtimeittooktorenderthepreviousframe.ThisisknownastheFixedUpdateTimestep,anditissettoavalueof20millisecondsbydefault,or50updatespersecond.

NoteItcanbeverydifficulttogenerateconsistentresultsforcollisionsandforcesbetweentwodifferentcomputersifaPhysicsEngineusesavariabletimestep.Suchenginestendtogenerateinconsistentresultsbetweenmultiplayerclients,andduringrecordedreplays.

Iftoomuchtimehaspassedbetweenframes(alowframerate),thenthePhysicsSystemmayupdatemultipletimesbeforerenderingbeginsagain.Conversely,ifnotenoughtimehaspassedsincethepreviousrender(ahighframerate),thenthephysicsupdatemaybeskippeduntilafterthenextrendercall.

TheFixedUpdate()methodrepresentsthemomentwhenthePhysicsSystemperformssimulationtimestepupdates.ItisoneofseveralimportantUnitycallbackswecandefineinaMonoBehaviourscriptand,ingeneral,FixedUpdate()isusedtodefineframe-rate-independentbehavior.Thiscallbackisusuallyusedforcalculationssuchasartificialintelligence(whicharealsoeasiertoworkwithifweassumeafixedupdatefrequency),butthisisalsowhereweshouldmodifyRigidbodyobjectsduringgameplay.

ThefollowingdiagramshowsanimportantsnippetoftheUnityOrderofExecutiondiagram:

Note


ThefullOrderofExecutiondiagramcanbefoundat:http://docs.unity3d.com/Manual/ExecutionOrder.html.

TheFixedUpdateloopAswecansee,FixedUpdate()isinvokedjustpriortothePhysicsSystemperformingitsownupdateandthetwoareinextricablylinked.TheprocessbeginswithdeterminingwhetherenoughtimehaspassedtobeginthenextFixedUpdate.TheoutcomewillvarydependingonhowmuchtimehaspassedsincethelastFixedUpdate.

Ifenoughtimehaspassed,thentheFixedUpdate()methodisinvokedglobally,andanyCoroutinestiedtoFixedUpdates(thatis,yieldstoWaitForFixedUpdate())arehandledimmediatelyafterward,followedbyphysicsupdatesandtrigger/collidercallbacks.

Iflessthan20mshasgonebysincethelastFixedUpdate,thenthecurrentFixedUpdateisskipped.Atthispoint,input,gameplaylogic,andrenderingmusttakeplaceandcompletebeforeUnityperformsthenextFixedUpdatecheck,andsoon,asthisprocessrepeatsitselfduringruntime.ThisdesigngivesbothFixedUpdatesandthePhysicsSystemahigherpriorityoverrendering,butforcesthephysicssimulationintoafixedframerate.

NoteInordertoensuresmoothmotionduringframeswherephysicsupdatesareskipped,somePhysicsEngines(includingUnity’s)interpolatethestatebetweenthepreviousstateandthecurrentstatebasedonhowmuchtimeremainsuntilthenextFixedUpdate.

Thisensuresthat,graphically,objectsappeartomovesmoothlyduringhighframerates,eventhoughtheyareonlybeingupdatedevery20ms.

MaximumAllowedTimestepItisimportanttonotethatifalotoftimehaspassedsincethelastFixedUpdate(forexample,thegamefrozemomentarily),thenphysicsandFixedUpdateswillcontinuetobecalculateduntiltheyhave“caughtup”withthecurrenttime.Forexample,ifthepreviousframetook100mstorender(forexample,asuddenperformancespikedroppingthegameto10FPS),thenthePhysicsSystemwillneedtoupdatefivetimes.TheFixedUpdate()methodwillthereforebecalledfivetimesbeforeUpdate()canbecalledagainduetothedefaultFixedUpdateTimestepof20ms.If,forwhateverreason,theprocessingofthesefiveupdatesconsumes20msormore,thenitwillneedtoinvokeasixthupdate!

Consequently,it’spossibleduringmomentsofheavyphysicsactivitythatthePhysicsEnginecantakemorethan20mstocompleteaphysicsupdate,whichitselftakesanother20ms,andsoon,suchthatitisneverabletoescapeandallowanotherframetorender(thisisoftenknownasthe“spiralofdeath”).TopreventthePhysicsEnginefromlockingupourgameduringthesemoments,thereisamaximumamountoftimethatthePhysicsEngineisallowedtoprocessbetweeneachrender.ThisthresholdiscalledtheMaximumAllowedTimestep,andifthecurrentFixedUpdateistakinglongertoprocessthanthisvalue,thenitwillsimplystopandforgofurtherprocessinguntiltheendofthenextrender.


http://docs.unity3d.com/Manual/ExecutionOrder.html

Thisdesignallowstherenderingsystemtoatleastrenderthecurrentstate,andallowforgameplaylogictomakesomedecisionsduringraremomentswherephysicscalculationhasgoneballistic(punintended).

PhysicsupdatesandruntimechangesWhenthePhysicsSystemprocessesthenexttimestep,itmustmoveanyactiveRigidbodyobjects,detectanycollision,andinvokethecollisioncallbacksonthecorrespondingobjects.It’sforexactlythisreasonthattheUnitydocumentationexplicitlywarnsustoonlymakechangestoRigidbodyobjectsinFixedUpdate()andotherphysicscallbacks.Thesemethodsaretightly-coupledwiththeupdatefrequencyofthePhysicsEngine,asopposedtootherpartsofthegameloop,suchasUpdate().

ThismeansthatcallbackssuchasOnTriggerEnter()aresafeplacestomakeRigidbodychanges,whilemethodssuchasUpdate()andtime-basedCoroutinesarenot.NotfollowingthisadvicecouldcauseunexpectedphysicsbehaviorasmultiplechangesaremadetothesameobjectbeforethePhysicsSystemisgivenachancetocatchandprocessallofthem,resultinginsomeespeciallyconfusinggameplaybugs.

ItlogicallyfollowsthatthemoretimewespendinanygivenFixedUpdateiteration,thelesstimewehaveforthenextgameplayandrenderingpass.Mostofthetimethisresultsinminor,unnoticeablebackgroundprocessingtasks,asthePhysicsEnginebarelyhasanyworktodo,andFixedUpdate()callbackshavealotoftimetocompletetheirwork.

But,insomegames,thePhysicsEnginecouldbeperformingalotofcalculationsduringeachandeveryFixedUpdate.Thiskindofbottleneckinginphysicsprocessingtimewillaffectourrenderingframerate,causingittoplummetasthePhysicsSystemistaskedwithgreaterandgreaterworkloads.Essentially,therenderingsystemwillproceedasnormal,butwheneverit’stimeforaFixedUpdate,thenitwouldbegivenverylittletimetogeneratethecurrentdisplay,causingasuddenstutter.ThisisinadditiontothevisualeffectofthePhysicsSystemstoppingearlybecauseithittheMaximumAllowedTimestep.Allofthistogetherwillgenerateapooruserexperience.

Hence,tokeepasmoothandconsistentframerate,thegoalistofreeupasmuchtimeaswecanforrenderingbyminimizingtheamountoftimethePhysicsSystemtakestoprocessanygiventimestep.Thisappliesinboththebest-casescenario(nothingmoving)andworst-casescenario(everythingsmashingintoeverythingelseatonce).Thereareanumberoftime-relatedfeaturesandvalueswecantweakwithinthePhysicsSystemtoavoidperformancepitfallssuchasthese.


StaticandDynamicCollidersThereisarathersignificantnamespaceconflictwiththeterm“static”inUnity.WehavealreadycoveredstaticGameObjects,thevariousStaticsubflags,theStaticBatchingfeature,andthenthere’stheuseofstaticvariablesandclassesinC#.Meanwhile,Unity’soriginalphysicsimplementationfor3DobjectshasitsownconceptofStaticColliders.Later,when2Dphysicswasimplemented,itkeptthesameconceptofStaticColliderstokeepthingsconsistentbetweenthem.

So,withthisinminditisveryimportanttorememberthatStaticCollidersarenotobjectswiththeStaticflagenabled,sincethoseflagsareaUnityEngineconcept.StaticCollidersaresimplycollidersthatdonothaveanattachedRigidbody.Meanwhile,colliderswithanattachedRigidbodyarecalledDynamicColliders.

ThePhysicsSystemcombinesStaticCollidersintoadifferent,optimizeddatastructure,whichhelpstosimplifyfutureprocessingtasks.Theseobjectswillnotreacttoimpulsesappliedbyobjectscollidingwiththem,butwillpreventotherobjectsfrommovingthroughthem.ThismakesStaticCollidersidealforworldbarriersandotherobstaclesthatmustnotmove.


CollisiondetectionTherearethreesettingsforcollisiondetectioninUnity:Discrete,Continuous,andContinuousDynamic.TheDiscretesettingeffectivelyteleportsobjectsasmalldistanceeverytimestepbasedontheirvelocityandhowmuchtimehaspassed.Afteralltheobjectshavebeenmoved,itthenperformsabounding-volumecheckforanyoverlaps,treatsthemascollisions,andresolvesthembasedontheirphysicalpropertiesandhowtheyoverlap.Thismethodriskscollisionsbeingmissedifsmallobjectsaremovingtooquickly.

Bothofthecontinuouscollisiondetectionmethodsworkbyinterpolatingobjectsfromtheirstartingandendingpositionsforthecurrenttimestepandcheckingforanycollisionsalongtheway.Thisreducestheriskofmissedcollisionsandgeneratesamoreaccuratesimulation,attheexpenseofsignificantlygreaterCPUoverheadcomparedtotheDiscretesetting.

TheContinuoussettingonlyenablescontinuouscollisiondetectionbetweenthegivencolliderandStaticColliders(recallthatStaticCollidersaresimplycolliderswithoutanyattachedRigidbody).ThesameobjectswillbesimultaneouslytreatedasusingtheDiscretesettingwhenitcomestocollisiondetectionwithotherdynamicobjects(thosewithanattachedRigidbody).Meanwhile,theContinuousDynamicsettingisslightlydifferentasitenablesthesamecontinuouscollisiondetection,butdoessobetweenthegivencolliderandallothercolliders,bothStaticandDynamic.

Thefollowingscreenshotshowshowthediscreteandcontinuouscollisiondetectionmethodswouldworkforapairofsmall,fast-movingobjects:

Thisisanextremeexampleforthesakeofillustration.Inthediscretecase,wecanseethattheobjectsare“teleporting”adistancearoundfourtimestheirownsizeinasingletimestep,whichwouldtypicallyonlyhappenwithverysmallobjectswithveryhighvelocities,andishenceveryrareifourgameisrunningoptimally.Inmostcases,thedistancestheobjectstravelinasingle20mstimesteparemuchsmallerrelativetothesizeoftheobject,andsothecollisioniseasilydetected.


CollidertypesTherearefivedifferenttypesof3DCollidersinUnity5.Inorderofthelowestperformancecosttothegreatest,theyare:Sphere,Capsule,Cylinder,Box,andMeshColliders.Thefirstfourcollidertypesareconsideredprimitivesandmaintainconsistentshapes,althoughtheycangenerallybescaledindifferentdirectionstomeetcertainneeds.MeanwhileMeshColliderscanbecustomizedtoaparticularshapedependingontheassignedmesh.

NoteTherearealsothreemain2DColliders:Circle,Box,andPolygon,whicharefunctionallysimilartoSphere,Box,andMeshCollidersin3D.Allofthefollowinginformationisessentiallytransferabletotheequivalent2Dshape.

Inaddition,therearetwovarietiesofMeshCollider:convexandconcave.Thedifferenceisthataconcaveshapefeaturesatleastoneinternalangle(ananglebetweentwoedgesinsidetheshape)ofgreaterthan180degrees.Toillustratethis,thefollowingscreenshotshowsthedistinguishingdifferencebetweenconvexandconcaveshapes:

TipAneasywaytorememberthedifferencebetweenconvexandconcaveshapesisthataconcaveshapehasatleastone“cave”withinit.

BothMeshCollidertypesusethesameComponent(aMeshCollider!),andwhichtypeofMeshCollidergetsgeneratedistoggledusingtheConvexcheckbox.EnablingthisoptionwillallowtheobjecttocollidewithotherMeshCollidersmarkedasConvex,aswellasprimitiveshapes(Spheres,Boxes,andsoon.).Inaddition,iftheConvexcheckboxisenabledforaMeshColliderwithaconcaveshape,thenthePhysicsSystemwillautomaticallysimplifytheconcaveshape,generatingacolliderwiththenearestconvexshapeitcan.Intheprecedingexample,ifweimporttheconcavemeshontheright,and


enabletheConvexcheckbox,itwouldgenerateacollidershapeclosertotheconvexmeshontheleft.

Ineithercase,thePhysicsSystemwillattempttogenerateacolliderthatmatchestheshapeoftheattachedmesh,withanupperlimitof255vertices.Ifthetargetmeshhasmoreverticesthanthis,thenitwillthrowanerrorduringgenerationofthemesh.NotethatConcaveMeshColliderswithattachedRigidbodyobjectsarenotsupportedinUnity5.ConcaveshapescanonlybeusedasStaticColliders(forexample,acollidableobjectintheworldthatdoesn’tmove),orTriggerVolumes(forexample,anoddly-shapedpoolofacid).


TheCollisionMatrixThePhysicsSystemfeaturesaCollisionMatrixthatdefineswhichobjectsareallowedtocollidewithwhichotherobjects.ObjectsthatdonotfitthismatrixareautomaticallyignoredbythePhysicsSystemwhenthetimecomestoresolveboundingvolumeoverlapsandcollisions.Thissavesonphysicsprocessingduringcollisiondetectionstages,andalsoallowstheobjectstomovethroughoneanotherwithoutanycollisionstakingplace.

TheCollisionMatrixsystemworksthroughUnity’sLayersystem.Thematrixrepresentseverypossiblelayer-to-layercombinationthatmightbepossible,andenablingacheckboxmeansthatcollidersinbothofthoselayerswillbecheckedduringthecollisiondetectionphase.Notethatthere’snowaytoallowonlyoneofthetwoobjectstorespondtothecollision.Ifonelayercancollidewithanother,thentheymustbothrespondtothecollision(withtheexceptionofStaticColliders,whicharen’tallowedtorespondtocollisions).

TheCollisionMatrixcanbeaccessedthroughEdit|ProjectSettings|Physics(orPhysics2D)|LayerCollisionMatrix.

Notethatwearelimitedtoonly32totallayersforourentireproject(sincethePhysicsSystemusesa32-bitbitmasktodetermineinter-layercollisionopportunities),sowemustorganizeourobjectsintosensiblelayersthatwillextendthroughouttheentirelifetimeoftheproject.If,forwhateverreason,32layersarenotenoughforourproject,thenwemightneedtofindcunningwaystoreuselayers,orremovelayersthataren’tnecessary.


RigidbodyactiveandsleepingstatesEverymodernPhysicsEnginesharesacommonoptimizationtechniquewherebyobjectsthathavecometoresthavetheirinternalstatechangedfromanactivestatetoasleepingstate.Whilesleeping,little-to-noprocessortimewillbespentupdatingtheobjectuntilithasbeenawokenbysomeexternalforceorevent.

Thevalueofmeasurementthatisusedtodetermine“rest”tendstovarybetweenengines;itcouldbecalculatedusinglinearandrotationalspeed,kineticenergy,momentum,orsomeotherphysicalpropertyoftheRigidbody.Inanycase,ifanobjecthasnotexceededsomethresholdvalueinashorttime,thenthePhysicsEnginewillassumetheobjectwillnolongerneedtomoveagainuntilithasundergoneanewcollision,oranewforcehasbeenappliedtoit.Untilthen,thesleepingobjectwillmaintainitscurrentposition.

Inessence,thePhysicsEngineisautomaticallycullingsomeprocessingtasksforobjectsthathaveasmallamountofkineticenergy.Butthisdoesnotremoveitentirelyfromthesimulation.IfamovingRigidbodyapproachesthesleepingobject,thenitmuststillperformcheckstoseewhethernearbyobjectshavecollidedwithit,whichwouldreawakenthesleepingobject,reintroducingittothesimulationforprocessing.ThethresholdvalueforthesleepingstatecanbemodifiedunderEdit|ProjectSettings|Physics|SleepThreshold.WecanalsogetacountofthetotalnumberofactiveRigidbodyobjectsfromthePhysicsareaoftheProfiler.


RayandobjectcastingAnothercommonfeatureofPhysicsEnginesistheabilityto“cast”arayfromonepointtoanother,andgatherdataaboutoneormoreoftheobjectsinitspath.Itisprettycommontoimplementimportantgameplaytasksthroughcastingandbounding-volumechecks.Firinggunsistypicallyimplementedbyperformingraycastsfromtheplayertothetargetlocationandfindinganyviabletargetsinitspath(evenifit’sjustawall).

Wecanalsoobtainalistoftargetswithinanexplosionradius,suchasfromagrenadeorfireball,usingaPhysics.OverlapSphere()check,andsothisistypicallyhowsucharea-of-effectabilitiesareimplemented.

Wecanevencastentireobjectsforwardinspace,usingPhysics.SphereCast()andPhysics.CapsuleCast().Thesemethodsareoftenusedifweneedraysoflargersizes,orwewishtoseewhatwouldbeinthepathofamovingcharacter.


PhysicsperformanceoptimizationsNowthatwehaveanunderstandingofthemostsignificantfeaturesoftheUnityPhysicsEngine,wecancoversomeoptimizationtechniquestoimproveourgame’sphysicsperformance.


ScenesetupFirstly,thereareanumberofbestpracticeswecanapplytoourScenestoimproveconsistencyofthephysicssimulation.NotethatthesetechniqueswillnotnecessarilyimproveCPUormemoryusage,buttheywillresultinareducedlikelihoodofinstabilityfromthePhysicsEngine.

ScalingWeshouldtrytokeepallphysicsobjectscalesintheworldascloseto1:1:1aswepossiblycan.Thismeansthatforthedefaultgravityvalueof-9.81,theunitscaleoftheworldisimpliedtobe1meterperunit,sincetheforceofgravityatthesurfaceoftheEarthis9.81m/s²(mostgamesaretryingtosimulatethissituation).Ourobjectsizesshouldreflectourimpliedworldscale,sincescalingthemtoolargewillcausegravitytoappeartomovetheobjectsmuchmoreslowlythanwewouldexpect.Theconverseisalsotrue;scalingobjectstoosmallwillmakethemappeartofalltooquicklyandwillnotseemrealistic.

Wecantweaktheworld’simpliedscalebymodifyingthestrengthofgravityunderEdit|ProjectSettings|Physics(orPhysics2D)|Gravity.However,beawarethatanyfloating-pointarithmeticwillbemoreaccuratewithvaluescloserto0,soifwehavesomeobjectsthathavescalevaluesfarabove(1,1,1),eveniftheymatchtheimpliedworld-scale,thenwecouldstillobserveerraticphysicsbehavior.So,earlyintheprojectweshouldimportandscaleourmostcommonphysicsobjectsaroundascalevalueof(1,1,1),andthenadjustthevalueofgravitytomatch.Thiswillgiveusareferencepointtoworkwithasweintroducenewobjects.

TipBewarnedthatUnity4alsohasavalueforSpeedofSoundinitsAudiosettings,whichisusedduringanyDoppler-basedaudioeffects.Thedefaultvalueis343tomatchthespeedofsoundinairof343ms-1.Changingtheimpliedworldscaleviagravitywillrequirethisvaluetobeadjustedtomaintainconsistency.Unity5calculatestheDopplerEffectdifferentlyandsothisvariablewasremoved,nolongermakingthisissueaconcern.

PositioningSimilarly,keepingallobjectscloseto(0,0,0)inpositionwillresultinbetterfloating-pointaccuracy,improvingtheconsistencyofthesimulation.SpaceSimulatorandFree-Runninggamestrytosimulateincrediblylargespaces,andtheytypicallyusethistechniqueasmuchaspossiblebysecretlyteleporting,(orsimplykeeping)theplayercharactercenteredintheworld.Atthispoint,eithereverythingelseismovedtosimulatetravel,orvolumesofspacearecompartmentalizedsothatphysicscalculationsarealwayscalculatedwithvaluesclosetozero.Thisensuresthatallobjectsremaincloseto(0,0,0)inordertoavoidfloating-pointinaccuraciesastheplayertravelsgreatdistances.

Othertypesofgamesshouldnotriskintroducingfloating-pointinaccuracy,sounlesswe’realreadydeepintoourproject(suchthatchangingandre-testingeverythingatalate


stagewouldbetoomuchhassle),weshouldtrytokeepallofourphysicsobjectscloseto(0,0,0).Plus,thisissimplygoodpracticeforourprojectworkflowasitmakesitmuchfastertoaddandpositionobjectsinourgameworld.

MassTheUnitydocumentationrecommendsthatobjectmassvaluesstayaround0.1,withnovaluesexceeding10,duetotheinstabilityitgenerates:http://docs.unity3d.com/ScriptReference/Rigidbody-mass.html.

Thismeansweshouldnotthinkofmassintermsofmeasurementssuchaspoundsorkilograms,butratherarelativevaluebetweenobjects.Weshouldtrytomaintainconsistentandreasonableratiosofmassbetweencollidingobjects.Havingobjectscollidingwithamassratioofgreaterthan1,000willmostcertainlyresultinerraticbehaviorduetothelargemomentumdifferenceandeventuallossoffloatingpointprecision.Weshouldtrytoensureinter-objectcollisionsoccurwithobjectswithsimilarvaluesoftheirmassproperty,andobjectpairsthathaveasignificantscaledifferenceshouldbeculledwiththeCollisionMatrix(moreonthisshortly).

TipImpropermassratiosarethemostcommoncauseforphysicsinstabilityanderraticbehavior.

NotethattheforceofgravityatthecentreoftheEarthaffectsallobjectsequally,regardlessoftheirmass,soitdoesnotmatterifweconsideramasspropertyvalueof1tobethemassofarubberballorthemassofawarship.There’snoneedtoadjusttheforceofgravitytocompensateforanyassumptionswe’remakingwiththeserelativemasspropertyvalues.Whatdoesmatter,however,istheamountofairresistancethegivenobjectundergoeswhilefalling(thisiswhyafeatherfallsslowerthanasolidobjectofidenticalmass).So,tomaintainrealisticbehavior,wemayneedtocustomizethedragpropertyforsuchobjectsorcustomizetheforceofgravityonaper-objectbasis(suchasdisablingtheUseGravitycheckboxandapplyingacustomgravitationalforceviaScriptcode).


http://docs.unity3d.com/ScriptReference/Rigidbody-mass.html

UseStaticCollidersappropriatelyAspreviouslymentioned,thePhysicsSystemautomaticallygeneratesadatastructurefromthedataofallStaticColliders(colliderswithoutRigidbodyobjects)separatelyfromthestructurethatmanagesDynamicColliders(colliderswithRigidbodyobjects).Unfortunately,ifnewobjectsareintroducedintothedatastructureatruntime,thenitmustberegenerated.ThisislikelytocauseasignificantCPUspike.ThismakesitvitalthatweavoidinstantiatingnewStaticCollidersduringgameplay.

Inaddition,merelymoving,rotating,orscalingStaticCollidersalsotriggersthisregenerationprocessandshouldbeavoided.Ifwehavecollidersthatwewishtomovearoundwithoutreactingtootherobjectscollidingwiththeminaphysicalway,thenweshouldattachaRigidbodytomakeitaDynamicColliderandsettheKinematicflagtotrue.Thisflagpreventstheobjectfromreactingtoexternalimpulsesfrominter-objectcollisions.ThisallowsittobehavesimilartoaStaticCollider,butitisnowinadatastructurethatproperlysupportsmovingobjects,sowecanmoveitaroundfromScriptcode(duringFixedUpdates!),anditwillapplyimpulsestootherobjects.

TipIt’sforthisreasonthattheKinematicflagisoftenusedonobjectscontrolledbyplayers;theycanpushotherobjectsaroundbutshouldn’tbepushedaroundthemselves.


OptimizetheCollisionMatrixAsweknow,thePhysicsSystem’sCollisionMatrixdefineswhichobjectsassignedtocertainlayersareallowedtocollidewithobjectsassignedtootherlayers.Ortoputitmoresuccinctly,whichobjectpairsareevenconsideredbythePhysicsSystem.Everyotherobject-layer-pairissimplyignoredbythePhysicsEngine,whichmakesthisanimportantavenueforminimizingPhysicsEngineworkloadsinceitreducesthenumberofbounding-volumechecksthatmustbeperformedateachandeverytimestep.

TipReminder:theCollisionMatrixcanbeaccessedthroughEdit|ProjectSettings|Physics(orPhysics2D)|LayerCollisionMatrix.

ThefollowingscreenshotshowsacommonCollisionMatrixforanarcadeshootergame:

Inthisexample,wehaveminimizedthenumberofpossibleinter-objectcollisionsforthePhysicsSystemtocheck.Sincepowerupscanonlybepickedupbytheplayer,thenthereisnoneedtocomparecollisionsbetweenpowerupsandobjectsfromanyotherlayers.Meanwhile,wedon’twishforprojectilestocollidewiththeobjectthatfiredit,whichexcludesEnemyProjectilesfromcollidingwithenemies,andPlayerProjectilesfromcollidingwiththeplayer.Wewanteverythingtocollidewiththegameworld(wallsandothersurfaces),andperhapswedon’twantprojectilescollidingwithotherprojectiles(althoughsomegamesmightwantthis!).

WeshouldperformlogicalsanitycheckslikethisforalloftheLayercombinationsintheCollisionMatrixtoseewhetherwe’rewastingprecioustimecheckingforinter-objectcollisionsbetweenobject-pairsthataren’tnecessary.


PreferdiscretecollisiondetectionWeshouldusetheDiscreteoptionbydefaultforthemajorityofobjects.Teleportingobjectsonceandperformingasingleoverlapcheckbetweennearbyobject-pairsisafairlytrivialamountofwork.However,theamountofcalculationittakestointerpolatetheobjectsbetweentheirstartingandendingpositions,andsimultaneouslyverifyanyslightbounding-volumeoverlapsbetweenthesepointsovertime,issignificantlygreater.

Consequently,theContinuouscollisiondetectionoptionisanorderofmagnitudemoreexpensivethantheDiscretedetectionmethod,andtheContinuousDynamiccollisiondetectionsettingisanorderofmagnitudemoreexpensivethanContinuous!HavingtoomanyobjectsofthecontinuoustypeswillcauseseriousperformancedegradationincomplexScenes.Ineithercase,thecostsaremultipliedbythenumberofobjectsthatneedtobecomparedduringanygivenframeandwhetherornotthecomparisoncolliderisStaticorDynamic.

Ergo,thecontinuousdetectionsettingsshouldonlybeusedinextremecircumstances.TheContinuoussettingshouldbeusedwhenimportantcollisionsarefrequentlymissedwiththestaticworld,forinstance,ifweexpectcertainobjectstomovequickly,andwewishtobecertaintheyneverfallthroughthegameworldorteleportthroughwalls.Finally,theContinuousDynamicsettingshouldonlybeusedifthesamesituationappliesbutwewishtocatchcollisionsbetweenpairsofvery-fastmovingDynamicColliders.Unlesswehavegoodreasontousethem,allothersituationsshouldfavortheDiscretesetting.

But,perhaps,theDiscretesettingisn’tworkingwell-enoughonalargescale.Perhapsourentiregamerevolvesaroundalotofsmallphysicsobjectsanddiscretecollisiondetectionsimplyisn’tcatchingenoughcollisionstomaintainproductquality.Well,we’reinluck,becausewecancustomizethephysicstimesteptogivetheDiscretecollisionoptionabetterchanceofcatchingsuchcollisionsbymodifyinghowfrequentlytheenginechecksforFixedUpdates.


ModifytheFixedUpdatefrequencyAsmentionedpreviously,FixedUpdatesandphysicstimestepprocessingarestrongly-coupled,sobymodifyingthefrequencyofFixedUpdatecheckswenotonlychangethefrequencythatthePhysicsSystemwillcalculateandresolvethenextcallback,butwewillalsochangehowfrequentlyFixedUpdate()callbacksarebeinginvoked.Consequently,changingthisvaluecanberiskyifwe’redeepintoourprojectandhavealotofbehaviorthatdependsonthesecallbacks.

AlteringtheFixedUpdatefrequencycanbeaccomplishedthroughtheEdit|ProjectSettings|Time|FixedTimesteppropertyintheEditor,orthroughtheTime.fixedDeltaTimepropertyinscriptcode.

Reducingthisvalue(increasingthefrequency)willforcethePhysicsSystemtoprocessmorefrequently,givingitabetterchanceofcatchingcollisionsbetweenourDynamic,Discreteobjects.Naturally,thiscomeswithaCPUcostsincewe’reinvokingmoreFixedUpdate()callbacks,aswellasaskingthePhysicsEnginetoupdatemorefrequently,havingitmoveobjectsandverifycollisionsmoreoften.

Conversely,increasingthisvalue(decreasingthefrequency)providesmoretimefortheCPUtocompleteothertasksbeforeitmusthandlephysicsprocessingagain,orlookingatitfromanotherperspective,givingthePhysicsSystemmoretimetoprocessthelasttimestepbeforeitbeginsprocessingthenextone.But,loweringtheFixedUpdatefrequencywouldessentiallylowerthemaximumvelocityatwhichobjectscanbemovingbeforethePhysicsSystemcannolongercapturecollisionsbetweendiscreteobjects(dependingontheobjects’sizes).

ThismakesitabsolutelyvitaltoperformasignificantamountoftestingeachtimetheFixedTimestepvalueischanged.Evenwithacompleteunderstandingofhowthisvalueworks,itisdifficulttopredictwhattheoveralloutcomewilllooklikeduringgameplay,


andwhethertheresultispassableforqualitypurposes.Hence,changestothisvalueshouldbemadeearlyintheproject’slifecycleandthenmadeinfrequentlyinordertogetasufficientamountoftestingagainstasmanyphysicssituationsaspossible.

ItmighthelptocreateatestScenethatflingssomeofourhigh-velocityobjectsatoneanothertoseeiftheresultsareacceptable,andrunthroughthisScenewheneverFixedTimestepchangesaremade.Butactualgameplaytendstoberathercomplex,withmanybackgroundtasksandunanticipatedplayerbehaviorthatcausesadditionalworkforthePhysicsSystem,orgivesitlesstimetoprocessthecurrentiteration.Actualgameplayconditionsaredifficulttoduplicateinavacuum,andthere’snosubstitutefortherealthing,sothemoretestingwecanaccomplishagainstthecurrentvalueofFixedTimestep,themoreconfidentwecanbethatthechangesmeetacceptablequalitystandards.

Wealwayshavethecontinuouscollisiondetectionoptionsasalastresorttooffsetsomeoftheresultinginstabilitywe’reobserving.Butunfortunately,evenifthechangesaretargeted,itismorelikelythatthiswillcausefurtherperformanceissuesthanwestartedwithduetotheoverheadcostsofcontinuouscollisiondetection.ItwouldbewisetoprofileourScenebeforeandafterenablingcontinuouscollisiondetectiontoverifythatthebenefitsareoutweighingthecosts.


AdjusttheMaximumAllowedTimestepIftheMaximumAllowedTimestepvaluegetshitregularly,thenitwillresultinsomeprettybizarre-lookingphysicsbehavior.Rigidbodyobjectswillappeartoslowdownorfreezeinspace,sincethePhysicsEngineneedstokeepexitingearlybeforeithasfullyresolveditsentiretimequota.Inthiscase,itisaclearsignthatweneedtooptimizeourphysicsfromotherangles.Butattheveryleastwecanbeconfidentthethresholdwillpreventthegamefromcompletelylockingupduringaphysicsprocessingspike.

ThissettingcanbeaccessedthroughEdit|ProjectSettings|Time|MaximumAllowedTimestep.Thedefaultsettingistoconsumeamaximumof0.333seconds,whichwouldmanifestitselfasaverynoticeabledropinframerate(amere3FPS)ifitwerebreached.Ifweeverfeeltheneedtochangethissetting,thenweobviouslyhavesomebigproblemswithourphysicsworkload,soitisrecommendedtoonlytweakthisvalueifwehaveexhaustedallotherapproaches.


Minimizecastandbounding-volumechecksAlloftheraycastingmethodsareincrediblyuseful,buttheyarerelativelyexpensive(particularlyCapsuleCast()andSphereCast()),requiringustominimizehowoftentheyarecalled.WeshouldavoidcallingthesemethodsregularlywithinUpdatecallbacksorCoroutines,savingthemonlyforkeyeventsinourscriptcode.

Ifweabsolutelymustrelyonpersistentline,ray,orarea-of-effectcollisionareasinourScene(examplesincludesecuritylasers,orcontinuouslyburningfires),thentheywouldbebettersimulatedusingasimpleTriggerCollider,ratherthanperformingcontinuousraycastingoroverlapchecks.

Ifsuchreplacementsarenotpossible,andwetrulyneedpersistentcastingchecksusingthesemethods(suchasared-dotlasersight),thenwecanminimizetheamountofprocessingeachcallmakesbyexploitingtheLayerMaskobjects.

Forexample,alazyraycastwouldlooklikeso:

[SerializeField]float_maxRaycastDistance;

voidPerformRaycast(){

RaycastHithitInfo=newRaycastHit();

if(Physics.Raycast(newRay(transform.position,transform.forward),

outhit,_maxRaycastDistance)){

//handleraycastresulthere

}

}

ButthisoverloadofPhysics.Raycast()willcausetheraytocollidewiththefirstobjectofanylayerinitspath.ThePhysics.RaycastmethodhasmultipleoverloadsthatacceptaLayerMaskobjectforanargument.Wecanusethistocustomizewhichobjectsshouldbecheckedbytheraycast,simplifyingtheworkloadforthePhysicsEngine:

[SerializeField]float_maxRaycastDistance;

[SerializeField]LayerMask_layerMask;

voidPerformRaycast(){

RaycastHithitInfo=newRaycastHit();

if(Physics.Raycast(newRay(transform.position,transform.forward),

outhit,_maxRaycastDistance,_layerMask)){

//handleraycastresulthere

}

}

TheLayerMaskobjectcanthenbeconfiguredthroughtheobject’sInspectorview:


TipNotethat,becausetheRaycastHitandRayclassesaremanagedbythenativememoryspaceoftheUnityEngine,theydon’tresultinmemoryallocationsthatdrawtheattentionoftheGarbageCollector.WewilllearnmoreaboutsuchactivityinChapter7,MasterfulMemoryManagement.


AvoidcomplexMeshCollidersInorderofefficiency,thevariouscollidersare:Spheres,Capsules,Cylinders,Boxes,ConvexMeshColliders,andfinallyConcaveMeshColliders.However,thefourmainprimitivesareanorderofmagnitudemoreefficientthaneitheroftheMeshColliders,asthemathematicalcalculationsfordetectingandresolvingcollisionsbetweenthemarefairlysuccinctandoptimized.Performingcomparisonsbetweenaconvexshapeandanothercollidercanbeacostlyprocess,whilecomparingbetweenaconcaveshapeandanythingelseisevenmoreexpensive.

NotePerformingruntimebounding-volumechecksbetweenpairsofconcaveshapesisperhapstheclosestthingto“MathematicalArmageddon”thatwemightfindinareal-timephysicssimulation(atleastforafewmoreyears!).Toprotectusfromourownstupidity,Unityeffectivelybansusfromperformingconcave-to-concaveMeshColliderboundingvolumechecks.

Agreatironybetweenphysicsandgraphicsin3Dapplicationsishowdifficultitistohandlesphericalandboxobjectsbetweenthetwoofthem.Theperfectsphericalmeshwouldrequireaninfinitenumberofpolygonstogenerate,buthowasphereisrepresentedinaPhysicsEngineisrelativelytrivialtoresolveforcontactpointsandcollisions.Conversely,asimpleboxtakesaminisculenumberofpolygonsandefforttoproducegraphically,andyettakessignificantlymoremathematicsandprocessingpowertofindcontactpointsandresolvecollisionsfor.Thisimpliesthatgettingthemostoutofbothgraphicsandphysicswouldbetopopulateourworldwithlow-polygongraphicalobjects,representedassphereswithinthePhysicsSystem.However,thiswouldmakeabsolutelynosensetoahumanobserverastheywitnesssharp,pointyobjectsrollingaroundlikeballs.

ItisalwaysimportanttorememberwhenworkingwithPhysicsEnginesthatthephysicalrepresentationofanobjectdoesnotnecessarilyneedtomatchitsgraphicalrepresentation.Thisisbeneficialasagraphicalmeshcanoftenbecondenseddownintoamuchsimplershape,generatingaverysimilarphysicsbehaviorandsparingustheneedtouseanoverly-complexMeshCollider.

Thisseparationofrepresentationsbetweengraphicsandphysicsallowsustooptimizetheperformanceofonesystemwithout(necessarily)negativelyaffectingtheother.Iftherewouldbenonoticeablerepercussionsongameplay,thenwearefreetorepresentcomplexgraphicalobjectswiththesimplestphysicsshapesbehind-the-scenes.Iftheplayernevernotices,thennoharmisdone!

So,wecansolvethisprobleminoneoftwoways:eitherbyapproximatingthephysicsbehaviorofthecomplexshapeusingone(ormore)ofthestandardprimitives,orausingamuchsimplerMeshCollider.

UsesimplerprimitivesMostshapescanbeapproximatedusingoneofthefourprimitivecolliders(inorderof


efficiency):Spheres,Capsules,Cylinders,orBoxes.Infact,wedonotneedtorepresenttheobjectusingonlyasinglecollider;wearefreetouseseveralcollidersifitservesourneedsforcreatingacomplexcollisionshapebyattachingadditionalchildGameObjectswiththeirowncolliders.ThisisalmostalwayslesscostlythanusingasingleMeshColliderandshouldbepreferredovermorecomplexsolutions.

Thefollowingimageshowsahandfulofcomplexgraphicalobjects,representedbyoneormoresimplerprimitivesinthePhysicsSystem:

UsingaMeshColliderforanyoneoftheseobjectswouldbesignificantlymorecostlythantheprimitivecollidersshownhere.Itisworthexploringanyandallopportunitiestosimplifyourobjectsdownusingtheseprimitivesasmuchaswecan,astheycanprovidesignificantperformancegains.

