Xcs 354 Computer Graphics

7/31/2019 Xcs 354 Computer Graphics

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COMPUTERGRAPHICS(XCS354)TwoMarkQuestion

UNITI

1.DefineComputergraphics.Computergraphicsremainsoneofthemostexistingandrapidlygrowingcomputerfields.Computergraphicsmaybedefinedasapictorialrepresentationorgraphicalrepresentationofobjectsinacomputer.

2.Whatismeantbyscancode?Whenakeyispressedonthekeyboard,thekeyboardcontrollerplacesacodecarrytothekeypressedintoapartofthememorycalledasthekeyboardbuffer.Thiscodeiscalledasthescancode.

3.Whatismeantbyrefreshingofthescreen?Somemethodisneededformaintainingthepictureonthescreen.Refreshingofscreenisdonebykeepingthephosphorusglowingtoredrawthepicturerepeatedly.(i.e.)Byquicklydirectingtheelectronicbeambacktothesamepoints.

4.DefineRandomscan/Rasterscandisplays?Randomscanisamethodinwhichthedisplayismadebytheelectronicbeamwhichisdirectedonlytothepointsorpartofthescreenwherethepictureistobedrawn.

TheRasterscansystemisascanningtechniqueinwhichtheelectronssweepfromtoptobottomandfromlefttoright.Theintensityisturnedonorofftolightandunlightthepixel.

5.ListoutthemeritsanddemeritsofPenetrationtechniques?ThemeritsanddemeritsofthePenetrationtechniquesareasfollows

ItisaninexpensivetechniqueIthasonlyfourcolorsThequalityofthepictureisnotgoodwhenitiscomparedtoothertechniquesItcandisplaycolorscansinmonitorsPoorlimitationetc.6.ListoutthemeritsanddemeritsofDVST?

Themeritsanddemeritsofdirectviewstoragetubes[DVST]areasfollows

IthasaflatscreenRefreshingofscreenisnotrequiredSelectiveorparterasingofscreenisnotpossibleIthaspoorcontrast


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PerformanceisinferiortotherefreshCRT.


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7.Whatdoyoumeanbyemissiveandnon-emissivedisplays?Theemissivedisplayconvertselectricalenergyintolightenergy.Theplasmapanels,thinfilmelectro-luminescentdisplaysaretheexamples.

TheNonemissiveareopticaleffectstoconvertthesunlightorlightfromanyothersourcetographicform.Liquidcrystaldisplayisanexample.

8.ListoutthemeritsanddemeritsofPlasmapaneldisplay?MeritsRefreshingisnotrequiredProduceaverysteadyimagefreeofFlickerLessbulkythanaCRT.DemeritsPoorresolutionofupto60d.p.iItrequirescomplexaddressingandwiringItiscostlierthanCRT.9.Whatispersistence?

Thetimeittakestheemittedlightfromthescreentodecayonetenthofitsoriginalintensityiscalledaspersistence.

10.Whatisresolution?ThemaximumnumberofpointsthatcanbedisplayedwithoutanoverlaponaCRTiscalledasresolution.

11.WhatisAspectratio?TheratioofverticalpointstothehorizontalpointsnecessarytoproducelengthoflinesinbothdirectionsofthescreeniscalledtheAspectratio.Usuallytheaspectratiois.

12.WhatismeantbyAddressability?TheAddressabilityisthenumberofindividualdotsperinch(d.p.i)thatcanbecreated.Iftheaddressofthecurrentdotis(x,y)thenthenextdotwillbe(x+y),(x+y+1)etc.

13.Whatisadotsize?Dotsizemaybedefinedasthediameterofasingledotonthedevicesoutput.DotsizeisalsocalledastheSpotsize.


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14.Whatisinterdotdistance?Interdotdistanceisthereciprocalofaddressability.Iftheaddressabilityislarge,theinterdotdistancewillbeless.Theinterdotdistanceshouldbelesstogetsmoothshapes.

15.Whatisthedifferencebetweenimpactandnon-impactprinters?Impactprinterpressformedcharacterfacesagainstaninkedribbonontothepaper.Alineprinteranddot-matrixprinterareexamples.

Non-impactprinterandplottersuseLasertechniques,inkjetsprays,Xerographicprocess,electrostaticmethodsandelectrothermalmethodstogetimagesontothepapers.Examplesare:Inkjet/Laserprinters.

16.WhatarethefeaturesofInkjetprinters?Theycanprint2to4pages/minutes.Resolutionisabout360d.p.i.Thereforebetterprintqualityisachieved.

Theoperatingcostisverylow.Theonlypartthatrequiresreplacementisinkcartridge.4colorscyane,yellow,majenta,blackareavailable.17.WhataretheadvantagesoflaserprinterHighspeed,precisionandeconomy.Cheaptomaintain.Qualityprinters.Lastsforlongertime.

Tonerpowerisverycheap.18.Whataretheadvantagesofelectrostaticplotters?Theyarefasterthanpenplottersandveryhighqualityprinters.Recentelectrostaticplottersincludeascan-conversioncapability.Colorelectrostaticplottersareavailable.Theymakemultiplepassesoverthepapertoplotcolorpictures.19.Definepixel?Pixelisshortenedformsofpictureelement.Eachscreenpointisreferredtoas

pixelorpel.

20.Whatisframebuffer?Picturedefinitionisstoredinamemoryareacalledframebufferorrefreshbuffer.


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21.Whatisbitmapandwhatispixmap?Theframebufferusedintheblackandwhitesystemisknownasbitmapwhichtakeonebitperpixel.Forsystemswithmultiplebitsperpixel,theframebufferisoftenreferredtoasapixmap.

22.WhatisaVectordisplayorstrokewritingorcalligraphicdisplay?Randomscanmonitorsdrawapictureonelineatatimeandforthisreasonarealsoreferredasvectordisplays.

23.Wherethevideocontrollerisused?Aspecialpurposeprocessor,whichisusedtocontroltheoperationofthedisplaydevice,isknownasvideocontrollerordisplaycontroller.

