MarkAssad,DavidJ.Carmichael,DanielCutting,AdamHudson
UniversityofSydney
{massad,dcarmich,dcutting,ahudson}@it.usyd.edu.au
Abstract
ThisdemonstrationpaperpresentstheARphone,amobilephoneactingasanaugmentedreality(AR)inter-faceintoanintelligentenvironment.Wedescribethede-signandimplementationofaprototypesystemwherebyaphonecancaptureimages,transferthemtoanintelli-gentenvironmentandreceivesomeformofvisuallyaug-mentedresult.Inconclusionweexploresomedemonstra-tionsofthesystem.
1.Introduction
Intelligentenvironments(IEs)aimtocomplementusers’dailyexperiencesbyprovidingthemwithcom-putationalresourcesandservicesthatblendseamlesslyintotheirsurroundings.Oneofthemostimportantas-pectsofsuchanenvironmentishowusersinteractwithit.Thisshouldbeasintuitiveandunobtrusiveaspossi-ble,whichmakestraditionalcomputinginterfacessuchaskeyboards,miceandmonitorsundesirable.TechniquesthatallowausertointeractwithanIEinamorenaturalmannerarepreferable.AugmentedReality(AR)offersmuchpromiseinthisarea.
CurrentARinterfacesaretypicallyheadmounteddis-plays(HMDs)orwebcamsattachedtoPCs.Bothofthesehavesignificantdrawbacks.HMDsareexpensiveandthusinaccessibletoordinaryusers.Webcamsarenon-intuitivesincetheinputdeviceisusuallyquitesepa-ratetothedisplaydevice.
TheubiquitoustechnologyofthemobilephoneisaplausibleplatformfordeployingAR-basedapplications.Inparticular,theemerginggenerationofphoneswithcolourscreens,camerasandwirelessnetworkinghaveallofthecapabilitiesrequiredtoimplementanARinterface,althoughtheymaynothavetheprocessingpowertoper-formtheaugmentationinternally.
ThispaperdescribestheimplementationoftheARphone,anaccessibleandintuitivesystembuiltaroundamobilephonewhichcanbeusedtopresentanARinter-faceintoanintelligentenvironment.Wediscusstheim-plementationofaprototypesystemandlookatwherethe
projectisheaded.Furthertechnicaldetailsontheback-groundanddesignoftheARphonecanbefoundin(1).
2.Architecture
OurinitialARphonearchitectureisasimple,dis-tributedprototypesystemcomprisingthreecomponents:•aninterfaceapplicationrunningonaphone•wirelessaccesspointsdistributedthroughoutthephysicalenvironment
•acentralisedaugmentedrealityservicemodule.Thephoneactsasa‘viewport’ofanARservice,withthebulkoftheprocessingtakingplaceinanIE.Thiskeepstheapplicationsonthephonesimpleandallowsthemtobedeployedacrossarangeofphonesandotherdeviceswithdifferinginputandoutputcapabilities.ThephonetakesavideostreamandrelaysitwirelesslytooneormoreaccesspointmodulesdeployedaroundanIE.Theaccesspointmodulesareresponsiblefordisseminatingthereceivedinputtoacentralisedaugmentedrealityser-vicemodule.Thisprocessestherawimageinputandre-turnstheaugmentedresultstotheaccesspoint,whichinturntransmitsitbacktothephonefordisplaytotheuser.TheprocessisillustratedinFigure1.
Figure1:TheARphonepipeline.
3.Implementation
3.1.PhoneApplication
TheapplicationrunningonthephoneisdesignedinasimilarfashiontotheAR-PDA(2)andHandheldAR(3)projects,althoughthesebothusePDAsasdistinctfromphones.Theapplicationcapturesanimage,sendsittoanaccesspointviaBluetooth,receivestheaugmentedresultandthendisplaysitonthephone’scolourdisplay.TheapplicationhasinitiallybeendevelopedonaSonyErics-sonP800mobilephonerunningversion7.0oftheSym-bianOS.TheP800isagoodchoicesinceitincludesabuilt-incamera,alargecolourscreenandBluetoothcom-municationinthestandardmodel.AsofAugust2003thereisnosupportforcapturingvideofromtheinternalcamera:itsupportsonlythecaptureofsnapshotimages.Wehopetobeabletouseavideostreaminthefuture.TheapplicationisabletoscanitslocalareaforanyavailableBluetoothaccesspointswhicharethendis-playedtotheuserforselection.OnceanaccesspointisselectedaL2CAPconnectionisestablishedbetweenitandthephone,whichtheapplicationusestoultimatelycommunicatewiththeARserver.3.2.AccessPoints
TheapplicationrunningonthephoneconnectstotheARservicethoughtheaccesspoints.TheseaccesspointshavebeendevelopedtorununderLinuxwiththeBlueZBluetoothstack.3.3.ARService
TheARserviceisagenericmodulethatisabletore-ceiveimageinputfromtheaccesspointsandperformprocessingandmanipulationofthedata.Thespecificsoftheprocessingaredependentontheserviceprovided.Thedecouplingoftheserviceprocessingallowsformul-tipleARapplicationstobedevelopedforthephoneus-ingcommonaccesspointsanduserinterfaces.Afterpro-cessingoftheimage,theresultisreturnedtotheaccesspointrequestingtheservice,whichthenpassesitontothephone.
4.Demonstration
WeimplementedabasicARserviceforourprototypewhichsimplyaugmentsarawimagewithathreedimen-sionalobject.Theimageaugmentationserviceexaminestheinputimageforaparticularfiducialmarkerwhich,iffound,isoverlaidinthreedimensionalspacewithavir-tualteapot.ThisisachievedwiththeARtoolkit(4)andtheOpenGLGLUTlibrary.ThelargestbottleneckinthissystemisthetransmissionoftheuncompressedbitmapimageoverBluetooth:Dependingonthechoseninput
resolution,theroundtriptimevariesfromtwoto15sec-onds.
5.FutureDirections
InthenearfuturewehopetocreateuserinterfacemodulesforothermobiledevicesincludingtheNokia7650mobilephoneandtheToshibae740PDAwithanattachedcamera.Inthecaseofthelatter,theuseofahigherbandwidth802.11bwirelessconnectioninsteadofBluetoothshouldleadtoagreatperformanceimprove-mentinourprototypeimplementation.
Itshouldalsobepossibletoimproveperformancebyapplyingcompressionalgorithmstothedatatransmit-tedoverBluetooth.Sincethedataformsanimage,weareabletouselossycompressiontechniqueslikeJPEGwhichshouldsignificantlyreducetheamountoftraffic.ItmayalsobepossibletomovesomepartsoftheARtoolkitintotheuserinterfacemodulesuchasthethresh-oldingofimagesordetectionofmarkers.ThiswouldmeanfarlessdatawouldneedtobetransmittedoverBluetoothandshouldincreaseperformance.ItshouldbenotedthatthisapproachisahybridcomputationalmodelwhichdiffersfromtheconceptuallycleanapproachofanIEperformingallcomputation“withinthewalls”.
References
[1]Assad,M.,Carmichael,D.J.,Cutting,
D.,Hudson,A.ARphone:AccessibleAugmentedRealityintheIntelligentEn-vironment.ToappearatOZCHI2003,November26-28,2003,Brisbane,Aus-tralia.[2]Geiger,C.,etal.MobileAR4ALL.
http://citeseer.nj.nec.com/kleinjohann01mobile.html[3]InteractiveMediaSystemsGroup,
InstituteforSoftwareTechnol-ogyandInteractiveSystems,Vi-ennaUniversityofTechnologyhttp://www.ims.tuwien.ac.at/research/handheld
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