Forexample,concavemeshesareuniqueinthattheycanfeaturegaps,orholes,thatallowothermeshesto“fall”into,oreventhroughthem,whichintroducesopportunitiesfortheobjectstofallthroughtheworldifconcaveshapesareusedforworldcollisionareas.ItisoftenbettertoplaceBoxCollidersinstrategiclocationsforthispurpose.

UsesimplerMeshCollidersThemeshassignedtotheMeshColliderdoesnotnecessarilyneedtomatchthegraphicalrepresentationofthesameobject(Unitysimplypicksitasthedefault).ThisgivesusanopportunitytoreplacetheMeshCollider’smeshpropertywithadifferent,simplermeshforanobject’scolliderfromtheoneweuseforitsgraphicalrepresentation.

ThefollowingimageshowsanexampleofacomplexgraphicalmeshthathasbeengivenasimplifiedmeshforitsMeshCollider:


Simplifyingtherenderedmeshintoconvexshapeswithlowerpolygoncountsinthiswaywillgreatlyreducetheoverheadneededtodeterminebounding-volumeoverlapswithothercolliders.Dependingonhowwelltheoriginalobjectisestimated,theremaybefewtononoticeablegameplaydifferences,especiallyinthecaseofthisaxe,whichweexpecttobemovingquicklyascreaturesswingitduringattacks,makingitunlikelythatplayerswillnoticethedifferencebetweenthetwomeshesascolliders.


AvoidcomplexphysicscomponentsCertainspecialphysicsColliderComponents,suchasTerrain,Cloth,andWheelColliders,areordersofmagnitudemorecostlythanallprimitivecolliders,andevenMeshCollidersinsomecases.WeshouldsimplynotincludesuchComponentsinourScenesunlesstheyareabsolutelynecessary.Forinstance,ifwehaveTerrainobjectsinthedistancethattheplayerwillneverapproach,thenthere’slittlereasontoincludeanattachedTerrainCollider.

GamesfeaturingClothComponentsshouldconsiderinstantiatingdifferentobjectswithoutthemwhenrunninginlower-qualitysettings,orsimplyanimatingclothbehavior(althoughitistotallyunderstandableiftheteamhasgrownattachedandfalleninlovewithhowthestuffmovesaround).

GamesusingWheelCollidersshouldsimplytrytousefewerwheelcolliders!Vehicleswithmorethanfourwheelsmaybeabletouseonlyfourwheelstogeneratethecorrectphysicsbehavior,whilefakingthegraphicalrepresentationofadditionalwheels.


LetphysicsobjectssleepThePhysicsEngine’ssleepfeaturecanposeseveralproblemsforourgame.

NoteReminder:thesleepthresholdcanbemodifiedunderEdit|ProjectSettings|Physics|SleepThreshold.

Firstly,somedevelopersdon’trealizethatmanyoftheirRigidbodyobjectsaresleepingduringmostofthelifetimeoftheirapplication.Thistendstoleaddeveloperstoassumethattheycangetawaywith(forexample)doublingthenumberofRigidbodyobjectsintheirgame,andthecostswillsimplydoubletomatchit.Thisisunlikely.Thefrequencyofcollisionsandtotalaccumulatedtimeofactiveobjectsismorelikelytoincreaseinanexponentialfashion,ratherthanalinearone.Thisleadstounexpectedperformancecostswhennewphysicsobjectsareintroducedintothesimulation.WeshouldkeepthisinmindwhenwedecidetoincreasethephysicscomplexityofourScenes.

Secondly,thereisthedangerof“islands”ofsleepingphysicsobjectsbeinggenerated.IslandsarecreatedwhenalargenumberofRigidbodyobjectsaretouchingoneanother,andhavegraduallycometorest—imagineapileofboxesthathavebeenspawnedandformedalargepile.Eventually,alloftheRigidbodyobjectswillfallasleeponceenoughenergyinthesystemislostandtheyallcometorest.However,becausethey’reallstilltouchingoneanother,assoonasoneoftheseobjectsisawoken,itwillstartachainreaction,awakeningallothernearbyRigidbodyobjects.SuddenlywehavealargespikeinCPUusagebecausedozensofobjectshavenowre-enteredthesimulation,andtherearesuddenlymanymorecollisionstoresolveuntiltheobjectsfallasleepagain.

Ifwecouldfindawaytodetectthatislandsareforming,wecouldstrategicallydestroy/despawnsomeofthemtopreventtoomanylargeislandsfrombeinggenerated.Butworkaroundssuchasthesewillbedependentuponthegameitself,asperformingregular,globalchecks,anddistancecomparisonsbetweenallofourRigidbodyobjectsisnotacheaptasktoaccomplish.Forexample,agamethatrequirestheplayertomovelotsofphysicsobjectsintoanarea(forexample,agamethatinvolvesherdingsheepintoapen)couldchoosetodespawntheDynamicColliderobjectassoonastheplayermovesitintoposition,lockingtheobjecttoitsfinaldestination,andeasingtheworkloadonthePhysicsEngine.

Thirdly,changinganyofaRigidbody’spropertiesatruntime,suchasmass,drag,UseGravity,andsoon,willalsoreawakentheobject.Ifwe’reregularlychangingthesevalues(suchasagamewhereobjectsizesandmasseschangeovertime),thentheywillremainactiveforlongerperiodsoftimethanusual.Thisisalsothecaseforapplyingforces,soifwe’reusingacustomgravitysolution(suchassuggestedbackinthesectionentitledMass),weshouldtrytoavoidapplyingthegravitationalforceeveryFixedUpdate,otherwisetheobjectwillbeunabletofallasleep.

Sleepingobjectscanbeablessingandacurse.Theycansaveusalotofprocessingpower,butiftoomanyofthemreawakenatthesametimeoroursimulationistoobusytoallow


enoughofthemtofallasleep,thenwecouldbeincurringsomeunfortunateperformancecostsduringgameplay.Weshouldstrivetolimitthesesituationsasmuchaspossiblebylettingourobjectsenterthesleepingstateasmuchaspossible,andavoidgroupingthemtogetherinlargeclusters.


ModifySolverIterationCountJoints,Springs,andotherconnectedRigidbodyobjectsarenottrivialtosimulateintheworldofPhysicsEngines.Becauseoftheco-dependentinteractivity(internallyrepresentedasmovementconstraints)thatoccurswithjoiningtwoobjectstogether,thesystemmustoftenmakeseveralattemptsatsolvingthenecessarymathematicalequations.Thismulti-iterationapproachisrequiredtocalculateanaccurateresultwheneverthereisachangeinvelocitytoanypieceoftheobject-chain.

Itthereforebecomesabalancingactoflimitingthemaximumnumberofattemptsthe“Solver”makestoresolveaparticularsituation,versushowaccuratearesultwecangetawaywith.Wedon’twanttheSolvertospendtoomuchtimeonasinglecollision,becausethereisalotofotherworkthePhysicsEnginehastodowithinthesameiteration.But,wealsodon’twanttoreducethemaximumnumberofiterationstoofarasitwillonlyapproximatewhatthefinalsolutionwouldhavebeenifithadbeengivenmoretimetocalculatetheresult.

NoteThesameSolveralsogetsinvolvedwhenresolvinginter-objectcollisionsandcontacts.Itcanalmostalwaysdeterminethecorrectresultwithasingleiteration,withtheexceptionofsomeveryrareandcomplexcollisionsituations.Itisonlywhenthird-partyobjectswillbeaffectedthroughJointsthattheSolverrequiresadditionalefforttomathematicallyintegratethefinalresult.

TheSolverIterationCountcanbemodifiedunderEdit|ProjectSettings|Physics|SolverIterationCount.Inmostcases,thedefaultvalueofsixiterations(seveniterationsinUnity4)isperfectlyacceptable.But,gamesthatincludeverycomplexjointsystemsmaywishtoincreasethiscounttosuppressanyerratic(ordownrightexplosive)CharacterJointbehaviors,whilesomeprojectsmaybeabletogetawaywithreducingthiscount.Testingmustbeperformedafterchangingthisvaluetoseewhethertheprojectstillmaintainstheintendedlevelsofquality.

Incidentally,ifwefindourgameregularlyrunsintojarring,erratic,andphysics-breakingsituationswithcomplexJoint-basedobjects(suchasragdolls),thenweshouldconsidergraduallyincreasingtheSolverIterationCountuntiltheproblemshavebeensuppressed.TheseproblemstypicallyoccurifourragdollsabsorbtoomuchenergyfromcollidingobjectsandtheSolverisunabletoiteratethesolutiondowntosomethingreasonablebeforeitisaskedtogiveup.Atthispoint,oneoftheJointsgoessupernova,draggingtherestofthemintoorbitalongwithit!

Weshouldalsodoublecheckthatourragdoll’sRigidbodymassesareobeyingtherulessetforthearlierinthischapter,sothattheresultantenergyexchangeandvelocitieswillbemorereasonable.


OptimizingragdollsSpeakingofCharacterJoints,ragdollsareincrediblypopularfeaturesforgoodreason;they’retonsoffun!Ignoringthemorbidityofflingingcorpsesaroundagameworldforthemoment,there’ssomethingaboutwatchingacomplexchainofobjectsflailaroundandsmashintothingsthathitsalotofpsychological“funbuttons”.

ThismakesitverytemptingtoallowmanyragdollstocoexistwithinourSceneatthesametime,butaswequicklydiscover,thisrisksanenormousperformancehitwhentoomanyragdollsareinmotionand/orcollidewithotherobjectsduetotheamountofiterationstheSolverwouldneedtoresolvethemall.So,let’sexploresomewaystoimprovetheperformanceofanyragdollswewishtouse.

ReduceJointsandCollidersUnityprovidesasimpleragdoll-generationtoolunderGameObject|3DObject|Ragdoll…inUnity5,orGameObject|CreateOther|Ragdoll…inUnity4.Thistoolcanbeusedtocreateragdollsfromagivenobjectbyselectingtheappropriatechildobjectstoattachcolliderstoforanygivenbodypartorlimb.Thistoolalwayscreates11differentcollidersandassociatedJoints(pelvis,chest,head,andtwocollidersperlimb),butwemightwishtoconsiderusingonlysixcolliders(body,head,andonecolliderperlimb)togreatlyreducetheoverheadcostattheexpenseofragdollrealism.ThiscanbeachievedbydeletingunwantedcollidersandreassigningtheCharacterJoint’sConnectedBodypropertiestotheproperparentjoints.

Suchsimplificationscouldbeimplementedasameansofreducingoverheadforweakerhardware/lowerqualitysettings,asasimplecompromisetoallowmoreragdollstocoexistinourScene.Itcouldevenbeuseddynamicallyifaparticularnumberofragdollsarealreadypresent.Agodclasswouldneedtokeeptrackofhowmanyragdollscurrentlyexist,butwhennewragdollsareintroduced,wecouldinstantiateasimplerversioninordertokeepthingsrunningsmoothly.

Avoidinter-ragdollcollisionsUnlesswereallydesireinter-ragdollcollisionsthenweshouldperhapsdisablethemusingtheCollisionMatrix.Theperformancecostofragdollsgrowsexponentiallywhenragdollscollidewithoneanother,sincewewouldbeaskingtheSolvertoworkextrahardandriskingerraticbehaviorduetotheapproximationsitisforcedtomake.

DisableorremoveinactiveragdollsFinally,wecouldconsiderdisallowingragdollsfromre-enteringthephysicssimulationaftertheyhavecometorest.Insomegames,oncearagdollhasreacheditsfinal“destination,”wenolongerneedittoremaininthegameworldasaninteractableobject.

Wecanpollanygivencollider’ssleepstatewiththeIsSleepingmethodand,onceithasreachedthisstate,wehaveanumberofoptionswecanpursue.Wecoulddisablealloftheragdoll’scolliders,preventingitfrombeingreintroducedtothesimulation,wecouldremovetheragdollfromtheSceneforthesakeofcleanup,orwecouldkeeptrackofthis


ragdollandonlyremoveitwhenadifferentragdollhasbeenintroducedtotheScene.

Whateverapproachwechoosetoimprovetheperformanceofourragdollswillnodoubtresultinlimitingragdollsasagameplayfeature,eitherbyinstantiatingfewerofthem,givingthemlesscomplexity,orgivingthemashorterlifetime,butthesearereasonablecompromisestomakegiventheperformance-savingopportunities.


KnowwhentousephysicsAsalways,thebestmethodofimprovingtheperformanceofafeatureistoavoidusingitasmuchaspossible.Forallmoveableobjectsinourgame,weshouldtakeamomenttoaskourselvesifgettingthePhysicsEngineinvolvedisevennecessary.Ifnot,weshouldlookforopportunitiestoreplacethemwithsomethingsimplerandlesscostly.

Perhapswe’reusingphysicstodetectwhethertheplayerfellintoakill-zone,butourgameissimpleenoughthatweonlyhavekill-zonesataspecificheight.Inthiscase,wecouldavoidphysicscollidersaltogetherandgetawaywithonlycheckingwhethertheplayer’sypositionfallsbelowaparticularvalue.

Asanotherexample,maybewe’retryingtosimulateameteorshower,andourfirstinstinctwastohavemanyfallingobjectsthatmoveviaphysicsRigidbodyobjects,detectcollisionswiththegroundviacolliders,andthengenerateanexplosionatthepointofimpact.ButperhapsthegroundisconsistentlyflatorwehaveaccesstotheTerrain’sHeightMapforsomerudimentarycollisiondetection.Inthiscase,objecttravelcouldbesimplifiedbytweeningtheobjects’transform.positionpropertiesovertimetosimulatethesamebehaviorwithoutrequiringanyphysicscomponents.Inbothcases,wecanreducethephysicsoverheadbysimplifyingthesituationandpushingtheworkintoScriptcode.

TipTweeningisacommonshort-handtermforin-betweening,whichistheactofinterpolatingpropertiesfromonevaluetoanothermathematicallyovertime.Therearemanyuseful(andfree!)tweeninglibraries,availableontheUnityAssetStore,thatprovidealotofusefulfunctionality.

Thereverseisalsopossible;theremightbeoccasionswherewe’reperformingagreatdealofcalculationthroughScriptcodethatcouldbehandledthroughphysicsrelativelysimply.Forexample,wemighthaveimplementedaninventorysystemwithmanyobjectsthatcanbepickedup.WhentheplayerhitsthePickupkey,eachoftheseobjectsmightbecomparedagainsttheplayer’spositiontofigureoutwhichobjectisclosest.WecouldconsiderreplacingalloftheScriptcodewithasinglePhysics.OverlapSphere()calltogetnearbyobjectswhenthekeyispressed,andthenfigureouttheclosestpickupobjectfromtheresult(orjustpickupallofthem!).Thiscouldgreatlyreducethetotalnumberofobjectsthatmustbecomparedeachtimethekeyispressed.

Theopportunitiesareaswideandfar-reachingasourowningenuity.Theabilitytorecognizeopportunitiestoremoveunnecessaryphysicsgrunt-workfromourScenes,and/orusephysicstoreplacebehaviorthatiscostlywhenperformedthroughScriptcode,isavitalskillthatwillserveuswellwhensavingperformanceincurrentandfuturegamedevelopmentprojects.


ConsiderupgradingtoUnity5Ifwe’rerunningUnity4,anabsolutelastresorttoimprovephysicsperformancewouldbetoconsiderupgradingtoUnity5.TherewereamultitudeofhugeperformanceenhancementswithUnity5’supgradefromPhysXversion2.8.3toversion3.3.TheseimprovementscannotbeoverstatedastheygrantaboutdoubletheperformanceofthePhysicsSystemascomparedtoUnity4.TheupgradeincludeslessoverheadinmovingStaticColliders,improvedperformanceincontinuouscollisiondetectionmethods,supportformorerigidbodies,improvedClothandWheelCollidercomponents,aswellasmulticorephysicssupport.Inshort,itallowsustoreducetheperformancecostofthesameScene,orcrammorephysicsactivityintoourScenesforthesamecost.

However,thesechangesresultedinsomesignificantAPIchangesforcertaintasks,whichmeansScriptingandComponentsinUnity4maynotbefullycompatiblewithUnity5(andnotjustforphysics-relatedtasks).Consequently,theupgradeitselfisunlikelytobetrivial,andweshouldnotforgettomakeabackupofourprojectbeforeattemptingtodoso.TheamountofworkwillultimatelydependonthecomplexityofourprojectandhowitaffectsanyAssetStorepurchaseswerelyon.Eachassetislikelytoneedupdatesofitsownandanyassetsthathavefallenoutofsupportwillneedtobereplaced.


SummaryWe’vecoverednumerousmethodstoimproveourgame’sphysicssimulationbothintermsofperformance,andconsistency.ThebesttechniquewhenitcomestocostlysystemssuchasPhysicsEnginesissimplyavoidance.Thelessweneedtousethesystem,thelessweneedtoworryaboutitgeneratingbottlenecks.Intheworstcase,wemayneedtoreducethescopeofourgametocondensephysicsactivitydowntoonlytheessentials,butaswe’velearned,thereareplentyofwaystoreducephysicscomplexitywithoutcausinganynoticeablegameplayeffects.

Inthenextchapter,wewillimmerseourselvesinUnity’sgraphicssystem,discoveringhowtomaximizegraphicalfidelityusingalloftheCPUcycleswe’vefreedupusingtheperformanceenhancementsfromearlierchapters.


Chapter6.DynamicGraphicsThereisnoquestionthattherenderingsystemofmoderngraphicsdevicesiscomplicated.Evenrenderingasingletriangletothescreenengagesmanyofthesecomponents,sinceGPUsaredesignedforlargeamountsofparallelism,asopposedtoCPUs,whicharedesignedtohandlevirtuallyanycomputationalscenario.Moderngraphicsrenderingisahigh-speeddanceofprocessingandmemorymanagementthatspanssoftware,hardware,multiplememoryspaces,multiplelanguages,multipleprocessors,multipleprocessortypes,andalargenumberofspecial-casefeaturesthatcanbethrownintothemix.

Tomakemattersworse,everygraphicssituationwewillcomeacrossisdifferentinitsownway.Runningthesameapplicationagainstadifferentdevice,evenbythesamemanufacturer,oftenresultsinanapples-versus-orangescomparisonduetothedifferentcapabilitiesandfunctionalitytheyprovide.Itcanbedifficulttodeterminewhereabottleneckresideswithinsuchacomplexchainofdevicesandsystems,anditcantakealifetimeofindustryworkin3Dgraphicstohaveastrongintuitionaboutthesourceofperformanceissuesinmoderngraphicssystems.

Thankfully,Profilingcomestotherescueonceagain.Ifwecangatherdataabouteachcomponent,usemultipleperformancemetricsforcomparison,andtweakourScenestoseehowdifferentgraphicsfeaturesaffecttheirbehavior,thenweshouldhavesufficientevidencetofindtherootcauseoftheissueandmakeappropriatechanges.Sointhischapter,youwilllearnhowtogathertherightdata,digjustdeepenoughintothegraphicssystemtofindthetruesourceoftheproblem,andexplorevarioussolutionstoworkaroundagivenproblem.

Asyoulearnedinearlierchapters,theCPUandGPUworkintandemtodeterminewhattextures,meshes,renderstates,Shaders,andsoon,areneededtorenderourScenesatanygivenmoment.We’vealsocoveredseveraltechniquestoreducesomeoftherenderingworkloadthroughStaticandDynamicBatching,andbymanipulatingourmeshandtexturefilesthroughcompressionandencoding,MipMapping,Atlasing,andevensomeproceduralalternatives.

However,therearestillmanymoretopicstocoverwhenitcomestoimprovingrenderingperformance,sointhischapterwewillbeginwithsomegeneraltechniquesonhowtodeterminewhetherourrenderingislimitedbytheCPUorbytheGPU,andwhatwecandoabouteithercase.WewilldiscussoptimizationtechniquessuchasOcclusionCullingandLevelOfDetail(LOD)andprovidesomeusefuladviceonShaderoptimization,aswellaslarge-scalerenderingfeaturessuchaslightingandshadows.Finally,sincemobiledevicesareacommontargetforUnityprojects,wewillalsocoversometechniquesthatmayhelpimproveperformanceonlimitedhardware.


ProfilingrenderingissuesPoorrenderingperformancecanmanifestitselfinanumberofways,dependingonwhetherthedeviceisCPU-bound,orGPU-bound;inthelattercase,therootcausecouldoriginatefromanumberofplaceswithinthegraphicspipeline.Thiscanmaketheinvestigatorystageratherinvolved,butoncethesourceofthebottleneckisdiscoveredandtheproblemisresolved,wecanexpectsignificantimprovementsassmallfixestendtoreapbigrewardswhenitcomestotherenderingsubsystem.

WebrieflytoucheduponthesubjectofbeingCPU/GPU-boundinChapter3,TheBenefitsofBatching.Tosummarizetheearlierdiscussion,weknowthattheCPUsendsrenderinginstructionsthroughthegraphicsAPI,thatfunnelthroughthehardwaredrivertotheGPUdevice,whichresultsincommandsenteringtheGPU’sCommandBuffer.ThesecommandsareprocessedbythemassivelyparallelGPUsystemonebyoneuntilthebufferisempty.Buttherearealotmorenuancesinvolvedinthisprocess.

Thefollowingshowsa(greatlysimplified)diagramofatypicalGPUpipeline(whichcanvarybasedontechnologyandvariousoptimizations),andthebroadrenderingstepsthattakeplaceduringeachstage:

ThetoprowrepresentstheworkthattakesplaceontheCPU,theactofcallingintothegraphicsAPI,throughthehardwaredriver,andpushingcommandsintotheGPU.Ergo,aCPU-boundapplicationwillbeprimarilylimitedbythecomplexity,orsheernumber,ofgraphicsAPIcalls.

Meanwhile,aGPU-boundapplicationwillbelimitedbytheGPU’sabilitytoprocessthosecalls,andemptytheCommandBufferinareasonabletimeframetoallowfortheintendedframerate.Thisisrepresentedinthenexttworows,showingthestepstakingplaceintheGPU.But,becauseofthedevice’scomplexity,theyareoftensimplifiedintotwodifferentsections:thefrontendandthebackend.


ThefrontendreferstothepartoftherenderingprocesswheretheGPUhasreceivedmeshdata,adrawcallhasbeenissued,andalloftheinformationthatwasfedintotheGPUisusedtotransformverticesandrunthroughVertexShaders.Finally,therasterizergeneratesabatchoffragmentstobeprocessedinthebackend.ThebackendreferstotheremainderoftheGPU’sprocessingstages,wherefragmentshavebeengenerated,andnowtheymustbetested,manipulated,anddrawnviaFragmentShadersontotheframebufferintheformofpixels.

TipNotethat“FragmentShader”isthemoretechnicallyaccuratetermforPixelShaders.Fragmentsaregeneratedbytherasterizationstage,andonlytechnicallybecomepixelsoncethey’vebeenprocessedbytheShaderanddrawntotheFrameBuffer.

Thereareanumberofdifferentapproacheswecanusetodeterminewheretherootcauseofagraphicsrenderingissuelies:

ProfilingtheGPUwiththeProfilerExaminingindividualframeswiththeFrameDebuggerBruteForceCulling


GPUprofilingBecausegraphicsrenderinginvolvesboththeCPUandGPU,wemustexaminetheproblemusingboththeCPUUsageandGPUUsageareasoftheProfilerasthiscantelluswhichcomponentisworkinghardest.

Forexample,thefollowingscreenshotshowstheProfilerdataforaCPU-boundapplication.Thetestinvolvedcreatingthousandsofsimpleobjects,withnobatchingtechniquestakingplace.ThisresultedinanextremelylargeDrawCallcount(around15,000)fortheCPUtoprocess,butgivingtheGPUrelativelylittleworktododuetothesimplicityoftheobjectsbeingrendered:

ThisexampleshowsthattheCPU’s“rendering”taskisconsumingalargeamountofcycles(around30msperframe),whiletheGPUisonlyprocessingforlessthan16ms,indicatingthatthebottleneckresidesintheCPU.

Meanwhile,ProfilingaGPU-boundapplicationviatheProfilerisalittletrickier.Thistime,thetestinvolvescreatingasmallnumberofhighpolycountobjects(foralowDrawCallpervertexratio),withdozensofreal-timepointlightsandanexcessivelycomplexShaderwithatexture,normaltexture,heightmap,emissionmap,occlusionmap,andsoon,(forahighworkloadperpixelratio).

ThefollowingscreenshotshowsProfilerdatafortheexampleScenewhenitisruninastandaloneapplication:


Aswecansee,therenderingtaskoftheCPUUsageareamatchescloselywiththetotalrenderingcostsoftheGPUUsagearea.WecanalsoseethattheCPUandGPUtimecostsatthebottomoftheimagearerelativelysimilar(41.48msversus38.95ms).ThisisveryunintuitiveaswewouldexpecttheGPUtobeworkingmuchharderthantheCPU.

TipBeawarethattheCPU/GPUmillisecondcostvaluesarenotcalculatedorrevealedunlesstheappropriateUsageAreahasbeenaddedtotheProfilerwindow.

However,let’sseewhathappenswhenwetestthesameexactScenethroughtheEditor:

ThisisabetterrepresentationofwhatwewouldexpecttoseeinaGPU-boundapplication.WecanseehowtheCPUandGPUtimecostsatthebottomareclosertowhatwewouldexpecttosee(2.74msvs64.82ms).

However,thisdataishighlypolluted.ThespikesintheCPUandGPUUsageareasarethe


resultoftheProfilerWindowUIupdatingduringtesting,andtheoverheadcostofrunningthroughtheEditorisalsoartificiallyincreasingthetotalGPUtimecost.

Itisunclearwhatcausesthedatatobetreatedthisway,andthiscouldcertainlychangeinthefutureifenhancementsaremadetotheProfilerinfutureversionsofUnity,butitisusefultoknowthisdrawback.

NoteTryingtodeterminewhetherourapplicationistrulyGPU-boundisperhapstheonlygoodexcusetoperformaProfilertestthroughtheEditor.


TheFrameDebuggerAnewfeatureinUnity5istheFrameDebugger,adebuggingtoolthatcanrevealhowtheSceneisrenderedandpiecedtogether,oneDrawCallatatime.WecanclickthroughthelistofDrawCallsandobservehowtheSceneisrendereduptothatpointintime.ItalsoprovidesalotofusefuldetailsfortheselectedDrawCall,suchasthecurrentrendertarget(forexample,theshadowmap,thecameradepthtexture,themaincamera,orothercustomrendertargets),whattheDrawCalldid(drawingamesh,drawingastaticbatch,drawingdepthshadows,andsoon),andwhatsettingswereused(texturedata,vertexcolors,bakedlightmaps,directionallighting,andsoon).

ThefollowingscreenshotshowsaScenethatisonlybeingpartiallyrenderedduetothecurrentlyselectedDrawCallwithintheFrameDebugger.Notetheshadowsthatarevisiblefrombakedlightmapsthatwererenderedduringanearlierpassbeforetheobjectitselfisrendered:

IfweareboundbyDrawCalls,thenthistoolcanbeeffectiveinhelpingusfigureoutwhattheDrawCallsarebeingspenton,anddeterminewhetherthereareanyunnecessaryDrawCallsthatarenothavinganeffectonthescene.Thiscanhelpuscomeupwithwaystoreducethem,suchasremovingunnecessaryobjectsorbatchingthemsomehow.WecanalsousethistooltoobservehowmanyadditionalDrawCallsareconsumedbyrenderingfeatures,suchasshadows,transparentobjects,andmanymore.Thiscouldhelpus,whenwe’recreatingmultiplequalitylevelsforourgame,todecidewhatfeaturestoenable/disableunderthelow,medium,andhighqualitysettings.


BruteforcetestingIfwe’reporingoverourProfilingdata,andwe’restillnotsurewecandeterminethesourceoftheproblem,wecanalwaystrythebruteforcemethod:cullaspecificactivityfromtheSceneandseeifitresultsingreatlyincreasedperformance.Ifasmallchangeresultsinabigspeedimprovement,thenwehaveastrongclueaboutwherethebottlenecklies.There’snoharminthisapproachifweeliminateenoughunknownvariablestobesurethedataisleadingusintherightdirection.

Wewillcoverdifferentwaystobruteforcetestaparticularissueineachoftheupcomingsections.


CPU-boundIfourapplicationisCPU-bound,thenwewillobserveagenerallypoorFPSvaluewithintheCPUUsageareaoftheProfilerwindowduetotherenderingtask.However,ifVSyncisenabledthedatawilloftengetmuddiedupwithlargespikesrepresentingpausesastheCPUwaitsforthescreenrefreshratetocomearoundbeforepushingthecurrentframebuffer.So,weshouldmakesuretodisabletheVSyncblockintheCPUUsageareabeforedecidingtheCPUistheproblem.

Brute-forcingatestforCPU-boundingcanbeachievedbyreducingDrawCalls.Thisisalittleunintuitivesince,presumably,we’vealreadybeenreducingourDrawCallstoaminimumthroughtechniquessuchasStaticandDynamicBatching,Atlasing,andsoforth.Thiswouldmeanwehaveverylimitedscopeforreducingthemfurther.

Whatwecando,however,isdisabletheDraw-Call-savingfeaturessuchasbatchingandobserveifthesituationgetssignificantlyworsethanitalreadyis.Ifso,thenwehaveevidencethatwe’reeitheralready,orveryclosetobeing,CPU-bound.Atthispoint,weshouldseewhetherwecanre-enablethesefeaturesanddisablerenderingforafewchoiceobjects(preferablythosewithlowcomplexitytoreduceDrawCallswithoutover-simplifyingtherenderingofourscene).Ifthisresultsinasignificantperformanceimprovementthen,unlesswecanfindfurtheropportunitiesforbatchingandmeshcombining,wemaybefacedwiththeunfortunateoptionofremovingobjectsfromoursceneastheonlymeansofbecomingperformantagain.

TherearesomeadditionalopportunitiesforDrawCallreduction,includingOcclusionCulling,tweakingourLightingandShadowing,andmodifyingourShaders.Thesewillbeexplainedinthefollowingsections.

However,Unity’srenderingsystemcanbemultithreaded,dependingonthetargetedplatform,whichversionofUnitywe’rerunning,andvarioussettings,andthiscanaffecthowthegraphicssubsystemisbeingbottleneckedbytheCPU,andslightlychangesthedefinitionofwhatbeingCPU-boundmeans.

MultithreadedrenderingMultithreadedrenderingwasfirstintroducedinUnityv3.5inFebruary2012,andenabledbydefaultonmulticoresystemsthatcouldhandletheworkload;atthetime,thiswasonlyPC,Mac,andXbox360.Gradually,moredeviceswereaddedtothislist,andsinceUnityv5.0,allmajorplatformsnowenablemultithreadedrenderingbydefault(andpossiblysomebuildsofUnity4).


MobiledeviceswerealsostartingtofeaturemorepowerfulCPUsthatcouldsupportthisfeature.Androidmultithreadedrendering(introducedinUnityv4.3)canbeenabledthroughacheckboxunderPlatformSettings|OtherSettings|MultithreadedRendering.MultithreadedrenderingoniOScanbeenabledbyconfiguringtheapplicationtomakeuseoftheAppleMetalAPI(introducedinUnityv4.6.3),underPlayerSettings|OtherSettings|GraphicsAPI.

Whenmultithreadedrenderingisenabled,tasksthatmustgothroughtherenderingAPI(OpenGL,DirectX,orMetal),arehandedoverfromthemainthreadtoa“workerthread”.Theworkerthread’spurposeistoundertaketheheavyworkloadthatittakestopushrenderingcommandsthroughthegraphicsAPIanddriver,togettherenderinginstructionsintotheGPU’sCommandBuffer.ThiscansaveanenormousnumberofCPUcyclesforthemainthread,wheretheoverwhelmingmajorityofotherCPUtaskstakeplace.Thismeansthatwefreeupextracyclesforthemajorityoftheenginetoprocessphysics,scriptcode,andsoon.

Incidentally,themechanismbywhichthemainthreadnotifiestheworkerthreadoftasksoperatesinaverysimilarwaytotheCommandBufferthatexistsontheGPU,exceptthatthecommandsaremuchmorehigh-level,withinstructionslike“renderthisobject,withthisMaterial,usingthisShader”,or“drawNinstancesofthispieceofproceduralgeometry”,andsoon.ThisfeaturehasbeenexposedinUnity5toallowdeveloperstotakedirectcontroloftherenderingsubsystemfromC#code.ThiscustomizationisnotaspowerfulashavingdirectAPIaccess,butitisastepintherightdirectionforUnitydeveloperstoimplementuniquegraphicaleffects.

NoteConfusingly,theUnityAPInameforthisfeatureiscalled“CommandBuffer”,sobesurenottoconfuseitwiththeGPU’sCommandBuffer.

ChecktheUnitydocumentationonCommandBuffertomakeuseofthisfeature:http://docs.unity3d.com/ScriptReference/Rendering.CommandBuffer.html.

Gettingbacktothetaskathand,whenwediscussthetopicofbeingCPU-boundingraphicsrendering,weneedtokeepinmindwhetherornotthemultithreadedrendererisbeingused,sincetheactualrootcauseoftheproblemwillbeslightlydifferentdependingonwhetherthisfeatureisenabledornot.

Insingle-threadedrendering,whereallgraphicsAPIcallsarehandledbythemainthread,andinanidealworldwherebothcomponentsarerunningatmaximumcapacity,ourapplicationwouldbecomebottleneckedontheCPUwhen50percentormoreofthetimeperframeisspenthandlinggraphicsAPIcalls.However,resolvingthesebottleneckscanbeaccomplishedbyfreeingupworkfromthemainthread.Forexample,wemightfindthatgreatlyreducingtheamountofworktakingplaceinourAIsubsystemwillimproveourrenderingsignificantlybecausewe’vefreedupmoreCPUcyclestohandlethegraphicsAPIcalls.

But,whenmultithreadedrenderingistakingplace,thistaskispushedontotheworkerthread,whichmeansthesamethreadisn’tbeingaskedtomanagebothengineworkand


http://docs.unity3d.com/ScriptReference/Rendering.CommandBuffer.html

graphicsAPIcallsatthesametime.Theseprocessesaremostlyindependent,andeventhoughadditionalworkmuststilltakeplaceinthemainthreadtosendinstructionstotheworkerthreadinthefirstplace(viatheinternalCommandBuffersystem),itismostlynegligible.Thismeansthatreducingtheworkloadinthemainthreadwillhavelittle-to-noeffectonrenderingperformance.

NoteNotethatbeingGPU-boundisthesameregardlessofwhethermultithreadedrenderingistakingplace.

GPUSkinningWhilewe’reonthesubjectofCPU-bounding,onetaskthatcanhelpreduceCPUworkload,attheexpenseofadditionalGPUworkload,isGPUSkinning.Skinningistheprocesswheremeshverticesaretransformedbasedonthecurrentlocationoftheiranimatedbones.Theanimationsystem,workingontheCPU,onlytransformsthebones,butanotherstepintherenderingprocessmusttakecareofthevertextransformationstoplacetheverticesaroundthosebones,performingaweightedaverageoverthebonesconnectedtothosevertices.

ThisvertexprocessingtaskcaneithertakeplaceontheCPUorwithinthefrontendoftheGPU,dependingonwhethertheGPUSkinningoptionisenabled.ThisfeaturecanbetoggledunderEdit|ProjectSettings|PlayerSettings|OtherSettings|GPUSkinning.


FrontendbottlenecksWehavealreadycoveredsometechniquesonmeshoptimizationinChapter4,KickstartYourArt,whichcanhelpreduceourmesh’svertexattributes.Asaquickreminder,itisnotuncommontouseameshthatcontainsalotofunnecessaryUVandNormalvectordata,soourmeshesshouldbedouble-checkedforthiskindofsuperfluousfluff.WeshouldalsoletUnityoptimizethestructureforus,whichminimizescachemissesasvertexdataisreadwithinthefrontend.

WewillalsolearnsomeusefulShaderoptimizationtechniquesshortly,whenwebegintodiscussbackendoptimizations,sincemanyoptimizationtechniquesapplytobothFragmentandVertexShaders.

Theonlyattackvectorlefttocoverisfindingwaystoreduceactualvertexcounts.Theobvioussolutionsaresimplificationandculling;eitherhavetheartteamreplaceproblematicmesheswithlowerpolycountversions,and/orremovesomeobjectsfromthescenetoreducetheoverallpolygoncount.Iftheseapproacheshavealreadybeenexplored,thenthelastapproachwecantakeistofindsomekindofmiddlegroundbetweenthetwo.


LevelOfDetailSinceitcanbedifficulttotellthedifferencebetweenahighqualitydistanceobjectandalowqualityone,thereisverylittlereasontorenderthehighqualityversion.So,whynotdynamicallyreplacedistantobjectswithsomethingmoresimplified?

LevelOfDetail(LOD),isabroadtermreferringtothedynamicreplacementoffeaturesbasedontheirdistanceorformfactorrelativetothecamera.Themostcommonimplementationismesh-basedLOD:dynamicallyreplacingameshwithlowerandlowerdetailedversionsasthecameragetsfartherandfartheraway.Anotherexamplemightbereplacinganimatedcharacterswithversionsfeaturingfewerbones,orlesssamplingfordistantobjects,inordertoreduceanimationworkload.

TipThebuilt-inLODfeatureisavailableintheUnity4ProEditionandalleditionsofUnity5.However,itisentirelypossibletoimplementitviaScriptcodeinUnity4FreeEditionifdesired.

MakinguseofLODcanbeachievedbyplacingmultipleobjectsintheSceneandmakingthemchildrenofaGameObjectwithanattachedLODGroupcomponent.TheLODGroup’spurposeistogenerateaboundingboxfromtheseobjects,anddecidewhichobjectshouldberenderedbasedonthesizeoftheboundingboxwithinthecamera’sfieldofview.Iftheobject’sboundingboxconsumesalargeareaofthecurrentview,thenitwillenablethemesh(es)assignedtolowerLODgroups,andiftheboundingboxisverysmall,itwillreplacethemesh(es)withthosefromhigherLODgroups.Ifthemeshistoofaraway,itcanbeconfiguredtohideallchildobjects.So,withthepropersetup,wecanhaveUnityreplacemesheswithsimpleralternatives,orcullthementirely,whicheasestheburdenontherenderingprocess.

