5.1.08 Ayman Hassaan Mahmoud Pp 114 126

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ASSESSMENT OF VISUAL PERCEPTION OF WEB-BASED VIRTUAL

ENVIRONMENTS SIMULATIONS OF AN URBAN CONTEXT.

Aym an Hassaa n A. Mahmoud

Archnet-IJAR, Interna tiona l Journa l of Architec tural Research

Copyright © 2011 Archne t-IJAR, Vo lume 5 - Issue 1 - Ma rch 2011 - (114-126)

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AbstractThe existing resea rch literature on environme nta lpe rcep tion is a b od y of work mainly ba sed on the useof static representation of environments. However,the real world is usually experienced in a dynamicexperience. Virtual environments’ technologies offerthe potential to produce simulated environmentsthat create the impression that we are in spacesother than those we actually occupy. A review of

literature on environmental perception revealedtwo c omp onents of percep tion: “ spa ce -based”and “ objec t-based” percep tion. An experiment wasco nduc ted to investiga te visual percep tion ob tainedfrom a direc t experience of an urban landsca pe a ndfrom its representa tions in desktop virtua l environm ents(desktop VEs). The issues investiga ted we re: ac c urac yof spa ce -based and objec t-based visual percep tionobtained from the physical environment and fromdesktop virtual environment. A series of tests were

administered to assess the visual perception ofparticipants who explored the urban environmentfollowing a direct experience, and X3D-VRMLmo de ls. The results indica ted that pa rtic ipants whoexperience d the X3D-VRML mo de ls cond uc ted fewe rerrors in spa c e-based percep tion tests. There wa sevidence that participants in X3D-VRML perceivedmore objects than their counterparts in the physicalenv ironm ent . Similarities and d ifferences betw eenthe physical and virtual environments were discussed

suggesting the potential and limitations of desktop

VEs in environmental representation. An agenda for

future resea rch w ork is sugg ested .

KeywordsVisual p ercep tion; web -ba sed virtualenvironme nts; X3D; VRML; simula tion; urba nspace.

Introduction

Bell et al. (1996) defined “environmental

perception” as “the processing of the sensoryinformation encountered in everyday life”.Theo ries of v isua l attention a rgue tha t o bservers

focus attention on an object in a complexsc ene . (Desimone a nd J. Dunc an, 1995) In avisual scene, objects’ forms are locally based

on a contiguous geometric structure, such ased ge s, bo unda ries and c onto urs. Disc rete loc alpa tches ca n be percep tually linked , based on

similarity o f texture, c olor and other fea tures, toform whole o b jec ts (Feldm an, 2003).

There a re two theories of visua l perc ep tion,including “ spa ce -ba sed” and “ ob jec t-ba sed ”theories. Advocates of the “space-based”

perception theory imply that perceptual



Archne t-IJAR, Interna tiona l Journal of A rchitec tural Research - Volume 5 - Issue 1 - Marc h 2011

Assessme nt o f Visua l Perc ep tion o f Web -Based Virtua l Environme nts Simulat ions of a n Urban Co nte xt

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att ention selec ts reg ions of spa c e indep end entof the o bjec ts they c onta in (Posner and Cohe n,

1984; Treisma n, a nd Ge lad e, 1980). This mo delhighlights the significant role of boundariesof the space (e.g., walls, and buildings) onour sense of perception; however, elementswithin the space do not play an equivalentrole. Advocates of “object-based” perceptionsugg est that p ercep tual attention selec t objec tsrathe r than reg ions of spa c e (Kahne ma n et a l.,1992). This, in c on trast w ith the spac e-b asedmodel, highlights the significance of elementswithin the space in establishing a consistentsense of pe rc ep tion.

Spa c e-ba sed theo ry of pe rc ep tion assumesthat space is represented by a two- or three-dimensional map of locations with objectsrep resented as points in spac e. This the oryassumes that distance between objects isrep resented by “ Euc lidea n” m etric va riab les

(Wolfe, 1994). The sign ific anc e o f these theo riesis tha t they provide gu idelines for unde rsta nd ingthe wa y the urba n environm ents are pe rc eivedby the potential users. A substantial body ofliterature investigated the perception of urbanspa c es indic ating a relationship be twe en shap eand pe rc eived area (Ishikawa et al. 1998).