24.Whatdoyoumeanbyscanconversion?Amajortaskofthedisplayprocessorisdigitizingapicturedefinitiongiveninanapplicationprogramintoasetofpixel-intensityvaluesforstorageintheframebuffer.Thisdigitizationprocessiscalledscanconversion.

25.Whatisrunlengthencoding?

Runlengthencodingisacompressiontechniqueusedtostoretheintensityvaluesintheframebuffer,whichstoreseachscanlineasasetofintegerpairs.Onenumbereachpairindicatesanintensityvalue,andsecondnumberspecifiesthenumberofadjacentpixelsonthescanlinethataretohavethatintensityvalue

UNITII

1.Whatisanoutputprimitive?Graphicsprogrammingpackagesprovidefunctiontodescribeasceneintermsofthesebasicgeometricstructures,referredtoasoutputprimitives.

2.Whatdoyoumeanbyjaggies?Linewithstairstepappearanceisknownasjaggies.3.Whatispointinthecomputergraphicssystem?Thepointisamostbasicgraphicalelement&iscompletelydefinedbyapairofusercoordinates(x,y).

4.Writeshortnotesonlines?Alineisofinfiniteextentcanbedefinedbyanangleofslope.andonepointonthelineP=P(x,y).ThiscanalsobedefinedasY=mx+CwhereCistheY-intercep

t.

5.DefineCircle?Circleisdefinedbyitscenterxc,ycanditsradiusinusercoordinateunits.Theequationofthecircleis(x-xc)+(y-yc)=r2.


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6.DefineEllipse?Anellipsecanusethesameparametersxc,yc,rasacircle,inadditiontotheeccentricitye.theeqnofanellipseis:(x-xc)2/a2+(y-yc)2/b2=1

7.Definepolygon?Apolygonisanyclosedcontinuessequenceoflinesegmentsie,apolylinewhoselastnodepointissameasthatofitsfirstnodepoint.Thelinesegmentsformthesidesofthepolygonandtheirintersectingpointsformtheverticesofthepolygon.

8.Distinguishbetweenconvexandconcavepolygons?Ifthelinejoininganytwopointsinthepolygonliescompletelyinsidethepolygonthen,theyareknownasconvexpolygons.Ifthelinejoininganytwopointsinthepolygonliesoutsidethepolygonthen,theyareknownasconcavepolygons.

9.Whatisseedfill?Onewaytofillapolygonistostartfromagivenpoint(seed)knowntobeinside

thepolygonandhighlightoutwardfromthispointi.eneighboringpixelsuntilencountertheboundarypixels,thisapproachiscalledseedfill.

10.Whatisscanlinealgorithm?Onewaytofillthepolygonistoapplytheinsidetest.i.etocheckwhetherthepixelisinsidethepolygonoroutsidethepolygonandthenhighlightthepixelwhichlieinsidethepolygon.Thisapproachisknownasscan-linealgorithm.

11.Definecoherenceproperties?Acoherencepropertyofasceneisapartofascenebywhichrelateonepartof

thescenewiththeotherpartsofthescene.

12.Whatisanactiveedgelistinthescanlinealgorithm?Theactiveedgelistforascanlinecontainsalledgescrossedbythatscanline.13.Whatisawindingnumber?Windingnumbermethodisusedtocheckwhetheragivenpointisinsideoroutsidethepolygon.Inthismethodgiveadirectionnumbertoalltheedgeswhichcrossthescanline.Iftheedgestartsbelowthelineandendsabovescanlinegivedirectionas-1.otherwise1.Frpolygonsortwodimensionalobjects,thepointissaidtobeinsi

dewhenthevalueofwindingnumberisnonzero.

14.Whatiscellarray?Thecellarrayisaprimitivethatallowsuserstodisplayanarbitraryshapedefinedasatwodimensionalgridpattern.

15.Whatistypeface?Letters,numbersandothercharacterscanbedisplayedinavarietyofsizesand


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styles.Theoveralldesignstyleforasetofcharactersiscalledatypeface.

16.Whatdoyoumeanbyfont?Thetermfontreferredtoasetofcastmetalcharacterformsinaparticularsizeandformat,suchas10-pointcourieritalic.


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17.Whatisabitmappedfont?Asimplemethodforrepresentingthecharactershapesinaparticulartypefaceistouserectangulargridpatterns.Thesetofcharactersarethenreferredtoasabitmapfont.

18.Whatisanoutlinefont?Aflexibleschemeistodescribecharactershapesusingstraight-lineandcurvesections.Inthiscase,thesetofcharacteriscalledanoutlinefont.

19.Whatisanattributeparameter?Anyparameterthataffectsthewayaprimitiveistobedisplayedisreferredtoasanattributeparameter.

20.Whatarethevariousattributesofaline?Thelinetype,widthandcoloraretheattributesoftheline.Thelinetypeincludesolidline,dashedlines,anddottedlines.

21.Whatispixelmask?Pixelmaskisastringcontainingthedigits1and0toindicatewhichpositionsto

plotalongthelinepath.Themask1111000,couldbeusedtodisplayadashedlinewithadashlengthof4andinterdotspacingofthree.

22.WhatisaLinecap?Linecapscanbeusedtoadjusttheshapeofthelineendstogiveabetterappearance.Therearethreetypesoflinecaps.Buttcapwhichhasasquareend,roundcapwhichhasasemicircleend,projectingsquarecapwhichhasonehalfofthelinewidthbeyondthespecifiedendpoints.

23.Listoutthemethodsusedforsmoothlyjoiningtwolinesegments?

.Mitterjoin-byextendingtheouterboundariesofeachofthetwolinesuntiltheymeet..Roundjoinbycappingtheconnectionbetweenthetwosegmentswithacircularboundarywhosediameterisequaltothelinewidth..Beveljoinbydisplayingthelinesegmentswithbuttcapsandfillinginthetriangulargapwherethesegmentmeet.24.WhatisColorLookuptable?Incolordisplays,24bitsperpixelarecommonlyused,where8bitsrepresent256levelforeachcolor.Itisnecessarytoread24-bitforeachpixelfromframeb

uffer.Thisisverytimeconsuming.ToavoidthisvideocontrolleruseslookuptabletostoremanyentriestopixelvaluesinRGBformat.Thislookuptableiscommonlyknownascolourtable.

