Kate DEVLIN1, Alan CHALMERS1 2, Duncan …mas01kd/publications/unesco_paper.pdf · Kate DEVLIN1,...
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Kate DEVLIN 1 , Alan CHALMERS 12 , Duncan BROWN 23 1 Department of Computer Science, University of Bristol, UK. 2 ArchLight Ltd., UK. 3 Southampton City Heritage, UK. The current trend for employing three-dimensional computer graphics to represent archaeological sites is limited because their level of realism cannot be guaranteed. The images that are gener- ated may look realistic, but often no attempt has been made to val- idate their accuracy. In order for the archaeologist to benefit from computer-generated representations and use them in a meaningful way, virtual past environments must be more than pretty pictures — they must accurately simulate all the physical evidence for the site being modelled. An often neglected facet of reconstructions is the lighting. Stan- dard three-dimensional modelling packages do not allow precise control over lighting values, and as a result, many simulations show the archaeological site under inappropriate or false lighting condi- tions such as the bright, steady light of the present. Experimental archaeology and realistic lighting simulation allow us to recreate the original lighting of an archaeological site and show it how it might have looked to those who built and used it. Predictive light- ing also opens up new avenues of exploring how past environments may have been perceived, allowing us to investigate on a computer new hypotheses about architecture, art, and artefacts in a safe, non- invasive manner. This paper outlines the need for perceptual realism in virtual her- itage, and examines case studies where the application of predictive lighting techniques have enhanced archaeological interpretation. Keywords: Archaeological reconstruction, realistic computer graphics, visual perception. Current use of realistic three-dimensional computer graphics in ar- chaeology provide the public with a glimpse of the past that might otherwise be difficult to visualise. However, often these images are chosen due to their artistic impact, and have been manipulated to provide the most aesthetically pleasing representation of a site. To date, the emphasis has been on using such images for display purposes, with interpretative and research purposes taking second place to the demand for visually stunning presentation. The per- vasive media of television and the Internet, and the public fasci- nation for the past have seen the adoption of computer-generated representations for entertainment and education of the interested layman, rather than as a research tool for archaeologists. For com- puter graphics to benefit the archaeological community, they must offer the archaeologist the chance to extend or enhance their anal- ysis of a site or artefact. The accuracy of the images produced must therefore be quantifiable — the archaeologist must be con- fident that what they see in the generated image is comparable to what they would have seen in the original example [Chalmers and Devlin 2002]. One area of realistic simulations that is often neglected is that of the original lighting of a site or artefact. Light cannot be cap- tured in the archaeological record and consequently its importance is rarely considered in interpretations of past environments. The ways in which we view, perceive and understand objects is gov- erned by our current lighting methods of steady, bright electric light or large windows, but in order to understand how an environment and its contents were viewed in the past we must consider how they were illuminated. Standard three-dimensional modelling software tends to base the lighting conditions on daylight, fluorescent light or filament bulbs and not the lamp and candlelight used in past. In some cases, scenes are illuminated with lighting values that would be impossible in the real world. Realistic lighting simulation must address both the physical interaction of light in a scene and the spectral profile of the light source. With control over this, an accurately-lit represen- tation of an environment can be achieved and the virtual version of an original site or artefact can be manipulated without having to physically touch or harm the real version. Much has already been discussed on the nature of realistic ar- chaeological representations [Spicer 1988; Reilly 1991; Molyneaux 1992; Reilly 1992; Chalmers et al. 1995; Miller and Richards 1995; Ryan 1996; Daniels 1997; Roberts and Ryan 1997; Gillings 1999; Bateman 2000; Eiteljorg II 2000; Kantner 2000; Chalmers and De- vlin 2002] and the dangers of conjecture and artistic licence. This paper deliberately does not debate the merits of realistic graph- ics, nor does it attempt to define realism. Instead, we provide a framework for creating computer-generated archaeological repre- sentations with quantifiably accurate lighting simulation, and show through the use of case studies how this can generate new hypothe- ses for the archaeologist. Once an archaeological site or artefact has been modelled in a three- dimensional modelling package it must be rendered, that is, the colours, textures, light and shading are computed, thus producing
Transcript of Kate DEVLIN1, Alan CHALMERS1 2, Duncan …mas01kd/publications/unesco_paper.pdf · Kate DEVLIN1,...