NoteChecktheUnitydocumentationformoredetailedinformationontheLODfeature:http://docs.unity3d.com/Manual/LevelOfDetail.html.

Thisfeaturecancostusalargeamountofdevelopmenttimetofullyimplement;artistsmustgeneratelowerpolygoncountversionsofthesameobject,andleveldesignersmustgenerateLODgroups,configurethem,andtestthemtoensuretheydon’tcausejarringtransitionsasthecameramovescloserorfartheraway.ItalsocostsusinmemoryandruntimeCPU;thealternativemeshesneedtobekeptinmemory,andtheLODGroupcomponentmustroutinelytestwhetherthecamerahasmovedtoanewpositionthatwarrantsachangeinLODlevel.

Inthiseraofgraphicscardcapabilities,vertexprocessingisoftentheleastofourconcerns.CombinedwiththeadditionalsacrificesneededforLODtofunction,developersshouldavoidpreoptimizingbyautomaticallyassumingLODwillhelpthem.Excessiveuseofthefeaturewillleadtoburdeningotherpartsofourapplication’sperformance,andchewuppreciousdevelopmenttime,allforthesakeofparanoia.Ifithasn’tbeenproventobeaproblem,thenit’sprobablynotaproblem!


http://docs.unity3d.com/Manual/LevelOfDetail.html

Scenesthatfeaturelarge,expansiveviewsoftheworld,andlotsofcameramovement,shouldconsiderimplementingthistechniqueveryearly,astheaddeddistanceandmassivenumberofvisibleobjectswillexacerbatethevertexcountenormously.Scenesthatarealwaysindoors,orfeatureacamerawithaviewpointlookingdownattheworld(real-timestrategyandMOBAgames,forexample)shouldprobablysteerclearofimplementingLODfromthebeginning.Gamessomewherebetweenthetwoshouldavoidituntilnecessary.Italldependsonhowmanyverticesareexpectedtobevisibleatanygiventimeandhowmuchvariabilityincameradistancetherewillbe.

TipNotethatsomegamedevelopmentmiddlewarecompaniesofferthird-partytoolsforautomatedLODmeshgeneration.Thesemightbeworthinvestigatingtocomparetheireaseofuseversusqualitylossversuscosteffectiveness.


DisableGPUSkinningAspreviouslymentioned,wecouldenableGPUSkinningtoreducetheburdenonaCPU-boundapplication,butenablingthisfeaturewillpushthesameworkloadintothefrontendoftheGPU.SinceSkinningisoneofthose“embarrassinglyparallel”processesthatfitswellwiththeGPU’sparallelarchitecture,itisoftenagoodideatoperformthetaskontheGPU.Butthistaskcanchewupprecioustimeinthefrontendpreparingtheverticesforfragmentgeneration,sodisablingitisanotheroptionwecanexploreifwe’rebottleneckedinthisarea.Again,thisfeaturecanbetoggledunderEdit|ProjectSettings|PlayerSettings|OtherSettings|GPUSkinning.

TipGPUSkinningisavailableinUnity4ProEdition,andalleditionsofUnity5.


ReducetessellationThereisonelasttaskthattakesplaceinthefrontendprocessandthatweneedtoconsider:tessellation.TessellationthroughGeometryShaderscanbealotoffun,asitisarelativelyunderusedtechniquethatcanreallymakeourgraphicaleffectsstandoutfromthecrowdofgamesthatonlyusethemostcommoneffects.But,itcancontributeenormouslytotheamountofprocessingworktakingplaceinthefrontend.

Therearenosimpletrickswecanexploittoimprovetessellation,besidesimprovingourtessellationalgorithms,oreasingtheburdencausedbyotherfrontendtaskstogiveourtessellationtasksmoreroomtobreathe.Eitherway,ifwehaveabottleneckinthefrontendandaremakinguseoftessellationtechniques,weshoulddouble-checkthattheyarenotconsumingthelion’sshareofthefrontend’sbudget.


BackendbottlenecksThebackendisthemoreinterestingpartoftheGPUpipeline,asmanymoregraphicaleffectstakeplaceduringthisstage.Consequently,itisthestagethatissignificantlymorelikelytosufferfrombottlenecks.

Therearetwobruteforcetestswecanattempt:

ReduceresolutionReducetexturequality

Thesechangeswilleasetheworkloadduringtwoimportantstagesatthebackendofthepipeline:fillrateandmemorybandwidth,respectively.Fillratetendstobethemostcommonsourceofbottlenecksinthemoderneraofgraphicsrendering,sowewillcoveritfirst.


FillrateByreducingscreenresolution,wehaveaskedtherasterizationsystemtogeneratesignificantlyfewerfragmentsandtransposethemoverasmallercanvasofpixels.Thiswillreducethefillrateconsumptionoftheapplication,givingakeypartoftherenderingpipelinesomeadditionalbreathingroom.Ergo,ifperformancesuddenlyimproveswithascreenresolutionreduction,thenfillrateshouldbeourprimaryconcern.

FillrateisaverybroadtermreferringtothespeedatwhichtheGPUcandrawfragments.But,thisonlyincludesfragmentsthathavesurvivedallofthevariousconditionaltestswemighthaveenabledwithinthegivenShader.Afragmentismerelya“potentialpixel,”andifitfailsanyoftheenabledtests,thenitisimmediatelydiscarded.Thiscanbeanenormousperformance-saverasthepipelinecanskipthecostlydrawingstepandbeginworkonthenextfragmentinstead.

OnesuchexampleisZ-testing,whichcheckswhetherthefragmentfromacloserobjecthasalreadybeendrawntothesamepixelalready.Ifso,thenthecurrentfragmentisdiscarded.Ifnot,thenthefragmentispushedthroughtheFragmentShaderanddrawnoverthetargetpixel,whichconsumesexactlyonedrawfromourfillrate.Nowimaginemultiplyingthisprocessbythousandsofoverlappingobjects,eachgeneratinghundredsorthousandsofpossiblefragments,forhighscreenresolutionscausingmillions,orbillions,offragmentstobegeneratedeachandeveryframe.Itshouldbefairlyobviousthatskippingasmanyofthesedrawsaswecanwillresultinbigrenderingcostsavings.

Graphicscardmanufacturerstypicallyadvertiseaparticularfillrateasafeatureofthecard,usuallyintheformofgigapixelspersecond,butthisisabitofamisnomer,asitwouldbemoreaccuratetocallitgigafragmentspersecond;howeverthisargumentismostlyacademic.Eitherway,largervaluestellusthatthedevicecanpotentiallypushmorefragmentsthroughthepipeline,sowithabudgetof30GPix/sandatargetframerateof60Hz,wecanaffordtoprocess30,000,000,000/60=500millionfragmentsperframebeforebeingbottleneckedonfillrate.Witharesolutionof2560x1440,andabest-casescenariowhereeachpixelisonlydrawnoveronce,thenwecouldtheoreticallydrawtheentiresceneabout125timeswithoutanynoticeableproblems.

Sadly,thisisnotaperfectworld,andunlesswetakesignificantstepstoavoidit,wewillalwaysendupwithsomeamountofredrawoverthesamepixelsduetotheorderinwhichobjectsarerendered.Thisisknownasoverdraw,anditcanbeverycostlyifwe’renotcareful.

TipThereasonthatresolutionisagoodattackvectortocheckforfillrateboundingisthatitisamultiplier.Areductionfromaresolutionof2560x1440to800x600isanimprovementfactorofabouteight,whichcouldreducefillratecostsenoughtomaketheapplicationperformwellagain.

OverdrawDetermininghowmuchoverdrawwehavecanberepresentedvisuallybyrenderingall


objectswithadditivealphablendingandaverytransparentflatcolor.Areasofhighoverdrawwillshowupmorebrightlyasthesamepixelisdrawnoverwithadditiveblendingmultipletimes.ThisispreciselyhowtheSceneview’sOverdrawshadingmoderevealshowmuchoverdrawoursceneissuffering.

Thefollowingscreenshotshowsascenewithseveralthousandboxesdrawnnormally,anddrawnusingtheSceneview’sOverdrawshadingmode:

Attheendoftheday,fillrateisprovidedasameansofgaugingthebest-casebehavior.Inotherwords,it’sprimarilyamarketingtermandmostlytheoretical.But,thetechnicalsideoftheindustryhasadoptedthetermasawayofdescribingthebackendofthepipeline:thestagewherefragmentdataisfunneledthroughourShadersanddrawntothescreen.

Ifeveryfragmentrequiredanabsoluteminimumlevelofprocessing(suchasaShaderthatreturnedaconstantcolor),thenwemightgetclosetothattheoreticalmaximum.TheGPUisacomplexbeast,however,andthingsareneversosimple.Thenatureofthedevicemeansitworksbestwhengivenmanysmalltaskstoperform.But,ifthetasksgettoolarge,thenfillrateislostduetothebackendnotbeingabletopushthroughenoughfragmentsintimeandtherestofthepipelineisleftwaitingfortaskstodo.

Thereareseveralmorefeaturesthatcanpotentiallyconsumeourtheoreticalfillratemaximum,includingbutnotlimitedtoalphatesting,alphablending,texturesampling,theamountoffragmentdatabeingpulledthroughourShaders,andeventhecolorformatofthetargetrendertexture(thefinalFrameBufferinmostcases).Thebadnewsisthatthisgivesusalotofsubsectionstocover,andalotofwaystobreaktheprocess,butthegoodnewsisitgivesusalotofavenuestoexploretoimproveourfillrateusage.

OcclusionCullingOneofthebestwaystoreduceoverdrawistomakeuseofUnity’sOcclusionCullingsystem.ThesystemworksbypartitioningScenespaceintoaseriesofcellsandflyingthroughtheworldwithavirtualcameramakingnoteofwhichcellsareinvisiblefrom


othercells(areoccluded)basedonthesizeandpositionoftheobjectspresent.

NotethatthisisdifferenttothetechniqueofFrustumCulling,whichcullsobjectsnotvisiblefromthecurrentcameraview.Thisfeatureisalwaysactiveinallversions,andobjectsculledbythisprocessareautomaticallyignoredbytheOcclusionCullingsystem.

TipOcclusionCullingisavailableintheUnity4ProEditionandalleditionsofUnity5.

OcclusionCullingdatacanonlybegeneratedforobjectsproperlylabeledOccluderStaticandOccludeeStaticundertheStaticFlagsdropdown.OccluderStaticisthegeneralsettingforstaticobjectswherewewantittohideotherobjects,andbehiddenbylargeobjectsinitsway.OccludeeStaticisaspecialcasefortransparentobjectsthatallowsobjectsbehindthemtoberendered,butwewantthemtobehiddenifsomethinglargeblockstheirvisibility.

Naturally,becauseoneofthestaticflagsmustbeenabledforOcclusionCulling,thisfeaturewillnotworkfordynamicobjects.

ThefollowingscreenshotshowshoweffectiveOcclusionCullingcanbeatreducingthenumberofvisibleobjectsinourScene:


Thisfeaturewillcostusinbothapplicationfootprintandincursomeruntimecosts.ItwillcostRAMtokeeptheOcclusionCullingdatastructureinmemory,andtherewillbeaCPUprocessingcosttodeterminewhichobjectsarebeingoccludedineachframe.

TheOcclusionCullingdatastructuremustbeproperlyconfiguredtocreatecellsoftheappropriatesizeforourScene,andthesmallerthecells,thelongerittakestogeneratethedatastructure.But,ifitisconfiguredcorrectlyfortheScene,OcclusionCullingcanprovidebothfillratesavingsthroughreducedoverdraw,andDrawCallsavingsbycullingnon-visibleobjects.

ShaderoptimizationShaderscanbeasignificantfillrateconsumer,dependingontheircomplexity,howmuchtexturesamplingtakesplace,howmanymathematicalfunctionsareused,andsoon.Shadersdonotdirectlyconsumefillrate,butdosoindirectlybecausetheGPUmustcalculateorfetchdatafrommemoryduringShaderprocessing.TheGPU’sparallelnaturemeansanybottleneckinathreadwilllimithowmanyfragmentscanbepushedintothethreadatalaterdate,butparallelizingthetask(sharingsmallpiecesofthejobbetween


severalagents)providesanetgainoverserialprocessing(oneagenthandlingeachtaskoneafteranother).

Theclassicexampleisavehicleassemblyline.Acompletevehiclerequiresmultiplestagesofmanufacturetocomplete.Thecriticalpathtocompletionmightinvolvefivesteps:stamping,welding,painting,assembly,andinspection,andeachstepiscompletedbyasingleteam.Foranygivenvehicle,nostagecanbeginbeforethepreviousoneisfinished,butwhateverteamhandledthestampingforthelastvehiclecanbeginstampingforthenextvehicleassoonasithasfinished.Thisorganizationallowseachteamtobecomemastersoftheirparticulardomain,ratherthantryingtospreadtheirknowledgetoothin,whichwouldlikelyresultinlessconsistentqualityinthebatchofvehicles.

Wecandoubletheoveralloutputbydoublingthenumberofteams,butifanyteamgetsblocked,thenprecioustimeislostforanygivenvehicle,aswellasallfuturevehiclesthatwouldpassthroughthesameteam.Ifthesedelaysarerare,thentheycanbenegligibleinthegrandscheme,butifnot,andonestagetakesseveralminuteslongerthannormaleachandeverytimeitmustcompletethetask,thenitcanbecomeabottleneckthatthreatensthereleaseoftheentirebatch.

TheGPUparallelprocessorsworkinasimilarway:eachprocessorthreadisanassemblyline,eachprocessingstageisateam,andeachfragmentisavehicle.Ifthethreadspendsalongtimeprocessingasinglestage,thentimeislostoneachfragment.Thisdelaywillmultiplysuchthatallfuturefragmentscomingthroughthesamethreadwillbedelayed.Thisisabitofanoversimplification,butitoftenhelpstopaintapictureofhowpoorlyoptimizedShadercodecanchewupourfillrate,andhowsmallimprovementsinShaderoptimizationprovidebigbenefitsinbackendperformance.

Shaderprogrammingandoptimizationhavebecomeaverynicheareaofgamedevelopment.Theirabstractandhighly-specializednaturerequiresaverydifferentkindofthinkingtogenerateShadercodecomparedtogameplayandenginecode.Theyoftenfeaturemathematicaltricksandback-doormechanismsforpullingdataintotheShader,suchasprecomputingvaluesintexturefiles.Becauseofthis,andtheimportanceofoptimization,Shaderstendtobeverydifficulttoreadandreverse-engineer.

Consequently,manydevelopersrelyonprewrittenShaders,orvisualShadercreationtoolsfromtheAssetStoresuchasShaderForgeorShaderSandwich.ThissimplifiestheactofinitialShadercodegeneration,butmightnotresultinthemostefficientformofShaders.Ifwe’rerelyingonpre-writtenShadersortools,wemightfinditworthwhiletoperformsomeoptimizationpassesoverthemusingsometried-and-truetechniques.So,let’sfocusonsomeeasilyreachablewaysofoptimizingourShaders.

ConsiderusingShadersintendedformobileplatformsThebuilt-inmobileShadersinUnitydonothaveanyspecificrestrictionsthatforcethemtoonlybeusedonmobiledevices.Theyaresimplyoptimizedforminimumresourceusage(andtendtofeaturesomeoftheotheroptimizationslistedinthissection).

DesktopapplicationsareperfectlycapableofusingtheseShaders,buttheytendtofeaturealossofgraphicalquality.Itonlybecomesaquestionofwhetherthelossofgraphical


qualityisacceptable.So,considerdoingsometestingwiththemobileequivalentsofcommonShaderstoseewhethertheyareagoodfitforyourgame.

Usesmalldatatypes

GPUscancalculatewithsmallerdatatypesmorequicklythanlargertypes(particularlyonmobileplatforms!),sothefirsttweakwecanattemptisreplacingourfloatdatatypes(32-bit,floatingpoint)withsmallerversionssuchashalf(16-bit,floatingpoint),orevenfixed(12-bit,fixedpoint).

NoteThesizeofthedatatypeslistedabovewillvarydependingonwhatfloatingpointformatsthetargetplatformprefers.Thesizeslistedarethemostcommon.Theimportanceforoptimizationisintherelativesizebetweenformats.

Colorvaluesaregoodcandidatesforprecisionreduction,aswecanoftengetawaywithlessprecisecolorvalueswithoutanynoticeablelossincoloration.However,theeffectsofreducingprecisioncanbeveryunpredictableforgraphicalcalculations.So,changessuchasthesecanrequiresometestingtoverifywhetherthereducedprecisioniscostingtoomuchgraphicalfidelity.

NotethattheeffectsofthesetweakscanvaryenormouslybetweenoneGPUarchitectureandanother(forexample,AMDversusNvidiaversusIntel),andevenGPUbrandsfromthesamemanufacturer.Insomecases,wecanmakesomedecentperformancegainsforatrivialamountofeffort.Inothercases,wemightseenobenefitatall.

Avoidchangingprecisionwhileswizzling

SwizzlingistheShaderprogrammingtechniqueofcreatinganewvector(anarrayofvalues)fromanexistingvectorbylistingthecomponentsintheorderinwhichwewishtocopythemintothenewstructure.Herearesomeexamplesofswizzling:

float4input=float4(1.0,2.0,3.0,4.0);//initialtestvalue

float2val1=input.yz;//swizzletwocomponents

float3val2=input.zyx;//swizzlethreecomponentsinadifferentorder

float4val3=input.yyy;//swizzlethesamecomponentmultipletimes

floatsclr=input.w;

float3val4=sclr.xxx//swizzleascalarmultipletimes

Wecanuseboththexyzwandrgbarepresentationstorefertothesamecomponents,sequentially.Itdoesnotmatterwhetheritisacolororvector;theyjustmaketheShadercodeeasiertoread.Wecanalsolistcomponentsinanyorderweliketofillinthedesireddata,repeatingthemifnecessary.

ConvertingfromoneprecisiontypetoanotherinaShadercanbeacostlyoperation,butconvertingtheprecisiontypewhilesimultaneouslyswizzlingcanbeparticularlypainful.Ifwehavemathematicaloperationsthatrelyonbeingswizzledintodifferentprecision


types,itwouldbewiserifwesimplyabsorbedthehigh-precisioncostfromtheverybeginning,orreducedprecisionacrosstheboardtoavoidtheneedforchangesinprecision.

UseGPU-optimizedhelperfunctions

TheShadercompileroftenperformsagoodjobofreducingmathematicalcalculationsdowntoanoptimizedversionfortheGPU,butcompiledcustomcodeisunlikelytobeaseffectiveasboththeCglibrary’sbuilt-inhelperfunctionsandtheadditionalhelpersprovidedbytheUnityCgincludedfiles.IfweareusingShadersthatincludecustomfunctioncode,perhapswecanfindanequivalenthelperfunctionwithintheCgorUnitylibrariesthatcandoabetterjobthanourcustomcodecan.

TheseextraincludefilescanbeaddedtoourShaderwithintheCGPROGRAMblocklikeso:

CGPROGRAM

//otherincludes

#include"UnityCG.cginc"

//Shadercodehere

ENDCG

ExampleCglibraryfunctionstouseareabs()forabsolutevalues,lerp()forlinearinterpolation,mul()formultiplyingmatrices,andstep()forstepfunctionality.UsefulUnityCG.cgincfunctionsincludeWorldSpaceViewDir()forcalculatingthedirectiontowardsthecamera,andLuminance()forconvertingacolortograyscale.

NoteCheckthefollowingURLforafulllistofCgstandardlibraryfunctions:http://http.developer.nvidia.com/CgTutorial/cg_tutorial_appendix_e.html.

ChecktheUnitydocumentationforacompleteandup-to-datelistofpossibleincludefilesandtheiraccompanyinghelperfunctions:http://docs.unity3d.com/Manual/SL-BuiltinIncludes.html.

Disableunnecessaryfeatures

PerhapswecanmakesavingsbysimplydisablingShaderfeaturesthataren’tvital.DoestheShaderreallyneedmultiplepasses,transparency,Z-writing,alpha-testing,and/oralphablending?Willtweakingthesesettingsorremovingthesefeaturesgiveusagoodapproximationofourdesiredeffectwithoutlosingtoomuchgraphicalfidelity?Makingsuchchangesisagoodwayofmakingfillratecostsavings.

Removeunnecessaryinputdata

SometimestheprocessofwritingaShaderinvolvesalotofbackandforthexperimentationineditingcodeandviewingitintheScene.ThetypicalresultofthisisthatinputdatathatwasneededwhentheShaderwasgoingthroughearlydevelopmentisnowsurplusfluffoncethedesiredeffecthasbeenobtained,andit’seasytoforgetwhatchangesweremadewhen/iftheprocessdragsonforalongtime.But,theseredundantdatavaluescancosttheGPUvaluabletimeastheymustbefetchedfrommemoryeveniftheyarenotexplicitlyusedbytheShader.So,weshoulddoublecheckourShaderstoensure


http://http.developer.nvidia.com/CgTutorial/cg_tutorial_appendix_e.html

http://docs.unity3d.com/Manual/SL-BuiltinIncludes.html

alloftheirinputgeometry,vertex,andfragmentdataisactuallybeingused.

Onlyexposenecessaryvariables

ExposingunnecessaryvariablesfromourShadertotheaccompanyingMaterial(s)canbecostlyastheGPUcan’tassumethesevaluesareconstant.ThismeanstheShadercodecannotbecompiledintoamoreoptimizedform.ThisdatamustbepushedfromtheCPUwitheverypasssincetheycanbemodifiedatanytimethroughtheMaterial’smethodssuchasSetColor(),SetFloat(),andsoon.Ifwefindthat,towardstheendoftheproject,wealwaysusethesamevalueforthesevariables,thentheycanbereplacedwithaconstantintheShadertoremovesuchexcessruntimeworkload.Theonlycostisobfuscatingwhatcouldbecriticalgraphicaleffectparameters,sothisshouldbedoneverylateintheprocess.

Reducemathematicalcomplexity

Complicatedmathematicscanseverelybottlenecktherenderingprocess,soweshoulddowhateverwecantolimitthedamage.ComplexmathematicalfunctionscouldbereplacedwithatexturethatisfedintotheShaderandprovidesapre-generatedtableforruntimelookup.Wemaynotseeanyimprovementwithfunctionssuchassinandcos,sincethey’vebeenheavilyoptimizedtomakeuseofGPUarchitecture,butcomplexmethodssuchaspow,exp,log,andothercustommathematicalprocessescanonlybeoptimizedsomuch,andwouldbegoodcandidatesforsimplification.Thisisassumingweonlyneedoneortwoinputvalues,whicharerepresentedthroughtheXandYcoordinatesofthetexture,andmathematicalaccuracyisn’tofparamountimportance.

Thiswillcostusadditionalgraphicsmemorytostorethetextureatruntime(moreonthislater),butiftheShaderisalreadyreceivingatexture(whichtheyareinmostcases)andthealphachannelisnotbeingused,thenwecouldsneakthedatainthroughthetexture’salphachannel,costingusliterallynoperformance,andtherestoftheShadercodeandgraphicssystemwouldbenone-the-wiser.Thiswillinvolvethecustomizationofartassetstoincludesuchdatainanyunusedcolorchannel(s),requiringcoordinationbetweenprogrammersandartists,butisaverygoodwayofsavingShaderprocessingcostswithnoruntimesacrifices.

Infact,MaterialpropertiesandtexturesarebothexcellententrypointsforpushingworkfromtheShader(theGPU)ontotheCPU.Ifacomplexcalculationdoesnotneedtovaryonaperpixelbasis,thenwecouldexposethevalueasapropertyintheMaterial,andmodifyitasneeded(acceptingtheoverheadcostofdoingsofromtheprevioussectionOnlyexposenecessaryvariables).Alternatively,iftheresultvariesperpixel,anddoesnotneedtochangeoften,thenwecouldgenerateatexturefilefromscriptcode,containingtheresultsofthecalculationsintheRGBAvalues,andpullingthetextureintotheShader.Lotsofopportunitiesarisewhenweignoretheconventionalapplicationofsuchsystems,andremembertothinkofthemasjustrawdatabeingtransferredaround.

Reducetexturelookups

Whilewe’reonthesubjectoftexturelookups,theyarenottrivialtasksfortheGPUtoprocessandtheyhavetheirownoverheadcosts.Theyarethemostcommoncauseof


memoryaccessproblemswithintheGPU,especiallyifaShaderisperformingsamplesacrossmultipletextures,orevenmultiplesamplesacrossasingletexture,astheywilllikelyinflictcachemissesinmemory.SuchsituationsshouldbesimplifiedasmuchaspossibletoavoidsevereGPUmemorybottlenecking.

Evenworse,samplingatextureinarandomorderwouldlikelyresultinsomeverycostlycachemissesfortheGPUtosufferthrough,soifthisisbeingdone,thenthetextureshouldbereorderedsothatitcanbesampledinamoresequentialorder.

Avoidconditionalstatements

InmoderndayCPUarchitecture,conditionalstatementsundergoalotofcleverpredictivetechniquestomakeuseofinstruction-levelparallelism.ThisisafeaturewheretheCPUattemptstopredictwhichdirectionaconditionalstatementwillgoinbeforeithasactuallybeenresolved,andspeculativelybeginsprocessingthemostlikelyresultoftheconditionalusinganyfreecomponentsthataren’tbeingusedtoresolvetheconditional(fetchingsomedatafrommemory,copyingsomefloatsintounusedregisters,andsoon).Ifitturnsoutthatthedecisioniswrong,thenthecurrentresultisdiscardedandtheproperpathistakeninstead.

Solongasthecostofspeculativeprocessinganddiscardingfalseresultsislessthanthetimespentwaitingtodecidethecorrectpath,anditisrightmoreoftenthanitiswrong,thenthisisanetgainfortheCPU’sspeed.

However,thisfeatureisnotpossibleonGPUarchitecturebecauseofitsparallelnature.TheGPU’scoresaretypicallymanagedbysomehigher-levelconstructthatinstructsallcoresunderitscommandtoperformthesamemachine-code-levelinstructionsimultaneously.So,iftheFragmentShaderrequiresafloattobemultipliedby2,thentheprocesswillbeginbyhavingallcorescopydataintotheappropriateregistersinonecoordinatedstep.Onlywhenallcoreshavefinishedcopyingtotheregisterswillthecoresbeinstructedtobeginthesecondstep:multiplyingallregistersby2.

Thus,whenthissystemstumblesintoaconditionalstatement,itcannotresolvethetwostatementsindependently.Itmustdeterminehowmanyofitschildcoreswillgodowneachpathoftheconditional,grabthelistofrequiredmachinecodeinstructionsforonepath,resolvethemforallcorestakingthatpath,andrepeatforeachpathuntilallpossiblepathshavebeenprocessed.So,foranif-elsestatement(twopossibilities),itwilltellonegroupofcorestoprocessthe“true”path,thenasktheremainingcorestoprocessthe“false”path.Unlesseverycoretakesthesamepath,itmustprocessbothpathseverytime.

So,weshouldavoidbranchingandconditionalstatementsinourShadercode.Ofcourse,thisdependsonhowessentialtheconditionalistoachievingthegraphicaleffectwedesire.But,iftheconditionalisnotdependentonperpixelbehavior,thenwewouldoftenbebetteroffabsorbingthecostofunnecessarymathematicsthaninflictingabranchingcostontheGPU.Forexample,wemightbecheckingwhetheravalueisnon-zerobeforeusingitinacalculation,orcomparingagainstsomeglobalflagintheMaterialbeforetakingoneactionoranother.Bothofthesecaseswouldbegoodcandidatesforoptimizationbyremovingtheconditionalcheck.


Reducedatadependencies

ThecompilerwilltryitsbesttooptimizeourShadercodeintothemoreGPU-friendlylow-levellanguagesothatitisnotwaitingondatatobefetchedwhenitcouldbeprocessingsomeothertask.Forexample,thefollowingpoorly-optimizedcode,couldbewritteninourShader:

floatsum=input.color1.r;

sum=sum+input.color2.g;

sum=sum+input.color3.b;

sum=sum+input.color4.a;

floatresult=calculateSomething(sum);

IfwewereabletoforcetheShadercompilertocompilethiscodeintomachinecodeinstructionsasitiswritten,thenthiscodehasadatadependencysuchthateachcalculationcannotbeginuntilthelastfinishesduetothedependencyonthesumvariable.But,suchsituationsareoftendetectedbytheShadercompilerandoptimizedintoaversionthatusesinstruction-levelparallelism(thecodeshownnextisthehigh-levelcodeequivalentoftheresultingmachinecode):

floatsum1,sum2,sum3,sum4;

sum1=input.color1.r;

sum2=input.color2.g;

sum3=input.color3.b

sum4=input.color4.a;

floatsum=sum1+sum2+sum3+sum4;

floatresult=CalculateSomething(sum);

Inthiscase,thecompilerwouldrecognizethatitcanfetchthefourvaluesfrommemoryinparallelandcompletethesummationonceallfourhavebeenfetchedindependentlyviathread-levelparallelism.Thiscansavealotoftime,relativetoperformingthefourfetchesoneafteranother.

However,longchainsofdatadependencycanabsolutelymurderShaderperformance.IfwecreateastrongdatadependencyinourShader’ssourcecode,thenithasbeengivennofreedomtomakesuchoptimizations.Forexample,thefollowingdatadependencywouldbepainfulonperformance,asonestepcannotbecompletedwithoutwaitingonanothertofetchdataandperformingtheappropriatecalculation.

float4val1=tex2D(_tex1,input.texcoord.xy);

float4val2=tex2D(_tex2,val1.yz);

float4val3=tex2D(_tex3,val2.zw);

Strongdatadependenciessuchastheseshouldbeavoidedwheneverpossible.

SurfaceShaders

Ifwe’reusingUnity’sSurfaceShaders,whichareawayforUnitydeveloperstogettogripswithShaderprogramminginamoresimplifiedfashion,thentheUnityEnginetakescareofconvertingourSurfaceShadercodeforus,abstractingawaysomeoftheoptimizationopportunitieswehavejustcovered.However,itdoesprovidesomemiscellaneousvaluesthatcanbeusedasreplacements,whichreduceaccuracybut


simplifythemathematicsintheresultingcode.SurfaceShadersaredesignedtohandlethegeneralcasefairlyefficiently,butoptimizationisbestachievedwithapersonaltouch.

Theapproxviewattributewillapproximatetheviewdirection,savingcostlyoperations.halfasviewwillreducetheprecisionoftheviewvector,butbewareofitseffectonmathematicaloperationsinvolvingmultipleprecisiontypes.noforwardaddwilllimittheShadertoonlyconsideringasingledirectionallight,reducingDrawCallssincetheShaderwillrenderinonlyasinglepass,butreducinglightingcomplexity.Finally,noambientwilldisableambientlightingintheShader,removingsomeextramathematicaloperationsthatwemaynotneed.

UseShader-basedLOD

WecanforceUnitytorenderdistantobjectsusingsimplerShaders,whichcanbeaneffectivewayofsavingfillrate,particularlyifwe’redeployingourgameontomultipleplatformsorsupportingawiderangeofhardwarecapability.TheLODkeywordcanbeusedintheShadertosettheonscreensizefactorthattheShadersupports.IfthecurrentLODleveldoesnotmatchthisvalue,itwilldroptothenextfallbackShaderandsoonuntilitfindstheShaderthatsupportsthegivensizefactor.WecanalsochangeagivenShaderobject’sLODvalueatruntimeusingthemaximumLODproperty.

Thisfeatureissimilartothemesh-basedLODcoveredearlier,andusesthesameLODvaluesfordeterminingobjectformfactor,soitshouldbeconfiguredassuch.


MemorybandwidthAnothermajorcomponentofbackendprocessingandapotentialsourceofbottlenecksismemorybandwidth.MemorybandwidthisconsumedwheneveratexturemustbepulledfromasectionoftheGPU’smainvideomemory(alsoknownasVRAM).TheGPUcontainsmultiplecoresthateachhaveaccesstothesameareaofVRAM,buttheyalsoeachcontainamuchsmaller,localTextureCachethatstoresthecurrenttexture(s)theGPUhasbeenmostrecentlyworkingwith.ThisissimilarindesigntothemultitudeofCPUcachelevelsthatallowmemorytransferupanddownthechain,asaworkaroundforthefactthatfastermemorywill,invariably,bemoreexpensivetoproduce,andhencesmallerincapacitycomparedtoslowermemory.

WheneveraFragmentShaderrequestsasamplefromatexturethatisalreadywithinthecore’slocalTextureCache,thenitislightningfastandbarelyperceivable.But,ifatexturesamplerequestismade,thatdoesnotyetexistwithintheTextureCache,thenitmustbepulledinfromVRAMbeforeitcanbesampled.ThisfetchrequestriskscachemisseswithinVRAMasittriestofindtherelevanttexture.Thetransferitselfconsumesacertainamountofmemorybandwidth,specificallyanamountequaltothetotalsizeofthetexturefilestoredwithinVRAM(whichmaynotbetheexactsizeoftheoriginalfile,northesizeinRAM,duetoGPU-levelcompression).

It’sforthisreasonthat,ifwe’rebottleneckedonmemorybandwidth,thenperformingabruteforcetestbyreducingtexturequalitywouldsuddenlyresultinaperformanceimprovement.We’veshrunkthesizeofourtextures,easingtheburdenontheGPU’smemorybandwidth,allowingittofetchthenecessarytexturesmuchquicker.GloballyreducingtexturequalitycanbeachievedbygoingtoEdit|ProjectSettings|Quality|TextureQualityandsettingthevaluetoHalfRes,QuarterRes,orEighthRes.

Intheeventthatmemorybandwidthisbottlenecked,thentheGPUwillkeepfetchingthenecessarytexturefiles,buttheentireprocesswillbethrottledastheTextureCachewaitsforthedatatoappearbeforeprocessingthefragment.TheGPUwon’tbeabletopushdatabacktotheFrameBufferintimetoberenderedontothescreen,blockingthewholeprocessandculminatinginapoorframerate.

Ultimately,properusageofmemorybandwidthisabudgetingconcern.Forexample,withamemorybandwidthof96GB/secpercoreandatargetframerateof60framespersecond,thentheGPUcanaffordtopull96/60=1.6GBworthoftexturedataeveryframebeforebeingbottleneckedonmemorybandwidth.

TipMemorybandwidthisoftenlistedonapercorebasis,butsomeGPUmanufacturersmaytrytomisleadyoubymultiplyingmemorybandwidthbythenumberofcoresinordertolistabigger,butlesspracticalnumber.Becauseofthis,researchmaybenecessarytoconfirmthememorybandwidthlimitwehaveforthetargetGPUhardwareisgivenonapercorebasis.

Notethatthisvalueisnotthemaximumlimitonthetexturedatathatourgamecan


containintheproject,norinCPURAM,noteveninVRAM.Itisametricthatlimitshowmuchtextureswappingcanoccurduringoneframe.ThesametexturecouldbepulledbackandforthmultipletimesinasingleframedependingonhowmanyShadersneedtousethem,theorderthattheobjectsarerendered,andhowoftentexturesamplingmustoccur,sorenderingjustafewobjectscouldconsumewholegigabytesofmemorybandwidthiftheyallrequirethesamehighquality,massivetextures,requiremultiplesecondarytexturemaps(normalmaps,emissionmaps,andsoon),andarenotbatchedtogether,becausetheresimplyisn’tenoughTextureCachespaceavailabletokeepasingletexturefilelongenoughtoexploititduringthenextrenderingpass.

Thereareseveralapproacheswecantaketosolvebottlenecksinmemorybandwidth.

UselesstexturedataThisapproachissimple,straightforward,andalwaysagoodideatoconsider.Reducingtexturequality,eitherthroughresolutionorbitrate,isnotidealforgraphicalquality,butwecansometimesgetawaywithusing16-bittextureswithoutanynoticeabledegradation.

MipMaps(Chapter4,KickstartYourArt)areanotherexcellentwayofreducingtheamountoftexturedatabeingpushedbackandforthbetweenVRAMandtheTextureCache.NotethattheSceneViewhasaMipmapsShadingMode,whichwillhighlighttexturesinoursceneblueorreddependingonwhetherthecurrenttexturescaleisappropriateforthecurrentSceneView’scamerapositionandorientation.Thiswillhelpidentifywhattexturesaregoodcandidatesforfurtheroptimization.

TipMipMapsshouldalmostalwaysbeusedin3DScenes,unlessthecameramovesverylittle.

TestdifferentGPUTextureCompressionformatsTheTextureCompressiontechniquesyoulearnedbackinChapter4,KickstartYourArt,weredescribedinsuchawaythathelpedreduceourapplication’sfootprint(executablefilesize),andruntimeCPUmemoryusage,thatis,thestorageareawherealltextureresourcedataiskeptuntilitisneededbytheGPU.However,oncethedatareachestheGPU,itusesadifferentformofcompressiontokeeptexturedatasmall.ThecommonformatsareDXT,PVRTC,ETC,andASTC.

Tomakemattersmoreconfusing,eachplatformandGPUhardwaresupportsdifferentcompressionformats,andifthedevicedoesnotsupportthegivencompressionformat,thenitwillbehandledatthesoftwarelevel.Inotherwords,theCPUwillneedtostopandrecompressthetexturetothedesiredformattheGPUwants,asopposedtotheGPUtakingcareofitwithaspecializedhardwarechip.

ThecompressionoptionsareonlyavailableifatextureresourcehasitsTextureTypefieldsettoAdvanced.Usinganyoftheothertexturetypesettingswillsimplifythechoices,andUnitywillmakeabestguesswhendecidingwhichformattouseforthetargetplatform,whichmaynotbeidealforagivenpieceofhardwareandthuswillconsumemorememorybandwidththannecessary.


ThebestapproachtodeterminingthecorrectformatistosimplytestabunchofdifferentdevicesandTextureCompressiontechniquesandfindonethatfits.Forexample,commonwisdomsaysthatETCisthebestchoiceforAndroidsincemoredevicessupportit,butsomedevelopershavefoundtheirgameworksbetterwiththeDXTandPVRTCformatsoncertaindevices.