Object-based theory of perception indicates

that spa c e is rep resented as a tw o-dimensiona lor three -dimensiona l a rray of ob jec ts orga nizedby “ Gestalt” grouping princ iples (i.e., go od nessof fo rm). This theo ry ab andons the Euc lidea ndistance. In vision, this mode of perceiving isdescribed as a biased competition betweenperceptual objects. (Desimone and Duncan,1995). Biased competition takes placeautomatically and ubiquitously when thereare multiple objects in a scene. Which object

wins the “competition” depends upon bothon the inherent salience of the objects and

the influence of volitional, top-down attention,which biases the competition to favor objects

with d esired pe rc ep tual fea tures (Desimone andDunc an, 1995; Yantis, 2005; Shinn-Cunningha m,2008).

The existing resea rch literature in e nvironm enta lperception is a body of work mainly based onthe use of static representation of environments(Nasar, 1994). How ever, the rea l world is usua lly

experienc ed in a d ynam ic experienc e. Throug ha program of research, Gibson (Gibson, 1979)indicated how movement enhances theprocess of perceiving environm enta l fea tures. Asma ll numb er of resea rche rs in the environm ent-behavior field have stressed the significance ofdynamic representation of the environment(Ap p leya rd et a l., 1964; Lync h, 1960; Thiel, 1997,Heft and Nasar, 2000).

Visual Perception of Virtual Environments

Virtua l environme nts a re desc ribed as a “ purerepresentation of the external world, extendingit by p enetrating inside o bjec ts, enlarging t hem,and transcending space and time” (Pragierand Faure-Pragier, 1995). Virtual environments’technologies offer the potential to producesimulated environments that create theimpression that we are in spaces other thanthose w e a c tua lly oc c up y (Amith, 1998). Therationale of using 3D-computer representationin further includ es tha t it c ont rols possible fa c to rsaffec ting the percep tion of the area o f an openspace. It also creates a hypothetical realityof walking in an actual city. It enables one toc ollec t d ata in a less c ostly way tha n in a fieldsetting.





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Percep tion of ab strac t virtual e nvironme nts hasbee n d isc ussed (Wann and Mo n-Williams, 1996).

“ Dep th sensitivity” w as defined as the ratio ofviewing distance to the depth discrimination

threshold, hence the sensation of reality ina picture occurs because of visual depthperc ep tion (Wa nn a nd Mo n-William s, 1996). This,in fact, indicate d that p erce ption of depth anddistance in virtual environments is no differentfrom physical environments as it depends oneq uivalent cues for dep th pe rce ption.

Wann and Mon-Williams (1996) argued thatdisplay of virtual environments should satisfycriteria that arise from the nature of humanspatial perception. Perceptual criteria wouldac t as the found at ion of a n effec tive VE d isp lay.They propo sed tha t VEs-ba sed design m ustconcentrate on the user’s “perceptual-motorcapabilities” in the context of the undertakentask. Shap e c onstanc y, ac cording to Borresen

& Lichte (1962), involves requesting that theviewer make some estimate of the geometricproperties of an object. It does not disappearduring stat ic, mo noc ula r view ing. This c onc lude sthat perception of a virtual environment couldbe enhanced if virtual objects are close tousers’ internal 3D-models and their geometry,and further, by relating them to the realisticsurroundings.

Most of the virtual environments-basedpresentations include desktop virtualenvironments (desktop VEs), which, are mostlyd isp laye d o n 2D sc reens (Pimente l and Teixeira ,1995, Burde a et a l., 1996). The p rob lem m ightbe that the 3D simulated environments aredisplayed in a pictorial display. Hence, ifthe desktop VEs are used in environmentalrepresentations, some limitations should be

considered, for example, the effect of viewinga pict orial d isplay from to o c lose o r in a dd ition

far. Percep tion of d esktop VE is expec ted to berathe r different from pe rc ep tion o f ob jec ts in 3Dimme rsive VE, and c onseq uent ly, mo re d ifferentfrom pe rcep tion in rea l environm ents. Som ede pth m isjudg ments would b e expec ted.

Ishikawa et al. (1998) empirically investigatedthe percep tion of the area o f an ope n spa ceusing desktop VEs to present subjects with asimulated environme nt. Their rep resenta tion

created a “hypothetical reality” of being inan actual city. However, it was limited by lackof rotation options, fixed masses’ he ights. The irresults showed that shape and location of anopen space affect the perception of the area(width/depth ratio effect & visible area effect).