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Kate DEVLIN1, Alan CHALMERS1 - 2, Duncan BROWN2 - 3
1 Departmentof ComputerScience, University of Bristol, UK.2ArchLightLtd.,UK.
3SouthamptonCity Heritage, UK.
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The current trend for employing three-dimensional computergraphicsto representarchaeologicalsitesis limited because theirlevel of realismcannot be guaranteed.The imagesthat aregener-atedmaylook realistic,but oftenno attempthasbeenmadeto val-idatetheir accuracy. In orderfor the archaeologist to benefitfromcomputer-generatedrepresentations andusethemin a meaningfulway, virtual pastenvironmentsmustbemorethanprettypictures—they mustaccuratelysimulateall thephysicalevidencefor thesitebeingmodelled.
An oftenneglectedfacetof reconstructionsis thelighting. Stan-dard three-dimensional modelling packagesdo not allow precisecontrolover lighting values,andasaresult,many simulationsshowthearchaeological siteunder inappropriateor falselighting condi-tions suchasthe bright, steadylight of the present.Experimentalarchaeology and realistic lighting simulationallow us to recreatethe original lighting of an archaeological site and show it how itmight have looked to thosewho built andusedit. Predictive light-ing alsoopensupnew avenuesof exploring how pastenvironmentsmayhave beenperceived,allowing usto investigateon a computernew hypothesesaboutarchitecture,art,andartefactsin a safe,non-invasive manner.
Thispaperoutlinestheneedfor perceptualrealismin virtual her-itage,andexaminescasestudieswheretheapplicationof predictivelighting techniqueshave enhancedarchaeological interpretation.
Keywords: Archaeological reconstruction,realistic computergraphics,visualperception.
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Currentuseof realisticthree-dimensional computergraphicsin ar-chaeology provide thepublic with a glimpseof thepastthatmightotherwisebe difficult to visualise. However, often theseimagesarechosendueto their artistic impact,andhave beenmanipulatedto provide the mostaestheticallypleasingrepresentationof a site.To date,the emphasishasbeenon usingsuchimagesfor display
purposes,with interpretative andresearchpurposestaking secondplaceto the demandfor visually stunningpresentation.The per-vasive mediaof television and the Internet,and the public fasci-nation for the pasthave seenthe adoptionof computer-generatedrepresentationsfor entertainment and education of the interestedlayman,ratherthanasa researchtool for archaeologists.For com-putergraphicsto benefitthe archaeological community, they mustoffer thearchaeologist the chanceto extendor enhance their anal-ysis of a site or artefact. The accuracy of the imagesproducedmust thereforebe quantifiable— the archaeologist must be con-fident that what they seein the generatedimageis comparabletowhat they would have seenin theoriginal example[ChalmersandDevlin 2002].
Oneareaof realisticsimulationsthat is often neglectedis thatof the original lighting of a site or artefact. Light cannotbe cap-turedin thearchaeological recordandconsequentlyits importanceis rarely consideredin interpretationsof pastenvironments. Theways in which we view, perceive and understandobjectsis gov-ernedby ourcurrentlighting methodsof steady, brightelectriclightor large windows, but in orderto understandhow an environmentandits contentswereviewedin thepastwemustconsiderhow theywereilluminated.