25.Whatistilingpatterns?Theprocessoffillinganareawithrectangularpatterniscalledtilingandrectangularfillpatternsaresometimesreferredtoastilingpatterns.


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26.Whatissoftfill?Softfillisafillingmethodinwhichfillcoloriscombinedwiththebackgroundcolors.


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27.Whatiskernedcharacter?Thecharacterswhichextendbeyondthecharacterbodylimitsisknownaskernedcharacter.Examplefandj.

28.Whatischaracterupvector?Theorientationforadisplayedcharacterstringissetaccordingtothedirectionofthecharacterupvector.

29.Definebundledattributes?Individualattributecommandsprovideasimpleanddirectmethodforspecifyingattributeswhenasingleoutputdeviceisused.Whenseveralkindsofoutputdeviceareavailableatagraphicsinstallation,itisconvenienttosetupatableforeachoutputdevicethatlistssetofattributevaluesthataretobeusedonthatdevicetodisplayeachprimitivetype.Attributespecifiedinthismannerisknownasbundledattribute.

30.Whatisaliasing?Inthelinedrawingalgorithms,allrasterzedlocationsdonotmatchwiththetruelineandhavetorepresentastraightline.Thisproblemissevereinlowresolu

tionscreens.Insuchscreenslineappearslikeastair-step.Thiseffectisknownasaliasing.

31.Whatisantialiasing?Theprocessofadjustingintensitiesofthepixelsalongthelinetominimizetheeffectofaliasingiscalledantialiasing.

32.Whatispixelphasing?Pixelphasingisanantialiasingtechnique,stairstepsaresmoothedoutbymovingtheelectronbeamtomorenearlyapproximatepositionsspecifiedbytheobjectg

eometry.

UNITIII

1.WhatisTransformation?Transformationistheprocessofintroducingchangesintheshapesizeandorientationoftheobjectusingscalingrotationreflectionshearing&translationetc.

2.Writeshortnotesonactiveandpassivetransformations?|

Intheactivetransformationthepointsxandxrepresentdifferentcoordinatesofthesamecoordinatesystem.Hereallthepointsareacteduponbythesametransformationandhencetheshapeoftheobjectisnotdistorted.Inapassive

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transformationthepointsxandxrepresentsamepointsinthespacebutinadifferentcoordinatesystem.Herethechangeinthecoordinatesismerelyduetothechang


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einthetypeoftheusercoordinatesystem.

3.Whatistranslation?Translationistheprocessofchangingthepositionofanobjectinastraight-linepathfromonecoordinatelocationtoanother.Everypoint(x,y)intheobjectmust

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undergoadisplacementto(x,y).thetransformationis:

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x=x+tx;y=y+ty


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4.Whatisrotation?A2-Drotationisdonebyrepositioningthecoordinatesalongacircularpath,in|

thex-yplanebymakingananglewiththeaxes.Thetransformationisgivenby:X=r

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cos(q+f)andY=rsin(q+f).

5.Whatisscaling?Thescalingtransformationschangestheshapeofanobjectandcanbecarriedoutbymultiplyingeachvertex(x,y)byscalingfactorSx,SywhereSxisthescalingfactorofxandSyisthescalingfactorofy.

6.Whatisshearing?TheshearingtransformationactuallyslantstheobjectalongtheXdirectionortheYdirectionasrequired.ie;thistransformationslantstheshapeofanobjectal

ongarequiredplane.

7.Whatisreflection?Thereflectionisactuallythetransformationthatproducesamirrorimageofanobject.Forthisusesomeanglesandlinesofreflection.

8.Distinguishbetweenwindowport&viewport?Aportionofapicturethatistobedisplayedbyawindowisknownaswindowport.Thedisplayareaofthepartselectedortheforminwhichtheselectedpartisviewedisknownasviewport.

9.Defineclipping?Clippingisthemethodofcuttingagraphicsdisplaytoneatlyfitapredefinedgraphicsregionortheviewport.

10.Whatiscovering(exteriorclipping)?Thisisjustoppositetoclipping.Thisremovesthelinescominginsidethewindowsanddisplaystheremaining.Coveringismainlyusedtomakelabelsonthecomplexpictures.

11.Whatistheneedofhomogeneouscoordinates?Toperformmorethanonetransformationatatime,usehomogeneouscoordinates

ormatrixes.Theyreduceunwantedcalculationsintermediatestepssavestimeandmemoryandproduceasequenceoftransformations.

12.Distinguishbetweenuniformscalinganddifferentialscaling?Whenthescalingfactorssxandsyareassignedtothesamevalue,auniformscalingisproducedthatmaintainsrelativeobjectproportions.Unequalvaluesforsxandsyresultinadifferentialscalingthatisoftenusedindesignapplication.


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13.Whatisfixedpointscaling?Thelocationofascaledobjectcanbecontrolledbyapositioncalledthefixedpointthatistoremainunchangedafterthescalingtransformation.


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14.DefineAffinetransformation?AcoordinatetransformationoftheformX=axxx+axyy+bx,yayxx+ayyy+byiscalledatwo-dimensionalaffinetransformation.Eachofthetransformedcoordinatesxandyisalinearfunctionoftheoriginalcoordinatesxandy,andparametersaijandbkareconstantsdeterminedbythetransformationtype.

15.DistinguishbetweenbitBltandpixBlt?Rasterfunctionsthatmanipulaterectangularpixelarraysaregenerallyreferredtoasrasterops.Movingablockofpixelsfromonelocationtoanotherisalsocalledablocktransferofpixelvalues.Onabilevelsystem,thisoperationiscalledabitBlt(bit-blocktransfer),onmultilevelsystemtiscalledpixBlt.