Bewarethat,ifwe’reatthepointwhereindividuallytweakingTextureCompressiontechniquesisnecessary,thenhopefullywehaveexhaustedallotheroptionsforreducingmemorybandwidth.Bygoingdownthisroad,wecouldbecommittingtosupportingmanydifferentdeviceseachintheirownspecificway.Manyofuswouldprefertokeepthingssimplewithageneralsolutioninsteadofpersonalcustomizationandtime-consuminghandiworktoworkaroundproblemslikethis.

MinimizetexturesamplingCanwemodifyourShaderstoremovesometexturesamplingoverhead?Didweaddsomeextratexturelookupfilestogiveourselvessomefillratesavingsonmathematicalfunctions?Ifso,wemightwanttoconsiderloweringtheresolutionofsuchtexturesorrevertingthechangesandsolvingourfillrateproblemsinotherways.Essentially,thelesstexturesamplingwedo,thelessoftenweneedtousememorybandwidthandthecloserwegettoresolvingthebottleneck.

OrganizeassetstoreducetextureswapsThisapproachbasicallycomesbacktoBatchingandAtlasingagain.Arethereopportunitiestobatchsomeofourbiggesttexturefilestogether?Ifso,thenwecouldsavetheGPUfromhavingtopullinthesametexturefilesoverandoveragainduringthesameframe.Asalastresort,wecouldlookforwaystoremovesometexturesfromtheentireprojectandreusesimilarfiles.Forinstance,ifwehavefillratebudgettospare,thenwemaybeabletousesomeFragmentShaderstomakeahandfuloftexturesfilesappearinourgamewithdifferentcolorvariations.


VRAMlimitsOnelastconsiderationrelatedtotexturesishowmuchVRAMwehaveavailable.MosttexturetransferfromCPUtoGPUoccursduringinitialization,butcanalsooccurwhenanon-existenttextureisfirstrequiredbythecurrentview.Thisprocessisasynchronousandwillresultinablanktexturebeinguseduntilthefulltextureisreadyforrendering.Assuch,weshouldavoidtoomuchtexturevariationacrossourScenes.

TexturepreloadingEventhoughitdoesn’tstrictlyrelatetographicsperformance,itisworthmentioningthattheblanktexturethatisusedduringasynchronoustextureloadingcanbejarringwhenitcomestogamequality.WewouldlikeawaytocontrolandforcethetexturetobeloadedfromdisktothemainmemoryandthentoVRAMbeforeitisactuallyneeded.

AcommonworkaroundistocreateahiddenGameObjectthatfeaturesthetextureandplaceitsomewhereintheSceneontheroutethattheplayerwilltaketowardstheareawhereitisactuallyneeded.Assoonasthetexturedobjectbecomesacandidatefortherenderingsystem(evenifit’stechnicallyhidden),itwillbegintheprocessofcopyingthedatatowardsVRAM.Thisisalittleclunky,butiseasytoimplementandworkssufficientlywellinmostcases.

WecanalsocontrolsuchbehaviorviaScriptcodebychangingahiddenMaterial’stexture:

GetComponent<Renderer>().material.texture=textureToPreload;

TexturethrashingIntherareeventthattoomuchtexturedataisloadedintoVRAM,andtherequiredtextureisnotpresent,theGPUwillneedtorequestitfromthemainmemoryandoverwritetheexistingtexturedatatomakeroom.Thisislikelytoworsenovertimeasthememorybecomesfragmented,anditintroducesariskthatthetexturejustflushedfromVRAMneedstobepulledagainwithinthesameframe.Thiswillresultinaseriouscaseofmemory“thrashing”,andshouldbeavoidedatallcosts.

ThisislessofaconcernonmodernconsolessuchasthePS4,XboxOne,andWiiU,sincetheyshareacommonmemoryspaceforbothCPUandGPU.Thisdesignisahardware-leveloptimizationgiventhefactthatthedeviceisalwaysrunningasingleapplication,andalmostalwaysrendering3Dgraphics.But,allotherplatformsmustsharetimeandspacewithmultipleapplicationsandbecapableofrunningwithoutaGPU.TheythereforefeatureseparateCPUandGPUmemory,andwemustensurethatthetotaltextureusageatanygivenmomentremainsbelowtheavailableVRAMofthetargethardware.

Notethatthis“thrashing”isnotpreciselythesameasharddiskthrashing,wherememoryiscopiedbackandforthbetweenmainmemoryandvirtualmemory(theswapfile),butitisanalogous.Ineithercase,dataisbeingunnecessarilycopiedbackandforthbetweentworegionsofmemorybecausetoomuchdataisbeingrequestedintooshortatimeperiodforthesmallerofthetwomemoryregionstoholditall.

NoteThrashingsuchasthiscanbeacommoncauseofdreadfulgraphicsperformancewhengamesareportedfrommodernconsolestothedesktopandshouldbetreatedwithcare.

Avoidingthisbehaviormayrequirecustomizingtexturequalityandfilesizesonaper-platformandper-devicebasis.Bewarnedthatsomeplayersarelikelytonoticetheseinconsistenciesifwe’redealingwithhardwarefromthesameconsoleordesktopGPUgeneration.Asmanyofuswillknow,evensmalldifferencesinhardwarecanleadtoalotofapples-versus-orangescomparisons,buthardcoregamerswillexpectasimilarlevelofqualityacrosstheboard.


LightingandShadowingLightingandShadowingcanaffectallpartsofthegraphicspipeline,andsotheywillbetreatedseparately.Thisisperhapsoneofthemostimportantpartsofgameartanddesigntogetright.GoodLightingandShadowingcanturnamundanesceneintosomethingspectacularasthereissomethingmagicalaboutprofessionalcoloringthatmakesitvisuallyappealing.Eventhelow-polyartstyle(thinkMonumentValley)reliesheavilyonagoodlightingandshadowingprofileinordertoallowtheplayertodistinguishoneobjectfromanother.But,thisisn’tanartbook,sowewillfocusontheperformancecharacteristicsofvariousLightingandShadowingfeatures.

Unityofferstwostylesofdynamiclightrendering,aswellasbakedlightingeffectsthroughlightmaps.Italsoprovidesmultiplewaysofgeneratingshadowswithvaryinglevelsofcomplexityandruntimeprocessingcost.Betweenthetwo,therearealotofoptionstoexplore,andalotofthingsthatcantripusupifwe’renotcareful.

TheUnitydocumentationcoversallofthesefeaturesinanexcellentamountofdetail(startwiththispageandworkthroughthem:http://docs.unity3d.com/Manual/Lighting.html),sowe’llexaminethesefeaturesfromaperformancestandpoint.

Let’stacklethetwomainlightrenderingmodesfirst.ThissettingcanbefoundunderEdit|ProjectSettings|Player|OtherSettings|Rendering,andcanbeconfiguredonaper-platformbasis.


http://docs.unity3d.com/Manual/Lighting.html

ForwardRenderingForwardRenderingistheclassicalformofrenderinglightsinourscene.EachobjectislikelytoberenderedinmultiplepassesthroughthesameShader.Howmanypassesarerequiredwillbebasedonthenumber,distance,andbrightnessoflightsources.Unitywilltrytoprioritizewhichdirectionallightisaffectingtheobjectthemostandrendertheobjectina“basepass”asastartingpoint.Itwillthentakeuptofourofthemostpowerfulpointlightsnearbyandre-renderthesameobjectmultipletimesthroughthesameFragmentShader.Thenextfourpointlightswillthenbeprocessedonaper-vertexbasis.Allremaininglightsaretreatedasagiantblobbymeansofatechniquecalledsphericalharmonics.

Someofthisbehaviorcanbesimplifiedbysettingalight’sRenderModetovaluessuchasNotImportant,andchangingthevalueofEdit|ProjectSettings|Quality|PixelLightCount.Thisvaluelimitshowmanylightswillbetreatedonaperpixelbasis,butisoverriddenbyanylightswithaRenderModesettoImportant.Itisthereforeuptoustousethiscombinationofsettingsresponsibly.

Asyoucanimagine,thedesignofForwardRenderingcanutterlyexplodeourDrawCallcountveryquicklyinsceneswithalotofpointlightspresent,duetothenumberofrenderstatesbeingconfiguredandShaderpassesbeingreprocessed.CPU-boundapplicationsshouldavoidthisrenderingmodeifpossible.

NoteMoreinformationonForwardRenderingcanbefoundintheUnitydocumentation:http://docs.unity3d.com/Manual/RenderTech-ForwardRendering.html.


http://docs.unity3d.com/Manual/RenderTech-ForwardRendering.html

DeferredShadingDeferredShadingorDeferredRenderingasitissometimesknown,isonlyavailableonGPUsrunningatleastShaderModel3.0.Inotherwords,anydesktopgraphicscardmadeafteraround2004.Thetechniquehasbeenaroundforawhile,butithasnotresultedinacompletereplacementoftheForwardRenderingmethodduetothecaveatsinvolvedandlimitedsupportonmobiledevices.Anti-aliasing,transparency,andanimatedcharactersreceivingshadowsareallfeaturesthatcannotbemanagedthroughDeferredShadingaloneandwemustusetheForwardRenderingtechniqueasafallback.

DeferredShadingissonamedbecauseactualshadingdoesnotoccuruntilmuchlaterintheprocess;thatis,itisdeferreduntillater.Fromaperformanceperspective,theresultsarequiteimpressiveasitcangenerateverygoodperpixellightingwithsurprisinglylittleDrawCalleffort.TheadvantageisthatahugeamountoflightingcanbeaccomplishedusingonlyasinglepassthroughthelightingShader.ThemaindisadvantagesincludetheadditionalcostsifwewishtopileonadvancedlightingfeaturessuchasShadowingandanystepsthatmustpassthroughForwardRenderinginordertocomplete,suchastransparency.

NoteTheUnitydocumentationcontainsanexcellentsourceofinformationontheDeferredShadingtechnique,itsadvantages,anditspitfalls:http://docs.unity3d.com/Manual/RenderTech-DeferredShading.html.


http://docs.unity3d.com/Manual/RenderTech-DeferredShading.html

VertexLitShading(legacy)Technically,therearemorethantwolightingmethods.Unityallowsustouseacoupleoflegacylightingsystems,onlyoneofwhichmayseeactualuseinthefield:VertexLitShading.Thisisamassivesimplificationoflighting,aslightingisonlyconsideredpervertex,andnotperpixel.Inotherwords,entirefacesarecoloredbasedontheincominglightcolor,andnotindividualpixels.

Itisnotexpectedthatmany,orreallyany,3Dgameswillmakeuseofthislegacytechnique,asalackofshadowsandproperlightingmakevisualizationsofdepthverydifficult.Itismostlyrelegatedto2Dgamesthatdon’tintendtomakeuseofshadows,normalmaps,andvariousotherlightingfeatures,butitisthereifweneedit.


Real-timeShadowsSoftShadowsareexpensive,HardShadowsarecheap,andNoShadowsarefree.ShadowResolution,ShadowProjection,ShadowDistance,andShadowCascadesareallsettingswecanfindunderEdit|ProjectSettings|Quality|Shadowsthatwecanusetomodifythebehaviorandcomplexityofourshadowingpasses.ThatsummarizesalmosteverythingweneedtoknowaboutUnity’sreal-timeshadowingtechniquesfromahigh-levelperformancestandpoint.Wewillcovershadowsmoreinthefollowingsectiononoptimizingourlightingeffects.


LightingoptimizationWithacursoryglanceatalloftherelevantlightingtechniques,let’srunthroughsometechniqueswecanusetoimprovelightingcosts.

UsetheappropriateShadingModeItisworthtestingbothofthemainrenderingmodestoseewhichonebestsuitsourgame.DeferredShadingisoftenusedasabackupintheeventthatForwardRenderingisbecomingaburdenonperformance,butitreallydependsonwhereelsewe’refindingbottlenecksasitissometimesdifficulttotellthedifferencebetweenthem.

UseCullingMasksALightComponent’sCullingMaskpropertyisalayer-basedmaskthatcanbeusedtolimitwhichobjectswillbeaffectedbythegivenLight.Thisisaneffectivewayofreducinglightingoverhead,assumingthatthelayerinteractionsalsomakesensewithhowweareusinglayersforphysicsoptimization.Objectscanonlybeapartofasinglelayer,andreducingphysicsoverheadprobablytrumpslightingoverheadinmostcases;thus,ifthereisaconflict,thenthismaynotbetheidealapproach.

NotethatthereislimitedsupportforCullingMaskswhenusingDeferredShading.Becauseofthewayittreatslightinginaveryglobalfashion,onlyfourlayerscanbedisabledfromthemask,limitingourabilitytooptimizeitsbehaviorthroughthismethod.

UseBakedLightmapsBakingLightingandShadowingintoaSceneissignificantlylessprocessor-intensivethangeneratingthematruntime.Thedownsideistheaddedapplicationfootprint,memoryconsumption,andpotentialformemorybandwidthabuse.Ultimately,unlessagame’slightingeffectsarebeinghandledexclusivelythroughLegacyVertexLightingorasingleDirectionalLight,thenitshouldprobablyincludeLightmappingtomakesomehugebudgetsavingsonlightingcalculations.Relyingentirelyonreal-timelightingandshadowsisarecipefordisasterunlessthegameistryingtowinanawardforthesmallestapplicationfilesizeofalltime.

OptimizeShadowsShadowingpassesmostlyconsumeourDrawCallsandfillrate,buttheamountofvertexpositiondatawefeedintotheprocessandourselectionfortheShadowProjectionsettingwillaffectthefrontend’sabilitytogeneratetherequiredshadowcastersandshadowreceivers.Weshouldalreadybeattemptingtoreducevertexcountstosolvefrontendbottleneckinginthefirstplace,andmakingthischangewillbeanaddedmultipliertowardsthateffort.

DrawCallsareconsumedduringshadowingbyrenderingvisibleobjectsintoaseparatebuffer(knownastheshadowmap)aseitherashadowcaster,ashadowreceiver,orboth.EachobjectthatisrenderedintothismapwillconsumeanotherDrawCall,whichmakesshadowsahugeperformancecostmultiplier,soitisoftenasettingthatgameswillexpose


tousersviaqualitysettings,allowinguserswithweakerhardwaretoreducetheeffectorevendisableitentirely.

ShadowDistanceisaglobalmultiplierforruntimeshadowrendering.Thefewershadowsweneedtodraw,thehappiertheentirerenderingprocesswillbe.Thereislittlepointinrenderingshadowsatagreatdistancefromthecamera,sothissettingshouldbeconfiguredspecifictoourgameandhowmuchshadowingweexpecttowitnessduringgameplay.Itisalsoacommonsettingthatisexposedtotheusertoreducetheburdenofrenderingshadows.

HighervaluesofShadowResolutionandShadowCascadeswillincreaseourmemorybandwidthandfillrateconsumption.Bothofthesesettingscanhelpcurbtheeffectsofartefactsinshadowrendering,butatthecostofamuchlargershadowmapsizethatmustbemovedaroundandofthecanvassizetodrawto.

NoteTheUnitydocumentationcontainsanexcellentsummaryonthetopicofthealiasingeffectofshadowmapsandhowtheShadowCascadesfeaturehelpstosolvetheproblem:http://docs.unity3d.com/Manual/DirLightShadows.html.

It’sworthnotingthatSoftShadowsdonotconsumeanymorememoryorCPUoverheadrelativetoHardShadows,astheonlydifferenceisamorecomplexShader.ThismeansthatapplicationswithenoughfillratetosparecanenjoytheimprovedgraphicalfidelityofSoftShadows.


http://docs.unity3d.com/Manual/DirLightShadows.html

OptimizinggraphicsformobileUnity’sabilitytodeploytomobiledeviceshascontributedgreatlytoitspopularityamonghobbyist,small,andmid-sizedevelopmentteams.Assuch,itwouldbeprudenttocoversomeapproachesthataremorebeneficialformobileplatformsthanfordesktopandotherdevices.

Notethatany,andall,ofthefollowingapproachesmaybecomeobsoletesoon,iftheyaren’talready.Themobiledevicemarketismovingblazinglyfast,andthefollowingtechniquesastheyapplytomobiledevicesmerelyreflectconventionalwisdomfromthelasthalfdecade.Weshouldoccasionallytesttheassumptionsbehindtheseapproachesfromtime-to-timetoseewhetherthelimitationsofmobiledevicesstillfitthemobilemarketplace.


MinimizeDrawCallsMobileapplicationsaremoreoftenbottleneckedonDrawCallsthanonfillrate.Notthatfillrateconcernsshouldbeignored(nothingshould,ever!),butthismakesitalmostnecessaryforanymobileapplicationofreasonablequalitytoimplementMeshCombining,Batching,andAtlasingtechniquesfromtheverybeginning.DeferredRenderingisalsothepreferredtechniqueasitfitswellwithothermobile-specificconcerns,suchasavoidingtransparencyandhavingtoomanyanimatedcharacters.


MinimizetheMaterialcountThisconcerngoeshandinhandwiththeconceptsofBatchingandAtlasing.ThefewerMaterialsweuse,thefewerDrawCallswillbenecessary.ThisstrategywillalsohelpwithconcernsrelatingtoVRAMandmemorybandwidth,whichtendtobeverylimitedonmobiledevices.


MinimizetexturesizeandMaterialcountMostmobiledevicesfeatureaverysmallTextureCacherelativetodesktopGPUs.Forinstance,theiPhone3Gcanonlysupportatotaltexturesizeof1024x1024duetorunningOpenGLES1.1withsimplevertexrenderingtechniques.MeanwhiletheiPhone3GS,iPhone4,andiPadgenerationrunOpenGLES2.0,whichonlysupportstexturesupto2048x2048.Latergenerationscansupporttexturesupto4096x4096.Doublecheckthedevicehardwarewearetargetingtobesureitsupportsthetexturefilesizeswewishtouse(therearetoomanyAndroiddevicestolisthere).However,later-generationdevicesareneverthemostcommondevicesinthemobilemarketplace.Ifwewishourgametoreachawideaudience(increasingitschancesofsuccess),thenwemustbewillingtosupportweakerhardware.

NotethattexturesthataretoolargefortheGPUwillbedownscaledbytheCPUduringinitialization,wastingvaluableloadingtime,andleavinguswithunintendedgraphicalfidelity.ThismakestexturereuseofparamountimportanceformobiledevicesduetothelimitedVRAMandTextureCachesizesavailable.


Maketexturessquareandpowerof2WehavealreadycoveredthistopicinChapter4,KickstartYourArt,butitisworthrevisitingthesubjectofGPU-levelTextureCompression.TheGPUwillfinditdifficult,orsimplybeunabletocompressthetextureifitisnotinasquareformat,somakesureyousticktothecommondevelopmentconventionandkeepthingssquareandsizedtoapowerof2.


UsethelowestpossibleprecisionformatsinShadersMobileGPUsareparticularlysensitivetoprecisionformatsinitsShaders,sothesmallestformatsshouldbeused.Onarelatednote,formatconversionshouldbeavoidedforthesamereason.


AvoidAlphaTestingMobileGPUshaven’tquitereachedthesamelevelsofchipoptimizationasdesktopGPUs,andAlphaTestingremainsaparticularlycostlytaskonmobiledevices.InmostcasesitshouldsimplybeavoidedinfavorofAlphaBlending.


SummaryIfyou’vemadeitthisfarwithoutskippingahead,thencongratulationsareinorder.ThatwasalotofinformationtoabsorbforjustonecomponentoftheUnityEngine,butthenitisclearlythemostcomplicatedofthemall,requiringamatchingdepthofexplanation.Hopefully,you’velearnedalotofapproachestohelpyouimproveyourrenderingperformanceandenoughabouttherenderingpipelinetoknowhowtousethemresponsibly!

Bynowweshouldbeusedtotheideathat,withtheexceptionofalgorithmimprovements,everyperformanceenhancementweimplementwillcomewithsomerelatedcostthatwemustbewillingtobearforthesakeofremovingonebottleneck.Weshouldalsobereadytoimplementmultipletechniquesuntilwe’vesquashedthemall.

We’vejustcoveredaveryabstractsystemingreatdetail,solet’smovethingsalongwithanexplorationofamoreconcretesystem:Unity’sunderlyingEngineandtheC#language.Inthenextchapter,wewilltakealookatourScriptcodeinamoreadvancedlightandinvestigatesomemethodstoimproveourCPUandmemorymanagement.


Chapter7.MasterfulMemoryManagementUsingmemoryproperlywithintheUnityEnginerequiresagoodamountofunderstandingoftheunderlyingUnityEngineandMonoFramework.Thiscanbeabitofanintimidatingplaceforsomedevelopers,sincemanypickedUnityastheirsolutionprimarilytoavoidthekindoflow-levelgruntworkthatcomesfromenginedevelopmentandmemorymanagement.Theywouldpreferinsteadtofocusonhigher-levelconcernsrelatedtogameplayimplementation,leveldesign,andartassetmanagement.

Manygamesoflimitedscopecangetawaywithfocusingonsuchhigher-levelconcerns,atthecostofwastedresources,andmayneverrunintoanyproblemsrelatedtomemory.Thisisallwellandgooduntilthedayitbecomesaproblem.Atthispoint,theirneglectinunderstandingtheimportantcomponentsoftheengineleadstoascrambletofindsolutionsthatcanbedifficulttounderstandandimplementwithoutproperknowledgetobackitup.

Therefore,understandingwhatishappeningwithmemoryallocationsandC#languagefeatures,howtheyinteractwiththeMonoPlatform,howMonointeractswiththeunderlyingengine,andthevariouslibrarieswehaveavailableareabsolutelyparamounttomakinghigh-quality,efficientscriptcode.So,inthischapter,youwilllearnaboutallofthenutsandboltsoftheunderlyingUnityEngine,MonoPlatform,C#language,and.NETFramework.

Let’sstartbyexploringthefamiliarpartoftheengine,whichhandlesmostoftheworkforourgame’sscriptingcode—theMonoplatform.


TheMonoplatformMonoisamagicalsauce,mixedintotheUnityrecipe,whichgivesitalotofitscross-platformcapability.MonoisanopensourceprojectthatbuiltitsownframeworkandlibrariesbasedontheAPI,specifications,andtoolsfromMicrosoft’s.NETFrameworkandcommonlibraries.Essentially,itisarecreationofthe.NETFramework,asitwasaccomplishedwithlittletonoaccesstothesourcecode.Notethat,despiteMono’slibrariesbeinganopensourcerecreationofMicrosoft’sbase.NETclasslibrary,itisfullycompatiblewiththeoriginallibraryfromMicrosoft.

ThegoaloftheMonoprojectistoprovideaframeworktoallowcross-platformcompatibilityusingthe.NETFrameworkasacommonlayer.Itallowsapplicationstobewritteninacommonprogramminglanguageandrunagainstmanydifferenthardwareplatforms,includingLinux,OSX,Windows,ARM,PowerPC,andmore.Monoalsosupportsmanylanguages,notjusttheC#,Boo,andUnityScriptwemaybefamiliarwith.Anylanguagethatcanbecompiledinto.NET’spureCommonIntermediateLanguage(CIL–moreonthislater)issufficienttointegratewiththeMonoplatform.ThisincludesC#,butevenincludeslanguagessuchasF#,Java,VisualBasic.NET,PythonNet,andIronPython.

AcommonmisconceptionabouttheUnityEngineisthatitisbuiltontopoftheMonoplatform.Thisisuntrue,astheMonosidedoesnothandlemanyimportantgametaskssuchasaudio,rendering,physics,andsoon.UnityTechnologiesbuiltanativeC++backendforthesakeofspeed,andallowsitsuserscontroloftheenginethroughMonoasascriptinginterface.Assuch,MonoismerelyacomponentoftheunderlyingUnityEngine.Thisisequivalenttomanyothergameengines,whichrunC++underthehood,handlingimportanttaskssuchasrendering,animation,resourcemanagement,andsoon,whilesimultaneouslyprovidingascriptinglanguageforgameplaylogictobeimplemented.TheMonoplatformwaschosenbyUnityTechnologiesforthistask.

TipNativecodesimplymeanscodethatiscompileddirectlytothetargetOS,andexecuteswithoutadditionallayersofcomplexityintheruntimeenvironment.Thiskeepsoverheadcostslow,butattheexpenseofneedingtomanagememoryandothertaskswithinthecodeinamoredirectfashion.

Scriptinglanguagestypicallyabstractawaycomplexmemorymanagementthroughautomaticgarbagecollection,andprovidevarioussafetyfeatures,whichsimplifytheactofprogrammingattheexpenseofruntimeoverhead.Somescriptinglanguagescanalsobeinterpretedatruntime,meaningthattheydon’tneedtobecompiledbeforeexecution.Therawinstructionsareconverteddynamicallyintomachinecodeandexecutedthemomenttheyarereadduringruntime.Thelastfeature,andprobablythemostimportantone,isthattheyallowsimplersyntaxofprogrammingcommands.Thisusuallyimprovesthedevelopmentworkflowimmensely,asteammemberswithoutmuchexperienceusinglanguagessuchasC++cancontributetothecodebase.Thisenablesthemtoimplementthingssuchasgameplaylogicinasimplerformat,attheexpenseofacertainamountof


controlandruntimeexecutionspeed.

Notethatsuchlanguagesareoftencalled“managed”languages,whichfeaturemanagedcode.Technically,thiswasatermcoinedbyMicrosofttorefertoanysourcecodethatmustruninsidetheirCommonLanguageRuntime(CLR)environment(morelater),asopposedtocodethatiscompiledandrunnativelythroughthetargetOperatingSystem(OS).But,becauseoftheprevalenceandcommonfeaturesthatexistbetweentheCLRandotherlanguagesthatfeaturetheirownsimilarlydesignedruntimeenvironments(suchasJava),theterm“managed”hassincebecomealittlevague.Ittendstobeusedtorefertoanylanguageorcodethatdependsonitsownruntimeenvironmentandthatmay,ormaynot,includeautomaticgarbagecollection.Fortherestofthischapter,wewillusetheterm“managed”torefertocodethatbothdependsonaseparateruntimeenvironmentandhasundergoneautomaticgarbagecollection.

Theruntimeperformancecostofmanagedlanguagesisbecominglessandlesssignificanteveryyear.Thisispartlyduetogradualoptimizationsintoolsandruntimeenvironments,andpartlyduetothecomputingpoweroftheaveragedevicegraduallybecominggreater.Butthemainpointofcontroversyinmanagedlanguagesstillremainstheirautomaticmemorymanagement.Managingmemorymanuallycanbeacomplextaskthatcantakemanyyearsofdifficultdebuggingtobeproficientat,butmanydevelopersfeelthatmanagedlanguagessolvethisprobleminwaysthataretoounpredictable,riskingtoomuchproductquality.Suchdevelopersmightcitethatmanagedcodewillneverreachthesamelevelofperformanceasnativecode,anditisfoolhardytobuildhigh-performanceapplicationswiththem.

Thisistruetoanextent,asmanagedlanguagesinvariablyinflictruntimeoverheads,andwelosepartialcontroloverruntimememoryallocations.But,aswithallthings,itbecomesabalancingact,sincenotallresourceusagewillnecessarilyresultinabottleneck,andthebestgamesaren’tnecessarilytheonesthatuseeverysinglebytetotheirfullest.Forexample,imagineauserinterfacethatrefreshesin30microsecondsvianativecodeversus60microsecondsinmanagedcodeduetoanextra100percentoverhead(extremeexample).Themanagedcodeversionisstillfastenoughsuchthattheuserwillneverbeabletonoticethedifference,soistherereallyanyharminusingmanagedcodeforsuchatask?

Inreality,workingwithmanagedlanguagesoftenjustmeansthatdevelopershaveauniquesetofconcernstoworryaboutcomparedtonativecodedevelopers.Assuch,choosingtouseamanagedlanguageispartlyamatterofpreference,andpartlyacompromiseofcontroloverdevelopmentspeed.


ThecompilationprocessWhenwemakechangestoourC#code,itistypicallycompiledimmediatelyafterweswitchbackfromourfavoriteIDE(whichistypicallyeitherMonoDevelopor,themuchmorefeature-richVisualStudio)totheUnityEditor.However,theC#codeisnotconverteddirectlyintomachinecode,aswewouldexpecttohappenwithstaticcompilersinthelandofC++.Instead,thecodeisconvertedintoanintermediatelanguagecalledCommonIntermediateLanguage(CIL),whichisanabstractionabovenativecode.CILissimilartoJavabytecode,uponwhichitisbased,butCILcodeisentirelyuselessonitsown,asCPUshavenoideahowtoruntheinstructionsdefinedinthislanguage.

Atruntime,thisintermediatecodeisrunthroughtheMonoVirtualMachine(VM),whichisaninfrastructurecomponentthatallowsthesamecodetorunagainstmultipleplatformswithoutneedingtochangethecodeitself.Thisisanimplementationofthe.NETCommonLanguageRuntimeorCLR.Ifwe’rerunningoniOS,werunontheiOS-basedVirtualMachineinfrastructure,andifwe’rerunningonLinux,thenwesimplyuseadifferentonethatisbettersuitedforLinux.

WithintheCLR,theintermediateCILcodewillactuallybecompiledintonativecodeondemand.Thison-demandnativecompilationcanbeaccomplishedeitherbyanAhead-Of-Time(AOT)orJust-In-Time(JIT)compiler,dependingonwhichplatformisbeingtargeted.Thesecompilersallowcodesegmentstobecompiledintonativecode(thatis,machinecodespecifictotheOSitisrunningagainst),andthemaindifferencebetweenthetwotypesiswhenthecodeiscompiled.

AOTcompilationhappensearly(aheadoftime),eitherduringthebuildprocessorduringinitialization.Ineithercase,thecodehasbeenprecompiledandnofurtherruntimecostsareinflictedduetodynamiccompilation.InthecurrentversionofUnity(Version5.2.2),theonlyplatformsthatsupportAOTcompilationareWebGL(andonlywhenUnityScriptisbeingused)andiOS.

JITcompilationhappensdynamicallyatruntimeinaseparatethreadandbeginsjustpriortoexecution(“justintime”forexecution).Often,thisdynamiccompilationcausesthefirstinvocationofapieceofcodetorunalittle(oralot!)moreslowly,becausethecodemustfinishcompilingbeforeitcanbeexecuted.But,fromthatpointforward,wheneverthesamecodeblockisexecuted,thereisnoneedforrecompilation,andtheinstructionsrunthroughthepreviouslycompilednativecode.

Itiscommoninsoftwarethat90percentoftheworkisbeingdonebyonly10percentofthecode.ThisgenerallymeansthatJITcompilationturnsouttobeanetpositiveonperformancethanifwesimplytriedtointerprettheCILcodedirectly.However,becausetheJITcompilermustcompilecodequickly,itisnotabletomakeuseofmanyoptimizationtechniquesthatstaticcompilersareabletoexploit.

ManualJITcompilationIntheeventthatJITcompilationiscausingaruntimeperformanceloss,beawarethatitisactuallypossibletoforceJITcompilationofamethodatanytimeviareflection.


ReflectionisausefulfeatureoftheC#language,thatallowsourcodebasetoexploreitselfintrospectivelyfortypeinformation,methods,values,andmetadata.Usingreflectionisoftenaverycostlyprocess.Itshouldbeavoidedatruntimeor,attheveryleast,onlyusedduringinitializationorotherloadingtimes.NotdoingsocaneasilycausesignificantCPUspikesandgameplayfreezing.

WecanmanuallyforceJITcompilationofamethodusingreflectiontoobtainafunctionpointertoit:

varmethod=typeof(MyComponent).GetMethod("MethodName");

if(method!=null){

method.MethodHandle.GetFunctionPointer();

Debug.Log("JITcompilationcomplete!");

}

Thiscodeonlyworksonpublicmethods.Obtainingnon-publicmethodscanbeaccomplishedthroughtheuseofBindingFlags:

usingSystem.Reflection;

//...

varmethod=typeof(MyComponent).GetMethod("MethodName",

BindingFlags.NonPublic|BindingFlags.Instance);

ThiskindofcodeshouldonlyberunforverytargetedmethodswherewearecertainthatJITcompilationiscausingCPUspikes.Thiscanbeverifiedbyrestartingtheapplicationandprofilingamethod’sfirstinvocationversusallsubsequentinvocations.ThedifferencewilltellustheJITcompilationoverhead.

TipNotethattheofficialmethodforforcingJITcompilationinthe.NETlibraryisRuntimeHelpers.PrepareMethod(),butthisisnotproperlyimplementedinthecurrentversionofMonothatcomeswithUnity(MonoVersion2.6.5).TheaforementionedworkaroundshouldbeuseduntilUnityhaspulledinamorerecentversionoftheMonoproject.


MemoryusageoptimizationInmostgameengines,wewouldhavetheluxuryofbeingabletoportinefficientscriptcodeintothefasterC++areaifwewerehittingperformanceissues.ThisisnotanoptionunlessweinvestseriouscashinobtainingtheUnitysourcecode,whichisofferedasalicenseseparatefromtheFree/Personal/Prolicensingsystem,andonapercase,pertitlebasis.ThisforcestheoverwhelmingmajorityofusintoapositionofneedingtomakeourC#script-levelcodeasperformantaspossible.So,whatdoesallofthisbackstorywe’vebeencoveringmeanforuswhenitcomestothetaskofperformanceoptimization?

Firstly,wewon’tbecoveringanythingthatisspecifictotheUnityScriptandBoolanguages(althoughmuchoftheknowledgetranslatestothoselanguages).

Secondly,eventhoughallofourscriptcodemightbeinC#,weneedtobeawarethattheoverallUnityEngineisbuiltfrommultiplecomponentsthateachmaintainsitsownmemorydomains.

Thirdly,onlysometasksweperformwillawakenthedreadedgarbagecollector.Therearequiteafewmemoryallocationapproachesthatwecanusetoavoiditentirely.

Finally,thingscanchangequiteabitdependingonthetargetplatformwe’rerunningagainstandeveryassumptionshouldbetestedforvalidityifwe’restumblingintounexpectedmemorybottlenecks.


UnitymemorydomainsThememoryspacewithintheUnityEnginecanbeessentiallysplitintothreedifferentmemorydomains.Eachdomainstoresdifferenttypesofdataandtakescareofaverydifferentsetoftasks.

ThefirstdomainistheNativeDomain.ThisistheunderlyingfoundationoftheUnityEngine,whichiswritteninC++andcompiledtonativecodedependingonwhichplatformisbeingtargeted.ThisareatakescareofallocatingmemoryspaceforthingssuchasAssetdata,forexampleTexturesandMeshes,memoryspaceforvarioussubsystems,suchastheRenderingsystem,Physics,Input,andsoon.Finally,itincludesnativerepresentationsofimportantgameplayobjectssuchasGameObjectandComponent.ThisiswherealotofthebaseComponentclasseskeeptheirdata,suchastheTransformandRigidbodyComponents.

Thesecondmemorydomain,theManagedDomain,iswheretheMonoplatformdoesitswork,andistheareaofmemorythatismaintainedbytheGarbageCollector.Anyscriptingobjectsandcustomclassesarestoredwithinthismemorydomain.ItalsoincludeswrappersfortheverysameobjectrepresentationsthatarestoredwithintheNativeDomain.ThisiswherethebridgebetweenMonocodeandNativecodederivesfrom;eachdomainhasitsownrepresentationforthesameentity,andcrossingthebridgebetweenthemtoomuchcaninflictsomefairlysignificantperformancehitsonourgame,aswelearnedinthepreviouschapters.

WhenanewGameObjectorComponentisinstantiated,itinvolvesallocatingmemoryinboththeManagedandNativeDomains.ThisallowssubsystemssuchasPhysicsandRenderingsystemstocontrolandrenderanobjectthroughitstransformdataontheNativeDomain,whiletheTransformComponentfromourscriptcodeismerelyawaytoreferencethroughthebridgeintotheNativememoryspaceandchangetheobject’stransformdata.Crossingbackandforthacrossthisbridgeshouldbeminimizedasmuchaspossible,duetotheoverheadinvolved,aswe’velearnedthroughtechniquessuchascachingposition/rotationchangesbeforeapplyingthem,backinChapter2,ScriptingStrategies.

Thethirdandfinalmemorydomain(s)arethoseofNativeandExternalDLLs,suchasDirectX,OpenGL,andanycustomDLLs,weattachtoourproject.ReferencingfromMonoC#codeintosuchDLLswillcauseasimilarmemoryspacetransitionasthatbetweenMonocodeandNativecode.

NativememoryWehavenodirectcontroloverwhatisgoingonintheNativeDomainwithouttheUnityEnginesourcecode,butwedohavealotofindirectcontrolbymeansofvariousscript-levelfunctions.Therearetechnicallyavarietyofmemoryallocatorsavailable,whichareusedinternallyforthingssuchasGameObjects,Graphicsobjects,andtheProfiler,butthesearehiddenbehindtheNativecodewall.

However,wecanobservehowmuchmemoryhasbeenallocatedandreservedinthis


memorydomainviatheMemoryAreaoftheProfiler.Nativememoryallocationsshowupunderthevalueslabeled“Unity”,andwecanevengetmoreinformationusingtheDetailedviewandsamplingthecurrentframe.

UndertheSceneMemorysectionoftheDetailedview,wecanobservethatMonoBehaviourobjectsalwaysconsumeaconstantamountofmemory,regardlessoftheirmemberdata.ThisisthememoryconsumedbytheNativerepresentationoftheobject.Notethat376bytesofmemoryisconsumedbyaMonoBehaviourinEditorMode,whileonly156bytesisconsumedwhenprofilingthroughastandaloneapplication.

TipMemoryconsumptioninEditorModeisalwayswildlydifferenttothatofastandaloneversion,duetovariousdebuggingandeditorhookdatabeingapplied.ThisaddsafurtherincentivetoavoidusingEditorModeforprofilingandbenchmarkingpurposes(althoughitcanstillbeusefulattimes).

WecanalsousetheProfiler.GetRuntimeMemorySize()methodtogettheNativememoryallocationsizeofaparticularobject.

ManagedobjectrepresentationsareintrinsicallylinkedtotheirNativerepresentations.ThebestwaytominimizeourNativememoryallocationsistosimplyoptimizeourManagedmemoryusage.