Standardthree-dimensionalmodellingsoftwaretendsto basethelighting conditions on daylight, fluorescentlight or filamentbulbsandnotthelampandcandlelightusedin past.In somecases,scenesare illuminated with lighting valuesthat would be impossibleintherealworld. Realisticlighting simulationmustaddressboth thephysicalinteractionof light in a sceneand the spectralprofile ofthe light source.With controlover this, anaccurately-litrepresen-tation of an environmentcan be achieved and the virtual versionof anoriginal siteor artefactcanbemanipulatedwithout having tophysicallytouchor harmtherealversion.
Much hasalreadybeendiscussedon the natureof realisticar-chaeologicalrepresentations[Spicer1988;Reilly 1991; Molyneaux1992;Reilly 1992;Chalmersetal.1995;Miller andRichards1995;Ryan1996;Daniels1997;RobertsandRyan1997; Gillings 1999;Bateman2000;Eiteljorg II 2000;Kantner2000;ChalmersandDe-vlin 2002]andthedangers of conjectureandartistic licence.Thispaperdeliberatelydoesnot debatethe merits of realistic graph-ics, nor doesit attemptto definerealism. Instead,we provide aframework for creatingcomputer-generatedarchaeological repre-sentationswith quantifiablyaccuratelighting simulation,andshowthroughtheuseof casestudieshow thiscangeneratenew hypothe-sesfor thearchaeologist.
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Onceanarchaeologicalsiteor artefacthasbeenmodelledin athree-dimensionalmodelling packageit must be rendered, that is, thecolours,textures,light andshadingarecomputed, thusproducing
thefinal two-dimensional imagefrom thethree-dimensional geom-etry. In orderto obtainanapproximationof theoriginal lighting inanarchaeological representation,two factorsmustbeaddressedintherenderingprocess.First,thespectralcompositionof thelight —thecolourof the light givenoff by theburningfuel — mustmatchthatof thefuel typethatwould havebeenusedin aspecificarchae-ological instance.Second,thedistribution of this light — thepathit takesarounda sceneandthereflectionsandinter-reflectionsthatoccur— mustmimic thebehaviour of light in therealworld.
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The only traceof light in the archaeological recordarethe meth-odsusedto provide it, bethey hearths,candles,lampsor windows.In pre-industrialsocieties,daylightwastheregulatingfactorof theworking hours. If we comparethat to conditionstoday, sunlightisfar lessrelevantto how we work [McNamaraet al. 1997].Theevi-dencefrom architecturetellsusthemostaboutlighting — alackofglassanda needfor securityoftenmeantsmallerwindows, there-fore dimmerinteriors. Going further backin time, the unyieldingdarknessof a deepcave would requiresomeform of artificial lightfor navigation purposesalone. It seemsplausiblethat objectsandenvironmentswereaffectedby the limitationsof lighting, andthisinfluencemay have extendedinto their design. By recreatingthemeansof illuminationfor agivenenvironmentandsimulatingit ac-curately, thearchaeologist may(literally) find new waysof viewingthings.
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Thetypeof flamesthatwewishto modelarediffusionwick flames.A typicalflameof thisnatureconsistsof threeparts:theinnercore,theblueintermediatezone,andtheoutercore[GaydonandWolfard1979]. Thesedifferentzonesproducedifferentemissionsdepend-ing on thefuel typeandenvironmentconditions.
Theinitial stepin recreatingthelight sourceinvolvesexperimen-tal archaeology. In consultation with the Departmentof Archae-ology at the University of Bristol, varioustypesof possiblelightsourceswerephysicallyrecreated(Figure1).
Figure 1: Experimentalarchaeology: physical reconstruction offuel types.
Theseincludedtallow candles(of vegetableorigin) and reedscoatedin vegetabletallow, a renderedanimal fat lamp, beeswaxcandles(processed and unrefined)and olive oil lamps(one witholiveoil only, onewith oliveoil andsalt,andonewith olive oil andwater).