16.ListoutthevariousTextclipping?.All-or-nonestringclipping-ifallofthestringisinsideaclipwindow,keepit

otherwisediscards..All-or-nonecharacterclippingdiscardonlythosecharactersthatarenotcompletelyinsidethewindow.Anycharacterthateitheroverlapsorisoutsideawindowboundaryisclipped..Individualcharactersifanindividualcharacteroverlapsaclipwindowboundary,clipoffthepartsofthecharacterthatareoutsidethewindow.UNITIV

1.Whatarethevariousrepresentationschemesusedinthreedimensionalobjects?

.Boundaryrepresentation(B-res)describethe3dimensionalobjectasasetofsurfacesthatseparatetheobjectinteriorfromtheenvironment..Space-portioningrepresentationdescribeinteriorproperties,bypartitioningthespatialregioncontaininganobjectintoasetofsmall,nooverlapping,contiguoussolids.2.WhatisPolygonmesh?Polygonmeshisamethodtorepresentthepolygon,whentheobjectsurfacesaretiled,itismoreconvenienttospecifythesurfacefacetswithameshfunction.

Thevariousmeshesare

Trianglestrip(n-2)connectedtrianglesQuadrilateralmeshgenerates(n-1)(m-1)Quadrilateral

3.WhatisBezierBasisFunction?BezierBasisfunctionsareasetofpolynomials,whichcanbeusedinsteadofthe


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primitivepolynomialbasis,andhavesomeusefulpropertiesforinteractivecurvedesign.

4.Whatissurfacepatch?Asinglesurfaceelementcanbedefinedasthesurfacetracedoutastwoparameters(u,v)takeallpossiblevaluesbetween0and1inatwo-parameterrepresentation.Suchasinglesurfaceelementisknownasasurfacepatch.


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5.Writeshortnotesonrenderingbi-cubicsurfacepatchesofconstantuandvmethod?Thesimplewayistodrawtheiso-parmetriclinesofthesurface.Discreteapproximationstocurvesonthesurfaceareproducedbyholdingoneparameterconstantandallowingtheothertovaryatdiscreteintervalsoveritswholerange.Thisproducecurvesofconstantuandconstantv.

6.Whataretheadvantagesofrenderingpolygonsbyscanlinemethod?i.Themaxandminvaluesofthescanwereeasilyfound.ii.Theintersectionofscanlineswithedgesiseasilycalculatedbyasimpleincrementalmethod.iii.Thedepthofthepolygonateachpixeliseasilycalculatedbyanincrementalmethod.7.Whataretheadvantagesofrenderingbypatchsplitting?i.Itisfast-especiallyonworkstationswithahardwarepolygon-renderingpipeline.ii.

Itsspeedcanbevariedbyalteringthedepthofsub-division.8.DefineB-Splinecurve?AB-Splinecurveisasetofpiecewise(usuallycubic)polynomialsegmentsthatpassclosetoasetofcontrolpoints.Howeverthecurvedoesnotpassthroughthesecontrolpoints,itonlypassesclosetothem.

9.Whatisaspline?Toproduceasmoothcurvethroughadesignedsetofpoints,aflexiblestripcalledsplineisused.Suchasplinecurvecanbemathematicallydescribedwithapiecewisecubicpolynomialfunctionwhosefirstandsecondderivativesarecontinuousacro

ssvariouscurvesection.

10.Whatistheuseofcontrolpoints?Splinecurvecanbespecifiedbygivingasetofcoordinatepositionscalledcontrolpoints,whichindicatesthegeneralshapeofthecurve,canspecifysplinecurve.

11.Whatarethedifferentwaysofspecifyingsplinecurve?Usingasetofboundaryconditionsthatareimposedonthespline.

UsingthestatematrixthatcharacteristicsthesplineUsingasetofblendingfunctionsthatcalculatethepositionsalongthecurvepathbyspecifyingcombinationofgeometricconstraintsonthecurve12.WhataretheimportantpropertiesofBezierCurve?ItneedsonlyfourcontrolpointsItalwayspassesthroughthefirstandlastcontrolpoints


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Thecurveliesentirelywithintheconvexhalfformedbyfourcontrolpoints.


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13.Differentiatebetweeninterpolationsplineandapproximationspline?Whenthesplinecurvepassesthroughallthecontrolpointsthenitiscalledinterpolate.Whenthecurveisnotpassingthroughallthecontrolpointsthenthatcurveiscalledapproximationspline.

14.Whatdoyoumeanbyparabolicsplines?Forparabolicsplinesaparabolaisfittedthroughthefirstthreepointsp1,p2,p3ofthedataarrayofkotpoints.Thenasecondparabolicarcisfoundtofitthesequenceofpointsp2,p3,p4.Thiscontinuesinthiswayuntilaparabolicarcisfoundtofitthroughpointspn-2,pn-1andpn.Thefinalplottedcurveisameshingtogetherofalltheseparabolicarcs.

15.Whatiscubicspline?Cubicsplinesareastraightforwardextensionoftheconceptsunderlyingparabolicspline.Thetotalcurveinthiscaseisasequenceofarcsofcubicratherthanparaboliccurves

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Eachcubicsatisfies:ax+bx+cx+d

16.WhatisaBlobbyobject?Someobjectsdonotmaintainafixedshape,butchangetheirsurfacecharacteristicsincertainmotionsorwheninproximitytootherobjects.Thatisknownasblobbyobjects.Examplemolecularstructures,waterdroplets.

17.DefineOctrees?Hierarchicaltreestructurescalledoctrees,areusedtorepresentsolidobjectsin

somegraphicssystems.Medicalimagingandotherapplicationsthatrequiredisplaysofobjectcrosssectionscommonlyuseoctreerepresentation.

18.DefineProjection?Theprocessofdisplaying3Dintoa2Ddisplayunitisknownasprojection.Theprojectiontransforms3Dobjectsintoa2Dprojectionplane.