ManagedmemoryMemoryinmostmodernoperatingsystemssplitsdynamicmemoryintotwocategories:thestackandtheheap.Thestackisaspecialreservedspaceinmemory,dedicatedtosmall,short-liveddatavalues,whichareautomaticallydeallocatedthemomenttheygooutofscope.Thestackcontainslocalvariables,aswellashandlestheloadingandunloadingoffunctionsasthey’recalled,andexpandsandcontractsalongwiththecallstack.Deallocationsinthestackarebasicallyfreebecausethedataisessentiallyinstantlyforgottenaboutandnolongerreferenceable.Newdatasimplyoverwritestheolddata,sincethestartofthenextmemoryallocationisalwaysknown,andthere’snoreasontoperformanyclean-upoperations.

Becausedatainthestackisveryshort-lived,thetotalstacksizeisusuallyverysmall;intheorderofMegabytes.It’spossibletocauseastackoverflowbyallocatingmorespacethanthestackcansupport.Thiscanoccurduringexceptionallylargecallstacks(forexample,infiniteloops),orhavingalargenumberoflocalvariables,butinmostcasescausingastackoverflowshouldnotbeaconcerndespiteitsrelativelysmallsize.

Theheaprepresentsallremainingmemoryspace,anditisusedfortheoverwhelming


majorityofdynamicmemoryallocation.Wheneveradatatypeistoobigtofitinthestackormustexistoutsidethefunctionitwasdeclaredin,thenitmustbeallocatedontheheap.Mono’sheapisspecialinthatitismanagedbyaGarbageCollector(itissometimesreferredtoasaManagedHeap).Duringapplicationinitialization,MonowillrequestagivenchunkofmemoryfromtheOSanduseittogeneratetheheap.Theheapstartsofffairlysmall,lessthanoneMegabyte,butwillgrowasnewblocksofmemoryareneededbyourscriptcode.

WecanverifyhowmuchmemoryhasbeenallocatedandreservedfortheheapusingtheMemoryAreaoftheProfiler,butunderthevalueslabeled“Mono”.

WecanalsodeterminethecurrentusedandreservedheapspaceatruntimeusingtheProfiler.GetMonoUsedSize()andProfiler.GetMonoHeapSize()methods,respectively.

Garbagecollection

Whenamemoryrequestismade,andthereisenoughemptyspaceinthereservedheapblocktosatisfytherequest,thenMonoallocatesthespaceandhandsitovertowhoeverrequestedit.But,iftheheapdoesnothaveroomforit,thentheGarbageCollectorwillawakenandscanalltheexistingmemoryallocationsforanythingwhichisnolongerbeingusedandcleansthemupfirst,beforeattemptingtoexpandthecurrentheapspace.

TheGarbageCollectorintheversionofMonothatUnityusesisatypeofTracingGarbageCollector,whichusesaMark-and-Sweepstrategy.Thisalgorithmworksintwophases:eachallocatedobjectistrackedwithanadditionalbit.Thisflagswhethertheobjecthasbeenmarkedornot.Theseflagsstartoffsetto0(orfalse).

Whenthecollectionprocessbegins,itmarks(setstheflagto1ortrue)allobjectsthatarestillreachabletotheprogram.Eitherthereachableobjectisadirectreference,suchasstaticorlocalvariablesonthestack,oritisanindirectreferencethroughthefields(memberdata)ofotherdirectlyorindirectlyaccessibleobjects.Inthisway,itisgatheringasetofobjectsthatarestillreferenceable.

Thesecondphaseinvolvesiteratingthrougheveryobjectreferenceintheheap(whichMonowillhavebeentrackingthroughoutthelifetimeoftheapplication)andverifyingwhetherornottheyaremarked.Ifso,thentheobjectisignored.But,ifitisnotmarked,thenitisacandidatefordeallocation.Duringthisphase,allmarkedobjectsareskippedover,butnotbeforesettingtheirflagbacktofalseforthefirstphaseofthenextgarbagecollection.

Oncethesecondphaseends,allunmarkedobjectsaredeallocatedtofreespace,andthentheinitialrequesttocreatetheobjectisrevisited.Ifthereisenoughspacefortheobject,thenitisallocatedinthatspaceandtheprocessends.But,ifnot,thenitmustallocatea


newblockfortheheapbyrequestingitfromtheOperatingSystem,atwhichpointthememoryallocationrequestcanfinallybecompleted.

Inanidealworld,whereweonlykeepallocatinganddeallocatingobjectsbutonlyafinitenumberofthemexistatonce,theheapwouldmaintainaconstantsizebecausethere’salwaysenoughspacetofittheobject.However,allobjectsinanapplicationarerarelydeallocatedinthesameordertheywereallocated,andevenmorerarelydotheyallhavethesamesizeinmemory.Thisleadstomemoryfragmentation.Memoryfragmentation

Fragmentationoccurswhenobjectsareallocatedanddeallocatedindifferentorders.Thisisbestexplainedthroughanexample.Thefollowingshowsfourstagesofmemoryallocationwithinatypicalheapmemoryspace:

Hereishowthememoryallocationtakesplace:

1. Westartwithanemptyheapspace(1).2. Wethenallocatefourobjectsontheheap,A,B,CandD,eachsizedat64bytes(2).3. Atsomelatertime,wedeallocatetwooftheobjectsAandC(3).4. Thistechnicallyfrees128bytesworthofspace,butsincetheobjectswerenot

contiguous(adjoiningneighbors)inmemory,wehavereallyonlydeallocatedtwoseparate64-byteregionsofmemory.If,atsomepointlater,wewishtoallocateanewobjectthatislargerthan64bytes(4),thenwecannotusethespacethatwaspreviouslyfreedbyobjectsAandC,sinceneitherisindividuallylargeenoughtofitthenewobject(objectsmustalwaysconsumecontiguousmemoryspaces).Therefore,thenewobjectmustbeallocatedinthenextavailable128contiguousbytesintheheapspace.


Overtime,ourheapmemorywillbecomeriddledwithmoreandmore,smallerandsmalleremptyspacessuchasthese,asobjectsofdifferentsizesaredeallocated,andthenthesystemlatertriestoallocatenewobjectswithinthesmallestavailablespacethatitcanfitwithin.Thesmallertheseregionsbecome,thelessusabletheyarefornewmemoryallocations.Touseananalogy,thememoryspacebeginstoresembleSwisscheesewithmanysmallholesthatbecomeunusabletous.Intheabsenceofbackgroundtechniquesthatautomaticallycleanupthisfragmentation,thiseffectwouldoccurinliterallyanymemoryspace—RAM,heapspace,andevenharddrives—whicharejustlarger,slower,andmorepermanentmemorystorageareas(thisiswhyit’sagoodideatodefragmentourharddrivesfromtime-to-time!).

Memoryfragmentationcausestwoproblems.Firstly,iteffectivelyreducesthetotalusablememoryspacefornewobjectsoverlongperiodsoftime,dependingonthefrequencyofallocationsanddeallocations.Secondly,itmakesnewallocationstakelongertoresolve,duetotheextratimeittakestofindanewmemoryspacelargeenoughtofittheobject.

Thisbecomesimportantwhennewmemoryallocationsaremadeinaheap,sincewherethefreespacesarelocatedbecomesjustasimportantashowmuchfreespaceisavailable.Evenifwetechnicallyhave128bytesoffreespacetofitanewobject,ifitisnotcontiguousspace,thentheheapmusteithercontinuesearchinguntilitfindsalargeenoughspaceortheentireheapsizemustbeincreasedtofitthenewobject,byrequestinganewmemoryallocationfromtheOSinordertoexpandtheheapspace.Garbagecollectionatruntime

So,inaworstcasescenario,whenanewmemoryallocationisbeingrequestedbyourgame,theCPUwouldhavetospendcyclescompletingthefollowingtasksbeforetheallocationisfinallycompleted:

1. Verifyifthereisenoughcontiguousspaceforthenewobject.2. Ifnot,iteratethroughallknowndirectandindirectreferences,markingthemas

reachable.3. Iteratethroughtheentireheap,flaggingunmarkedobjectsfordeallocation.4. Verifyasecondtimeifthereisenoughcontiguousspaceforthenewobject.5. Ifnot,requestanewmemoryblockfromtheOS,inordertoexpandtheheap.6. Allocatethenewobjectatthefrontofthenewlyallocatedblock.

ThiscanbealotofworkfortheCPUtohandle,particularlyifthisnewmemoryallocationisanimportantgameobjectsuchasaparticleeffect,anewcharacterenteringthescene,acutscenetransition,andsoon.UsersarelikelytonotemomentswheretheGarbageCollectorisfreezinggameplaytohandlethesetasks.Tomakemattersworse,thegarbagecollectionworkloadscalesastheallocatedheapspacegrows,sincesweepingthroughafewmegabytesofspacewillbesignificantlyfasterthanscanningseveralgigabytesofspace.

Allofthismakesitabsolutelycriticaltocontrolourheapspaceintelligently.Thelazierourmemoryusagetacticsare,theworsetheGarbageCollectorwillbehaveinanalmostexponentialfashion.So,it’salittleironicthat,despitetheeffortsofmanagedlanguagesto


solvethememorymanagementproblem,managedlanguagedeveloperscanstillfindthemselvesbeingjustas,ifnotmore,concernedwithmemoryconsumptionthandevelopersofnativeapplications!Threadedgarbagecollection

TheGarbageCollectorrunsontwoseparatethreads:theMainthreadandtheFinalizerthread.WhentheGarbageCollectorisinvoked,itwillrunontheMainthreadandflagheapmemoryblocksforfuturedeallocation.Thisdoesnothappenimmediately.TheFinalizerthread,controlledbyMono,canhaveadelayofseveralsecondsbeforethememoryisfinallyfreedandavailableforreallocation.

WecanobservethisbehaviorintheTotalAllocatedblock(thegreenlinewithapologiestothat5percentofthepopulationwithdeuteranopia/deuteranomaly)oftheMemoryAreawithintheProfiler.Itcantakeseveralsecondsforthetotalallocatedvaluetodropafteragarbagecollectionhasoccurred.Becauseofthedelay,weshouldnotrelyonmemorybeingavailablethemomentithasbeendeallocated,andassuch,weshouldneverwastetimetryingtoekeouteverylastbyteofmemorythatwebelieveshouldbeavailable.Wemustensurethatthereisalwayssomekindofbufferzoneavailableforfutureallocations.

BlocksthathavebeenfreedbytheGarbageCollectormaysometimesbegivenbacktotheOperatingSystemaftersometime,whichwouldreducethereservedspaceconsumedbytheheapandallowthememorytobeallocatedforsomethingelse,suchasanotherapplication.But,thisisveryunpredictableanddependsontheplatformbeingtargeted,soweshouldn’trelyonit.Theonlysafeassumptiontomakeisthat,assoonasthememoryhasbeenallocatedtoMono,it’sthenreservedandisnolongeravailabletoeithertheNativeDomainoranyotherapplicationrunningonthesamesystem.Garbagecollectiontactics

Onestrategytominimizegarbagecollectionproblemsisconcealment;manuallyinvoketheGarbageCollectoratopportunemoments,whentheplayermaynotnotice.Acollectioncanbeinvokedbysimplycallingthefollowingmethod:

System.GC.Collect();

Goodopportunitiestoinvokeacollectionmaybeduringlevelloading,whengameplayispaused,shortlyafteramenuinterfacehasbeenopened,inthemiddleofcutscenetransitions,orreallyanybreakingameplaythattheplayerwouldnotwitness,orcareaboutasuddenperformancedrop.WecouldevenusetheProfiler.GetMonoUsedSize()andProfiler.GetMonoHeapSize()methodsatruntimetodetermineifagarbagecollectionneedstobeinvokedinthenearfuture.

Wecanalsocausethedeallocationofahandfulofspecificobjects.IftheobjectinquestionisoneoftheUnityobjectwrappers,suchasaGameObjectorMonoBehaviourcomponent,thentheFinalizerwillfirstinvoketheDispose()methodwithintheNativeDomain.Atthispoint,thememoryconsumedbyboththeNativeandManagedDomainswillthenbefreed.Insomerareinstances,iftheMonowrapperimplementstheIDisposableinterface(thatis,ithasaDispose()methodavailablefromscriptcode),thenwecanactuallycontrolthisbehaviorandforcethememorytobefreedinstantly.


Theonlyknownandusefulcaseofthis(thatthisauthoriscurrentlyawareof)istheWWWclass.ThisclassismostoftenusedtoconnecttoawebserveranddownloadAssetdataduringruntime.ThisclassneedstoallocateseveralbuffersintheNativeDomaininordertoaccomplishthistask.Itneedstomakeroomforthecompressedfile,adecompressionbuffer,andthefinaldecompressedfile.Ifwekeptallofthismemoryforalongtime,itwouldbeacolossalwasteofpreciousspace.So,bycallingitsDispose()methodfromscriptcode,wecanensurethatthememorybuffersarefreedpromptlyandpreciselywhentheyneedtobe.

AllotherAssetobjectsoffersomekindofunloadingmethodtocleanupanyunusedassetdata,suchasResources.UnloadUnusedAssets().ActualassetdataisstoredwithintheNativeDomain,sotheGarbageCollectortechnicallyisn’tinvolvedhere,buttheideaisbasicallythesame.ItwilliteratethroughallAssetsofaparticulartype,checkifthey’renolongerbeingreferenced,and,ifso,deallocatethem.But,again,thisisanasynchronousprocessandwecannotguaranteewhendeallocationwilloccur.ThismethodisautomaticallycalledinternallyafteraSceneisloaded,butthisstilldoesn’tguaranteeinstantdeallocation.

Attheveryleast,Resources.UnloadAsset()(thatis,unloadingonespecificAssetatatime)isthepreferredwaytocleanupAssetdata,sincetimewillnotbespentiteratingthroughtheentirecollection.However,it’sworthnotingthattheseunloadingmethodswereupgradedtobemultithreadedinUnity5,whichimprovestheperformancecostofcleaningupAssetdatarathersignificantlyonmostplatforms.

However,thebeststrategyforgarbagecollectionwillalwaysbeavoidance;ifweallocateaslittleheapmemoryandcontrolitsusageasmuchaspossible,thenwewon’thavetoworryabouttheGarbageCollectorinflictingperformancecostsasfrequentlyorashard.Youwilllearnmanytacticsforthisduringtheremainderofthechapter,butyoushouldfirstcoversometheoryonhowandwherememoryisallocated.


ValuetypesandReferencetypesNotallmemoryallocationswemakewithinMonowillgothroughtheheap.The.NETFramework(andbyextensiontheC#language,whichmerelyimplementsthe.NETspecification)hastheconceptofValuetypesandReferencetypes,andonlythelatterofwhichneedstobemarkedbytheGarbageCollectorwhileitisperformingitsMark-and-Sweepalgorithm.Referencetypesareexpectedto(orneedto)lastalongtimeinmemoryeitherduetotheircomplexity,theirsize,orhowthey’reused.Largedatasets,andanykindofobjectinstantiatedfromaclass,isaReferencetype.Thisalsoincludesarrays(whetheritisofValuetypesorReferencetypes),delegates,allclasses,suchasMonoBehaviour,GameObject,andanycustomclasseswedefine.

Valuetypesarenormallyallocatedonthestack.Primitivedatatypessuchasbools,ints,andfloatsareexamplesofValuetypes,butonlyifthey’restandaloneandnotamemberofaReferencetype.AssoonasaprimitivedatatypesiscontainedwithinaReferencetype,suchasaclassoranarray,thenitisimpliedthatitiseithertoolargeforthestackorwillneedtosurvivelongerthanthecurrentscopeandmustbeallocatedontheheapinstead.

Allofthiscanbebestexplainedthroughexamples.ThefollowingcodewillcreateanintegerasaValuetypethatexistsonthestackonlytemporarily:


voidStart(){

intdata=5;//allocatedonthestack

DoSomething(data);

}//integerisdeallocatedfromthestackhere

}

AssoonastheStart()methodends,thentheintegerisdeallocatedfromthestack.Thisisessentiallyafreeoperationsince,asmentionedpreviously,itdoesn’tbotherdoinganycleanup;itjustmovesthestackpointerbacktothepreviousmemorylocationinthecallstack.Anyfuturestackallocationssimplyoverwritetheolddata.Mostimportantly,noheapallocationtookplacetocreatethedata,andso,theGarbageCollectorwouldbecompletelyunawareofitsexistence.

But,ifwecreatedanintegerasamembervariableoftheMonoBehaviourclassdefinition,thenitisnowcontainedwithinaReferencetype(aclass)andmustbeallocatedontheheapalongwithitscontainer:


privateint_data=5;

voidStart(){

DoSomething(_data);

}

}

Similarly,ifweputtheintegerintoanindependentclass,thentherulesforReferencetypesstillapply,andtheobjectisallocatedontheheap:


publicclassTestData{

publicintdata=5;

}


voidStart(){

TestDatadataObj=newTestData();//allocatedontheheap

DoSomething(dataObj.data);

}//'dataObj'isnotdeallocatedhere,butitwillbecomeacandidate

duringthenextgarbagecollection

}

So,thereisabigdifferencebetweentemporarilyallocatingmemorywithinaclassmethodandstoringlong-termdatainaclass’memberdata.Inbothcases,we’reusingaReferencetype(aclass)tostorethedata,whichmeansitcanbereferencedelsewhere.Forexample,imagineDoSomething()storedthereferencetodataObjwithinamembervariable:

privateTestData_testDataObj;

voidDoSomething(TestDatadataObj){

_testDataObj=dataObj;//anewreferencecreated!Thereferenced

objectwillnowbemarkedduringmark-and-sweep

}

Inthiscase,wewouldnotbeabletodeallocatetheobjectpointedtodataObjassoonastheStart()methodendedbecausethetotalnumberofthingsreferencingtheobjectwouldgofrom2to1.Thisisnot0,andhencetheGarbageCollectorwouldstillmarkitduringmark-and-sweep.Wewillalsoneedtoset_testDataObjtonull,ormakeitreferencesomethingelse,beforetheobjectwasnolongerreachable.

NotethataValuetypemusthaveavalue,andcanneverbenull.Ifastack-allocatedValuetypeisassignedtoaReferencetype,thenthedataissimplycopied.ThisistrueevenforarraysoftheValuetypes:

publicclassTestClass{

privateint[]_intArray=newint[1000];//Referencetypefullof

Valuetypes

voidStoreANumber(intnum){

_intArray[0]=num;//storeaValuewithinthearray

}

}

Whentheinitialarrayiscreated(duringobjectinitialization),1,000integerswillbeallocatedontheheapsettoavalueof0.WhentheStoreANumber()methodiscalled,thevalueofnumismerelycopiedintothezerothelementofthearray,ratherthanstoringareferencetoit.

ThesubtlechangeinthereferencingcapabilityiswhatultimatelydecideswhethersomethingisaReferencetypeoraValuetype,andweshouldtrytousestandaloneValuetypeswheneverwehavetheopportunity,sothattheygeneratestackallocationsinsteadofheapallocations.Anysituationwherewe’rejustsendingaroundapieceofdatathatdoesn’tneedtolivelongerthanthecurrentscopeisagoodopportunitytouseaValuetypeinsteadofaReferencetype.Ostensibly,itdoesnotmatterifwepassthedataintoanother


methodofthesameclassoramethodofanotherclass;itstillremainsaValuetypethatwillexistonthestackuntilthemethodthatcreateditgoesoutofthescope.

PassbyvalueandpassbyreferenceTechnically,somethingisduplicatedeverytimeadatavalueispassedasanargumentfromonemethodtoanother,andthisistruewhetheritisaValuetypeoraReferencetype.Thisisknownaspassingbyvalue.ThemaindifferenceisthataReferencetypeismerelyapointerwhichconsumesonly4or8bytesinmemory(32-bitor64-bit,dependingonthearchitecture)regardlessofwhatitisactuallypointingto.WhenaReferencetypeispassedasanargumentitisactuallythevalueofthispointerthatgetscopied,whichisveryquicksincethedataisverysmall.

Meanwhile,aValuetypecontainsthefullandcompletebitsofdatastoredwithintheobject.Hence,allofthedataofaValuetypegetscopiedwhenevertheyarepassedbetweenmethods,orstoredinotherValuetypes.Insomecases,itcanmeanthatpassingalargeValuetypeasargumentsaroundtoomuchcanbemorecostlythanjustusingaReferencetype.FormostValuetypes,thisisnotaproblem,sincetheyarecomparableinsizetoapointer.Butthisbecomesimportantwhenwebegintotalkaboutstructs,inthenextsection.

Datacanbepassedaroundbyreferenceaswell,byusingtherefkeyword,butthisisverydifferentfromtheconceptofValueandReferencetypes,anditisveryimportanttokeepthemdistinctinourmindwhenwetrytounderstandwhatisgoingonunderthehood.WecanpassaValuetypebyvalue,orbyreference,andwecanpassaReferencetypebyvalue,orbyreference.Thismeansthattherearefourdistinctdatapassingsituationsthatcanoccurdependingonwhichtypeisbeingpassedandwhethertherefkeywordisbeingusedornot.

Whendataispassedbyreference(evenifitisaValuetype!)thenmakinganychangestothedatawillchangetheoriginal.Forexample,thefollowingcodewouldprintthevalue10:

voidStart(){

intmyInt=5;

DoSomething(refmyInt);

Debug.Log(String.Format("Value={0}",myInt));

}

voidDoSomething(refintval){

val=10;

}

Removingtherefkeywordfrombothplaceswouldmakeitprintthevalue5instead.Thisunderstandingwillcomeinhandywhenwestarttothinkaboutsomeofthemoreinterestingdatatypeswehaveaccessto.Namely,structs,arrays,andstrings.

StructsareValuetypesStructsareaninterestingspecialcaseinC#.IfwecomefromaC++backgroundtoC#,thenwewouldprobablyassumethattheonlydifferencebetweenastructandaclassis


thatastructhasadefaultaccessspecifier,public,whileaclassdefaultstoprivate.However,inC#,structsaresimilartoclassesinthattheycancontainotherprivate/protected/publicdata,havemethods,canbeinstantiatedatruntime,andsoon.ThecoredifferencebetweenthetwoisthatstructsareValuetypesandclassesareReferencetypes.

TherearesomeotherimportantdifferencesbetweenhowstructsandclassesaretreatedinC#;structsdon’tsupportinheritance,theirpropertiescannotbegivencustomdefaultvalues(memberdataalwaysdefaultstovaluessuchas0ornull,sinceitisaValuetype),andtheirdefaultconstructorscannotbeoverridden.Thisgreatlyrestrictstheirusagecomparedtoclasses,sosimplyreplacingallclasseswithstructs(undertheassumptionthatitwilljustallocateeverythingonthestack)isnotawisecourseofaction.

However,ifwe’reusingaclassinasituationwhoseonlypurposeistosendablobofdatatosomewhereelseinourapplication,anditdoesnotneedtolastbeyondthecurrentscope,thenweshoulduseastructinstead,sinceaclasswouldresultinaheapallocationfornoparticularlygoodreason:

publicclassDamageResult{

publicCharacterattacker;

publicCharacterdefender;

publicinttotalDamageDealt;

publicDamageTypedamageType;

publicintdamageBlocked;

//etc

}

publicvoidDealDamage(Character_target){

DamageResultresult=CombatSystem.Instance.CalculateDamage(this,

_target);

CreateFloatingDamageText(result);

}

Inthisexample,we’reusingaclasstopassabunchofdatafromonesubsystem(thecombatsystem)toanother(theUIsystem).Theonlypurposeofthisdataistobecalculatedandreadbyvarioussubsystems,sothisisagoodcandidatetoconvertintoastruct.

MerelychangingtheDamageResultdefinitionfromaclasstoastructcouldsaveusquiteafewunnecessarygarbagecollections,sinceitwouldbeallocatedonthestack.

publicstructDamageResult{

//...

}

Thisisnotacatch-allsolution.SincestructsareValuetypes,thismeanssomethingratheruniquewhenitispassedasanargumentbetweenmethods.Aswepreviouslylearned,everytimeaValuetypeispassedasanargumentbetweenonefunctionandanother,itwillbeduplicatedsinceitispassedbyvalue.ThiscreatesaduplicateValuetypeforthenextmethodtouse,whichwillbedeallocatedassoonasthatmethodgoesoutofscope,andsooneachtimeitispassedaround.So,ifastructispassedbyvaluebetweenfivedifferent


methodsinalongchain,thenfivedifferentstackcopieswilloccuratthesametime.Recallthatstackdeallocationsarefree,butdatacopyingisnot.

Thecopyingisprettymuchnegligibleforsmallvalues,suchasasingleintegerorfloat,butpassingaroundridiculouslylargedatasetsthroughstructsoverandoveragainisobviouslynotatrivialtaskandshouldbeavoided.Insuchcases,itwouldbewisertopassthestructbyreferenceusingtherefkeywordtominimizetheamountofdatabeingcopiedeachtime(justa32-bitor64-bitintegerforthememoryreference).However,thiscanbedangeroussincepassingbyreferenceallowsanysubsequentmethodstomakechangestothestruct,inwhichcaseitwouldbeprudenttomakeitsdatavaluesreadonly(itcanonlybeinitializedintheconstructor,andneveragain,evenbyitsownmemberfunctions)topreventlaterchanges.

AlloftheaboveisalsotruewhenstructsarecontainedwithinReferencetypes:

publicstructDataStruct{

publicintval;

}

publicclassStructHolder{

publicDataStruct_memberStruct;

publicvoidStoreStruct(DataStructds){

_memberStruct=ds;

}

}

Totheuntrainedeye,theprecedingcodeappearstobeattemptingtostoreastack-allocatedstructwithinaReferencetype.DoesthismeanthataStructHolderobjectontheheapcannowreferenceanobjectonthestack?WhatwillhappenwhentheStoreStruct()methodgoesoutofscopeandthestructiserased?Itturnsoutthatthesearethewrongquestions.

What’sactuallyhappeningisthat,whileaDataStructobject(_memberStruct)hasbeenallocatedontheheapwithintheStructHolderobject,itisstillaValuetypeanddoesnotmagicallytransformintoaReferencetype.So,alloftheusualrulesforValuetypesapply.The_memberStructvariablecannothaveavalueofnullandallofitsfieldswillbeinitializedto0ornullvalues.WhenStoreStruct()iscalled,thedatafromdswillbecopiedinto_memberStruct.Therearenoreferencestostackobjectstakingplace,andthereisnoconcernaboutlostdata.

ArraysareReferencetypesArrayscanpotentiallycontainahugeamountofdatawithinthem,whichmakethemdifficulttotreatasaValuetypesincethere’sprobablynotenoughroomonthestacktosupportthem.Therefore,theyaretreatedasaReferencetypesothattheentiredatasetcanbepassedaroundviaasinglereference,insteadofduplicatingtheentirearrayeverytimeitispassedaround.ThisistrueirrespectiveofwhetherthearraycontainsValuetypesorReferencetypes.

Thismeansthatthefollowingcodewillresultinaheapallocation:

TestStruct[]dataObj=newTestStruct[1000];


for(inti=0;i<1000;++i){

dataObj[i].data=i;

DoSomething(dataObj[i]);

}

Thefollowing,functionallyequivalentcode,wouldnotresultinanyheapallocations,sincethestructsareValuetypes,andhencewouldbecreatedonthestack:

for(inti=0;i<1000;++i){

TestStructdataObj=newTestStruct();

dataObj.data=i;

DoSomething(dataObj);

}

Thesubtledifferenceinthesecondcode-blockisthatonlyoneTestStructexistsonthestackatatime(atleastforthisfunctionDoSomething()canpotentiallycreatemore),whereasthefirstblockneedstoallocate1,000ofthemviaanarray.Obviously,thesemethodsarekindofridiculousasthey’rewritten,buttheyillustrateanimportantpointtoconsider.Thecompilerisn’tsmartenoughtoautomaticallyfindthesesituationsforusandmaketheappropriatechanges.OpportunitiestooptimizeourmemoryusagethroughValuetypereplacementswillbeentirelydowntoourabilitytodetectthem,andunderstandwhyachangewillresultinstackallocations,ratherthanheapallocations.

Notethat,whenweallocateanarrayofReferencetypes,we’recreatinganarrayofreferences,whichcaneachreferenceotherlocationsontheheap.However,whenweallocateanarrayofValuetypes,we’recreatingapackedlistofValuetypesontheheap.EachoftheseValuetypeswillbeinitializedwithavalueof0(orequivalent),sincetheycannotbenull,whileeachreferencewithinanarrayofReferencetypeswillalwaysinitializetonull,sincenoreferenceshavebeenassigned,yet.

StringsareimmutableReferencetypesWebrieflytoucheduponthesubjectofstringsbackinChapter2,ScriptingStrategies,butnowit’stimetogointomoredetailaboutwhyproperstringusageisextremelyimportant.

Becausestringsareessentiallyarraysofcharacters(chars),theyareReferencetypes,andfollowallofthesamerulesasotherReferencetypes;thevaluethatisactuallycopiedandpassedbetweenfunctionsismerelyapointer,andtheywillbeallocatedontheheap.

Theconfusingpartreallybeginswhenwediscoverthatstringsareimmutable,meaningtheycannotbechangedafterthey’vebeenallocated.Beinganarrayimpliesthattheentirelistofcharactersmustbecontiguousinmemory,whichcannotbetrueifweallowedstringstoexpandorcontractat-willwithinadynamicmemoryspace(howcouldwequicklyandsafelyexpandthestringifwe’veallocatedsomethingelseimmediatelyafterit?).

Thismeansthat,ifastringismodified,thenanewstringmustbeallocatedtoreplaceit,wherethecontentsoftheoriginalwillbecopiedandmodifiedas-neededintoawholenewcharacterarray.Inwhichcase,theoldversionwillnolongerbereferencedanywhere,willnotbemarkedduringmark-and-sweepandwillthereforeeventuallybegarbage-collected.Asaresult,lazystringprogrammingcanresultinalotofunnecessaryheapallocations

andgarbagecollection.

Forexample,ifwebelievedthatstringsworkedjustlikeotherReferencetypes,wemightbeforgivenforassumingthelogoutputofthefollowingtobeWorld!:

voidStart(){

stringtestString="Hello";

DoSomething(testString);

Debug.Log(testString);

}

voidDoSomething(stringlocalString){

localString="World!";

}

However,thisisnotthecase,anditwillstillprintoutHello.WhatisactuallyhappeningisthatthelocalStringvariable,withinthescopeofDoSomething(),startsoffreferencingthesameplaceinmemoryastestString,duetothereferencebeingpassedbyvalue.ThisgivesustworeferencespointingtothesamelocationinmemoryaswewouldexpectifweweredealingwithanyotherReferencetype.Sofar,sogood.

But,assoonaswechangethevalueoflocalString,werunintoalittlebitofaconflict.Stringsareimmutable,andwecannotchangethem,sothereforewemustallocateanewstringcontainingthevalueWorld!andassignitsreferencetothevalueoflocalString;nowthenumberofreferencestotheHellostringreturnsbacktoone.Theoriginalstring(Hello)willremaininmemorybecausethevalueoftestStringhasnotbeenchanged,andthatisstillthevaluewhichwillbeprintedbyDebug.Log().Allwe’vesucceededindoingbycallingDoSomething()iscreatinganewstringontheheapwhichgetsgarbage-collected,anddoesn’tchangeanything.Thisisthetextbookdefinitionofwasteful.

IfwechangethemethoddefinitionofDoSomething()topassthestringbyreference,viatherefkeyword,theoutputwouldindeedchangetoWorld!.ThisiswhatwewouldexpecttohappenwithaValuetype,whichleadsalotofdeveloperstoincorrectlyassumethatstringsareValuetypes.But,thisisanexampleofthefourthandfinaldata-passingcasewhereaReferencetypeisbeingpassedbyreference,whichallowsustochangewhattheoriginalreferenceisreferencing!

NoteSo,torecap;ifwepassaValuetypebyvalue,wecanonlychangethevalueofthecopy.IfwepassaValuetypebyreference,wecanchangetheactualvalueattributedtotheoriginalversion.IfwepassaReferencetypebyvalue,wecanmakechangestotheobjectthattheoriginalreferenceisreferencing.Andfinally,ifwepassaReferencetypebyreference,wecanchangewhichobjecttheoriginalreferenceisreferencing.

Stringconcatenation

Concatenationistheactofappendingstringstooneanothertoformalargerstring.Aswe’velearned,anysuchcasesarelikelytoresultinexcessheapallocations.Thebiggestoffenderinstring-basedmemorywasteisconcatenatingstringsusingthe+and+=operators,becauseoftheallocationchainingeffecttheycause.


Forexample,thefollowingcodetriestocombineagroupofstringstogethertoprintsomeinformationaboutacombatresult:

voidCreateFloatingDamageText(DamageResultresult){

stringoutputText=result.attacker.GetCharacterName()+"dealt"+

result.totalDamageDealt.ToString()+""+result.damageType.ToString()+"

damageto"+result.defender.GetCharacterName()+"("+

result.damageBlocked.ToString()+"blocked)";

//...

}

Anexampleoutputofthisfunctionmightbeastringthatreads:

Dwarfdealt15SlashingdamagetoOrc(3blocked)

Thisfunctionfeaturesahandfulofstringliterals(hard-codedstringsthatareallocatedduringapplicationinitialization)suchasdealt,damageto,andblocked.But,becauseoftheusageofvariableswithinthiscombinedstring,itcannotbecompiledawayatbuildtime,andthereforemustbegenerateddynamicallyatruntime.

Anewheapallocationwillbegeneratedeachtimea+,or+=,operatorisexecuted;onlyasinglepairofstringswillbemergedatatime,anditallocatesanewstringeachtime.Then,theresultofonemergerwillbefedintothenext,andmergedwithanotherstring,andsoonuntiltheentirestringhasbeenbuilt.

So,thepreviousexamplewillresultin9differentstringsbeingallocatedallinonego.Allofthefollowingstringswouldbeallocatedtosatisfythisinstruction,andallwouldeventuallyneedtobegarbagecollected(notethattheoperatorsareresolvedfromright-to-left):

"3blocked)"

"(3blocked)"

"Orc(3blocked)"

"damagetoOrc(3blocked)"

"SlashingdamagetoOrc(3blocked)"

"SlashingdamagetoOrc(3blocked)"

"15SlashingdamagetoOrc(3blocked)"

"dealt15SlashingdamagetoOrc(3blocked)"

"Dwarfdealt15SlashingdamagetoOrc(3blocked)"

That’s262charactersbeingused,insteadof49;orbecauseacharisa2-bytedatatype,that’s524bytesofdatabeingallocatedwhenweonlyneed98bytes.Chancesarethat,ifthiscodeexistsinthecodebaseonce,thenitexistsallovertheplace,soforanapplicationthat’sdoingalotoflazystringconcatenationlikethis,thatisatonofmemorybeingwastedongeneratingunnecessarystrings.

TipNotethatbig,constantstringliteralscanbesafelycombinedusingthe+and+=operatorstomakethemmorereadablewithinthecodebase,butonlyiftheywillresultinaconstantstring.Ifso,thecompilerwilltakecareofmergingallofthestringliteralstogetheratcompiletime.


BetterapproachesforgeneratingstringsaretouseeithertheStringBuilderclass,oroneofseveralstringclassmethods.

TheStringBuilderclassiseffectivelyamutable(changeable)stringclass.Itworksbyallocatingabuffertocopythetargetstringsintoandallocatesadditionalspacewheneveritisneeded.WecanretrievethestringusingtheToString()methodwhich,naturally,resultsinamemoryallocationfortheresultantstring,butatleastweavoidedalloftheunnecessarystringallocationswewouldhavegeneratedusingthe+or+=operators.

Conventionalwisdomsaysthatifweroughlyknowthefinalsizeoftheresultantstring,thenwecanallocateanappropriatebufferaheadoftimeandsaveourselvesundueallocations.Forourexampleabove,wemightallocateabufferof100characterstomakeroomforlongcharacternamesanddamagevalues:

usingSystem.Text;

//...

StringBuildersb=newStringBuilder(100);

sb.Append(result.attacker.GetCharacterName());

sb.Append("dealt");

sb.Append(result.totalDamageDealt.ToString());

//etc…

stringresult=sb.ToString();

Ifwedon’tknowthefinalsize,thenusingaStringBuilderclassislikelytogenerateabufferthatdoesn’tfitthesizeexactly,orclosely.Wewilleitherendupwithabufferthat’stoolarge(wastedallocationtimeandspace),or,worse,abufferthat’stoosmall,whichmustkeepexpandingaswegeneratethecompletestring.Ifwe’reunsureaboutthetotalsizeofthestring,thenitmightbebesttouseoneofthevariousstringclassmethods.

Therearethreestringclassmethodsavailableforgeneratingstrings;Format(),Join(),andConcat().Eachoperatesslightlydifferently,buttheoveralloutputisthesame;anewstringisallocatedcontainingthecontentsofthestring(s)wepassintothem,anditisalldoneinasingleactionwhichreducesexcessstringallocations.

Itissurprisinglyhardtosaywhichoneofthetwoapproacheswouldbemorebeneficialinagivensituationastherearealotofreallydeepnuancesinvolved.There’salotofdiscussionsurroundingthetopic(justdoaGooglesearchfor"csharpstringconcatenationperformance"andyou’llseewhatImean),sothebestapproachistoimplementoneortheotherusingtheconventionalwisdomdescribedpreviously.Wheneverwerunintobadperformancewithonemethod,weshouldtrytheother,profilethemboth,andpickthebestoptionofthetwo.

BoxingTechnically,everythinginC#isanobject(caveatsapply).Evenprimitivedatatypessuchasints,floats,andboolsarederivedfromSystem.Objectattheirlowestlevel(aReferenceType!),whichallowsthemaccesstohelpermethodssuchasToString(),sothattheycancustomizetheirstringrepresentation.

ButtheseprimitivetypesaretreatedasspecialcasesviabeingtreatedasValuetypes.WheneveraValuetypeisimplicitlytreatedinsuchawaythatitmustactlikeanobject,


theCLRautomaticallycreatesatemporaryobjecttostore,or“box”,thevalueinsidesothatitcanbetreatedasatypicalReferencetypeobject.Asweshouldexpect,thisresultsinaheapallocationtocreatethecontainingvessel.