Eachof thesefuels producesa differentcolour whenburnt. Toobtain this unique spectralprofile for eachfuel, detaileddatawasgatheredusinga spectroradiometer, a device thatmeasurestheab-solutevalueof thespectralcharacteristicswithout makingphysicalcontactwith theflame. Thespectroradiometermeasurestheemis-sionspectrumof the light sourcein thevisible bandwidthsin 5nm
increments,thus providing an accuratebreakdown of the flame-light compositionof eachfuel type. The measurements werealltakenin acompletelydarkroom,andthemeasurementsweretakenagainstadiffusewhitepowder(EastmanKodak Standard,99%op-tically pure). An averageof ten readings wascalculatedfor eachfuel type.
The resultingluminairedatawasconvertedinto red, greenandblue(RGB)valuesto enabledisplayon acomputermonitor. TheseRGB valuesprovide uswith thedatarequiredduringtherenderingprocessto simulatethefuel typeof theoriginal light source.
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The advent of ray-tracingand radiosity in computer graphicshasenabledthe simulation of light interaction, providing renderingtechniquesthat mimic the physicalbehaviour of light in a scene.Despite the availability of physically-basedrendering softwaremany userspreferto produceimagesthatareaestheticallypleasingratherthanperceptuallyaccurate[Ward1994]. Also, wheretheuseof predictive lighting softwaremayrequiresomespecialistknowl-edge,accessto standardmodellingsoftwareis oftenavailablein amoreuser-friendly form. In many casesthis canleadto problemswith the validity of computersimulationswherethe usermay —dueto time or varying areasof expertise— lack theskills desiredto createa meaningful model, though be fully able to produce anattractivepicture.
The renderingpackageusedto createthe imagesfor the casestudiesin this paperis Greg Ward’s Radiance[Ward 1994]. Ra-diance is a lighting visualisationtool kit that accuratelycapturesluminanceand radiances,modelsa variety of illumination types,supportsa variety of reflectancemodelsandsupports complicatedgeometry[Ward Larsonand Shakespeare1998]. The RGB val-uesthat have beenmeasuredfrom the original light sourcescanbe usedin Radianceas lighting valuesfor a computer-generatedmodel,meaningthata scenecanberenderedunderits appropriatelighting conditions.
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Conversionof thespectralprofile of theilluminantsto RGBvaluesfor usein a computersimulationdoesleadto anapproximationofthe colourspresent.However, at presentthis is the mosteffectivemethodin termsof computational time andefficiency. Even withtheapproximation,significantperceptualdifferencesrelatedto vari-ationsin fuel type areapparent. Psychophysicaltestscanbe usedto validatesimulationsandcompare themwith realscenes[McNa-maraetal. 1998;McNamaraet al. 2000; Chalmerset al. 2001].
Figure2: Simulationwith mod-ern 55wlighting.
Figure3: Thesamesceneundertallow lighting.
Figures2 and3 show a testscenecontaininga MacBethcolourchartilluminatedwith modernlighting andlight from atallow can-dle. The differencein fuel type has a discernibleeffect on theappearanceof the MacBethchart. Given the type of lighting that
would have beenusedin pastenvironments, this demonstratestheneedto investigatesitesandartefactsundertheir original lightingconditionsto ensureweseethemasthey wereintendedto look.
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Thefollowing casestudiesdemonstratehow predictive lighting canbe usedto benefitthe archaeologist throughthe developmentandtestingof new hypotheses.All threeexamplesusethe techniquesdescribedabove, with the archaeological datasettaken from, re-spectively, measurementsmadeby a tapemeasure,a scaleplan,anda laserscanner. All textureswerecreatedfrom photographs,with theinclusionof a colourchartfor calibration.
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Theinitial impetusfor work onvalidatedilluminationwastheques-tion as to how medieval potswould have looked in their originalsetting[McNamaraetal. 1997].
Figure4: Examplesof medieval pottery.
This casestudyconsidersthe waysin which medieval interiorswereilluminatedandhow lighting conditionsmightaffect thewaysin which objectswereperceivedanddesigned.
Figure5: Medieval housesimulation.