The o b jec tive of this paper is to e xplore thedifferences in visual perception in virtual

and real environments. An experiment wasc ond uc ted to investigate the visual percep tionsob tained from a direc t experience of an urbanlandscape and from its representations indesktop virtua l environm ents (desktop VEs). Theissues investigated were: accuracy of space-based and object-based visual perceptionobtained from the physical environment andfrom desktop virtual environment.

VRML is one of Web 3d technologies that hasbe en in existenc e sinc e 1995 and has bec om ethe most popular tool for providing interactive3D mod els on the Web Seve ra l Web 3dtec hno log ies suc h as Pulse3D, Cult3D, Viewpointand Shoc kwave3D, etc. are developed orbeing developed now but only VRML can bepractically used for walk-through simulation.VRML is a high-performance language for 3D


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visualization on the WWW (world wide web).As a p rog ram ming langua ge and library for 3D

computer graphics, VRML has many functionssuch as shading, setting objects, projection,and texture ma pp ing. Virtual reality wo rlds ca nbe easily built on the WWW with this tec hnolog y.VRML 1.0 wa s introd uc ed in 1994 and VRML2.0 (97) with more dynamic and interactivefunctions was made in 1996. GeoVRML andX3D, whic h a re the suc c essors of VRML, arecurrently being developed. In this study, VRML97 wa s used in the p resen t syste m. Users workingwith a browser who supports VRML can easilydownload programs written in VRML from theWWW and view 3D images on their personalc om pute rs. These VRML b rowsers a re ava ilab lefor the Window s, Mac intosh and Unix op eratingsystems, as well as other platforms. In this study,Co smo Playe r2.1.1 (Silico n Graphics Inc .) wa sused as a VRML browser with Internet Explorer6(Microsoft Inc.) on Windows (Microsoft Inc.).

Severa l VRML b rowsers were tested on Inte rnetExplorer and on Netscape with Windows XP(Servic e p ac k 3).

The rend ering spee ds of these VRML browserswe re almo st the same . To w rite and run VRMLc od e only a VRML b rowser and Inte rnet b rowserare required. Cosmo Player and other VRMLbrowsers c an b e d ow nloa de d a s freew are, and

the development environment can be builtec ono mica lly. VRML c rime ma ps a re more usefulas they allow a better understanding of data.3D VRML mod els a llow users to explore the da taby animations and various manipulation tools,e.g . tilting a nd rota ting (Lod ha et a l., 1999).VRML is rec ent ly be ing rep lac ed by X3D (Bulla rd,2003) based on the “eXtensible” MarkupLang ua ge (XML). The Web3D Consortiumand the World Wide Web Consortium (W3C)

have established X3D as an XML-compliantISO sta nd ard for inte rac tive 3D on the w eb

(Kumaradevan and Kumar, 2001). X3D usesXML to express the geometry and behaviorc ap ab ilities of 3d mo dels (Brutzma n, 2002), yetas it is extensible, meta da ta m ay b e em be dd edin the file a nd linked to any o ther spa tial or non-spa tial d ata set. The p ow er of this tec hnologyis that it permits a user to interact with theembedded datasets in the 3D model in realtime o ver the Inte rnet . The use o f level-of-deta ilnode s enab les da ta tha t is ‘o ut of sc ope ’ to b eignored, assisting na viga tion and ma nag eme ntof complex large environments (Barton et al.,2005).

Previous stud ies ha ve suc c essfully presente dvirtual tourism sites, through which users canaccess virtual models of towns and cities, orinterrogate information regarding culturalherita ge. These inc lude we b sites c onta ining

navigable VRML models, where an emphasisis placed on providing pertinent data as usersmo ve throug h a spa c e (for examp le, Salga doet al. 2001; Webb and Brotherhood, 2002).These stud ies we re c onc urrent with resea rc h,which concentrated on the developmentof the VRML technologies themselves, whichallowed users to navigate interactive andphoto-rende red spac es (Sc haerf and Tessicini,

1999). A key streng th o f suc h systems a re tha tthey are ca pa ble of c ontaining a nd d isplayinga suitab le rang e of text and image ba sed da ta,potentially selected and presented in responseto specific user characteristics (for example,Bonfigl et a l. 2004; Tan e t a l., 2006).

Developments in the construction andpresenta tion o f virtua l environm ents sugge st tha tit is time to rec onsider experiential ap proa c hes




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to preference resea rc h rejec ted a s too c om plexin the 1980’s. Som e a spec ts of b eha vior in the

land sca pe c an now be effectively observed in ac omp uter-generated world at rea sonab le co stand with more complete control of variables(Groner, R., at al., 2004; Bishop et al., 2001).