19.Whatarethestepsinvolvedin3Dtransformation?ModelingTransformationViewingTransformation

ProjectionTransformationWorkstationTransformation20.Whatdoyoumeanbyviewplane?Aviewplaneisnothingbutthefilmplaneincamerawhichispositionedandorientedforaparticularshotofthescene.

21.Whatisview-planenormalvector?Thisnormalvectoristhedirectionperpendiculartotheviewplaneandit


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iscalledas[DXNDYNDZN]


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22.Whatisviewdistance?Theviewplanenormalvectorisadirectedlinesegmentfromtheviewplanetotheviewreferencepoint.Thelengthofthisdirectedlinesegmentisreferredtoasviewdistance

23.Defineprojection?Theprocessofconvertingthedescriptionofobjectsfromworldcoordinatestoviewingcoordinatesisknownasprojection

24.Whatyoumeanbyparallelprojection?Parallelprojectionisoneinwhichzcoordinatesisdiscardedandparallellinesfromeachvertexontheobjectareextendeduntiltheyintersecttheviewplane.

25.WhatdoyoumeanbyPerspectiveprojection?Perspectiveprojectionisoneinwhichthelinesofprojectionarenotparallel.Instead,theyallconvergeatasinglepointcalledthecenterofprojection.

26.WhatisProjectionreferencepoint?InPerspectiveprojection,thelinesofprojectionarenotparallel.Instead,theyallconvergeatasinglepointcalledProjectionreferencepoint.

27.WhatistheuseofProjectionreferencepoint?InPerspectiveprojection,theobjectpositionsaretransformedtotheviewplanealongtheseconvergedprojectionlineandtheprojectedviewofanobjectisdeterminedbycalculatingtheintersectionoftheconvergedprojectionlineswiththeviewplane.

28.Whatarethedifferenttypesofparallelprojections?Theparallelprojectionsarebasicallycategorizedintotwotypes,dependingontherelationbetweenthedirectionofprojectionandthenormaltothe

viewplane.Theyareorthographicparallelprojectionandobliqueprojection.

29.Whatisorthographicparallelprojection?Whenthedirectionoftheprojectionisnormal(perpendicular)totheviewplanethentheprojectionisknownasorthographicparallelprojection

30.Whatisorthographicobliqueprojection?Whenthedirectionoftheprojectionisnotnormal(notperpendicular)totheviewplanethentheprojectionisknownasobliqueprojection.

31.Whatisanaxonometricorthographicprojection?Theorthographicprojectioncandisplaymorethanonefaceofanobject.Suchanorthographicprojectioniscalledaxonometricorthographicprojection.

32.Whatiscavalierprojection?Thecavalierprojectionisonetypeofobliqueprojection,inwhichthedirectionofprojectionmakesa45-degreeanglewiththeviewplane.


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33.Whatiscabinetprojection?Thecabinetprojectionisonetypeofobliqueprojection,inwhichthedirectionofprojectionmakesanangleofarctan(2)=63.4-withtheviewplane.

34.Whatisvanishingpoint?Theperspectiveprojectionsofanysetofparallellinesthatarenotparalleltotheprojectionplaneconvergetoappointknownasvanishingpoint.

35.Whatdoyoumeanbyprinciplevanishingpoint.Thevanishingpointofanysetoflinesthatareparalleltooneofthethreeprincipleaxesofanobjectisreferredtoasaprinciplevanishingpointoraxisvanishingpoint.

36.Whatisviewreferencepoint?Theviewreferencepointisthecenteroftheviewingcoordinatesystem.Itisoftenchosentobeclosetooronthesurfaceofthesomeobjectinthescene.

UNITV

1.Definecomputergraphicsanimation?

Computergraphicsanimationistheuseofcomputergraphicsequipmentwherethegraphicsoutputpresentationdynamicallychangesinrealtime.Thisisoftenalsocalledrealtimeanimation.

2.Whatistweening?Itistheprocess,whichisapplicabletoanimationobjectsdefinedbyasequenceofpoints,andthatchangeshapefromframetoframe.

3.Defineframe?Oneoftheshapephotographsthatafilmorvideoismadeofisknownasframe.

4.Whatiskeyframe?Oneoftheshapephotographsthatafilmorvideoismadeoftheshapeofanobjectisknowninitiallyandforasmallnoofotherframescalledkeyframe

5.Whatispseudoanimation?Pseudoanimationiscreatingasequenceofstills,photographingorvideographingeachstillasoneframe,andthenlaterplayingbacktheframesatafasterspeed.

6.Whatisthenormalspeedofavisualanimation?Visualanimationrequiresaplaybackofatleast25framespersecond.


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7.Whatarethedifferenttricksusedincomputergraphicsanimation?a.ColorlookUpTablemanipulationb.Bitplanemanipulationc.UseofUDCSd.Specialdrawingmodese.Spritesf.Bitblitting

8.Whatiscolorlookuptable?Incolordisplayunititisnecessarytoread44-bitforeachpixelfrombuffer.Thisverytimeconsumingprocess.ToavoidthisvideocontrolleruseslookuptabletostoremanyentriesofpixelvalesinRGBformat.Thislookuptableiscommonlyknownascolorlookuptable.

9.Whatissolidmodeling?Theconstructionof3dimensionalobjectsforgraphicsdisplayisoftenreferredtoassolidmodeling.

10.Whatisanintuitiveinterface?Theintuitiveinterfaceisone,whichsimulatesthewayapersonwouldperformacorrespondingoperationonrealobjectratherthanhavemenucommand.

11.WhatisSprite?ASpriteisgraphicsshapeinanimationandgamesprograms.EachspriteprovidedinthesystemhasitsownmemoryareasimilartobutsmallerthanpixelRAM.

12.WhatistheUDCtechnique?UDCstandsforUserDefinedCharacterset.Itisgraphicsanimationtrick,whichisusedinearlymicrocomputersystem.

13.Whatistheuseofhiddenlineremovingalgorithm?Thehiddenlineremovalalgorithmdeterminesthelines,edges,surfacesorvolumesthatarevisibleorinvisibletoanobserverlocatedataspecificpoint

inspace.