A computer-generatedmodel of the hall of a medieval townhousewascreated.Themodel is basedon theMedieval Merchant’sHousemuseumin Southampton,a half-timberedstructurereno-vatedby EnglishHeritageasaccuratelyaspossibleto representa13thcenturydwelling of someeconomic status.
Figure6: Medieval housesimulation(elevatedview).
This modelallows usto examinethemedieval potteryin a closeapproximationto its original setting(Figures5 and6. This revealsdetailsthat may bring insight into medieval ways of living. Forexample,only the top half of somejugs areglazedanddecorated,andthis is perhapsindicative of how they wereilluminatedin use,perhapsby daylight throughwindowsor perhapsfrom torcheshungon walls, suggestingmany potswould have looked brightestwhenlit from above (Figure4).
Even morecrucial is the relationshipbetweenlight andcolour.As shown, colourswill changein appearanceaccordingto thetypesof light sourcepresent.Therecreationof medieval lighting condi-tionsis thereforeseenasa vital stepin comprehending attitudestocolour, andeventuallyperhaps,shapeanddecoration. If thereis anysymbolicmeaningin theuseof colouronpotterythenthismightberevealedthroughanexplorationof medieval perception,throughtherecreationof a medieval environment.Themodellingof a realisticenvironment throughtheapplicationof computergraphicsandpsy-chophysics,is potentiallythemostfar-reachingandflexible way ofexploring humanperceptionsin thepast.
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For highly-decorative interiors,predictive lighting canbeusefulintestinghow a roommayhave beenlaid out or usedby theoriginalinhabitants. The UNESCOWorld Heritagesite of the Archaeo-logical Areasof Pompeii,ErcolanoandTorre Annunziatacontainfine examplesof Romanfrescoes.TheHouseof theVettii in Pom-peii waschosenfor thestudy, with thework focusingonareceptionroomoff thecolonnadedsculpturegarden[Nappo1998]. Thisroomis lavishly decoratedin theIV Style(Figure7) andwaschosendueto the rich colours,goodstateof preservation, andartistic effectssuchas trompel’oeil , a painting technique that deceives the eyeinto viewing a two-dimensional imageashaving three-dimensionalstructure. The frescoeswere recordedphotographically, with the
Figure7: Theroomin theHouseof theVettii asit appears today.
useof a colour chart for calibrationpurposesandto identify illu-minationlevels. A three-dimensional modelwasgeneratedfrom ascaleplan. The mostreadily availablefuel type for this areawasdeemedto beolive oil, sothespectralprofile of theolive oil lampswasusedto illuminate the scene.Also, a technique for includingreal flamecapturedfrom video footageandinsertedin the virtualscenegave a realisticappearanceto the lampswithout having tomodeltheactualflame. Therefore,thevirtual scenecontained thecorrectillumination levels for a scenelit by olive oil lamps,with arealflameincorporated(Figure10). Full detailsof thiswork appearin Devlin andChalmers[2001].
In theresultingimagesit is plainly demonstrable how thescenesvary depending on how they areilluminated. Undermodernlight-ing conditions (Figure8) suchaswe might seetoday, the coloursarenotasvibrantasthey appearunderlamplight (Figure9). Whenviewed underolive oil lamp, the red andyellow paint of the fres-coesis particularlywell-emphasised.Also, the trompel’oeil art-work resemblingmockwindows andexternalarchitectureactuallytakeson theappearanceof a realview to theexterior asthe three-dimensional depthcuesareincreased.
Figure8: Simulationviewedun-der modernlighting.
Figure9: Simulationviewedun-der oliveoil lamp.
By changingthenumberandthepositionsof thelight sourcesintheroom,variouseffectscanbeachieved.
It is possibleto testhow lighting may have beendistributed inorderto highlight the artwork in the mosteffective manner. Suchpositioningof lighting may have determinedthe arrangementoffurniture in a room. Again, suchmanipulationsarepossiblewhenworking with avirtual versionof thescene.