TipNotethatboxingisnotthesamethingasusingValuetypesasmembervariablesofReferencetypes.ItonlytakesplacewhenValuetypesaretreatedlikeobjectsthemselves.

Forexample,thefollowingcodewouldcausethevariableitobeboxedinsideobjectobj:

inti=128;

objectobj=i;

Thefollowingwouldusetheobjectrepresentationobjtoreplacethevaluestoredwithintheinteger,and“unbox”itbackintoaninteger,storingitini.Thefinalvalueofiwouldbe256:

obj=256;

i=(int)obj;

Thesetypescantechnicallybechangeddynamically.ThefollowingisperfectlylegalC#code,whichusesthesameobjectobjasabove,whichwasoriginallyboxedfromanint:

obj=512f;

floatf=(float)obj;

Thefollowingisalsolegal:

obj=false;

boolb=(bool)obj;

Notethatattemptingtounboxobjintoatypethatisn’tthemostrecentlyassignedtypewouldresultinanInvalidCastException.Allofthiscanbealittletrickytowrapourheadarounduntilwerememberthat,attheendoftheday,everythingisjustbitsinmemory.What’simportantisknowingthatwecantreatourprimitivetypesasobjectsbyboxingthem,convertingtheirtypes,andthenunboxingthemintoadifferenttypeatalatertime.

NoteNotethatit’spossibletoconvertaboxedobject’stypeusingoneofthemanySystem.Convert.To…()methods.

Boxingcanbeeitherimplicit,aspertheexamplesabove,orexplicit,bytypecastingtoSystem.Object.Unboxingmustalwaysbeexplicitbytypecastingbacktoitsoriginaltype.WheneverwepassaValuetypeintoamethodwhichusesSystem.Objectasarguments,boxingwillbeappliedimplicitly.

MethodssuchasString.Format(),whichtakeSystem.Objectsasarguments,areonesuchexample.WetypicallyusethembypassinginValuetypessuchasints,floats,boolsandsoon,togenerateastringwith.Boxingisautomaticallytakingplaceinthesesituations,causingadditionalheapallocationswhichweshouldbeawareof.


Collections.Generic.ArrayListisanothersuchexample,sinceArrayListsalwayscontainSystem.Objectreferences.

AnytimeweuseafunctiondefinitionthattakesSystem.Objectasarguments,andwe’repassinginValuetypes,weshouldbeawarethatwe’reimplicitlycausingheapallocationsduetoboxing.


TheimportanceofdatalayoutTheimportanceofhowourdataisorganizedinmemorycanbesurprisinglyeasytoforgetabout,butcanresultinafairlybigperformanceboostifitishandledproperly.Cachemissesshouldbeavoidedwheneverpossible,whichmeansthatinmostcases,arraysofdatathatarecontiguousinmemoryshouldbeiteratedoversequentially,asopposedtoanyotheriterationstyle.

Thismeansthatdatalayoutisalsoimportantforgarbagecollection,sinceitisdoneinaniterativefashion,andifwecanfindwaystohavetheGarbageCollectorskipoverproblematicareas,thenwecanpotentiallysavealotofiterationtime.

Inessence,wewanttokeeplargegroupsofReferencetypesseparatedfromlargegroupsofValuetypes.IfthereisevenjustoneReferencetypewithinaValuetype,suchasastruct,thentheGarbageCollectorconsiderstheentireobject,andallofitsdatamembers,indirectlyreferenceableobjects.Whenitcomestimetomark-and-sweep,itmustverifyallfieldsoftheobjectbeforemovingon.But,ifweseparatethevarioustypesintodifferentarrays,thenwecanmaketheGarbageCollectorskipthemajorityofthedata.

Forinstance,ifwehaveanarrayofstructscontainingdatalikeso,thentheGarbageCollectorwillneedtoiterateovereverymemberofeverystruct,whichcouldbefairlytimeconsuming:

publicstructMyStruct{

intmyInt;

floatmyFloat;

boolmyBool;

stringmyString;

}

MyStruct[]arrayOfStructs=newMyStruct[1000];

But,ifwereplaceallofthisdatawithsimplearrays,thentheGarbageCollectorwillignorealloftheprimitivedatatypes,andonlycheckthestrings.Thiswouldresultinmuchafastergarbagecollectionsweep:

int[]myInts=newint[1000];

float[]myFloats=newfloat[1000];

bool[]myBools=newbool[1000];

string[]myStrings=newstring[1000];

Thereasonthisworksisbecausewe’regivingtheGarbageCollectorfewerindirectreferencestocheck.Whenthedataissplitintoseparatearrays(Referencetypes),itfindsthreearraysofValuetypes,marksthearrays,andthenimmediatelymovesonbecausethere’snoreasontomarkValuetypes.Itmuststilliteratethroughallofthestringswithinthestringarray,sinceeachisaReferencetypeanditneedstoverifythattherearenoindirectreferenceswithinit.Technically,stringscannotcontainindirectreferences,buttheGarbageCollectorworksatalevelwhereitonlyknowsiftheobjectisaReferencetypeorValuetype.However,wehavestillsparedtheGarbageCollectorfromneedingtoiterateoveranextra3,000piecesofdata(all1,000ints,floats,andbools).


TheUnityAPIThereareseveralinstructionswithintheUnityAPIwhichresultinheapmemoryallocations,whichweshouldbeawareof.Thisessentiallyincludeseverythingthatreturnsanarrayofdata.Forexample,thefollowingmethodsallocatememoryontheheap:

GetComponents<T>();//(T[])

Mesh.vertices;//(Vector3[])

Camera.allCameras;//(Camera[])

Suchmethodsshouldbeavoidedwheneverpossible,orattheveryleastcalledonceandcachedsothatwedon’tcausememoryallocationsmoreoftenthannecessary.

NotethatUnityTechnologieshashinteditmightcomeoutwithallocation-lessversionsofthesemethodssometimeinthelifecycleofUnity5.Presumably,itmightlooksomethinglikethewayParticleSystemsallowsaccesstoParticledata,whichinvolvesprovidingaParticle[]arrayreferencetopointtotherequireddata.Thisavoidsallocationsincewereusethesamebufferbetweencalls.

TheforeachloopsTheforeachloopkeywordisabitofacontroversialissueinUnitydevelopmentcircles.ItturnsoutthatalotofforeachloopsimplementedinUnityC#codewillincurunnecessaryheapmemoryallocationsduringthesecalls,astheyallocateanEnumeratorobjectasaclassontheheap,insteadofastructonthestack.Italldependsonthegivencollection’simplementationoftheGetEnumerator()method.

ItturnsoutthateverysinglecollectionthathasbeenimplementedintheversionofMonothatcomeswithUnity(Monoversion2.6.5)willcreateclassesinsteadofstructs,whichresultsinheapallocations.Thisincludes,butisnotlimitedto,List<T>,LinkedList<T>,Dictionary<K,V>,ArrayList,andsoon.But,notethatitisactuallysafetouseforeachloopsontypicalarrays!TheMonocompilersecretlyconvertsforeachoverarraysintosimpleforloops.

Thecostisfairlynegligibleastheheapallocationcostdoesnotscalewiththenumberofiterations.OnlyoneEnumeratorobjectisallocated,andreusedoverandoveragain,whichonlycostsahandfulofbytesofmemoryoverall.Sounlessourforeachloopsarebeinginvokedeveryupdate(whichistypicallydangerousinandofitself)thenthecostswillbemostlynegligibleonsmallprojects.Thetimetakentoconverteverythingtoaforloopmaynotbeworththetime.Butit’sdefinitelysomethingtokeepinmindforthenextprojectwebegintowrite.

Ifwe’reparticularlysavvywithC#,VisualStudio,andmanualcompilationoftheMonoassembly,thenwecanhaveVisualStudioperformcodecompilationforus,andcopytheresultingassemblyDLLintotheAssetsfolder,whichwillfixthismistakeforthegenericcollections.

NotethatperformingforeachoveraTransformComponentisatypicalshortcuttoiteratingoveraTransform’schildren.Forexample:

foreach(Transformchildintransform){

//dostuffwith'child'

}

However,thisresultsinthesameheapallocationsmentionedabove.Asaresult,thatcodingstyleshouldbeavoidedinfavorofthefollowing:

for(inti=0;i<transform.childCount;++i){

Transformchild=transform.GetChild(i);

//dostuffwith'child'

}

CoroutinesStartingaCoroutinecostsasmallamountofmemorytobeginwith,butnotethatnofurthercostsareincurredwhenthemethodyields.Ifmemoryconsumptionandgarbagecollectionaresignificantconcerns,weshouldtrytoavoidhavingtoomanyshort-livedCoroutines,andavoidcallingStartCoroutine()toomuchduringruntime.


ClosuresClosuresareuseful,butdangeroustools.AnonymousmethodsandlambdaexpressionsarenotalwaysClosures,buttheycanbe.Italldependsonwhetherthemethodusesdataoutsideofitsownscopeandparameterlist,ornot.

Forexample,thefollowinganonymousfunctionwouldnotbeaClosure,sinceitisself-containedandfunctionallyequivalenttoanyotherlocallydefinedfunction:

System.Func<int,int>anon=(x)=>{returnx;};

intresult=anon(5);

But,iftheanonymousfunctionpulledindatafromoutsideitself,thenitbecomesaClosure,asit“closestheenvironment”aroundtherequireddata.ThefollowingwouldresultinaClosure:

inti=1024;

System.Func<int,int>anon=(x)=>{returnx+i;};

intresult=anon(5);

Inordertocompletethistransaction,thecompilermustdefineanewclassthatcanreferencetheenvironmentwherethedatavalueiwouldbeaccessible.Atruntimeitcreatesthecorrespondingobjectontheheapandprovidesittotheanonymousfunction.NotethatthisincludesValuetypes(aspertheaboveexample),whichwereoriginallyonthestack,possiblydefeatingthepurposeofthembeingallocatedonthestackinthefirstplace.So,weshouldexpecteachinvocationofthesecondmethodtoresultinheapallocationsandinevitablegarbagecollection.

.NETlibraryfunctionsThe.NETlibraryoffersahugeamountofcommonfunctionalitythathelpssolvenumerousproblemsthatprogrammersmaycomeacrossduringday-to-dayimplementation.Mostoftheseclassesandfunctionsareoptimizedforgeneralusecases,whichmaynotbeoptimalforaspecificsituation.Itmaybepossibletoreplaceaparticular.NETlibraryclasswithacustomimplementationthatismoresuitedtoourspecificusecase.

Therearealsotwobigfeaturesinthe.NETlibrarythatoftenbecomebigperformancehogswheneverthey’reused.Thistendstobebecausetheyareonlyincludedasaquick-and-hackysolutiontoagivenproblemwithoutmucheffortputintooptimization.ThesefeaturesareLINQandRegularExpressions.

LINQprovidesawaytotreatarraysofdataasminiaturedatabasesandperformqueriesagainstthemusingSQL-likesyntax.Thesimplicityofitscodingstyle,andcomplexityoftheunderlyingsystem(throughitsusageofClosures),impliesthatithasafairlylargeoverheadcost.LINQisahandytool,butisnotreallyintendedforhigh-performance,real-timeapplicationssuchasgames,anddoesnotevenfunctiononplatformsthatdonotsupportJITcompilation,suchasiOS.

Meanwhile,RegularExpressions,usingtheRegexclass,allowustoperformcomplexstringparsingtofindsubstringsthatmatchaparticularformat,replacepiecesofastring,orconstructstringsfromvariousinputs.RegularExpressionisanotherveryusefultool,buttendstobeoverusedinplaceswhereitislargelyunnecessary,orinseemingly“clever”waystoimplementafeaturesuchastextlocalization,whenstraightforwardstringreplacementwouldbefarmoreefficient.

Specificoptimizationsforbothofthesefeaturesgofarbeyondthescopeofthisbook,astheycouldfillentirevolumesbythemselves.Weshouldeithertrytominimizetheirusageasmuchaspossible,replacetheirusagewithsomethinglesscostly,bringinaLINQorRegexexperttosolvetheproblemforus,ordosomeGooglingonthesubjecttooptimizehowwe’reusingthem.

TipOneofthebestwaystofindthecorrectansweronlineistosimplypostthewronganswer!Peoplewilleitherhelpusoutofkindness,ortakesuchgreatoffensetoourimplementationthattheyconsiderittheircivicdutytocorrectus!Justbesuretodosomekindofresearchonthesubjectfirst.Eventhebusiestofpeoplearegenerallyhappytohelpiftheycanseethatwe’veputinourfairshareofeffortbeforehand.


TemporaryworkbuffersIfwegetintothehabitofusinglarge,temporaryworkbuffersforonetaskoranother,thenitjustmakessensethatweshouldlookforopportunitiestoreusethem,insteadofreallocatingthemoverandoveragain,asthislowerstheoverheadinvolvedinallocation,aswellasgarbagecollection(so-called“memorypressure”).Itmightbeworthwhiletoextractsuchfunctionalityfromcase-specificclassesintoagenericgodclassthatcontainsabigworkareaformultipleclassestoreuse.


ObjectpoolingSpeakingoftemporaryworkbuffers,objectpoolingisanexcellentwayofbothminimizingandestablishingcontroloverourmemoryusagebyavoidingdeallocationandreallocation.Theideaistoformulateourownsystemforobjectcreation,whichhidesawaywhethertheobjectwe’regettinghasbeenfreshlyallocatedorhasbeenrecycledfromanearlierallocation.Thetypicaltermstodescribethisprocessareto“spawn”and“despawn”theobject,ratherthancreatinganddeletingthem,sinceanytimeanobjectisdespawnedwe’resimplyhidingitfromviewuntilweneeditagain,atwhichpointitisrespawnedandreused.

Let’scoveraquickimplementationofanobjectpoolingsystem.

Thefirstrequirementistoallowthepooledobjecttodecidehowtorecycleitselfwhenthetimecomes.Thefollowinginterfacewillsatisfytherequirementsnicely:

publicinterfaceIPoolableObject{

voidNew();

voidRespawn();

}

Thisinterfacedefinestwomethods;New()andRespawn().Theseshouldbecalledwhentheobjectisfirstcreated,andwhenithasbeenrespawned,respectively.

Thesecondrequirementistoprovideabaseimplementationofthisinterfacethatallowsobjectsofanytypetohandleanybookkeepingrequiredtotakecareoftheinitialcreationandrespawningofobjects.

ThefollowingObjectPoolclassdefinitionisafairlysimpleimplementationoftheobjectpoolingconcept.Itusesgenericstosupportanyobjecttypesolongasitfitstwocriteria;itmustimplementtheIPoolableObjectinterface,andmustallowforaparameter-lessconstructor(thenew()keywordintheclassdeclaration).

publicclassObjectPool<T>whereT:IPoolableObject,new(){

privateStack<T>_pool;

privateint_currentIndex=0;

publicObjectPool(intinitialCapacity){

_pool=newStack<T>(initialCapacity);

for(inti=0;i<initialCapacity;++i){

Spawn();//instantiateapoolofNobjects

}

Reset();

}

publicintCount{

get{return_pool.Count;}

}

publicvoidReset(){

_currentIndex=0;

}

publicTSpawn(){

if(_currentIndex<Count){

Tobj=_pool.Pop();

_currentIndex++;

IPoolableObjectip=objasIPoolableObject;

ip.Respawn();

returnobj;

}else{

Tobj=newT();

_pool.Push(obj);

_currentIndex++;

IPoolableObjectip=objasIPoolableObject;

ip.New();

returnobj;

}

}

}

AnexamplePoolableobjectwouldlooklikeso.Itmustimplementtwopublicmethods,New()andRespawn(),whichareinvokedbytheObjectPoolclassattheappropriatetimes:

publicclassTestObject:IPoolableObject{

publicvoidNew(){

//veryfirstinitializationhere

}

publicvoidRespawn(){

//resetdatawhichallowstheobjecttoberecycledhere

}

}

Andfinally,anexampleusagetocreateapoolof100TestObjectobjects:

privateObjectPool<TestObject>_objectPool=newObjectPool<TestObject>

(100);

Thefirst100callstoSpawn()onthe_objectPoolobjectwillcausetheobjectstoberespawnedandprovidedtothecaller.Ifthestackrunsoutofspace,thenitwilladdevenmoreTestObjectobjectstothestack.Finally,ifReset()iscalledon_objectPool,thenitwillbeginagainfromthestart,recyclingobjectsandprovidingthemtothecaller.

Notethatthispoolingsolutionwillnotworkforclasseswehaven’tdefined,andcannotderivefrom,suchasVector3,andQuaternion.Inthesecases,wewouldneedtodefineacontainingclass:

publicclassPoolableVector3:IPoolableObject{

publicVector3vector=newVector3();

publicvoidNew(){

Reset();

}

publicvoidRespawn(){

Reset();

}

publicvoidReset(){

vector.x=vector.y=vector.z=0f;

}

}

Wecouldextendthissysteminanumberofways,suchasdefiningaDespawn()methodtohandledestructionoftheobject,makinguseoftheIDisposableinterfaceandusingblockswhenwewishtoautomaticallyspawnanddespawnobjectswithinasmallscope,and/orallowingobjectsinstantiatedoutsidethepooltobeaddedtoit.


PrefabpoolingThepreviouspoolingsolutionisusefulfortypicalclasses,butitwon’tworkforspecialUnityobjects,suchasGameObjectandMonoBehaviour.Theseobjectstendtoconsumealargechunkofourruntimememory,cancostusagreatdealofCPUusagewhenthey’recreatedanddestroyed,andtendtoriskalargeamountofgarbagecollectionatruntime.Inotherwords,themaingoalofPrefabpoolingistopushtheoverwhelmingmajorityofobjectinstantiationtoSceneinitialization,ratherthanlettingthemgetcreatedatruntime.ThiscanprovidesomebigruntimeCPUsavings,andavoidsalotofspikescausedbyobjectcreation/destructionandgarbagecollection,attheexpenseofSceneloadingtimes,andruntimememoryconsumption.Asaresult,therearequiteafewpoolingsolutionsavailableontheAssetStoreforhandlingthistask,withvaryingdegreesofsimplicity,quality,andfeaturesets.

NoteItisoftenrecommendedthatpoolingshouldbeimplementedinanygamethatintendstodeployonmobiledevices,duetothegreateroverheadcostsinvolvedintheallocationanddeallocationofmemorycomparedtodesktopapplications.

However,creatingapoolingsolutionisaninterestingtopic,andbuildingonefromscratchisagreatwayofgettingtogripswithalotofimportantinternalUnityEnginebehavior.Also,knowinghowsuchasystemisbuiltmakesiteasiertoextendifwewishittomeettheneedsofourparticulargame,ratherthanrelyingonaprebuiltsolution.

ThegeneralideaofPrefabpoolingistocreateasystemthatcontainslistsofactiveandinactiveGameObjectsthatwereallinstantiatedfromthesamePrefabreference.Thefollowingdiagramshowshowthesystemmightlookafterseveralspawns,despawns,andrespawnsofvariousobjectsderivedfromfourdifferentPrefabs(Orc,Troll,Ogre,andDragon):


NoteNotethattheHeapMemoryarearepresentstheobjectsastheyexistinmemory,whilethePoolingSystemarearepresentsreferencestothoseobjects.

Inthisexample,severalinstancesofeachPrefabwereinstantiated(11Orcs,8Trolls,5Ogres,and1Dragon).Currentlyonlyelevenoftheseobjectsareactive,whiletheotherfourteenhavepreviouslybeendespawned,andareinactive.Notethatthedespawnedobjectsstillexistinmemory,althoughtheyarenotvisibleandcannotinteractwiththegameworlduntiltheyhavebeenrespawned.Naturally,thiscostsusaconstantamountofheapmemoryatruntimeinordertomaintaintheinactiveobjects,butwhenanewobjectisinstantiated,wecanreuseoneoftheexistinginactiveobjects,ratherthanallocatingmorememoryinordertosatisfytherequest.ThissavessignificantruntimeCPUcostsduringobjectcreationanddestruction,andavoidsgarbagecollection.

ThefollowingdiagramshowsthechainofeventsthatneedstooccurwhenanewOrcisspawned:

ThefirstobjectintheInactiveOrcpool(Orc7)isreactivatedandmovedintotheActivepool.Wenowhave6activeOrcs,and5inactiveOrcs.

ThefollowingfigureshowstheorderofeventswhenanOgreobjectisdespawned:


ThistimetheobjectisdeactivatedandmovedfromtheActivepoolintotheInactivepool,leavinguswith1activeOgreand4inactiveOgres.

Finally,thefollowingdiagramshowswhathappenswhenanewobjectisspawned,buttherearenoinactiveobjectstosatisfytherequest:

Inthisscenario,morememorymustbeallocatedtoinstantiatethenewDragonobject,sincetherearenoDragonobjectsinitsInactivepooltoreuse.Therefore,inordertoavoidruntimememoryallocationsforourGameObjects,itiscriticalthatweknowbeforehandhowmanywewillneed.Thiswillvarydependingonthetypeofobjectinquestion,and


requiresoccasionaltestinganddebuggingtoensurewehaveasensiblenumberofeachPrefabinstantiatedatruntime.

Withallofthisinmind,let’screateapoolingsystemforPrefabs!


PoolableComponentsLet’sfirstdefineaninterfaceforaPoolableComponent:

publicinterfaceIPoolableComponent{

voidSpawned();

voidDespawned();

}

TheapproachforIPoolableComponentwillbeverydifferentfromtheapproachtakenforIPoolableObject.TheobjectsbeingcreatedthistimeareGameObjects,whicharealottrickiertoworkwiththanstandardobjectsbecauseofhowmuchoftheirruntimebehaviorisalreadyhandledthroughtheUnityEngine,andhowlittleaccesswehavetoit.

GameObjectsdonotgiveusaccesstoanequivalentNew()methodthatwecaninvokeanytimetheobjectiscreated,andwecannotderivefromtheGameObjectclassinordertoimplementone.GameObjectsarecreatedeitherbyplacingtheminaScene,orbyinstantiatingthematruntimethroughGameObject.Instantiate(),andtheonlyinputswecanapplyareaninitialpositionandrotation.Ofcourse,theirComponentshaveanAwake()methodwecandefine,whichisinvokedthefirsttimetheComponentisbroughttolife,butthisismerelyacompositionalobject—it’snottheactualparentobjectwe’respawninganddespawning.

So,becauseweonlyhavecontroloveraGameObjectclass’sComponents,itisassumedthattheIPoolableComponentinterfaceisimplementedbyatleastoneoftheComponentsthatisattachedtotheGameObjectwewishtopool.

TheSpawned()methodshouldbeinvokedoneveryimplementingComponenteachtimethepooledGameObjectisrespawned,whiletheDespawned()methodgetsinvokedwheneveritisdespawned.ThisgivesusentrypointstocontrolthedatavariablesandbehaviorduringthecreationanddestructionoftheparentGameObject.

TheactofdespawningaGameObjectistrivial;turnitsactiveflagtofalse(throughSetActive()).ThisdisablestheColliderandRigidbodyforphysicscalculations,removesitfromthelistofrenderableobjects,andessentiallytakescareofdisablinginteractionswithallbuilt-inUnityEnginesubsystemsinasinglestroke.TheonlyexceptionisanyCoroutinesthatarecurrentlyinvokingontheobject,sinceaswelearnedearlierinChapter2,ScriptingStrategies,CoroutinesareinvokedindependentlyofUpdate()andGameObjectactivity.WewillthereforeneedtocallStopCoroutine(),orStopAllCoroutines()duringthedespawningofsuchobjects.

Inaddition,Componentstypicallyhookintoourowncustomgameplaysubsystemsaswell,andsotheDespawn()methodgivesourComponentstheopportunitytotakecareofanycustomcleanupbeforeshuttingdown.Forexample,wewouldprobablywanttouseDespawn()toderegistertheComponentfromtheMessagingSystemwedefinedbackinChapter2,ScriptingStrategies.

Unfortunately,successfullyrespawningtheGameObjectisalotmorecomplicated.Whenwerespawnanobject,therewillbemanysettingsthatwereleftbehindwhentheobject


waspreviouslyactive,andthesemustberesetinordertoavoidconflictingbehaviors.AcommonproblemwiththisisRigidbodyvelocity.Ifthisvalueisnotexplicitlyresetbeforetheobjectisreactivated,thenthenewlyrespawnedobjectwillcontinuemovingwiththesamevelocitytheoldversionhadwhenitwasdespawned.

Thisproblembecomesfurthercomplicatedbythefactthatbuilt-inComponentsaresealed,andthereforecannotbederivedfrom.So,toavoidtheseissues,wecancreateacustomComponentthatresetstheattachedRigidbodywhenevertheobjectisdespawned:

publicclassResetPooledRigidbodyComponent:MonoBehaviour,

IPoolableComponent{

Rigidbody_body;

publicvoidSpawned(){}

publicvoidDespawned(){

if(_body==null){

_body=GetComponent<Rigidbody>();

if(_body==null){

//noRigidbody!

return;

}

}

_body.velocity=Vector3.zero;

_body.angularVelocity=Vector3.zero;

}

}

Notethatthebestplacetoperformthistaskisduringdespawning,becausewecannotbecertaininwhatordertheGameObjectclass’sIPoolableComponentinterfaceswillhavetheirSpawned()methodsinvoked.ItisunlikelythatanotherIPoolableComponentwillchangetheobject’svelocityduringdespawning,butitispossiblethatadifferentIPoolableComponentattachedtothesameobjectmightwanttosettheRigidbody’sinitialvelocitytosomeimportantvalueduringitsownSpawned()method.Ergo,performingthevelocityresetduringtheResetPooledRigidbodyComponentclass’sSpawned()methodcouldpotentiallyconflictwithotherComponentsandcausesomeveryconfusingbugs.

TipInfact,creatingPoolableComponentsthatarenotself-contained,andtendtotinkerwithotherComponentslikethis,isoneofthebiggestdangersofimplementingapoolingsystem.Weshouldminimizesuchimplementations,androutinelyverifythemwhenwe’retryingtodebugstrangeissuesinourgame.

Forthesakeofillustration,hereisthedefinitionofasimplePoolableComponentthatreplacestheTestMessageListenerclasswedefinedbackinChapter2,ScriptingStrategies.ThisComponentautomaticallyhandlessomebasictaskseverytimetheobjectisspawnedanddespawned:

publicclassPoolableTestMessageListener:MonoBehaviour,

IPoolableComponent{

publicvoidSpawned(){

MessagingSystem.Instance.AttachListener(typeof(MyCustomMessage),

}

boolHandleMyCustomMessage(BaseMessagemsg){

MyCustomMessagecastMsg=msgasMyCustomMessage;

Debug.Log(string.Format("Gotthemessage!{0},{1}",

castMsg._intValue,castMsg._floatValue));

returntrue;

}

publicvoidDespawned(){

if(MessagingSystem.IsAlive){

MessagingSystem.Instance.DetachListener(typeof(MyCustomMessage),


}

}

}


ThePrefabpoolingsystemHopefully,wenowhaveanunderstandingofwhatweneedfromourpoolingsystem,soallthat’sleftistoimplementit.Therequirementsareasfollows:

ItmustacceptrequeststospawnaGameObjectfromaPrefab,aninitialposition,andaninitialrotation:

Ifadespawnedversionalreadyexists,itshouldrespawnthefirstavailableoneIfitdoesnotexist,thenitshouldinstantiateanewGameObjectfromthePrefabIneithercase,theSpawned()methodshouldbeinvokedonallIPoolableComponentinterfacesattachedtotheGameObject

ItmustacceptrequeststodespawnaspecificGameObject:

Iftheobjectismanagedbythepoolingsystem,itshoulddeactivateitandcalltheDespawned()methodonallIPoolableComponentinterfacesattachedtotheGameObjectIftheobjectisnotmanagedbythepoolingsystem,itshouldsendanerror

Therequirementsarefairlystraightforward,buttheimplementationrequiressomeinvestigationifwewishtomakethesolutionperformance-friendly.Firstly,atypicalSingletonwouldbeagoodchoiceforthemainentrypoint,sincewewantthissystemtobegloballyaccessiblefromanywhere:

publicstaticclassPrefabPoolingSystem{

}

ThemaintaskforobjectspawninginvolvesacceptingaPrefabreference,andfiguringifwehaveanydespawnedGameObjectsthatwereoriginallyinstantiatedfromthesamereference.Todothis,wewillessentiallywantourpoolingsystemtokeeptrackoftwodifferentlistsforanygivenPrefabreference:alistofactive(spawned)GameObjects,andalistofinactive(despawned)objectsthatwereinstantiatedfromit.Thisdatawouldbebestabstractedintoaseparateclass,whichwewillnamePrefabPool.

Inordertomaximizetheperformanceofthissystem(andhencemakethelargestgainspossible,relativetojustallocatinganddeallocatingobjectsfrommemoryallofthetime),wewillwanttousesomefastdatastructuresinordertoacquirethecorrespondingPrefabPoolobjectswheneveraspawnordespawnrequestcomesin.

BecausespawninginvolvesbeinggivenaPrefab,wewillwantonedatastructurethatcanquicklymapPrefabstothePrefabPoolthatmanagesthem.AndbecausedespawninginvolvesbeinggivenaGameObject,wewillwantanotherdatastructurethatcanquicklymapspawnedGameObjectstothePrefabPoolthatoriginallyspawnedthem.ADictionaryisagoodchoiceforbothoftheseneeds.

Let’sdefinethesemapsinourpoolingsystem:

publicstaticclassPrefabPoolingSystem{

staticDictionary<GameObject,PrefabPool>_prefabToPoolMap=new

Dictionary<GameObject,PrefabPool>();

staticDictionary<GameObject,PrefabPool>_goToPoolMap=new

Dictionary<GameObject,PrefabPool>();

}

Nextwe’lldefinewhathappenswhenwespawnanobject:

publicstaticGameObjectSpawn(GameObjectprefab,Vector3position,

Quaternionrotation){

if(!_prefabToPoolMap.ContainsKey(prefab)){

_prefabToPoolMap.Add(prefab,newPrefabPool());

}

PrefabPoolpool=_prefabToPoolMap[prefab];

GameObjectgo=pool.Spawn(prefab,position,rotation);

_goToPoolMap.Add(go,pool);

returngo;

}

TheSpawn()methodwillbegivenaPrefabreference,aninitialposition,andaninitialrotation.WeneedtofigureoutwhichPrefabPoolthePrefabbelongsto(ifany),askittospawnanewGameObjectusingthedataprovided,andthenreturnthespawnedobjecttotherequestor.Wefirstcheckour“Prefab-to-Pool”map,toseeifapoolalreadyexistsforthisPrefab.Ifnot,wequicklycreateone.Ineithercase,wethenaskthePrefabPooltospawnusanewobject.ThePrefabPoolwilleitherenduprespawninganobjectthatwasdespawnedearlier,orinstantiateanewone(iftherearen’tanyinactiveinstancesleft).

Eitherway,thisclassdoesn’tparticularlycare.ItjustwantstheinstancegeneratedbythePrefabPoolclasssothatitcanbeenteredintothe“GameObject-to-Pool”mapandreturnedtotherequestor.

Forconvenience,wecanalsodefineanoverloadwhichplacestheobjectattheworld’scenter(usefulforGameObjectsthataren’tvisible,andjustneedtoexistsomewhere):

publicstaticGameObjectSpawn(GameObjectprefab){

returnSpawn(prefab,Vector3.zero,Quaternion.identity);

}

NoteNotethatnoactualspawninganddespawningaretakingplace,yet.ThistaskwilleventuallybehandledwithinthePrefabPoolclass.

DespawninginvolvesbeinggivenaGameObject,andthenfiguringoutwhichPrefabPoolismanagingit.ThiscouldbeachievedbyiteratingthroughourPrefabPoolclassesandcheckingiftheycontainthegivenGameObject.ButifweendupgeneratingalotofPrefabPools,thenthisiterativeprocesscantakeawhile.WewillalwaysendupwithasmanyPrefabPoolclassesaswehavePrefabs(atleastsolongaswemanageallofthemthroughthepoolingsystem).Mostprojectstendtohavedozens,hundreds,ifnotthousandsofdifferentPrefabs.

So,theGameObject-to-PoolmapismaintainedtoensurethatwealwayshaverapidaccesstothePrefabPoolthatoriginallyspawnedtheobject.ItcanalsobeusedtoquicklyverifyifthegivenGameObjectisevenmanagedbythepoolingsystemtobeginwith.Hereisthemethoddefinitionforthedespawningmethod,whichtakescareofthesetasks:

publicstaticboolDespawn(GameObjectobj){

if(!_goToPoolMap.ContainsKey(obj)){

Debug.LogError(string.Format("Object{0}notmanagedbypool

system!",obj.name));

returnfalse;

}

PrefabPoolpool=_goToPoolMap[obj];

if(pool.Despawn(obj)){

_goToPoolMap.Remove(obj);

returntrue;

}

returnfalse;

}

TipNotethattheDespawn()methodofbothPrefabPoolingSystemandPrefabPoolreturnsaBooleanthatcanbeusedtoverifywhetherornottheobjectwassuccessfullydespawned.

Asaresult,thankstothetwomapswe’remaintaining,wecanquicklyaccessthePrefabPoolthatmanagesthegivenreference,andthissolutionwillscaleforanynumberofPrefabthatthesystemmanages.


PrefabpoolsNowthatwehaveasystemthatcanhandlemultiplePrefabpoolsautomatically,theonlythingleftistodefinethebehaviorofthepools.Asmentionedpreviously,wewillwantthePrefabPoolclasstomaintaintwodatastructures:oneforactive(spawned)objectsthathavebeeninstantiatedfromthegivenPrefabandanotherforinactive(despawned)objects.

Technically,thePrefabPoolingSystemclassalreadymaintainsamapofwhichPrefabisgovernedbywhichPrefabPool,sowecanactuallysavealittlememorybymakingthePrefabPoolaslavetothePrefabPoolingSystemclass,bynothavingitkeeptrackofwhichPrefabitismanaging.Consequently,thetwodatastructuresaretheonlymembervariablesthePrefabPoolneedstokeeptrackof.

However,foreachspawnedGameObject,itmustalsomaintainalistofallofitsIPoolableComponentreferencesinordertoinvoketheSpawned()andDespawned()methodsonthem.Acquiringthesereferencescanbeacostlyoperationtoperformatruntime,soitwouldbebesttocachethedatainasimplestruct:

publicstructPoolablePrefabData{

publicGameObjectgo;

publicIPoolableComponent[]poolableComponents;

}

ThisstructwillcontainareferencetotheGameObject,andtheprecachedlistofitsIPoolableComponents.

NowwecandefinethememberdataofourPrefabPoolclass:

publicclassPrefabPool{

Dictionary<GameObject,PoolablePrefabData>_activeList=new

Dictionary<GameObject,PoolablePrefabData>();

Queue<PoolablePrefabData>_inactiveList=newQueue<PoolablePrefabData>

();

}

ThedatastructurefortheactivelistshouldbeadictionaryinordertodoaquicklookupforthecorrespondingPoolablePrefabDatafromanygivenGameObjectreference.Thiswillbeusefulduringobjectdespawning.

Meanwhile,theinactivedatastructureisdefinedasaQueue,butitwillworkequallywellasaList,aStack,orreallyanydatastructurethatneedstoregularlyexpandorcontract,andwhereweonlyneedtopopitemsfromoneendofthelist,sinceitdoesnotmatterwhichobjectitis.Itonlymattersthatweretrieveoneofthem.AQueueisusefulinthiscasebecausewecanbothretrieveandremovetheobjectfromthedatastructureinasinglecall.

ObjectspawningLet’sdefinewhatitmeanstospawnaGameObjectinthecontextofourpoolingsystem:atsomepoint,PrefabPoolwillgetarequesttospawnaGameObjectfromagivenPrefab,ataparticularpositionandrotation.ThefirstthingweshouldcheckiswhetherornotwehaveanyinactiveinstancesofthePrefab.Ifso,thenwecanpopthenextavailableonefromtheQueueandrespawnit.Ifnot,thenweneedtoinstantiateanewGameObjectfromthePrefabusingGameObject.Instantiate().Atthismoment,weshouldalsocreateaPoolablePrefabDataobjecttostoretheGameObjectreference,andacquirethelistofallIPoolableComponentsthatareattachedtoit.

Eitherway,wecannowactivatetheGameObject,setitspositionandrotation,andcalltheSpawned()methodonallofitsIPoolableComponents.Oncetheobjecthasbeenrespawned,wecanaddittothelistofactiveobjectsandreturnittotherequestor.

HereisthedefinitionoftheSpawn()methodthatdefinesthisbehavior:

publicGameObjectSpawn(GameObjectprefab,Vector3position,Quaternion

rotation){

PoolablePrefabDatadata;

if(_inactiveList.Count>0){

data=_inactiveList.Dequeue();

}else{

//instantiateanewobject

GameObjectnewGO=GameObject.Instantiate(prefab,position,

rotation)asGameObject;

data=newPoolablePrefabData();

data.go=newGO;

data.poolableComponents=newGO.GetComponents<IPoolableComponent>

();

}

data.go.SetActive(true);

data.go.transform.position=position;

data.go.transform.rotation=rotation;

for(inti=0;i<data.poolableComponents.Length;++i){

data.poolableComponents[i].Spawned();

}

_activeList.Add(data.go,data);

returndata.go;

}

InstanceprespawningBecauseweareusingGameObject.Instantiate()wheneverthepoolhasrunoutofdespawnedinstances,thissystemdoesnotcompletelyridusofruntimeobjectinstantiationandhence,heapmemoryallocation.It’simportanttoprespawntheexpectednumberofinstancesthatwewillneedduringthelifetimeofthecurrentScene,sothatwedon’tneedtoinstantiatemoreduringruntime.

TipItwouldbewastefultoprespawn100explosionparticleeffects,ifthemostwewilleverexpecttoseeintheSceneatanygiventimeisthreeorfour.Conversely,spawningtoofewinstanceswillcauseexcessiveruntimememoryallocations,andthegoalofthissystemistopushthemajorityofallocationtothestartofaScene’slifetime.Weneedtobecarefulabouthowmanyinstanceswemaintaininmemorysothatwedon’twastemorememoryspacethannecessary.