Methods

Participants

Participants included undergraduate and

postgraduate students and workers randomlyselected from an Egyptian University Campuswithin the Grea ter Cairo Reg ion. 110 participa ntswere recruited to take part in between users’experime nt. 58 pa rticipants we re fem ale a nd 52we re ma le. Their ave rage age wa s 32. Further,96% of participants had a minimum of a highschool standard education. Participants wererandomly assigned into two groups, including,c ontrol group (N = 20), and experime ntal groups(N = 20).

The Environm enta l Displa y

The University c amp us wa s utilized in thisinvestigation based on a number of criteria.Ac c ording t o Boo th (1983), since the resea rc h isde signa ted to p rovide enhanc eme nt to the visualsimulation o f a n environm ent , it w as essentia l toconsider the use of an environmental contextthat rep resents a variety o f land sc ap e e lem ents.Danford and Williams (1975) provided a set ofcriteria that could be used in selecting studyareas for landscape preference investigations.Ac c ording to their c riteria, the study a rea wo uldfulfill (a) homogeneity in design; (b) relativeisolation from external environments; and (c)accessibility and proximity for participants.Fig. (1) illustrates the layout of the university

campus.

The Stim uli-Set

The stimuli-set em ployed in this investiga tioninclude d t wo urba n spac es within the UniversityCa mp us. The stimuli set for the expe rime nta lgroup (X3D -VRML group) included an X3D-VRML simulation model of the same urbanspac es. The deskto p V.E. system inc lude dhardwa re, software, and a geo metry data ba se.The ha rdw are included an IBM c om pa tible

PC equipped with an Intel Pentium Duo 2Co re p roc essor 3.4G, 4 GB RAM , 320 GB ha rddisk, and 512 MB graphics card. Input deviceinc lude d stand ard op tica l 2-D mouse, while theoutp ut de vic e included 17 inc hes PC true co lorLCD monitor. The softw are used to c rea te thevirtua l mod el include d 3D Stud io Ma x version9.0 software, Flux Player version 2.1 plug-In asan X3D-VRML brow ser. All sof tware w as running

und er the M icrosoft Windo ws 7 op erating systemplatform.

Perce pt ion o f d esktop VEs representa tions wo uldbe more successful in replicating perceptionof the real environment if few guidelines wereapp lied (1997). Synthesis of c om pone nts of t hevirtual environment followed the “geometricalp rinc iples” of the ir real w orld c ount erpa rts. Thisincludes replicating the actually proportions,sha pe s and units. The g eo me try da ta basewas adapted from a former digital surveyof the campus. On-site measurements werec onduc ted to ed it the existing d ata ba se a ndto up da te impo rtant g eom etric al de tails. The3D CAD model followed basic morphologicaldetails of both masses (e.g., openings, massgeometry, and projected/recessed ornaments)and spa c es (e.g., ground a nd spa tial veg eta tion




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elements, land topography, stairs and ramps).Prima ry 265-colour ind ex wa s used to rep resen t

a te xture d ifferenc e.

Surround ings (e.g., b uild ing fa c ades) a s we ll asthe discrete elements within the space (e.g.,furniture elements) were carefully considered.“Landmarks” were emphasized by contrastingc olors or sha pe s. Multiple “ va nta ge points”were provided within the virtual environmentsusing “cameras” to offer alternative viewpointsfor users to start their navigation. Objects

were related to foreground and backgroundaccording to actual physical relationships.Sense o f naviga tion wa s ma intained using a35-mm (Focal length) camera representinga human eye placed 170-cm above theground. Eac h of the three c am eras wa scarefully placed to maintain a vantage pointfrom which participants would be asked tostart their navigation. Desktop VEs, however,

were expected to show some limitations ofunderstanding of depth; these limitations werema nag ed providing sc ale referenc es within thevirtual environment, for example, consideringfloo r pa tte rns. The final model is illustrated infigure (2).