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As a way of illustrating thepotentialcomputer graphicshasto of-fer archaeology we considertheprehistoricsiteof CapBlanc. Therocksheltersiteof CapBlanc,overlookingtheBeaunevalley in the
Figure10: Simulationviewedunder olive oil lamp, with furnitureto showshadoweffects.
Dordogne,containsperhapsthe mostdramaticandimpressive ex-ampleof UpperPalaeolithichaut-reliefcarving.A friezeof horses,bison and deer— someoverlaid on other images— was carvedsome15,000yearsagointo thelimestoneasdeeplyas45cms,cov-ering13mof thewall of theshelter. Sinceits discovery in 1909 byRaymondPeyrille severaldescriptions,sketches,andsurveysof thefriezehave beenpublished, but they appear to be variablein theirdetailandaccuracy .
In 1999, a laserscanof was taken of part of the frieze (Fig-ure 11) at 20mm precision[RobsonBrown et al. 2001], usinganeye safelaserto ensuretherewasno possibility of damageto thesite. Figure 11 shows part of the frieze from Cap Blanc. Some
Figure11: Part of thefriezefromCapBlanc.
55,000pointswereobtainedandconvertedinto a triangularmesh.Using detailedphotographs astextures(eachwith a rock art chartto enable colour calibration)and appropriatelighting values,themodelwasthenrenderedin Radiance. Figure12 shows the horseilluminated by a simulated55W incandescentbulb (as in a low-power floodlight), which is how visitorsview theactualsitetoday.In Figure13 the horseis now illuminatedby an animalfat tallowcandleasit mayhavebeenviewed15,000yearsago.Ascanbeseenthedifferencebetweenthetwo imagesis significantwith thecandleillumination giving a warmerglow to thescene,aswell asincreas-ing theshadows. Thedynamic natureof theflame,andits position
Figure12: Thesimulationunder55wincandescentbulb.
Figure13: Thesimulationunderanimalfat lamplight.
in theenvironment alsocontributeto changesin perception.For this site,we wantedto investigatewhetherthe dynamicna-
ture of flame, coupledwith the careful useof three-dimensionalstructure,mayhavebeenusedby ourprehistoricancestorsto createanimationsin the cave art sitesof France,15,000yearsago. Theshadows createdby themoving flamedo indeedappearto give thehorsemotion. We will never know for certainwhetherthe artistsof the UpperPalaeolithicwerein fact creatinganimations15,000yearsago,however the reconstructionsdo show that the effect iscertainly possible. There is other intriguing evidence to supportthis hypothesis.As canbeseenin thefigures,thelegsof thehorsearenot presentin any detail. This haslong beenbelievedto bedueto erosion,but this doesnot explain why is therestof thehorsenotequally eroded. The possibility exists that the legs weredeliber-atelynot carved in any detail, therebyaccentuatingany motion bycreatingsomeform of motionblur. Furthermoretracesof redochrehavebeenfoundon thecarvings. It is interestingto speculateagainwhetherthe applicationof red ochreat key points on the horse’sanatomymay alsohave beenusedto enhance any motion effects.Again, lighting simulationprovidesanopportunity to exploresuchscenarios.
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Theaccuratesimulationof lighting typeanddistributiongoessomewayto quantifyingthelevel of realismin acomputer-generatedrep-resentation,but the imagemuststill be placedin context to avoidmisinterpretation.Theprovisionof additionalinformation— meta-data— is still necessary.
In a subjectsuchasarchaeology wherealternative explanationsmay be equally plausible,the option to move betweena numberof different interpretationsis undoubtedly important. A form ofstandardisationis mostdesirable,but ratherimpracticalgiven thediversescopeof thesubject.In thesameway that thearchaeolog-ical evidenceon anexcavation needsto berecordedasthoroughlyaspossible,so too doesthe processusedto createthe computer-
generatedrepresentationssothatall thefactorsmight bedisplayed,allowing theuserto make up their own mind basedon thesupport-ing material. If we strive to provide informationaboutthe under-lying decisionstaken in the creationof our work thenour virtualworldshave thepotentialof beingmeaningful, usefulpiecesof in-formation.