14.Whatiscomputergraphicsrealism?Thecreationofrealisticpictureincomputergraphicsisknownasrealism.Itisimportantinfieldssuchassimulation,design,entertainments,advertising,research,education,command,andcontrol.

15.Howrealisticpicturesarecreatedincomputergraphics?Tocreatearealisticpicture,itmustbeprocessthesceneorpicturethroughviewing-coordinatetransformationsandprojectionthattransformthree-dimensionalviewingcoordinatesontotwo-dimensionaldevicecoordinates.

16.WhatisFractals?AFractalisanobjectwhoseshapeisirregularatallscales.


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17.WhatisaFractalDimension?Fractalhasinfinitedetailandfractaldimension.Afractalimbeddedinn-dimensionalspacecouldhaveanyfractionaldimensionbetween0andn.TheFractalDimensionD=LogN/LogSWhereNistheNoofPiecesandSistheScalingFactor.

18.Whatisrandomfractal?Thepatternsintherandomfractalsarenolongerperfectandtherandomdefectsatallscale.

19.Whatisgeometricfractal?Ageometricfractalisafractalthatrepeatsself-similarpatternsoverallscales.

20.WhatisKochcurve?TheKochcurvecanbedrawnbydividinglineinto4equalsegmentswithscalingfactor1/3.andmiddle2segmentsaresoadjustedthattheyformadjustmentsidesofanequilateraltriangle.

21.Whatisturtlegraphicsprogram?TheturtleprogramisaRobertthatcanmovein2dimensionsandithasa

pencilfordrawing.Theturtleisdefinedbythefollowingparameters.

g.Positionoftheturtle(x,y)h.Headingoftheturtle0theanglefromthexaxis.22.Whatisgraftals?Graftalsareapplicabletorepresentrealisticrenderingplantsandtrees.AtreeisrepresentedbyaStringofsymbols0,1,[,]

23.WhatisaParticlesystem?Aparticlesystemisamethodformodelingnaturalobjects,orotherirregularlyshapedobjects,thatexhibitfluid-likeproperties.Particlesystemsa

resuitableforrealisticrenderingoffuzzyobjects,smoke,seaandgrass.

24.Givesomeexamplesforcomputergraphicsstandards?i.CORETheCoregraphicsstandardj.GKS--TheGraphicsKernelsystemk.PHIGSTheProgrammersHierarchicalInteractiveGraphicsSystem.l.GSXTheGraphicssystemextensionm.

NAPLPSTheNorthAmericanpresentationlevelprotocolsyntax.DetailedAnswers

UNITI

1.Explainrefreshcathoderaytube?.


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Abeamofelectrons,emittedbyanelectrongun,passesthroughfocusinganddeflectionsystemsthatdirectthebeamtowardspecifiedpositionsonthephosphorcoatedarea.


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Theyproduceawiderrangeofcolors.Hasthreephosphorcolordotsateachpixelposition


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.Oneemitsredlight,anotheremitsgreenlight,andthethirdemitsabluelight.Thethreebeamsaredeflectedandfocusedasagroupontotheshadowmask,whichcontainsaseriesofholesalignedwithaphosphordotpatterns..Whenthethreebeamspassesthroughaholeintheshadowmask,theyactivateadottriangle,whichappearsasasmallcolorspotonthescreen.3.Explaindirectviewstoragetubesandliquidcrystaldisplays?LiquidcrystaldisplaysReferstothecompoundshavingcrystallinearrangementofmoleculesflowofliquidTwoplateseachglassplatecontainsalightpolarizedthatarerightanglestoeachotherTwotypesPassivematrixLCD

ActivematrixLCDDirectviewstoragetubes

AlternativemethodformaintainingascreenimageStorespictureinformationasachargedistributionVerycomplexpicturescanbedisplayedatveryhighresolutionsToeliminatethepicturesectiontheentirescreenmustbeerasedTheerasingandredrawingprocesscantakeseveralsecondsfora

picture4.ExplainRasterscansystems?

.Severalprocessingunits.Containsaspecialpurposeprocessor,calledvideocontrollerordisplaycontroller.VideocontrollerAfixedareaofthesystemmemoryisreservedfortheframebuffer,andthevideocontrollerisgivenaccesstotheframe-

buffermemoryTowregistersareusedtostorethecoordinatesofthescreenpixelsThevalueisstoredintheframebufferforthispixelpositionisthenretrievedandusedtosettheintensityoftheCRTbeamInitiallythexregisterissetto0andtheyregisterissettoymax


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Thenthexregisterisincrementedby1,andtheprocessrepeatedforthenextpixelonthetopscanlineThisprocessisrepeatedforeachpixelalongthescanline


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Afterthelastpixelsonthetopscanlinehasbeenprocessed,thexregisterisresetto0andtheyregisterisdecrementedby1.Theprocedureisrepeatedfroeachsuccessiveline.FramebufferlocationsandthecorrespondingscreenpositionsarereferencedasCartesiancoordinatesSystemBusCPUSystemFrameMemoryBufferVideocontrollerI/Odevice

4.Explainthefollowing?1.Z-mouse2.Joysticks

3.Touchpanels4.Imagescanners5.DatagloveZ-Mouse:.Includethreebuttons.Athumbwheelontheside,atrackballonthetop,andastandardmouseballunderneath..Thisdesignprovidessixdegreesoffreedomtoselectanobjectfrom

thespatialposition..Witthiswecanpickupanobject,rotateitandwecanmoveitinanydirection.UsedinvirtualrealityandCADsystemsJoysticks

ConsistsofsmallverticallivermountedonabaseUsedtomovethecursoraroundthescreen

ThescreencursorismovedaccordingtothedistanceOneortwobuttonsisusuallyintendedforsignalingcertainactionsTouchpanels

ThreetypesOpticaltouchpanel


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ElectricaltouchpanelAcousticaltouchpanelAllowselectingthescreenpositionwiththetouchoffinger.Touchinputcanberecordedusingoptical,electricalmethodsImagescanners