“ Bitma p” textures we re no t used for three reasons.First, the resea rch was no t inte rested in simula tingthe very details of textures of the environmentbe ca use this wa s not recom mend ed by Kap lan(1977). Sec ond , to avoid large r file sizes in o rde rnot to affect the rendering speed of the X3D-VRML brow sers a t the end . Third , 3D Stud io Maxrecommended minimizing the use of “texturemaps” and keeping the “polygon count” ofthe objects down as they were consideredeffec tive fac tors in enha nc ing the pe rformanc eof the X3D-VRML mo del. The X3D-VRML mo del

wa s expo rted from 3D Stud io Ma x using theVRML 2.0 exp ort p lug-In. The final VRML model

inc lude d the three-d ime nsional ge om etry, initialview po int for a nima tion and textures.

Procedure

The Rea l Environm ent Experienc e

Partic ipa nts we re hand ed a self-rep ort form tha tinclude d the p ercep tion tests. They w ere askedto spe nd 10 minutes mo ving throug h the spa c e

A respectively, they were asked not to moveoutside the boundaries and to move freely toexplore d ifferent sides of the spac e.

The o ff-site pa rt o f the t est includ ed sketc h-map-drawing task. Participants were asked togather in a room that was isolated from theenvironmenta l context, and were given a blankA4 size shee t o f p aper. They we re asked torecall their guided tour within the spaces and

represent it in a d rawn sketc h. Participa nts we reasked to inc lude all eleme nts they c ould reca llfrom me mo ry to assist in d irec ting the strang er.

Proc ed ure for Virtua l Environm ent Naviga tionParticipants of the VRML group performed allthe tasks in a lab-like condition. Participantsperformed the test one at a time. After beinghanded the self-report form, participants were

asked to take a seat and were introd uced to thedesktop virtual environment system providedto the m. The test p roc eed ed throug h threephases, including pre-training, desktop virtualenvironment navigation test, and sketch-mapdraw ing test.

In pre-training, the researcher demonstratedthe functions of each device of navigationtoo ls of the d esktop virtua l environm ent system .

A t f Vi l P ti f W b B d Vi t l E i t Si l t i f U b C t t




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Participants were asked to practice on thedesktop virtual environments system for about

5 minutes in an abstract simulation that wasd ifferent from t he simulation selec ted for the testpha se. The p rac tice environme nt wa s of a simila rstructu re to those used in the c orrespond ing te stc ond ition. They we re a sked to naviga te throughthe virtual environment to reach a particularpoint a nd retu rn to the sta rt po int. This p re-training e xerc ise w as thought to e nha nc e users’familiarity with the na viga tion too ls. A number ofpa rtic ipants rep orted d iffic ulty in ma nag ing thenaviga tion d evice s; yet, they ma stered the m b ythe end of the 5-minute p re-training session.

Participants started the navigation from thesame point from which the participants ofthe control group started. Participants usedthe two-dimensional navigation device tonavigate through the three-dimensional virtual

environm ent using a set o f butto ns at the b otto mof the sc reen.

Participants were given the same instructionsas those g iven to the p artic ipants of the c ontrolgroup . They w ere a lso restric ted with the sametime-allocation for each task. Participantshad the freedom to decide the route of theirnaviga tion within the spa c e. A few p artic ipa ntsexpe rienc ed p rob lems in retu rning to their initia lview po int, at that stag e. The resea rc her had tointerfere in order to he lp the p artic ipant.

In order to extract components of visualpe rce ption data from sketch ma ps two m ethodswere applied. First, to extract the space-ba sed p ercep tion ac curac y, eac h map wa sc onverted into a d igital forma t by sc anne r, and

files were imported into AutoCAD Architecture2008 software in order to be converted into a

Figure 1: Layo ut o f the University Ca mp us.(Sourc e: Auth or). Figure 2: Sna pshot o f the VRML simulatio n from p osition A .(Sourc e: Autho r).

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vec tor format. The a im of c onverting the m ap sinto a vector format was to determine the

geometrical parameters of the shapes of thedraw n eleme nts of spa c e. Those g eo met ric alparameters -including shape indices reportedby Ebdon (1985)- would be considered aquantitative measure of environmentalperception equivalent of the visual sketchma p. Four shap e indice s we re c om pute d, S1,S2, S3 and S4. Sha pe index is defined by theequation:

S = 1.27AL2Where A = area o f shap e in km2 and L = the length

of the longe st a xis in km.

A va lue of 1.0 expresses ma ximum c om pa c tion,where the shape is circular. As the shape iselongated, the less compact is the slope, andthe lowe r the va lue o f the index. A Mea n Shap eInde x (S) for the spa c e ha s be en c alculate das a measure for space-based perception

of the urba n landsc ap e. Sec ond , in order toanalyze the object-based perception data,landscape elements included in each sketchmap was quantified. Landscape elementsincluded buildings, furniture, pavement, spatialvegetation, ground cover vegetation, and sitestruc tures.