Additionally, displayfactorsneedto betakeninto considerationso that coloursand light levels areportrayedeffectively, whetherthefinal imageis shown on acomputermonitor, onanaudio-visualdisplaysystem,or asa printedpage[ChalmersandDevlin 2002].
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This researchinto colour and light hasshown how easyit is forour own preconceptionsto intrudeinto the wayswe view archae-ological objectsor sites. The aim is to find methodsof analysisthat could take us beyond thosetypical questionsof chronologyandprovenance. If the goal of archaeology is to provide insightsinto thelivesof pastindividuals, communitiesandculturesthenweneedto show a greaterrespectfor the thingsthey have left behindandattemptmorerefinedwaysof understanding them.
A definitive explanationshouldnever be expectedin archaeol-ogy. Archaeologyby its verynatureis dynamic,with new ideassur-facingdaily. Visualisingapastenvironmentis fraughtwith difficul-ties from the outset,so a meansof validatingcomputer-generatedrepresentationsprovidesanexciting opportunity to exploreandtestnew ideas,with computergraphics becomingasbeneficialto thearchaeologistasthey areto thepublic.
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ThankstoPatrickLeddafor theuseof hisimagesfrom theMedievalHouseproject.
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Kate Devlin is a PhD student and research mem-ber of the graphics group in the Department ofComputer Science at the University of Bristol, UK.
Her undergraduatedegreewasin archaeologyand sheworked as a field archaeologist andsite draughtsman for two yearsbeforestudy-ing for an MSc in ComputerScience. Herresearchinterestsare realistic archaeologicalreconstructionsof flame-lit environments andaccuratedisplayof suchscenes.Her personalinterestslie in representationand interpreta-tion of archaeological records. She may becontactedat: Dept. of ComputerScience,
UniversityofBristol,WoodlandRoad,BristolBS81UB,UK. Email:[email protected]: http://www.cs.bris.ac.uk/˜devlin/
Alan Chalmers is a Reader in the Department ofComputer Science at the University of Bristol, UK.
He haspublishedover 80 papersin journalsandinternationalconferences on very realisticgraphics. His researchis investigating theuseof very realistic graphicsin the accuratevisualisationof archaeological sitereconstruc-tions and techniques which may be usedtoreducedcomputationtimes without affectingthe perceptualquality of the images. He isTechnicalDirector of ArchLight, a companydedicatedto creatinghigh fidelity computer
generatedflame-lit environments. He may be contactedat: Dept.of Computer Science, University of Bristol, Woodland Road,Bristol BS8 1UB, UK. Email: [email protected]:http://www.cs.bris.ac.uk/˜alan/andhttp://www.archlight.co.uk/
Duncan Brown is the Curator of Archaeological Collec-tions at Southampton City Heritage, UK; a visiting Re-search Fellow at the University of Southampton, UK; anda freelancemedieval pottery specialist who has spent severalyears digging in Bucks, Northants, Wales, Sussex, Cheshire.
He hasworked on assemblagesfrom FyfieldDown, Winchester, the Tower of London,Reading, the Mary Rose, Guernsey, Isle ofWight and elsewhere. Duncanspecialisesinpottery imported from mainlandEuropeandhas taughtceramicanalysisat BournemouthUniversity andarchaeologicaltheoryat KingAlfred’s College. Duncanhasbeenco-editorof the newsletterof the Societyfor MedievalArchaeology, Secretaryof the Medieval Pot-
teryResearchGroup,foundercommitteememberandsubsequentlychair of the IFA Finds Group. He may be contactedat: CityHeritage Services,SouthamptonCity Council, Southampton,UK.Email: [email protected]