.Drawings,colorandblackandwhitephotosortextcanbegivenasaninputtothecomputerwithanopticalscanningmechanism..AccordingtoreflectedlightintensitythegradationsofgrayscaleorcolorcanbestoredinanarrayDataglove

.Constructedwithaseriesofsensorsthatcandetecthandandfingermotions.Thetransmittingandreceivingantennascanbestructuredasasetofthreemutuallyperpendicularcols,formingathreedimensional

Cartesiancoordinatessystem..Electromagneticcouplingbetweenthethreepairsofcoilisusedtoprovideinformationaboutthepositionandorientationofhand.UNITII

1.ExplainindetailabouttheDDAscanconversionalgorithm?Thedigitaldifferentialanalyzerisascanconversionalgorithmbasedoncalculationeitheryorxusingthefollowingeuations

y=mx

x=y/m

Samplethelineatunitintervalsinonecoordinateanddeterminecorrespondingintegervaluesnearestthelinepathforthecoordinates

SampleatXintervals(x=1)andcomputeeachsuccessiveYvalueasYk+1=Yk+m


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Forlineswithpositiveslopegreaterthan1,reversetherolesofXandY.SampleatunitYintervals(y=1)andcalculateeachsuccessiveXvalueasXk+1=Xk+1/m

Algorithm

Step1:Inputthelineendpointsandstoretheleftendpointin(x1,y1)andright

endpointin(x2,y2)Step2:Calculatethevaluesofxandyusingx=xbxa,y=ybyaStep3:ifthevaluesofx>yassignvaluesofstepsasxotherwisethevalues

ofstepsasyStep4:CalculatethevaluesofXincrementandYincrementandassignthevaluex=xaandy=ya

Step5:fork=1tostepsdoX=X+XincrementY=Y+YincrementPutpixel(ceil(x),ceil(y),15)

Step6:End

2.ExplainBresenhamslinedrawingalgorithm?InBresenhamsapproachthepixelpositionalongalinepatharedeterminedbysamplingunitXintervals.Startingfromtheleftendpoint(X0,Y0)ofagivenlinewesteptoeachsuccessivecolumnsandplotthepixelwhosescanlineY-valueisclosesttothelinepath.AssumingtheKthstepinprocess,determinedthatthepixelat(Xk,Yk)decidewhichpixeltoplotincolumnXk+1.Thechoicesare(Xk+1,Yk)and(Xk+1,

Yk+1)

Algorithm

Step1:Inputthelineendpointsandstoretheleftendpointin(X0,Y0)Step2:Load(X0,Y0)intotheframebufferStep3:Calculateconstantsx,y,2y,-2x,andobtainthedecisionparametersas

P0=2yxStep4:AteachXkalongtheline,startingatk=0,performthefollowingtestIfPk


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thecircumferenceofacirclecenteredontheoriginas(X0,Y0)=(0,r)Step2:CalculatetheinitialvaluesofthedecisionparameterasP0=5/4rStep3:Ateachpositionstartingatkperformthefollowingtest:IfPk=YPk+1=Pk+2YOtherwise,thenextpointis(Xk+1,Yk+1)andPk+1=Pk+2Y-2XStep5:Repeatsteps4Xtimes

4.ExplainEllipsegeneratingAlgorithm?AlgorithmStep1:Inputradiusrx,ryandellipsecenter(Xc,Yc)andobtainthefirstpointonthecircumferenceofacirclecenteredontheoriginas(X0,Y0)=(0,ry)Step2:Calculatetheinitialvaluesofthedecisionparameterinregion1as

P10=ry2-rx2ry+1/4rx2

Step3:AteachpositionstartingatXkpositioninregion1,startingatk=0,performthefollowingtest:IfPk0,thenextpointtoplotis(Xk,Yk-1)and


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22

P2k+1=P2k-2ryYk+1+rxOtherwisethenextpointis(Xk+1,Yk-1)and

222

P2k+1=P2k-2ryYk+1-2rxYk+1+rxStep6:DeterminesymmetrypointsintheotherthreeoctantsStep7:Moveeachpixelposition(X,Y)ontothecircularpathcentredon

(Xc,Yc)andplotthecoordinatevaluesasX=X+XcY=Y+Yc

22

Step8:Repeatstepsforregion1until2ryX>=2ryY

5.ExplainBoundaryfillAlgorithm?

.Iftheboundaryisspecifiedinasinglecolor,thefillalgorithm

proceedsoutwardpixel-by-pixeluntiltheboundarycolorisencountered.Thisiscalledboundaryfillalgorithm.Theboundaryfillprocedureacceptsasinputthecoordinatesofaninteriorpoint(x,y),afillcolor,andaboundarycolor..Startingfrom(x,y),theprocedureteststheneighboringpositionstodeterminewhethertheyareboundarycolor..Ifnot,theyarepaintedwiththefillcolor,andtheneighborsaretested..Thisprocesscontinuesuntilallpixelsuptotheboundarycolorfortheareahavebeentested

.Twomethods

.4-connected4neighbouringpointsareconected.8-connectedcorrectlyfilltheinterioroftheareadefinedprogram

voidboundaryfill(intx,inty,intfill,intboundary)

{intcurrent;

current=getpixel(x,y);if((current!=boundary)&&(current!=nil){setColor(fill);setPixel(x,y);boundaryfill(x+1,y,fill,boundary);boundaryfill(x-1,y,fill,boundary);


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boundaryfill(x,y+1,fill,boundary);boundaryfill(x,y-1,fill,boundary);}


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}

UNITIII

1.Explainreflectionandshear?ReflectionItisamirrorimageofanobjectRotatingabout180degreeFlatobjectmovinginthexyplaneReflectionaboutyaxisflipsxcoordinatesReflectionpointaspivotpointissameasaboveToobtainthetransformationmatrixforreflectiondiagonalisy=-xSequence