Results

Initially, each self-report form was given a labelto indicate the group type of the participantand an ID number. Personal data as well ascollected numerical data were entered intoSPSS version 13 (Sta tistic a l Pac kage fo r Soc ialSc ientists) softw are in the form o f a rec ta ngularda ta ma trix (sc ale in co lumns and respo nde ntsin rows). Form-recognition results wereconverted from the nominal scale (true/false)

into a numerical scale (true = 1, false = zero).Sketch-ma p d ata we re ente red in the sam e

ordinal sc ale ob tained .The differenc e b etw ee n-group s da ta w ereana lyzed on a pa ir-wise b asis. The interest o fthis phase of investigation is to test the effectof stimuli type as an independent variable onpreference variables. Hence, the MultivariateANOVA test would be used to investigate thesignific ant d ifference betw een g roups.

Sketc h Ma p Analysis

In the shap e index test, it wa s found that the m ea nerror of shape index for the space was slightlylower in the PE group than in the VRML group(p > 0.05). Another measure of environmentalpe rc ep tion wa s the qua ntitative a nalysis of thesketch ma ps, in w hic h, land sc ap e e lements ofea c h sketch ma p we re listed , and c lassified into

Booth’s elements of landscape architecturaldesign. Those elements included build ings,furniture, p ave me nt, spa tial vege ta tion, g roundc over, and site struc tures (1983).

Table (1) de pic ts the desc riptive sta tistics ofobjects that appeared in sketch maps. Meanfreq uenc y of “ build ings” wa s slightly less inthe PE group than in the VRML group (p >

0.05). Co nsidering “ furniture” , it wa s foundthat the mea n freq uency o f the PE group wa sc onsiderab ly higher tha n the VRML group , therewas a sta tistica lly significa nt difference betweenfreq uenc ies of b oth group s (p < 0.05). Tab le (2)depicts results of ANOVA test.

Results of ANOVA revealed that the meanfreq uenc y of the PE group wa s c onsiderab ly lessthan the VRML rega rding “ pa vement” element,





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with a sta tistica lly significa nt differenc e betwe en-group differenc e (p < 0.05). Reg arding “ spa tialveg eta tion”, it wa s found tha t the PE group w asconsiderably less than the VRML group, anda significant between-group difference wasfound (p < 0.05). Considering the site structures,it wa s found tha t the me an frequenc y of the PEgroup wa s c onside rab ly g rea ter than the VRML,with a strongly significant between-groupsdifference (p < 0.05). In summary, the VRMLgroup wa s d ifferent from the PE group in differentlandscape components as less furniture, more

pavements, and more spatial-vegetation; andfewer site structure elements were perceived.However, they were no different in perceptionof build ings.

Group Bldg Furnit. Pavem. Veg. Struc t.

PE 5.241

(0.236)

0.483

(0.146)

0.034

(0.034)

0.931

(0.192)

2.172

(0.243)

VRML 5.444(0.422)

0.111(0.076)

0.167(0.090)

1.944(0.286)

0.944(0.347)

Tab le 1: Mea ns and Stand ard d eviations (betw eenpa rentheses) of frequenc ies of o bjec ts mentioned in sketchma ps as a function o f group type (Source: Autho rs).

Variab le SS df MS F P

Sha pe Error 0.0168 1 0.0168 3.157 0.08

Buildings 0.4130 1 0.4130 0.186 0.669

Furniture 2.0540 1 2.0540 4.491 0.041

Pavement 0.2690 1 0.2690 3.985 0.053

Vegetation 6.9900 1 6.9900 5.305 0.027

Struc tures 17.437 1 17.4370 8.810 0.005

Tab le 2: Results of ANO VA test (Source : Autho r).

Discussion

This stud y aime d to investiga te the d ifferenc es

and similarities between visual perceptionobtained from a direct experience of areal environment and the experience of itsrepresentat ion in three typed of d esktop VEs.

Spa c e-ba sed Visual Percep tion

This stud y revea led tha t p a rticipa nts within theVRML group were successful in maintaining acompetent space-based visual perception

of the space. However, they tended to showmore errors in the shape index, yet this wasnot statistically significant when consideringindividua l errors. It is impo rtant to me ntion he rethat the p artic ipa nts we re instruc ted to includethe d eta ils of the e nvironme nt and not o nly theoutline o f spa c e b ound aries.