Let’sdefineamethodinourPrefabPoolingSystemclassthatwecanusetoquicklyprespawnagivennumberofobjectsfromaPrefab.ThisessentiallyinvolvesspawningNobjects,andthenimmediatelydespawningthemall:

publicstaticvoidPrespawn(GameObjectprefab,intnumToSpawn){

List<GameObject>spawnedObjects=newList<GameObject>();

for(inti=0;i<numToSpawn;i++){

spawnedObjects.Add(Spawn(prefab));

}

for(inti=0;i<numToSpawn;i++){

Despawn(spawnedObjects[i]);

}

spawnedObjects.Clear();

}

WewouldusethismethodduringSceneinitialization,toprespawnacollectionofobjectstouseinthelevel.Forexample:

publicclassOrcPreSpawner:MonoBehaviour

[SerializeField]GameObject_orcPrefab;

[SerializeField]int_numToSpawn=20;

voidStart(){

PrefabPoolingSystem.Prespawn(_orcPrefab,_numToSpawn);

}

}

ObjectdespawningFinally,thereistheactofdespawningtheobjects.Asmentionedpreviously,thisprimarilyinvolvesdeactivatingtheobject,butwealsoneedtotakecareofvariousbookkeepingtasksandinvokingDespawned()onallofitsIPoolableComponentreferences.

HereisthemethoddefinitionforthePrefabPoolclass’sDespawn()method:

publicboolDespawn(GameObjectobjToDespawn){

if(!_activeList.ContainsKey(objToDespawn)){

Debug.LogError("ThisObjectisnotmanagedbythisobjectpool!");

returnfalse;

}

PoolablePrefabDatadata=_activeList[objToDespawn];

for(inti=0;i<data.poolableComponents.Length;++i){

data.poolableComponents[i].Despawned();

}

data.go.SetActive(false);

_activeList.Remove(objToDespawn);

_inactiveList.Enqueue(data);

returntrue;

}

Firstweverifytheobjectisbeingmanagedbythepool,andthenwegrabthecorrespondingPoolablePrefabDatainordertoaccessthelistofIPoolableComponentreferences.OnceDespawned()hasbeeninvokedonallofthem,wedeactivatetheobject,removeitfromtheactivelist,andpushitintotheinactivequeuesothatitcanberespawnedlater.

PrefabpooltestingThefollowingclassdefinitionallowsustoperformasimplehands-ontestwiththePrefabPoolingSystemclass.ItwillsupportthreePrefabs,andprespawnfiveinstancesduringapplicationinitialization.Wecanpressthe1,2,or3keystospawnaninstanceofeachtype,andthenpressQ,W,orEtodespawnarandominstanceofeachtype.

publicclassPoolTester:MonoBehaviour{

[SerializeField]GameObject_prefab1;



List<GameObject>_go1=newList<GameObject>();



voidStart(){

PrefabPoolSystem_AsSingleton.Prespawn(_prefab1,5);



}

voidUpdate(){

if(Input.GetKeyDown(KeyCode.Alpha1)){SpawnObject(_prefab1,

_go1);}


_go2);}


_go3);}

if(Input.GetKeyDown(KeyCode.Q)){DespawnRandomObject(_go1);}

if(Input.GetKeyDown(KeyCode.W)){DespawnRandomObject(_go2);}

if(Input.GetKeyDown(KeyCode.E)){DespawnRandomObject(_go3);}

}

voidSpawnObject(GameObjectprefab,List<GameObject>list){

GameObjectobj=PrefabPoolingSystem.Spawn(prefab,

Random.insideUnitSphere*8f,Quaternion.identity);

list.Add(obj);

}

voidDespawnRandomObject(List<GameObject>list){

if(list.Count==0){

//Nothingtodespawn

return;

}

inti=Random.Range(0,list.Count);

PrefabPoolingSystem.Despawn(list[i]);

list.RemoveAt(i);

}

}

OncewespawnmorethanfiveinstancesofanyofthePrefabs,itwillneedtoinstantiatea

newoneinmemory,costingussomememoryallocation.But,ifweobservetheMemoryAreaintheProfiler,whileweonlyspawnanddespawninstancesthatalreadyexist,thenwewillnoticethatabsolutelynonewallocationstakeplace.


PrefabpoolingandSceneloadingThereisonesubtlecaveattothissystemthathasnotyetbeenmentioned:thePrefabPoolingSystemclasswilloutlastScenelifetimesinceitisastaticclass.Thismeansthat,whenanewSceneisloaded,thepoolingsystem’sdictionarieswillattempttomaintainreferencestoanypooledinstancesfromthepreviousScene,butUnityforciblydestroystheseobjectsregardlessofthefactthatwearestillkeepingreferencestothem(unlesstheyweresettoDontDestroyOnLoad()!),andsothedictionarieswillbefullofnullreferences.ThiswouldcausesomeseriousproblemsforthenextScene.

WeshouldthereforecreateamethodinPrefabPoolingSystemthatresetsthepoolingsysteminpreparationforthislikelyevent.ThefollowingmethodshouldbecalledbeforeanewSceneisloaded,sothatitisreadyforanyearlycallstoPrespawn()inthenextScene:

publicstaticvoidReset(){

_prefabToPoolMap.Clear();

_goToPoolMap.Clear();

}

Notethat,ifwealsoinvokeagarbagecollectionduringScenetransitions,there’snoneedtoexplicitlyemptythePrefabPoolsthesedictionarieswerereferencing.SincetheseweretheonlyreferencestothePrefabPoolobjects,theywillbedeallocatedduringthenextgarbagecollection.Ifwearen’tinvokinggarbagecollectionbetweenScenes,thenthePrefabPoolandPooledPrefabDataobjectswillremaininmemoryuntilthattime.


PrefabpoolingsummaryWehavefinallysolvedtheproblemofruntimememoryallocationsforGameObjectsandPrefabsbut,asaquickreminder,weneedtobeawareofthefollowingcaveats:

Weneedtobecarefulaboutproperlyresettingimportantdatainrespawnedobjects(suchasRigidbodyvelocity)Wemustensurewedon’tprespawntoofew,ortoomany,instancesofaPrefabWeshouldbecarefuloftheorderofexecutionofSpawned()andDespawned()methodsonIPoolableComponentsWemustcallReset()onPrefabPoolingSystembeforeSceneloading

Thereareseveralotherfeatureswecouldimplement.Thesewillbeleftasacademicexercisesifwewishtoextendthissysteminthefuture:

AnyIPoolableComponentsaddedtotheGameObjectafterinitializationwillnotbeinvoked.WecouldfixthisbychangingPrefabPooltokeepacquiringIPoolableComponentseverytimeSpawned()andDespawned()areinvoked,atthecostofadditionaloverheadduringspawning/despawning.IPoolableComponentsattachedtochildrenofthePrefab’srootwillnotbecounted.ThiscouldbefixedbychangingPrefabPooltouseGetComponentsInChildren<T>,atthecostofadditionaloverheadifwe’reusingPrefabswithdeephierarchies.PrefabinstancesthatalreadyexistintheScenewillnotbemanagedbythepoolingsystem.WecouldcreateaComponentthatneedstobeattachedtosuchobjectsandthatnotifiesthePrefabPoolingSystemclassofitsexistenceandpassesthereferenceintothecorrespondingPrefabPool.WecouldimplementawayforIPoolableComponentstosetapriorityduringacquisition,anddirectlycontroltheorderofexecutionfortheirSpawned()andDespawned()methods.WecouldaddcountersthatkeeptrackofhowlongobjectshavebeensittingintheInactivelistrelativetototalScenelifetime,andprintoutthedataduringshutdown.Thiscouldtelluswhetherornotwe’represpawningtoomanyinstancesofagivenPrefab.ThissystemwillnotinteractkindlywithPrefabinstancesthatsetthemselvestoDontDestroyOnLoad().ItmightbewisetoaddaBooleantoeverySpawn()calltosaywhethertheobjectshouldpersistornot,andkeeptheminaseparatedatastructurethatisnotclearedoutduringReset().WecouldchangeSpawn()toacceptanargumentthatallowstherequestortopasscustomdatatotheSpawned()functionofIPoolableObjectforinitializationpurposes.ThiscoulduseasystemsimilartohowcustommessageobjectswerederivedfromtheBaseMessageclassforourMessagingSystembackinChapter2,ScriptingStrategies.

ThefutureofMonoandUnityAsweknow,UnitydoesnotusethelatestandgreatestMonoprojectcodefromhttp://www.mono-project.com,butaninternally-customizedversionwithsomeinternalbugfixes.

NoteTheactualMonotweaksmadebyUnityTechnologiescanbefoundinthefollowingGitHubrepository:

https://github.com/Unity-Technologies/mono/

AsanunfortunateconsequenceofhowvariouscomponentsoftheMonoFrameworkarelicensed,UnityTechnologieshasonlybeenabletoupdateMonoonaninfrequentbasis.TheoccasionsonwhichthistaskwereaccomplishedwaswiththereleaseofUnity4,whentheyupgradedtoMono2.6,andshortlyafterwardsversion2.6.5backinmid-2010,whichsupports.NET2.0/3.5features.But,atthetimeofpublication,thelatestversionofMono,version4.0,wasreleasedinMay2015,andsupports.NET4.5features.ThisputsUnity’simplementationabout5yearsbehindintermsofC#languageand.NETframeworkfeatures,whichhasdrawntheireofmanyUnitydevelopers.

UnityTechnologieshassuggestedtheremightbeaMonoupgradesometimeinthelifecycleofUnity5,butthelastofficialupdateonthissubjectwasbackinAugust2014.TheUnityroadmap(https://unity3d.com/unity/roadmap)placesitinthe“LongandUncertain”timeline,andUnityv5.2wasreleasedinearlySeptember2015,whichdidnotincludethisupgrade.So,itisdifficulttosaywhenMonowillbereceivingitsmuch-neededupgrade.UnityTechnologieshasalsobeenworkingwithMicrosofttobringreplacementstosomeMonoComponents(suchasupgradedversionsofthestatic,JIT,andAOTcompilers,aswellastheCLR).

NoteMicrosoft’sannouncementonthefutureof.NET:

http://blogs.msdn.com/b/dotnet/archive/2014/04/03/the-next-generation-of-net.aspx

Meanwhile,UnityTechnologieshasbeenworkingontheproblemoflong-termindependencefromthesethird-partydependenciesforawhile.WiththereleaseofUnity5theyunveiledanewapproachforscriptcodecompilation,whichstartedasawaytoprovideimprovedscriptingsupportforWebGL-basedUnityapplications,buthasalsobeenadoptedasthemainsolutiontothesewoes:IL2CPP.

NoteUnityTechnologies’IL2CPPannouncement:

http://blogs.unity3d.com/2014/05/20/the-future-of-scripting-in-unity/

IL2CPPisshorthandforIntermediateLanguageToC++,andcomeswithitsown.NETruntimethatcanberolledouttomultipleplatforms.ThebasicideaisthatC#scriptcode


http://www.mono-project.com

https://github.com/Unity-Technologies/mono/

https://unity3d.com/unity/roadmap

http://blogs.msdn.com/b/dotnet/archive/2014/04/03/the-next-generation-of-net.aspx

http://blogs.unity3d.com/2014/05/20/the-future-of-scripting-in-unity/

willbeconvertedintoanintermediatelanguageandthenconvertedagaintoC++duringthebuildprocess.TheresultingC++willbepushedthroughoneofseveralavailableplatform-specificcompilerstosupportcross-platformcapability,takingawaytheburdenofhavingtocreateandmanagetheirowncompilers.

Thisprocesswillbemostlydisguisedfromtheuser,andnaturallytherewillbealossofcontrolasthecodeispushedthroughmultiple“codefilters”withvaryinglevelsofoptimizations.Itremainstobeseeniftheyallowsomehookstocontrolthecompilationprocessforadvanceddevelopers.TheEditorisstillexpectedtorunontheC#.NETruntimeforfasterdevelopmentiteration.

Thesuggestedbenefitsofthisapproachincludeperformanceenhancements(sinceevennear-nativecodegeneratedbytheJITcompilerstillpalesincomparisontostatically-compilednativeC++),fasterportingandfeaturedevelopmentfortheUnityEngine,andimprovedgarbagecollection.ThefirstplatformtogettheIL2CPPtreatmentinUnity5isWebGL,andwilleventuallybepushedtootherplatformsasthesystemmatures,andbecomesmorereliable.

NoteFormoreinformationonIL2CPPcheckoutthevariousblogpostsfromUnityTechnologiesonthesubject.Thefollowingpostcontainslotsofinformation,aswellasfurtherlinksonimportanttopics:

http://blogs.unity3d.com/2015/05/06/an-introduction-to-ilcpp-internals/

Whydoesn’tUnityTechnologiesjustprovideaC++APIforUnity?Onecanonlyspeculate,butit’saprettysafeassumptionthatUnitysupportsaverylargeuserbaseofdeveloperswhowouldbeuncomfortableworkinginC++directly.LosingtheaccessibilityofC#andUnityScriptwouldresultinaverydifferentproduct.Long-term,itwouldlikelysplitthecustomerbaseintotwocamps,whichrarelybodeswellsincewhicheveronebringsinthemostrevenuewillbecometheonethatissupportedtoagreaterdegree,leavingtheothertorot(asaninterestinganalogy,gamestypicallysufferfromthesameproblem,asexpansionsandmappackstendtosegregatethemultiplayeruserbase).

Inaddition,therearemany.NETlanguagesthatsharethesameintermediatecodeaftercompilation(CIL),andtheyhaveacommonbinaryinterface,whichmakesitordersofmagnitudeeasiertosupportcross-platformdevelopmentandmultiplelibrariesthanwithC++.Presumably,IL2CPPisacompromisefortheseconcerns.

So,tomakealongstoryshort,thereareagreatmanychangesgoingonwiththeunderlyingUnityEngineandit’stooearlytosaywhethertheIL2CPPapproachwillworksufficientlywellonallplatformstokeepfeatureparityandeaseofdeployment.Onethingisforsure;thenextcoupleofyearsofUnitydevelopmentwillbringsomeinterestingtransitions!


http://blogs.unity3d.com/2015/05/06/an-introduction-to-ilcpp-internals/

SummaryWe’vecoveredahumungousamountoftheoryandlanguageconceptsinthischapter,whichhavehopefullyshedsomelightonhowtheinternalsoftheUnityEngineandC#languagework.Thesetoolstrytheirbesttospareusfromtheburdenofcomplexmemorymanagement,butthereisstillawholehostofconcernsweneedtokeepinmindaswedevelopourgame.Betweenthecompilationprocesses,multiplememorydomains,thecomplexitiesofValuetypesversusReferencetypes,passingbyvalueversuspassingbyreference,boxing,objectpooling,andvariousquirkswithintheUnityAPI,wehavealotofthingstoworryabout.But,withenoughpractice,wewilllearntoovercomethemwithoutneedingtokeepreferringtogianttomessuchasthis!

Thischaptereffectivelyconcludesallofthetechniqueswecanbestowthatexplicitlyaimtoimproveapplicationperformance.Workflowoptimizationsarealwaysusefulthingstokeepinmind,however,astherearealotofneatlittlenuancestotheUnityEnginethataren’twellknownorclearlydocumented,andthatonlybecomeapparentthroughexperienceandcommunityinvolvement.Assuch,thenextchapterwillbefullofhintsandtipsforimprovinghowtomanageourprojectandScenesmoreeffectively,howtomakethemostoftheEditor,andhopefullysaveourselvesenoughdevelopmenttimetoactuallyimplementalloftheoptimizationtechniqueswe’vetalkedaboutthroughthisentirebook.


Chapter8.TacticalTipsandTricksTherearealotoflittlenuancestousingtheUnityEnginethatcanhelpimproveourprojectworkflow.However,quitealotoftheEditor’sfunctionalityisnotwelldocumented,wellknown,orjustnotsomethingwethinkaboutuntilafterthefactthatitcouldhavebeenappliedperfectlytosolveaparticularproblemwewerehaving6monthsago.

TheInternetiscrammedfullofblogsandforumpoststhattrytohelpotherUnitydeveloperslearnabouttheseusefulfeatures,buttheyonlytendtofocusonahandfuloftipsatatime.Theredon’tseemtobeanyonlineresourcesthatgrouptogethermanyoftheminoneplace.Asaresult,intermediateandadvancedusersprobablyhavebookmarkedmanagersburstingattheseamswithlinkstothesetipsthattheyrunintoatonepointoranother,butwhichsitandrotuntilitcomestimetodosomespringcleaning.

So,becausethisbookisprimarilyforintermediateandadvancedusers,itfeltlikeitwasworththrowinginashortchaptertobringtonsofthesetipsandtrickstogetherinonelocation.Itworksasareferencelistinthehopeofsavingusalotoffuturedevelopmenteffort.


EditorhotkeytipsTheEditorisrifewithhotkeysthatcanaidrapiddevelopment.It’sworthcheckingoutthedocumentation.Butlet’sbehonest,nobodyreadsthemanualuntiltheyneedsomethingfromit.Herearesomeofthemostuseful,yetlesser-knownhotkeysavailablewhenplayingwiththeUnityEditor.

NoteInallcases,theWindowshotkeyislisted.IftheOSXhotkeyrequiresadifferentsetofkeystrokes,thenitwillbeshowninparentheses.


GameObjectsGameObjectscanbeduplicatedbyselectingtheminthehierarchyandpressingCtrl+D(Cmd+D).

New,emptyGameObjectscanbecreatedusingCtrl+Shift+N(Cmd+Shift+N).

PressCtrl+Shift+A(Cmd+Shift+A)toquicklyopentheAddComponentmenu.Fromthere,youcantypeinthenameoftheComponentyouwishtoadd.


SceneViewPressingShift+Fordouble-tappingtheFkeywillfollowanobjectintheSceneView,whichcanbehelpfulfortrackinghigh-velocityobjectsorfiguringoutwhyobjectsmightbefallingoutofourScene.

HoldingAltandleft-clickdraggingwiththemousewillmaketheSceneViewcameraorbitthecurrentlyselectedobject(asopposedtolookingaroundit).HoldingAltandright-clickdraggingwillzoomthecamerain/out.

HoldingCtrlandleft-clickdraggingwillcausetheselectedobjecttosnaptothegridasitmoves.ThesamecanbedoneforrotationbyholdingCtrlasweadjusttherotationwidgetsaroundtheobject.SelectingEdit|SnapSettings…opensawindowwherewecaneditthegridthatobjectssnaptoonaper-axisbasis.

Wecanforceobjectstosnapbyvertex,holdingtheVkeyaswemovetheobjectaround.Theselectedobjectwillattachitselftothenearestvertex,tothecursorofthenearestobject.Thisisveryusefulforaligninglevelpiecesintoplace,suchasplatformsandothertile-basedsystems,withoutneedingtohand-adjustpositionvectors.

NoteAtonepoint,inUnityversions4.2to4.6,itwaspossibletoholdShiftwithaColliderobjectselectedtoreveallittlehooksthroughwhichwecouldadjusttheColliderthroughtheSceneView.ThiswasremovedinrecentversionsofUnityduetoconflictswithothercontrols.WemustusetheEditColliderbuttonwithintheCollidercomponenttoaccessthisfeaturegoingforward.


ArraysWecanduplicatearrayelementsthathavebeenexposedintheInspectorViewbyselectingthemandpressingCtrl+D(Cmd+D).Thiswillcopytheelementandinsertitintothearrayimmediatelyafterthecurrentselection.

Wecanremoveentriesfromanarrayofreferences(forexample,anarrayofGameObjects)bypressingShift+Delete(Cmd+Delete).Thiswillstripawaytheelementandcondensethearray.Notethatthefirstpresswillclearthereferencesettingittonull,butthesecondpresswillremovetheelement.Removingelementsinarraysofprimitivetypes(ints,floats,andsoforth)canbeaccomplishedbysimplypressingDeletewithouttheShiftkey(Cmd)modifier.

WecanusetheW,A,S,Dkeyswhileright-clickdraggingontheSceneViewtoflyaroundwiththecamera,inatypicalfirst-personcameracontrolstyle.TheQandEkeyscanbeusedtotranslatethecameraontheverticalaxis,respectively.


InterfaceWecanholdAltandclickonanyhierarchyarrow(thesmallgreyarrowtotheleftofanyparentobjectname)toexpandtheobject’sfullhierarchyandnotjustthenextlayer.ThisworksonGameObjectsintheHierarchyView,foldersandPrefabswithintheProjectView,listsintheInspectorView,andsoon.

WecansaveandrestoreselectionsfromobjectsintheHierarchyorProjectViewsintypicalRTSgamestyle!MaketheselectionandpressCtrl+Alt+<0-9>(Cmd+Alt+<0-9>)tosavetheselection.PressCtrl+Shift+<0-9>(Cmd+Shift+<0-9>)torestoreit.Thisisexceptionallyusefulifwefindourselvesselectingthesamehandfulofobjectsoverandoveragainwhilewemakeadjustments.

PressingShift+SpacebarwillexpandthecurrentwindowtofilltheentireEditorscreen.Pressingitagainwillshrinkthewindowandrestoreittoitspreviouslocation.

PressingCtrl+Shift+P(Cmd+Shift+P)willtogglethePausebuttonwhileinPlayMode.

OtherWecanquicklyaccessthedocumentationofanyUnitykeywordorclass,byhighlightingitinMonoDevelopandpressingCtrl+‘(Cmd+‘).ThiswillopenthedefaultbrowserandperformasearchontheUnitydocumentationforthegivenkeywordorclass.

TipNotethatuserswithEuropeankeyboardsmayalsoneedtoholddowntheShiftkey.

WiththerecentreleaseofVisualStudioToolsforUnity(VSTU),itispossibletoaccessthedocumentationinthesamewaythroughVisualStudiobypressingCtrl+Alt+M,followedbyCtrl+H(noequivalentOSXhotkey,obviously).


EditorinterfacetipsThefollowingcollectionoftipsrelatestotheEditoranditsinterfacecontrols.


GeneralWecanprioritizewhichScriptswillhavetheirUpdateandFixedUpdatemethodscalledbeforeothers,bynavigatingtoEdit|ProjectSettings|ScriptExecutionOrder.Withtheexceptionofsometime-sensitivesystems,suchasaudioprocessing,ifwefindourselvestryingtosolvecomplexproblemsusingthisfeature,itimpliesthatwe’vegotsomefragileandtightcouplingbetweenourComponents.Fromasoftwaredesignperspective,thiscanbeawarningsignthatwemightneedtoapproachtheproblemfromanotherangle.However,itcanbehelpfultohaveparticularobjectsgettheirUpdate()andLateUpdate()functionscalledbeforeotherobjects,inordertodosomebookkeeping.

IntegratingUnityprojectswithaSourceControlsolutioncanbealittletricky.Thefirststepistoforcetheprojecttogenerate.metafilesforassets;ifwedon’tdothis,thenanyonepullingdataintotheirlocalUnityprojectmustregeneratetheirownmetadatafiles.Thiscaneasilycauseconflicts,soitisessentialthateveryoneusesthesameversions.VisiblemetadatafilescanbeenabledbynavigatingtoEdit|ProjectSettings|Editor|VersionControl|Mode|VisibleMetaFiles.Allofthe.metafileswillnowbevisiblewithinthefilestructureandavailableforuploadintoSourceControl.

ItcanalsobehelpfultoconvertcertainassetdataintoaText-onlyformat,ratherthanbinarydata,toallowmanualeditingofdatafiles.Thisturnsmanydatafilesintothemuchmorehuman-readableYAMLformat.Forinstance,ifwe’reusingScriptableObjectstostorecustomdata,wecanuseatexteditortosearchandeditthesefileswithouthavingtodoitallthroughtheUnityEditorandserializationsystem.Thiscansavealotoftime,especiallywhenhuntingforaparticulardatavalueorwhenmultieditingacrossdifferentderivedtypes.ThisoptioncanbeenabledbynavigatingtoEdit|ProjectSettings|Editor|AssetSerialization|Mode|ForceText.

TheEditorhasalogfile,whichcanbeaccessedbyopeningtheConsolewindow(wherelogmessagesareprintedoutto),clickingonthe“hamburgericon”(madefromthreehorizontallines)atthetop-right,andselectingOpenEditorLog.Ifwerecentlybuiltourproject,itwillcontainabreakdownofcompressedfilesizesofallassetsthatwerepackedintotheexecutableandorderedbysize.Thisisanextremelyhelpfulwayoffiguringoutwhichassetsareconsumingthemajorityofourapplicationfootprint(hint:it’salmostalwaysTexturefiles),andwhichfilesaretakingupmorespacethanwewouldexpect.


AdditionalwindowscanbeaddedtotheEditorbyright-clickingonthetitleofanexistingwindowandselectingAddTab.Thisalsoallowsustoaddduplicatewindows,suchashavingmorethanoneInspectorViewopenatatime:

Havingduplicateviewscanbekindofredundant,unlessweusethe“lockicon”tolockthegivenviewtoitscurrentselection.Whenweselectanobject,allInspectorViewswillupdatetoshowtheobject’sdata,exceptforanylockedInspectorViews,whichcontinuetoshowthedataoftheobjecttheywerelockedto.

Commontricksthatmakeuseofwindowlockingincludethefollowing:

UsingtwoofthesameView(Inspector,Animation,andsoforth)tocomparetwoobjectsside-by-sideoreasilycopydatafromonetoanother


UsingaduplicateProjectViewtomovelargedatasetsaroundTestingwhathappenstoanydependentobjectsifanobjectistweakedduringruntimeSelectingmultipleobjectsintheProjectView,thendragging-and-droppingthemintoaserializedarrayintheInspectorViewwithoutlosingtheoriginalselection


TheInspectorViewWecanentercalculationsintonumericinspectorfields.Forexample,typing4*128intoanintfieldwillresolvethevalueto512,sparingusfromhavingtopulloutacalculatorordothemathinourhead.

Arrayelementscanbeduplicatedanddeletedfromalist(inthesamefashionasthehotkeysmentionedpreviously)byright-clickingontherootelementandselectingDuplicateArrayElementorDeleteArrayElement.

AComponent’scontextmenucanbeaccessedthroughboththesmallcogiconintheupper-rightorbyright-clickingonthenameoftheComponent.EveryComponent’scontextmenucontainsaResetoption,whichresetsallvaluesbacktotheirdefault,sparingusfromhavingtoresetvaluesmanually.ThisisusefulwhenworkingwithTransformComponents,asthisoptionwillsettheobject’spositionandrotationto(0,0,0)anditsscaleto(1,1,1).

It’scommonlyknownthat,ifaGameObjectwasspawnedfromaPrefab,thentheentireobjectcanberevertedbacktoitsinitialPrefabstateusingtheRevertbuttonatthetopoftheInspectorView.However,it’slesswellknownthatindividualvaluescanberevertedbyright-clickingonthenameofthevalueandselectingRevertValuetoPrefab.Thisrestorestheselectedvalue,leavingtherestuntouched.

TheInspectorViewhasadebugmodethatcanbeaccessedbyclickingonthehamburgericonnexttothelockiconandselectingDebug.ThiswilldisableallcustomInspectordrawingandrevealallrawdatawithinthegivenGameObjectanditscomponents,evenprivatedatafields.Privatefieldsaregrayed-outandcannotbemodifiedthroughtheInspectorView,butthisgivesusausefulwayofexaminingprivatedataandotherhiddenvaluesduringPlayMode.TheDebugviewalsorevealsinternalObjectIDs,whichcanbeusefulifwe’redoing“interesting”thingswithUnity’sserializationsystemandwanttoresolveconflicts.

IfwehaveanarrayofdataelementsserializedintheInspectorView,thentheyaretypicallylabeledElement<N>where<N>isthearrayindex.Thiscanmakeittrickytofindaspecificelementifourarrayelementsareaseriesofserializedclassesorstructs,whichtendtohavemultiplechildrenthemselves.However,iftheveryfirstfieldintheobjectisastring,thentheelementswillbenamedafterthevalueofthestringfield.

Whenameshobjectisselected,thePreviewwindowatthebottomoftheInspectorViewisoftenfairlysmall,makingithardtoseedetailsinthemeshandhowitwilllookwhenit

appearsinourScene.But,ifweright-clickonthetopbarofthePreviewwindow,itwillbedetachedandenlarged,makingitmucheasiertoseeourmesh.Wedon’thavetoworryaboutsettingthedetachedwindowbacktoitsoriginalhomebecause,ifthedetachedwindowisclosed,thenthePreviewwindowwillreturntothebottomoftheInspectorView.


TheProjectViewTheProjectView’ssearchbarallowsustofilterforobjectsofaparticulartypebyclickingonthesmallicontotherightofthesearchbar.Thisprovidesalistofdifferenttypeswecanfilterby,revealingallobjectsofthattypewithintheentireproject.However,selectingtheseoptionssimplyfillsthesearchbarwithastringofthet:<type>format,whichappliestheappropriatefilter.

Thus,wecansimplytypetheequivalentstringsintothesearchbarforthesakeofspeed.Forinstance,typingt:prefabwillfilterforallPrefabs,nomatterwheretheycanbefoundinthehierarchy;t:texturewillrevealtextures,t:scenewillrevealScenes,andsoon.Addingmultiplesearchfiltersinthesearchbarwillincludeobjectsofalltypes(itdoesnotrevealobjectswhichonlysatisfybothfilters).Thesefiltersaremodifiersinadditiontoname-basedfiltering,soaddingaplaintextstringwillcauseaname-basedsearchthroughthefilteredobjects.Forexample,t:texturenormalmapwillfindalltexturefilesthatincludethewordnormalmapintheirname.

Ifwe’remakinguseofAssetBundlesandthebuilt-inlabelingsystem,theProjectView’ssearchbaralsoallowsustohuntdownbundledobjectsbytheirlabelusingl:<labeltype>.

IfaMonoBehaviourscriptcontainsserializedreferences(using[SerializeField]orpublic)toUnityAssets,suchasMeshesandTextures,thenwecanassigndefaultvaluesdirectlyintothescriptitself.SelectthescriptfileintheProjectViewandtheInspectorViewshouldcontainafieldfortheassetforustodrag-and-dropthedefaultassignmentinto.

Bydefault,theProjectViewsplitsfilesandfoldersintotwocolumnsandtreatsthemseparately.IfweprefertheProjectViewtohaveatypicalhierarchyfolderandfilestructure,thenwecansetittoOneColumnLayoutinitscontextmenu(thehamburgericonatthetopright).ThiscanbeagreatspacesaverinsomeEditorlayouts.

Right-clickingonanyobjectintheProjectViewandselectingSelectDependencieswillrevealallobjectsuponwhichthisassetreliesinordertoexist,suchasTextures,Meshes,MonoBehaviourscriptfiles,andsoon.ForScenefiles,itwilllistallentitiesreferencedwithinthatScene.Thisishelpfulifwe’retryingtoperformsomeassetcleanup.


TheHierarchyViewAlesser-knownfeatureoftheHierarchyViewistheabilitytoperformcomponent-basedfilteringwithinthecurrentlyactiveScene.Confusingly,itusesthesamesyntaxasperformingtype-basedfilteringintheProjectViewandcanthereforebeaccomplishedbytypingt:<componentname>.Forexample,typingt:lightintotheHierarchyViewsearchbarwillrevealallobjectsintheScenethatcontainaLightcomponent.

Upper-orlower-casecharactersareunimportant,butthestringmustmatchthefullcomponentnameinorderforthesearchtocomplete.Componentsthatderivefromthegiventypewillalsoberevealed,sotypingt:rendererwillrevealallobjectswithderivedcomponentssuchasMeshRenderers,SkinnedMeshRenderers,andsoon.

TheSceneandGameViewsTheSceneViewcameraisnotvisiblefromtheGameView,butitisgenerallyaloteasiertomovearoundandplacethroughtheuseofthehotkeysmentionedpreviously.TheEditorallowsustoaligntheselectedobjecttothesamepositionandrotationoftheScenecamerabynavigatingtoGameObject|AlignwithView(Ctrl+Shift+F/Cmd+Shift+F).ThismeansthatwecanusethecameracontrolstoplacetheScenecamerawherewewouldlikeourobjecttobe,andplacetheobjecttherebyaligningittothecamera.

Similarly,wecanaligntheSceneviewtotheselectedobjectbynavigatingtotheGameObject|AlignViewtoSelectedoption.Thisisusefulforcheckingifthegivenobjectispointingintherightdirection.

Wecanperformsimilarcomponent-basedfilteringontheSceneView,aswecanwiththeHierarchyView,usingthet:<component>syntaxwithinitssearchbar.

AttheverytoprightoftheUnityEditorisadropdownlabeledLayers.ThiscontainsaLayer-basedfilteringandlockingsystemfortheSceneView.Togglingonthe“eye”iconwillshow/hideallobjectsofthatLayerwithintheSceneView.Togglingthelockiconwillalloworpreventobjectsofthegivenlayerfrombeingselected.Thisishelpfulforthingssuchaspreventingsomeonefromaccidentallyselectingandmovingbackgroundobjectsthathavealreadybeensituatedintheperfectlocation.

AcommonlyknownandusefulfeatureoftheEditoristhatGameObjectscanbegivenspecialiconsorlabelstomakethemeasiertofindintheSceneView.Thisisparticularlyhelpfulforobjectswithnorendererbutthatwewishtofindeasily.Forinstance,objectssuchasLightsandCamerashavebuilt-iniconsthatidentifytheminourSceneViewmoreeasily.

However,thesamegizmoscanberevealedwithintheGameViewbyclickingontheGizmosbuttonatthetoprightoftheGameView.Thedropdownforthisoptiondetermineswhatgizmoswillbevisiblewhenthisoptionisenabled.

PlayModeSincePlayModechangesarenotautomaticallysaved,itiswisetomodifythetintcolorappliedduringPlayModetomakeitblatantlyobviouswhichmodewe’recurrentworkingwith.ThisvaluecanbesetbynavigatingtoEdit|Preferences|Colors|Playmodetint.

ChangescanbesavedfromPlayModebysimplyusingtheclipboard.Ifwe’retweakinganobjectinPlayModeandwe’rehappywithitssettings,thenwecancopytheobjectintotheclipboardusingCtrl+C(Cmd+C),andpasteitbackintotheSceneoncePlayModeendswithCtrl+V(Cmd+V).Allsettingsontheobjectatthetimeofthecopywillbekept.ThesamecanbedonewithindividualvaluesorentirecomponentsusingtheCopyComponentandPasteComponentoptionsinthecomponent’scontextmenu.However,theclipboardcanonlycontaindataforoneobject,component,orvalue,atatime.

Anotherapproach,whichallowsustosavethedataofmultipleobjectsduringPlayMode,istocreatePrefabsfromthembydragginganddroppingthemintotheProjectWindowatruntime,oncewe’rehappywiththesettings.IftheoriginalobjectwasderivedfromaPrefab,andwewishtoupdateitacrossallinstances,thenweonlyneedtooverwritetheoldPrefabwiththenewonewecreatedbydragginganddroppingthecopyontopoftheoriginal.NotethatthisalsoworksduringPlayModeruntime,butitcanbedangeroussincethereisnodialogpop-uptoconfirmtheoverwrite.BeverycarefulnottooverwritethewrongPrefab.

WecanusetheFrameSkipbutton(thebuttontotherightofthePausebuttonintheEditor)toiterateoneframeatatime.Thiscanbeusefulforwatchingframe-by-framephysicsorgameplaybehavior.KeepinmindthatthiscausesbothoneFixedUpdateandoneUpdatetobecalledeachstep,inequalcounts,whichmaynotexactlyreflectactualruntimebehaviorwherewetendtohaveunequalcallstothesemethods.

IfthePausebuttonisenabledwhenPlayModebegins,thenthegamewillbepausedjustaftertheveryfirstframe,givingusachancetoobserveanyanomaliesthatoccurredfrominitializationofourScene.


ScriptingtipsThefollowingtipsareusefulfeaturestoknowwhenscripting.


GeneralWecanmodifyvarioustemplatesofnewScript,Shader,andComputeShaderfiles.ThiscanbehelpfultoremovetheemptyUpdatestubswhich,aswelearned,cancauseunnecessaryruntimeoverhead.Thesefilescanbefoundinthefollowinglocations:

Windows:<Unityinstall>\Editor\Data\Resources\ScriptTemplates\OSX:/Applications/Unity/Editor/Data/Resources/ScriptTemplates/

TherecentreleaseofUnityVersion5.1introducedtheAssertclassandallowsforassert-baseddebugging,whichsomedevelopersaremorecomfortablewithasopposedtoexception-baseddebugging.ChecktheUnitydocumentationformoreinformationonAsserts:http://docs.unity3d.com/ScriptReference/Assertions.Assert.html

CallingDebug.Break()isfunctionallyequivalenttopausingtheEditorduringPlayMode,whichcanbeusefulforcatchingawkwardgraphicalbehavior,orasamoreconvenientalternativetotheabsurdhotkeyrequiredtopausetheScene(Ctrl+Shift+P).


http://docs.unity3d.com/ScriptReference/Assertions.Assert.html

AttributesAttributesareveryusefulmeta-leveltagsthatcanbegiventoalmostanytargetinC#.Theyaremostcommonlyusedonmemberdata(fields)andclasses,allowingustoflagthemwithspecialpropertiessothattheycanbeprocesseddifferently.IntermediateandadvancedUnitydeveloperswillfinditworthwhiletoreadtheC#documentationonattributesandusetheirimaginationtocomeupwiththeirownattributesthathelpacceleratetheirworkflow.TherearequiteafewattributesbuiltintotheUnityenginethatcanbeexceptionallyusefulwhenusedintherightplace.

NoteAdvanceduserswillnotethatattributescanalsobegiventoenums,delegates,methods,parameters,events,modules,andevenassemblies.

VariableattributesPublicvariablesarefairlydangerousthingstoaddtoourcomponents,asanythingcancomealongandchangethevalueatruntime,makingithardtotracebugs,aswellasrequiringspecialhandholdingtopreventthevariablefrombeinggivenaninvalidvalue.However,publicvariablesareusuallythefirstwaythatUnitydeveloperslearntoexposevariablesintheInspectorView.Insomecases,thepublicvariableisabsolutelyintendedtobepublic,butwedon’twishittobeseenintheInspector.Insuchacase,the[HideInInspector]attributecanbeusedtohidethevariablefromtheInspector,whenevernecessary.