Clockwiserotationby45degreeReflectionaboutyaxisCounterwiserotationby45degreeShear

Internallayercausetoslideovereachothercalledshear


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TransformscoordinatepositionasX=x+shx.y,Y=yShiftinthepositionofobjectsrelativetoshearingreferencelinesareequivalenttotranslations2.ExplainLiangBarskylineclippingFasterlineclipperoftheparametricequationofalinesegmentLineparalleltooneoftheclippingboundariesLineintersectstheextensionofboundarykIfu1>u2lineisoutsidetheclippingwindowElseinsidetheclippingwindowClippingisdoneusingthereflectionintheclipwindow3.ExplainSutherlandHodgemanpolygonclippingClippingpolygonwhichliesinsidetheclippingwindow

FourpossiblecasesIfthefirstvertexisoutsidethewindowboundaryandthesecondvertexinsideIfthefirstvertexisinsidethewindowboundaryandthesecondvertexoutsideIfbothareoutsideIfbothareinside

RepeattheprocessofalgorithmConvexpolygonarecorrectlyclippedusingthisclippingConcaveandconvexpolygonarealsoused4.ExplainaboutclippingoperationsClipapicturefromeitheroutsideorinsidearegionknownasclippingAlsocalledasclippingalgorithmTheregionagainsttheobjectisknownasclipwindow

Clippingoperationsondifferenttypesofobjects


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PointclippingPolygonclippingAreaclippingLineclippingCurveclippingTextclippingPolygonandlineclippingarethestandardclippingcomponentsUNITIV

1.Explainthethreedimensionaldisplaymethods?ParallelprojectionTheproductionofthe2Ddisplayofthe3Dsceneiscalledprojection

ProjectpointsontheobjectsurfacealongtheparallellinesontothedisplayplaneDifferent2DviewsofobjectscanbeproducedbyprojectingthevisiblepointsPerspectiveprojectionDonebytheprojectingpointstothedisplayplanealongtheconvergingpointsCausestheobjectsfartherfromtheviewingpoint

shouldbesmallerofthesamesizedobjectpresenthere.DepthCUEINGBasicproblemforvisualizationtechniquesiscalleddepthcueingSome3DobjectsarewithoutdepthinformationVisiblelineandsurfaceidentificationTohighlightthevisiblelines

Displayvisiblelinesasdashedlines


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RemovingtheinvisiblelinesSurfacerenderingLighteningconditionsinthescreenAssignedcharacteristicsDegreeoftransparencyHowroughorsmooththesurfacesaretobeExplodedandcutawayviewsThreedimensionalandstereoscopicviews2.ExplainsplinerepresentationItisreferredtoacurvedrawninadifferentmannerInterpolationandapproximationsplinesSetofcoordinatepointscalledcontrolpoints

Curvecanbetranslated,rotatedandscaledEnclosingasetofpointscalledconvexhullSetofconnectedpointsisoftencalledcontrolgraphParametriccontinuityconditionGeometriccontinuityconditionSplinespecification3.ExplainBeziercurvesandsurfaces

HavenumberofpropertiesCanbefittedtoanynumberofcontrolpointsPolynomialfunctionsbetweenp0andpnnP(u)=pkBEZk,n(u)K=0

Calculatedx(u),y(u),z(u)

PropertiesofBeziercurvesCubicBeziercurvesDesigntechniquesinBeziercurvesBeziersurfaces


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4.ExplaingeneralthreedimensionalrotationsTransformationsequencesP=T.Rx().T.PRotationinfivestepsTranslatetheobjectthatrotatesinparallelcoordinateaxisRotatetheobjectwithonecoordinateaxisApplyinverserotationtoitsoriginalpositionApplyinversetranslationtoitsoriginalpositionV=p2p1AfterrotationtooriginalpositionR()=T.M.T


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UNITV

1.ExplainBackfacedetectionmethodandDepthbuffermethodBackfaceDetectionmethodFastandsimpleobjectspacemethodForidentifyingthebackfacesofapolyhedronBasedioninsideoutsidetestPlaneparametersA,B,C,DAx+By+Cz+D


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2.ExplainareasubdivisionandA-BuffermethodABufferMethodExtensionideaofthedepthbuffermethodItrepresentsanantialiased,areaaveraged,accumulation-buffermethodOnlyonevisiblesurfaceTwofieldsDepthfieldStoresapositiveornegativerealnumberIntensityfieldStoresasurfaceintensityinformationorapointervalueDataforeachsurfaceinthelinkedlistincludesRGBintensitycomponents

OpacityparametersDepthPercentofareacoverageSurfaceidentifierPointertonextsurfaceAreaSubDivisionMethod

Imagespacemethod

TherelativecharacteristicofsurfaceareSurroundingsurfaceInsidesurfaceOutsidesurfaceConditionsforsubdivisionAllsurfacesareoutsidesurfaceswithrespecttothearea


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OnlyoneinsideAsurroundingsurfacewithintheareaboundaries3.ExplainDepthsortingmethodBothimageandobjectspaceoperations]PerformthebasicfunctionSurfacearesortedinorderofdecreasingdepthSurfacearescanconvertedinorder,startingwiththesurfaceofgreatestdepthOftenreferredaspaintersalgorithmTestlistedintheorderofincreasingdifficultySurfacedonotoverlapProjectionsofthetwosurfacesontotheviewplanedonotoverlap4.Explainkeyframesystems

KeyframesystemsMotionpathcanbegivenwithakinematicsdescriptionPhysicallybasedonforceactingobjectFrameintoindividualcomponentorobjectcalledcellsMorphing

Transformationofobjectshapesfromoneformtoanotheriscalledmorphing

TwokeyframesforanobjecttransformationPreprocessingusingvertexcountSimulatingaccelerations

Timeintervalbetweenkeyframeisdividedinton+1t=(t2t1)/n=1tBj=t1+jt,j=1,2,3,Timeforjthin-betweenistBj=t1+t[(1-cos[j/(n+1)])/2],j=1,2,3,.


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Xcs 354 Computer Graphics

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