Object-based Perception

The results for ob jec t-ba sed visua l pe rcep tionin VRML suggest that participants tended tope rc eive m ore b uild ings than real-environme ntparticipants. Even though this observation wasno t sta tistica lly significa nt, it might be a rgued thatbuild ings in VRML we re the d om inant land sc ap eelement because of their legible geometricalforms and well-defined edges that enhancetheir perception. When Gibson’s phenomenon

is applied (Gibson, 1979), it a ppea rs tha t VRMLsustained continuous dynamic changes thatwe re ma inly do minated by b uild ings.

Furniture and site structure elements wereless perc eived in the VRML than in the PE. Thisobservation might be related to four facts.Firstly, using fu rniture or site struc ture elementswas a part of experience within the PE group,yet participants within the VRML were certainly

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unab le to use and feel them . Sec ond ly, VRMLparticipants tended to “ fly” over the normalviewpoint and could not make sense of thesma ll-sc a le furniture e lements or site struc tures,including ramps and stairs on the ground.Third ly, furniture e lements by na ture a re “ very”sma ll com pa red with other land sc ap e elementslimiting the c hanc e o f p erceiving them. Thefourth fact is that furniture elements were not“ physica l ob sta c les” in VRML as they we re, inreality, since people could go through thembe ca use o f the lac k of “ co llision d etec tion” .

Sinc e p ave me nt textures and ground c overvegetation in the VRML model were based onthe AutoC AD 256-c olours inde x, pa vem ent d idnot appear either realistic or harmonious withother elements of space. Additionally, largeareas of pa vement c olors tended to d ominatethe d ispla y within the VRML presenta tion. On t heother hand, ground c over vegeta tion ap pea red

to b e m ore rea listic in their da rk g ree n c olor. Forthis reason, it wa s found tha t VRML participa ntsreported more pavement textures than PEpa rtic ipants did. How ever, it w as not d iffic ult forreal-environment participants to perceive theground cover elements, since they consistedof c onside rab le large area s of the two spa c es.Spa tial veg eta tion elements we re a bstrac tedin the VRML mo de l in orde r to reduc e the fina l

file size. However, it see ms tha t th is abstrac tionwas a reason for enhancing their perception

ac c ording to the “ goo dness of shap e” theory,hence it was found that VRML participantsperceived more spatial vegetation elementstha n PE participan ts d id.

Conclusions

To c onc lude , this stud y intended to emp irica lly

investigate the similarities and differences

between visual perception obtained fromdirect experience of a physical environmenton an urban landscape and the experienceof its rep resenta tion in d esktop VEs. This stud yrevealed important observations concerningvisual perception in VRML, which providedparticipants with sufficient information tomaintain a space-based visual perception ofsmaller and well-defined spaces rather thanlarger less-defined spaces. VRML was foundmore effic ient o n representing informa tion a ndpe rce ptua l cues that enab led the pa rticipa nts

to develop a better understanding of space-based visual perception. Another outcome ofthis study is that abstracting spatial elementsin VRML might enhance their perception bypa rtic ipants’. The latter outc om e might p oint atthe potential of VRML simulation in enhancingobject-based visual perception of landscapesettings.

This stud y sugge sts tha t p erce p tion o f the desktopVEs used to represen t th is spec ific environmenta lcontext was replicating the perception of therea l environme nt. This resea rch w as, however,limited to the typology of a specific exampleof urban landscape (a university campus). Ithas also been limited to the hardware andsoftw are a va ilable for this investiga tion. Furtherempirical investigations are needed to apply

using desktop VEs, as representation media, tomeasure the visual perception of various typesof env ironm enta l sett ings. The d eve lopm entof hardware technology might provideenvironm enta l resea rc hers with mo re enha nc edand a fforda b le de sktop VEs too ls.

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Aym an Hassaa n A. MahmoudAyma n Ma hmo ud is currently an assoc iate p rofessor in the de pa rtment of Architec ture Engineering, Cairo University, Egypt. He received his BSc. in Architecture





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with highest honours followe d b y MSc . in Urba n Design from Cairo University and Ph.D. in landscape a rchitec ture from the University of Shef fi eld, UK. His

resea rch interests inc lude de sign visua lisat ion in environmental design, thermal comfort in outdoor spaces, and aesthetic resources in landscape. He ca n be c ontacted at [email protected].

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