However,thepreferredapproachistomakeourvariablesprivateorprotectedandallowEditor-baseddevelopmentbyexposingvaluesthroughthe[SerializeField]attribute.ThisattributeallowsprivateandprotectedvariablestoberevealedintheInspectorfordesignerstomanipulate,withoutriskingothercomponentsaccidentallychangingthevariableatruntime.

The[Range]attributecanbeaddedtoanintegerorfloating-pointfieldtoconvertitintoasliderintheInspectorView.Wecangiveminimumandmaximumvalues,limitingtherangethatthevaluecancontain.

Normally,ifavariableisrenamed,evenifwedoarefactorthroughourIDE(whetheritsMonoDeveloporVisualStudio)thenthevaluesarelostassoonasUnityrecompilestheMonoBehaviourandmakestheappropriatechangestoanyinstancesofthecomponent.However,the[FormerlySerializedAs]attributeisincrediblyhelpfulifwewishtorenameavariablethathasbeenpreviouslyserialized,asitwillcopythedatafromthevariablenamedwithintheattributeintothegivenvariableduringcompilationtime.Nomorelostdataduetorenamingstuff!

Notethatitisnotsafetoremovethe[FormerlySerializedAs]attributeaftertheconversioniscompleted,unlessthevariablehasbeenmanuallychangedandresavedsincecompletion.The“.prefab”datafilewillstillcontaintheoldvariablename,andsoitstillneedsthe[FormerlySerializedField]attributetofigureoutwheretoplacethedatathenexttimethefileisloaded(forexample,whentheEditorisclosedandreopened).Thus,


thisisahelpfulattribute,butextendedusedoestendtoclutterupourcodebasealot.

ClassattributesThe[SelectionBase]attributewillmarkanyGameObjectthecomponentisattachedtoastherootofselectionfortheSceneView.Thisisespeciallyusefulifwehavemeshesthatarechildrenofotherobjects,aswemightwanttheparentobjecttobeselectedwiththefirstclick,insteadoftheobjectwiththeMeshRenderercomponent.

Wecanusethe[RequireComponent]attributetoforcedesignerstoattachvitalcomponentstothesameGameObjectiftheyattempttoattachthiscomponent.Thisensuresanydependenciesthatourcodebasereliesonwillbesatisfiedbydesigners,withouthavingtowriteoutawholebunchofdocumentationforthem.

The[ExecuteInEditMode]attributewillforcetheobject’sUpdate(),OnGUI(),andOnRenderObject()methodstobecalledevenduringEditMode.However,therearecaveats:

TheUpdate()methodisonlycalledifsomethingchangesintheSceneOnGUI()isonlycalledduringGameViewevents,notforotherviewssuchastheSceneViewOnRenderObject()iscalledduringanyrepainteventfortheSceneandGameViews

However,thisgivessuchobjectsadifferentsetofeventhooksandentrypointscomparedtotypicalEditorscripts,sothisattributestillhasitsuses.


LoggingWecanaddrichtexttagstodebugstrings.Tagssuchas<size>,(bold),(italics),and<color>allworkondebugstrings.Thiscanbehelpfulfordifferentiatingthedifferentkindsoflogmessagesandhighlightingspecificelements.

Debug.Log("<color=red>[ERROR]</color>Thisisavery<size=14>

specific</size>kindoflogmessage");

TheMonoBehaviourclasshasaprint()methodforconvenience,whichdoesthesamethingasDebug.Log().

Itcanhelptocreateacustomloggerclass,whichautomaticallyappends\n\ntotheendofeverylogmessage.ThiswillpushandhideawaytheunnecessaryUnityEngine.Debug:Log(Object)clutterthattendstofilltheConsolewindow.

UsefullinksUnitytechnologiesprovidemanyusefultutorialsontheusageofvariousscriptingfeatures,whichareprimarilytargetedatbeginnerandintermediate-leveldevelopers.Thetutorialscanbefoundathttps://unity3d.com/learn/tutorials/topics/scripting.

There’sahelpfulpostonUnityAnswers,whichprovidesareferencelistthatcoversmanyofthedifferentscriptingandcompilationerrorswemightrunacrossduringdevelopment,whichcanbefoundathttp://answers.unity3d.com/questions/723845/what-are-the-c-error-messages.html.

ScriptableObjectsareveryusefulobjectsandanexcellentwayofstoringgamedatainaformthatdoesnotneedtobeinstantiatedatruntime.Theyworklikeanyotherclassinthattheycancontainmethodsandvariables,canbeserialized,allowpolymorphism,andsoon.Theonlytrickypartistheycanonlybecreatedthroughscripting,andmustbeloadedintomemoryatanytimeusingResources.Load().ButthisallowsustocontrolwhichScriptableObjectsarepresentinmemoryatanygiventime,givingusmorecontroloverruntimememoryconsumption.ExplainingthenuancesofScriptableObjectsherewouldtaketoomuchspace,butUnitytechnologieshaveprovidedagoodintroductoryexaminationofScriptableObjectsinthefollowingtutorialvideo:

https://unity3d.com/learn/tutorials/modules/beginner/live-training-archive/scriptable-objects

NoteNotethat,despitethecategoryoftheScriptableObjectvideo,it’sgenerallyconsideredmoreofanintermediate-leveltopic.BeginnerswouldbebestservedbyfocusingonbecomingcomfortablewithPrefabs,beforeturningthingsontheirheadthroughScriptableObjectsandtheimportantserializationtopicsthatneedtobeunderstood.

NestedCoroutinesareanotherinterestingandusefulareaofscriptingthatisnotwelldocumented.But,thefollowingthird-partyblogpost,whichcoversalotoftheinterestingdetails,shouldbeconsideredwhenworkingwithNestedCoroutines:

http://www.zingweb.com/blog/2013/02/05/unity-coroutine-wrapper

WecanfigureoutwhenaparticularfeaturewasaddedtotheUnityAPIbycheckingtheAPIhistorypageathttp://docs.unity3d.com/ScriptReference/40_history.html.


https://unity3d.com/learn/tutorials/topics/scripting

http://answers.unity3d.com/questions/723845/what-are-the-c-error-messages.html

https://unity3d.com/learn/tutorials/modules/beginner/live-training-archive/scriptable-objects

http://www.zingweb.com/blog/2013/02/05/unity-coroutine-wrapper

http://docs.unity3d.com/ScriptReference/40_history.html

Customeditors/menustipsWecansetcustomhotkeysforMenuItems.Forexample,wecanmaketheKkeytriggerourMenuitemmethod,bydefiningtheMenuItemattributeasfollows:

[MenuItem("MyMenu/MenuItem_k")]

WecanalsoincludemodifierkeyssuchasCtrl(Cmd),Shift,andAltusingthe%,#,and&characters,respectively.

MenuItemsalsohavetwooverloads,whichallowsustosettwoadditionalparameters:aBooleanthatdetermineswhetherthemenuitemrequiresavalidationmethod,andanintegerthatdeterminesthemenuitem’spriorityinthehierarchy.

CheckthedocumentationforMenuItemsforacompletelistofavailablehotkeymodifiers,specialkeys,andhowtocreatevalidationmethods:

http://docs.unity3d.com/ScriptReference/MenuItem.html

Itispossibleto“ping”anobjectintheHierarchy,similartowhathappenswhenweclickonaGameObjectreferenceintheInspectorView,bycallingEditorGUIUtility.PingObject().

TheoriginalimplementationoftheEditorclass,andthewaythatmostpeoplelearnedhowtowriteEditorscripts,originallyinvolvedwritingalllogicandcontentdrawinginthesameclass.However,PropertyDrawersareaneffectivewayofdelegatingInspectordrawingtoadifferentclassfromthemainEditorclass.Thiseffectivelyseparatesinputandvalidationbehaviorfromdisplaybehavior,allowingmorefine-tunedcontrolofrenderingonaper-fieldbasisandmoreeffectivereuseofcode.WecanevenusePropertyDrawerstooverridedefaultUnitydrawingforbuilt-inobjects,suchasVectorsandQuaternions.

PropertyDrawersmakeuseofSerializedPropertiestoaccomplishserializationofindividualfields,andtheyshouldbepreferredwhenwritingeditorscripts,sincetheymakeuseofbuilt-inundo,redo,andmultieditfunctionality.Datavalidationcanbealittleproblematic,andthebestsolutionistouseOnValidate()callsonsetterpropertiesforfields.AsessionatUnite2013byUnityTechnologiesdeveloperTimCooper,whichexplainsthebenefitsandpitfallsofvariousserializationandvalidationapproachesingreatdetailathttps://www.youtube.com/watch?v=Ozc_hXzp_KU.

WecanaddentriestoComponentcontextmenusandeventhecontextmenusofindividualfieldswiththe[ContextMenu]and[ContextMenuItem]attributes.ThisallowsaneasywaytocustomizeInspectorbehaviorforourComponentswithoutneedingtowritebroadEditorclassesorcustomInspectors.

AdvancedusersmayfinditusefultostorecustomdatawithinUnitymetadatafilesthroughtheAssetImporter.userDatavariable.TherearealsoamultitudeofopportunitiestomakeuseofReflectionoftheUnitycodebase.RyanHipple’ssessionatUnite2014outlinesahugenumberofneatlittlehacksandtricksoneachievewithReflectionintheUnityEditor:


http://docs.unity3d.com/ScriptReference/MenuItem.html

https://www.youtube.com/watch?v=Ozc_hXzp_KU

https://www.youtube.com/watch?v=SyR4OYZpVqQ

AnundocumentedfeaturewasintroducedinUnityv4.5,ReorderableLists.TheseallowustohaveanInspectorViewofagenericList<T>,whichcanbeeasilyreorderedbydragginganddroppingtheelementsaround.However,thisfeatureappearstobeunfinished,asitrequiresacustomEditorclasstomakeuseofthemproperly.ThefollowingpostonUnityAnswersexplainshowtouseReorderableListsfairlysuccinctly:

http://answers.unity3d.com/questions/826062/re-orderable-object-lists-in-inspector.html


https://www.youtube.com/watch?v=SyR4OYZpVqQ

http://answers.unity3d.com/questions/826062/re-orderable-object-lists-in-inspector.html

ExternaltipsThefollowingtipsandtricksrelatetotopicsoutsidetheUnityEditoritselfthatcanhelpUnitydevelopmentworkflowenormously.

GooglingUnity-relatedproblemsorconcernscangoalotfasterifwestartthesearchwith“site:unity3d.com“.

IftheUnityEditorcrashes,forwhateverreason,thenwecanpotentiallyrestoreourScenebyrenamingthefollowingfiletoincludethe.unityextension(forScenefiles),andcopyingitintoourAssetsfolder:

\<projectfolder>\Temp\_EditModeScene

Ifwe’redevelopingonWindows,thenthere’sverylittlereasonnottouseVisualStudioatthispoint.MonoDevelophasbeendraggedalongkickingandscreamingformanyyears,andmanydevelopershavebeenswitchingovertothemorefeature-richVisualStudioCommunityeditionformostoftheirdevelopmentworkflowneeds,particularlywithincrediblyhelpfulpluginssuchasResharper.

Forsomedevelopers,theonlyreasontobootupMonoDevelophasbeenforruntimedebuggingofcode,butwiththerecentreleaseofVisualStudioToolsforUnity(VSTU),VisualStudionowoffersbetterintegrationwiththeUnityEditor.ItevenallowsourC#codetoberuntime-debuggedthroughVisualStudioitself.Unlesswehaveparticularhangupsabouttheinterfaceorthefactthatit’smadebythebig,badMicrosoft,weshouldwanttogiveVisualStudioCommunityatryasitaccelerateourscriptcodedevelopmentinwayswehadn’texpected.

CheckoutthefollowingvideoformoreinformationonVisualStudioanditsintegrationwithUnitythroughVSTU:

https://channel9.msdn.com/Events/Visual-Studio/Visual-Studio-2015-Final-Release-Event/Building-Unity-games-in-Visual-Studio

Thereisagreatresourceforgameprogrammingpatterns(orrather,typicalprogrammingpatternsexplainedinawaythatispertinenttogamedevelopment)anditiscompletelyfreeandavailableonline:

http://gameprogrammingpatterns.com/contents.html

KeepaneyeonanysessionvideosthatcomefromUniteconferences,whenevertheyhappen(orbetteryet,trytoattendthem).There’susuallyacoupleofpanelsateachconferenceheldbyexperienceddeveloperssharinglotsofcoolandinterestingthingsthey’vebeenabletoaccomplishwiththeEngineandEditor.Inadditiontothis,makesuretokeepinvolvedintheUnitycommunity,eitherthroughtheforumsonunity3d.com,Twitter,reddit,StackOverflowandUnityAnswers,oratwhateversocialgatheringplacespopoutofthewoodworkinthecomingyears.

Everysingletipthatwasincludedinthisbookstartedoutasanideaortidbitofknowledgethatsomeonesharedsomewhereatsomepoint.So,thebestwaytokeepup-to-dateonthe


https://channel9.msdn.com/Events/Visual-Studio/Visual-Studio-2015-Final-Release-Event/Building-Unity-games-in-Visual-Studio

http://gameprogrammingpatterns.com/contents.html

http://unity3d.com

besttips,tricks,andtechniquesistokeepourfingersonthepulseofwhereUnityisheadingbystayinginvolvedinitscommunity.


OthertipsFinally,thefollowingsectioncontainstipsthatdidn’tquitefitintoothercategories.

It’salwaysagoodideatoorganizeourScenesusingemptyGameObjectsandnamethemsomethingsensible.Theonlydrawbacktothismethodisthattheemptyobject’sTransformisincludedduringpositionorrotationchangesandgetsincludedduringrecalculations.Properobjectreferencing,Transformchangecaching,and/oruseoflocalPosition/localRotationsolvestheproblemadequately.Inalmostallcases,thebenefitstoworkflowfromSceneorganizationaresignificantlymorevaluablethansuchtrivialperformancelosses.

AnimatorOverrideControllerswereintroducedwaybackinUnityv4.3,buttendtobeforgottenorrarelymentioned.TheyareanalternativetostandardAnimationControllersthatallowustoreferenceanexistingAnimationController,andthenoverridespecificstatestousedifferentanimationfiles.Thisallowsformuchfasterworkflowssincewedon’tneedtoduplicateandtweakAnimationControllersmultipletimes;weonlyneedtochangeahandfulofanimationstates.

WhenUnity5islaunched,itautomaticallyopenstheProjectWizard,allowingustoopenarecentproject.However,ifwepreferthedefaultbehaviorfromUnity4,whichistoautomaticallyopenthepreviousproject,wecaneditthisbehaviorbynavigatingtoEdit|Preferences|General|LoadPreviousProjectonstartup.NotethatthissettinghasadifferentnameunderUnity4andworksintheoppositefashion.YoucanseethisbynavigatingtoEdit|Preferences|General|AlwaysShowProjectWizard.NotethatiftheProjectWizardisenabled,wecanalsoopenmultipleinstancesofUnityEditorsimultaneously.

TheamazingcustomizabilityoftheUnityEditoranditsever-growingfeaturesetmeansthereareabsolutelytonsoflittleopportunitiestoimproveworkflowsandmorearebeingdiscoveredorinventedeverysingleday.TheAssetStoremarketplaceisabsolutelyrifewithassets,whichtrytosolvesomekindofproblemthatmoderndevelopersarehavingtroublewith,whichmakesitagreatplacetobrowseifwe’relookingforideasor,ifwe’rewilling,dropsomemoneytosaveusatonofhassle.Becausetheseassetstendtoselltoabroadaudience,thistendstokeeppriceslow,andwecanpickupsomeamazinglyusefultoolsandscriptsforsurprisinglylittlecost.Inalmostallcases,itwouldtakeusasignificantnumberofhourstodevelopthesamesolutionourselves.Ifweconsiderourtimeasvaluable,thenscanningtheAssetStoreonoccasioncanbeaverycost-effectiveapproachtodevelopment.


SummaryThisbringsustothebook’sconclusion,andhopefullyyouenjoyedtheride.Toreiterateperhapsthemostimportanttipinthisbook,alwaysmakesuretoverifythesourceoftheperformancebottleneckviaprofilingbeforemakingasinglechange.Thelastthingwewanttowastetimeonischasingghostsinthecodebase,whenfiveminutesofprofilertestingcansaveusanentiredayofwork.Also,inalotofcases,thesolutionrequiresacost-benefittinganalysistodetermineifwe’renotsacrificingtoomuchinanyotherareaattheriskofaddingfurtherbottlenecks.Makesuretohaveareasonableunderstandingoftherootcauseofthebottleneck,toavoidputtingotherperformancemetricsatrisk.

Performanceenhancementcanbealotoffunsince,duetothecomplexityofmoderncomputerhardware,smalltweakscanyieldbigrewards.Therearemanytechniquesthatcanbeimplementedtoimproveapplicationperformanceorspeedupourworkflows.Someofthesearehardtofullyrealizewithouttheexperienceandskillsnecessarytospendareasonableamountoftimeimplementingthem.Inmostcasesthefixesarerelativelysimple,oncewefindthesourceoftheproblem.So,goforthanduseyourrepositoryofknowledgetomakeyourgamesthebesttheycanbe!


IndexA

Ahead-Of-Time(AOT)/ThecompilationprocessAndroidDebugBridge(ADB)tool/RemoteconnectiontoanAndroiddeviceanimationfiles

about/MeshandanimationfilesAPIhistorypage

URL/Usefullinksapproaches,performanceanalysis

about/Bestapproachestoperformanceanalysisscriptpresence,verifying/Verifyingscriptpresencescriptcount,verifying/Verifyingscriptcountongoingcodechanges,minimizing/Minimizingongoingcodechangesinternaldistractions,minimizing/Minimizinginternaldistractionsexternaldistractions,minimizing/Minimizingexternaldistractions

artefacts/Manageresolutiondownscalingexternallyattributes

variableattributes/Variableattributesclassattributes/Classattributes

audioabout/Audiofiles,loading/Loadingaudiofilesprofiling/Profilingaudioformats,encoding/Encodingformatsandqualitylevelsqualitylevels,encoding/Encodingformatsandqualitylevelsperformanceenhancements/Audioperformanceenhancements

AudioClips/TheAudioAreaaudiofiles

loading/Loadingaudiofilesadditionalloadingoptions/Additionalloadingoptions

AudioMixersURL/ApplyFiltereffectsthroughMixergroupstoreduceduplication

audioperformanceenhancementsabout/AudioperformanceenhancementsactiveAudioSourcecount,minimizing/MinimizeactiveAudioSourcecountAudioClipreferences,minimizing/MinimizeAudioClipreferencesforce,enablingtoMonofor3Dsounds/EnableForcetoMonofor3Dsoundslowerfrequencies,resampling/Resampletolowerfrequenciesencodingformats,considering/Considerallencodingformatsstreaming,preventing/Bewareofstreamingfiltereffects,applying/ApplyFiltereffectsthroughMixergroupstoreduceduplication


WWW.audioClip,using/Use“WWW.audioClip”responsiblyAudioModulefiles,consideringforbackgroundmusic/ConsiderAudioModulefilesforbackgroundmusic

AudioSources/TheAudioArea


Bbackendbottlenecks

about/Backendbottlenecksfillrate/Fillratememorybandwidth/MemorybandwidthVRAMlimits/VRAMlimits

boxing/Boxingbruteforcetesting/Bruteforcetesting


Ccachecomponent

references/CacheComponentreferencesobtaining,withfastestmethod/ObtainingComponentsusingthefastestmethod

caveats,StaticBatchingabout/StaticBatchingcaveatsEditModedebugging/EditModedebuggingofStaticBatchingstaticmeshesinstantiationatruntime,avoiding/Avoidinginstantiatingstaticmeshesatruntimerendering/Visibilityandrenderingvisibility/Visibilityandrendering

CgstandardlibraryfunctionsURL/UseGPU-optimizedhelperfunctions

Closures/Closurescodesegments,targetedprofiling

about/TargetedprofilingofcodesegmentsProfilerscriptcontrol/ProfilerscriptcontrolcustomCPUProfiling/CustomCPUProfiling

CollisionMatrix/TheCollisionMatrixCommandBuffer

URL/MultithreadedrenderingCommonIntermediateLanguage(CIL)/TheMonoplatformCommonLanguageRuntime(CLR)/TheMonoplatformcompilationprocess,Monoplatform

about/ThecompilationprocessmanualJITcompilation/ManualJITcompilation

complexMeshCollidersavoiding/AvoidcomplexMeshColliderssimplerprimitives,using/UsesimplerprimitivessimplerMeshColliders,using/UsesimplerMeshCollidersragdolls,optimizing/OptimizingragdollsJointsandcolliders,reducing/ReduceJointsandCollidersinter-ragdollcollisions,avoiding/Avoidinter-ragdollcollisionsinactiveragdolls,disabling/Disableorremoveinactiveragdollsinactiveragdolls,removing/Disableorremoveinactiveragdolls

controls,UnityProfilerwindowabout/Controls,CPUAreaAddProfiler/ControlsRecord/ControlsDeepProfile/ControlsProfileEditor/ControlsActiveProfiler/ControlsClear/Controls


FrameSelection/ControlsTimelineView/ControlsCPUArea/CPUAreaGPUArea/TheGPUAreaRenderingArea/TheRenderingAreaMemoryArea/TheMemoryAreaMemoryArea,simplemode/TheMemoryAreaMemoryArea,detailedmode/TheMemoryAreaAudioArea/TheAudioAreaPhysics3D/2DArea/ThePhysics3D/2DArea

coroutineabout/SavingProfilerdataURL/SavingProfilerdatausing/Update,Coroutines,andInvokeRepeating

Coroutines/CoroutinesCPU-boundapplication

about/CPU-boundmultithreadedrendering/MultithreadedrenderingGPUSkinning/GPUSkinning

CustomEditors/Menustips/Customeditors/menustips


D2DColliders

circle/CollidertypesPolygon/Collidertypesbox/Collidertypes

3DCollidersMeshColliders/CollidertypesCapsule/CollidertypesCylinder/CollidertypesBox/Collidertypes

DeferredShadingURL/DeferredShading

Dispose()method/CustomCPUProfilingdistance-squared

considering,overdistance/Considerusingdistance-squaredoverdistanceDrawCall

about/DrawCallsRenderState,modifying/DrawCalls

DynamicBatchingabout/DynamicBatchingrequirements,URL/DynamicBatchingvertexattributes/Vertexattributesuniformscaling/Uniformscalingsummary/DynamicBatchingsummaryapplying/DynamicBatchingsummary

DynamicCollidersabout/StaticandDynamicColliders


EEditor

hotkeytips/Editorhotkeytipsabout/Editorhotkeytipsinterfacetips/Editorinterfacetips

emptycallbackdeclarationsremoving/Removingemptycallbackdeclarations

ExecutionOrderURL/SavingProfilerdata

externaltipsabout/Externaltipsothertips/Othertips


Ffillrate,backendbottlenecks

about/Fillrateoverdraw/OverdrawOcclusionCulling/OcclusionCullingshaderoptimization/ShaderoptimizationShadersintendedformobileplatforms,using/ConsiderusingShadersintendedformobileplatforms

Find()methodavoiding,atruntime/AvoidingtheFind()andSendMessage()methodsatruntime

FirstInFirstOut(FIFO)queue/DrawCallsFixedUpdate()method/MaximumAllowedTimestepFixedUpdateTimestep/Physicsandtimeforeachloops/TheforeachloopsForwardRendering

URL/ForwardRenderingfragmentShader/ProfilingrenderingissuesFrameDebugger/TheFrameDebuggerfront-endbottlenecks

about/FrontendbottlenecksLevelOfDetail(LOD)/LevelOfDetailGPUSkinning,disabling/DisableGPUSkinningtessellation,reducing/Reducetessellation


GGameObjectnullreferencecheck

performing/FasterGameObjectnullreferencechecksgameprogrammingpatterns

URL/Externaltipsgarbagecollection,managedmemory

about/Garbagecollectionmemoryfragmentation/Memoryfragmentationatruntime/GarbagecollectionatruntimethreadedGarbagecollection/Threadedgarbagecollectiontactics/Garbagecollectiontactics

GarbageCollectormainthread/Threadedgarbagecollectionfinalizerthread/Threadedgarbagecollection

globalmessagingsystemabout/Aglobalmessagingsystemgloballyaccessibleobject/Agloballyaccessibleobjectregistration/Registrationmessageprocessing/Messageprocessingimplementing/Implementingthemessagingsystemmessage,queuing/Messagequeuingandprocessingmessage,processing/Messagequeuingandprocessingcustommessage,implementing/Implementingacustommessagemessageregistration/Messageregistrationmessage,sending/Messagesendingmessagecleanup/Messagecleanupwrappingup/Wrappingupthemessagingsystem

GPUProfiling/GPUprofilinggreedymethods/CPUArea


Hheap/Managedmemoryhotkeytips,Editor

about/EditorhotkeytipsGameObjects/GameObjectsSceneView/SceneViewarrays/Arraysinterface/InterfaceUnitykeyword,accessing/Other


IimmutableReferencetypes

strings/StringsareimmutableReferencetypesabout/StringsareimmutableReferencetypesstringconcatenation/Stringconcatenation

inter-objectcommunicationissuestaticclassapproach/StaticclassesSingletonComponents/SingletonComponentsreferences,assigningtopre-existingobjects/Assigningreferencestopre-existingobjectsglobalmessagingsystem/Aglobalmessagingsystem

interfacetips,Editorabout/Editorinterfacetipsgeneral/GeneralInspectorView/TheInspectorViewProjectView/TheProjectViewHierarchyView/TheHierarchyViewSceneView/TheSceneandGameViewsGameView/TheSceneandGameViewsPlayMode/PlayMode

IntermediateLanguageToC++(IL2CPP)about/ThefutureofMonoandUnityURL/ThefutureofMonoandUnity

InvokeRepeatingusing/Update,Coroutines,andInvokeRepeating

IsAliveproperty/Messagecleanupissue

focusingon/Focusingontheissue


JJust-In-Time(JIT)/Thecompilationprocess


LLevelOfDetail(LOD)

about/LevelOfDetailURL/LevelOfDetail

LightingandShadowingabout/LightingandShadowingURL/LightingandShadowingForwardRendering/ForwardRenderingDeferredShading/DeferredShadingVertexLitShading(legacy)/VertexLitShading(legacy)real-timeShadows/Real-timeShadows

lightingoptimizationabout/LightingoptimizationappropriateShadingMode,using/UsetheappropriateShadingModeCullingMasks,using/UseCullingMaskslightmapping,using/UseBakedLightmapsshadows,optimizing/OptimizeShadows


MManagedDomain/UnitymemorydomainsManagedHeap/Managedmemorymassvalues

URL/MassMaterials

about/MaterialsandShadersMaximumAllowedTimestep/MaximumAllowedTimestep

adjusting/AdjusttheMaximumAllowedTimestepmeaninglessdata(noise)

reducing/Reducingnoisememorybandwidth,backendbottlenecks

about/Memorybandwidthlesstexturedata,using/UselesstexturedataGPUTextureCompressionformats,testing/TestdifferentGPUTextureCompressionformatstexturesampling,minimizing/Minimizetexturesamplingassetsorganization,forreducingtextureswaps/Organizeassetstoreducetextureswaps

memoryusageoptimizationabout/MemoryusageoptimizationUnitymemorydomains/Unitymemorydomainsvaluetypes/ValuetypesandReferencetypesreferencetypes/ValuetypesandReferencetypespassingbyvalue/Passbyvalueandpassbyreferencedatalayout/TheimportanceofdatalayoutUnityAPI/TheUnityAPIforeachloops/TheforeachloopsCoroutines/CoroutinesClosures/Closures.NETlibraryfunctions/.NETlibraryfunctionstemporaryworkbuffers/Temporaryworkbuffersobjectpooling/Objectpooling

meshabout/Meshandanimationfiles

MeshColliderconcave/Collidertypesconvex/Collidertypes

mobilegraphicsoptimizationabout/OptimizinggraphicsformobileDrawCalls,minimizing/MinimizeDrawCallsMaterialCount,minimizing/MinimizetheMaterialcounttexturesize,minimizing/MinimizetexturesizeandMaterialcount


power-of-2,creating/Maketexturessquareandpowerof2Texturessquare,creating/Maketexturessquareandpowerof2lowestpossibleprecisionformats,usinginShaders/UsethelowestpossibleprecisionformatsinShadersAlphaTesting,allowing/AvoidAlphaTesting

Monoabout/TheMonoplatformfuture/ThefutureofMonoandUnityURL/ThefutureofMonoandUnity

MonoBehaviourUnitydocumentationURL/Removingemptycallbackdeclarations

Monoplatformabout/TheMonoplatformcompilationprocess/Thecompilationprocess


N.NET

URL/ThefutureofMonoandUnity.NETlibraryfunctions/.NETlibraryfunctionsnameproperty

retrieving,avoiding/AvoidretrievingstringpropertiesfromGameObjectsNativeDomain/UnitymemorydomainsNestedCoroutines

URL/Usefullinks


OOnGUI()method/LoadingProfilerdataOperatingSystem(OS)/TheMonoplatformOrderofExecution

URL/Physicsandtimeoverdraw/Fillrate


Ppassbyreference/Passbyvalueandpassbyreferencepassingbyvalue/Passbyvalueandpassbyreferenceperformance-enhancingtechniques

polygoncount,reducing/Reducingpolygoncountnecessarydata,importing/Import/calculateonlywhat’sneedednecessarydata,calculating/Import/calculateonlywhat’sneededbakedanimations,considering/ConsiderbakedanimationsOptimizeMeshesoption/LetUnityoptimizemeshesmeshes,combining/Combinemeshes

performanceanalysisapproaches/Bestapproachestoperformanceanalysis

PhysicsEngineinternals/Physicsandtimeabout/PhysicsEngineinternalstime/Physicsandtimephysics/PhysicsandtimeFixedUpdateloop/TheFixedUpdateloopMaximumAllowedTimestep/MaximumAllowedTimestepphysicsupdates/Physicsupdatesandruntimechangesruntimechanges/PhysicsupdatesandruntimechangesDynamicColliders/StaticandDynamicCollidersStaticColliders/StaticandDynamicColliderscollisiondetection/CollisiondetectionCollidertypes/CollidertypesCollisionMatrix/TheCollisionMatrixRigidbodyactivestate/RigidbodyactiveandsleepingstatesRigidbodysleepingstates/Rigidbodyactiveandsleepingstatesraycasting/Rayandobjectcastingobjectcasting/Rayandobjectcasting

physicsperformanceoptimizationsabout/Physicsperformanceoptimizationsscenesetup/ScenesetupStaticColliders,using/UseStaticCollidersappropriatelyCollisionMatrix,optimizing/OptimizetheCollisionMatrixdiscretecollisiondetection,preferring/PreferdiscretecollisiondetectionFixedUpdatefrequency,modifying/ModifytheFixedUpdatefrequencyMaximumAllowedTimestep,adjusting/AdjusttheMaximumAllowedTimestepcastandbounding-volumechecks,minimizing/Minimizecastandbounding-volumecheckscomplexMeshColliders,avoiding/AvoidcomplexMeshCollidersphysicsobjects,allowingtosleep/LetphysicsobjectssleepSolverIterationCount,modifying/ModifySolverIterationCount


ragdolls,optimizing/Optimizingragdollsphysics,using/Knowwhentousephysicsupgrading,toUnity5/ConsiderupgradingtoUnity5

polygoncountreducing/ReducingpolygoncountTweakMeshCompression/TweakingMeshCompressionRead-WriteEnabledflag,using/UseRead-WriteEnabledappropriately

prefabpoolingabout/Prefabpooling,PrefabpoolsPoolableComponent/PoolableComponentssystemrequirements/ThePrefabpoolingsystemobjectspawning/Objectspawninginstanceprespawning/Instanceprespawningobjectdespawning/Objectdespawningtesting/Prefabpooltestingandsceneloading/PrefabpoolingandSceneloadingsummary/Prefabpoolingsummary

ProceduralMaterialsabout/ProceduralMaterialsURL/ProceduralMaterials

Profiler.enableBinaryLogmethod/SavingandloadingProfilerdataProfiler.enabledmethod/SavingandloadingProfilerdataProfiler.logFilemethod/SavingandloadingProfilerdataProfilingandAnalysis

about/FinalthoughtsonProfilingandAnalysis


RReferencetypes

about/ValuetypesandReferencetypesarrays/ArraysareReferencetypes

reflection/ManualJITcompilationrenderingissues

profiling/Profilingrenderingissuesrenderingissues,profiling

GPUProfiling/GPUprofilingFrameDebugger/TheFrameDebuggerbruteforcetesting/BruteforcetestingCPU-bound/CPU-bound

ReorderableListsabout/Customeditors/menustipsURL/Customeditors/menustips

rigidbodyproperty/ObtainingComponentsusingthefastestmethodRuntimeHelpers.PrepareMethod()method/ManualJITcompilation


Sscenesetup

about/Scenesetupscaling/Scalingpositioning/Positioningmassvalues/Mass

ScriptableObjectsURL/Usefullinks

scriptingtipsabout/Scriptingtipsgeneral/Generalattributes/Attributeslogging/Loggingusefullinks/Usefullinks

SendMessage()methodavoiding,atruntime/AvoidingtheFind()andSendMessage()methodsatruntime

Shaderabout/MaterialsandShaders

Shaders,intendedformobileplatformsusing/ConsiderusingShadersintendedformobileplatformssmalldatatypes,using/Usesmalldatatypeschangingprecision,avoiding/Avoidchangingprecisionwhileswizzlingswizzling/AvoidchangingprecisionwhileswizzlingGPU-optimizedhelperfunctions,using/UseGPU-optimizedhelperfunctionsunnecessaryfeatures,disabling/Disableunnecessaryfeaturesunnecessaryinputdata,removing/Removeunnecessaryinputdatanecessaryvariables,exposing/Onlyexposenecessaryvariablesmathematicalcomplexity,reducing/Reducemathematicalcomplexity,Reducetexturelookupsconditionalstatements,avoiding/Avoidconditionalstatementsdatadependencies,reducing/ReducedatadependenciesSurfaceShaders/SurfaceShadersShader-basedLOD,using/UseShader-basedLOD

ShadowCascadesfeatureURL/OptimizeShadows

skinning/GPUSkinningSparseTexturing

about/SparseTexturesURL/SparseTextures

sphericalharmonics/ForwardRenderingstack/ManagedmemoryStaticBatching


about/StaticBatchingrequirements/StaticBatchingStaticflag/TheStaticflagmemoryrequirements/MemoryrequirementsMaterialreferences/Materialreferencescaveats/StaticBatchingcaveatssummary/StaticBatchingsummary

StaticCollidersabout/StaticandDynamicCollidersusing/UseStaticCollidersappropriately


Ttagproperty

retrieving,avoiding/AvoidretrievingstringpropertiesfromGameObjectstemporaryworkbuffers/TemporaryworkbuffersTexture/Texturefilestexturefiles

about/Texturefilescompressionformats/Compressionformatsperformanceenhancements/Textureperformanceenhancements

textureperformanceenhancementsabout/Textureperformanceenhancementsfilesize,reducing/ReduceTexturefilesizeMipMaps,using/UseMipMapswiselyresolutiondownscaling,managing/ManageresolutiondownscalingexternallyAnisotropicFilteringlevels,adjusting/AdjustAnisotropicFilteringlevelsatlasing,considering/ConsiderAtlasingcompressionratesfornon-squaretextures,adjusting/Adjustcompressionratesfornon-squareTexturesSparseTexturing/SparseTexturesProceduralMaterials/ProceduralMaterials

theMSDNC#ProgrammingGuideURL/Registration

TotalAllocatedblock/ThreadedgarbagecollectionTransformchanges

caching/ConsidercachingTransformchanges


UUnity

URL/SavingProfilerdata,ThefutureofMonoandUnityfuture/ThefutureofMonoandUnity

Unity3D/TheUnityProfilerUnity5.0/TheUnityProfilerUnityAPI/TheUnityAPIUnitydocumentation

URL/ConsiderAtlasingUnityEditor

profiling/Editorprofilingreflection,URL/Customeditors/menustips

UnityEditor;about/TheUnityProfilerUnitymemorydomains

about/Unitymemorydomainsnativememory/Nativememorymanagedmemory/Managedmemory

UnityProfilerabout/TheUnityProfiler,UnderstandingtheProfilerlaunching/LaunchingtheProfilerUnityEditor/EditororstandaloneinstancesStandaloneInstances/EditororstandaloneinstancesUnityWebplayerconnection,connecting/TheUnityWebplayerconnectionconnecting,toiOSdevice/RemoteconnectiontoaniOSdeviceconnecting,toAndroiddevice/RemoteconnectiontoanAndroiddevicewindow/TheProfilerwindow

UnityProfilerdatasaving/SavingandloadingProfilerdata,SavingProfilerdataloading/SavingandloadingProfilerdata,LoadingProfilerdata

UnityProfilerwindowabout/TheProfilerwindowcontrols/Controls

UnityroadmapURL/ThefutureofMonoandUnity

UnityWebplayer/LaunchingtheProfilerUnloadAudioData()method/Additionalloadingoptionsunusedscriptsandobjects

disabling/Disablingunusedscriptsandobjectsdisabling,byvisibility/Disablingobjectsbyvisibilitydisabling,bydistance/Disablingobjectsbydistance


Vvaluetypes

about/ValuetypesandReferencetypesstructs/StructsareValuetypes

VerticalSync(VSync)/MinimizinginternaldistractionsVisualStudio

URL/ExternaltipsVisualStudioToolsforUnity(VSTU)/OtherVRAMlimits,backendbottlenecks

about/VRAMlimitstexturepreloading/Texturepreloadingtexturethrashing/Texturethrashing


Unity 5 Game Optimization - smactech.in · There are further alternatives that we can explore, such...

Documents

Transcript of Unity 5 Game Optimization - smactech.in · There are further alternatives that we can explore, such...