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外文翻译--延长搅拌机.doc

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外文翻译--延长搅拌机.doc

英文原文ExtendingBlenderDevelopmentofaHepaticAuthoringToolAbstractInthispaper,wepresentourworktoextendawellknown3DgraphicmodelerBlendertosupporthepaticmodelingandrendering.TheextensiontoolisnamedHAMLAThepaticApplicationMarkupLanguageAuthoringTool.WedescribethemodificationsandadditionstotheBlendersourcecodewhichhavebeenusedtocreateHAMLATFurthermore,wepresentanddiscussthedesigndecisionsusedwhendevelopingHAMLAT,andalsoanimplementationroadmapwhichdescribesthechangestotheBlendersourcecode.Finally,weconcludewithdiscussionofourfuturedevelopmentandresearchavenues.KeywordsHepaticsHAMLGraphicModelersBlenderVirtualEnvironments.I.IntroductionA.MotivationTheincreasingadoptionofhepaticmodalityinhumancomputerinteractionparadigmshasledtoahugedemandfornewtoolsthathelpnoviceuserstoauthorandedithepaticapplications.Currently,thehepaticapplicationdevelopmentprocessisatimeconsumingexperiencethatrequiresprogrammingexpertise.ThecomplexityofhepaticapplicationsdevelopmentrisesfromthefactthatthehepaticapplicationcomponentssuchasthehepaticAPI,thedevice,thehepaticrenderingalgorithms,etc.needtointeractwiththegraphiccomponentsinordertoachievesynchronicity.Additionally,thereisalackofapplicationportabilityastheapplicationistightlycoupledtoaspecificdevicethatnecessitatestheuseofitscorrespondingAPI.Therefore,deviceandAPIheterogeneityleadtothefragmentationanddisorientationofbothresearchersanddevelopers.Inviewofalltheseconsiderations,thereisaclearneedforanauthoringtoolthatcanbuildhepaticapplicationswhilehidingprogrammingdetailsfromtheapplicationmodelersuchasAPI,device,orvirtualmodel.ThispaperdescribesthetechnicaldevelopmentofthehepaticApplicationMarkupLanguageAuthoringToolHAMLAT.ItisintendedtoexplainthedesigndecisionsusedfordevelopingHAMLATandalsoprovidesanimplementationroadmap,describingthesourcecodeoftheproject.B.BlenderHAMLATisbasedontheblender1softwaresuite,whichisanopensource3Dmodelingpackagewitharichfeatureset.Ithasasophisticateduserinterfacewhichisnotedforitsefficiencyandflexibility,aswellasitssupportsformultiplefileformats,physicsengine,modemcomputergraphicrenderingandmanyotherfeatures.Becauseofblendersopenarchitectureandsupportivecommunitybase,itwasselectedastheplatformofchoicefordevelopmentofHAMLAT.TheopensourcenatureofBlendermeansHAMLATcaneasilyleverageitsexistingfunctionalityandfocusonintegratinghepaticfeatureswhichmakeitacompletehaptovisualmodelingtool,sincedevelopinga3Dmodelingplatformfromscratchrequiresconsiderabledevelopmenttimeandexpertiseinordertoreachtheleveloffunctionalityofblender.Also,wecantakeadvantageoffutureimprovementstoblenderbymergingchangesfromitssourcecodeintotheHAMLATsourcetree.HAMLATbuildsonexistingBlendercomponents,suchastheuserinterfaceandeditingtools,byaddingnewcomponentswhichfocusontherepresentation,modification,andrenderingofhepaticpropertiesofobjectsina3Dscene.ByusingBlenderasthebasisforHAMLAT,wehopetodevelopa3DhepaticmodelingtoolwhichhasthematurityandfeaturesofBlendercombinedwiththenoveltyofhepaticrendering.C.ProjectGoalsAspreviouslystated,theoverallgoalfortheHAMLATprojectistoproduceapolishedsoftwareapplicationwhichcombinesthefeaturesofamodemgraphicmodelingtoolwithhepaticrenderingtechniques.HAMLAThasthelookandfeelofa3Dgraphicalmodelingpackage,butwiththeadditionoffeaturessuchashepaticrenderingandhepaticpropertydescriptors.Thisallowsartists,modelers,anddeveloperstogeneraterealistic3Dhippovisualvirtualenvironments.AhighlevelblockdiagramofHAMLATisshowninFigure1.Itillustratestheflowofdatainthehepaticmodeling.HAMLATassiststhemodeler,orapplicationdeveloper,inbuildinghaptovisualapplicationswhichmaybestoredinadatabaseforlaterretrievalbyanotherhepaticapplication.Byhippovisualapplicationwerefertoanysoftwarewhichdisplaysa3Dscenebothvisuallyandhecticallytoauserinavirtualsetting.AnXMLfileformat,calledHAML2,isusedtodescribethe3Dscenesandstorethehippovisualenvironmentsbuiltbyamodelerforlaterplaybacktoanenduser.Traditionally,buildinghippovisualenvironmentshasrequiredastrongtechnicalandprogrammingbackground.Thetaskofhecticallyrenderinga3Dsceneistedioussincehepaticpropertiesmustbeassignedtoindividualobjectsinthesceneandcurrentlytherearefewhighleveltoolsforaccomplishingthistask.HAMLATbridgesthisgapbyintegratingintotheHAMLframeworkanddeliveringacompletesolutionfordevelopmentofhippovisualapplicationsrequiringnoprogrammingknowledge.TheremainderofthepaperisorganizedasfollowsinSection2,wepresenttheproposedarchitectureextensionsanddiscussdesignconstraints.Section3describestheimplementationdetailsandhowhepaticpropertiesareaddedandrenderedwithintheblenderframework.Insection4wediscussrelatedissuesandfutureworkavenues.II.SYSTEMOVERVIEWANDARCHITECTURETheblenderdesignphilosophyisbasedonthreemaintasksdatastorage,editing,andvisualization.Accordingtothelegacydocumentation3,itfollowsadatavisualizeeditdevelopmentcycleforthe3DmodelingA3DsceneisrepresentedusingdatastructureswithintheBlenderarchitecture.Themodelerviewsthescene,makeschangesusingtheeditinginterfacewhichdirectlymodifiestheunderlyingdatastructures,andthenthecyclerepeats.Tobetterunderstandthisdevelopmentcycle,considertherepresentationofa3DobjectinBlender.A3Dobjectmayberepresentedbyanarrayofverticeswhichhavebeenorganizedasapolygonalmesh.Usersmaychoosetooperateonanysubsetofthisdataset.Editingtasksmayincludeoperationstorotate,scale,andtranslatethevertices,orperhapsaremeshingalgorithmtocleanupredundantverticesandtransformfromaquadtoatriangletopology.Thedataisvisualizedusingagraphical3Drenderedwhichiscapableofdisplayingtheobjectasawireframeorasashaded,solidsurface.Thevisualizationisnecessaryinordertoseetheeffectsofeditingonthedata.Inanutshell,thisexampledefinesthedesignphilosophybehindblendersarchitecture.Inblender,dataisorganizedasaseriesoflistsandbasedatatypesarecombinedwithlinksbetweenitemsineachlist,creatingcomplexscenesfromsimplestructures.Thisallowsdataelementsineachlisttobereused,thusreducingtheoverallstoragerequirements.Forexample,ameshmaybelinkedbymultiplesceneobjects,butthepositionandorientationmaychangeforeachobjectandthetopologyofthemeshremainsthesame.AdiagramillustratingtheorganizationofdatastructuresandreuseofsceneelementsisshowninFigure2.Asceneobjectlinkstothreeobjects,eachofwhichlinktotwopolygonalmeshes.Themeshesalsoshareacommonmaterialproperty.Theentiresceneisrenderedononeofseveralscreens,whichvisualizesthescene.WeadopttheBlenderdesignapproachforourauthoringtool.Thedatastructureswhichareusedtorepresentobjectsina3Dscenehavebeenaugmentedtoincludefieldsforhepaticpropertiese.g.,stiffness,dampinguserinterfacecomponentse.g.,buttonpanelswhichallowthemodelertochangeobjectpropertieshavealsobeenupdatedtoincludesupportformodifyingthehepaticpropertiesofanobject.Additionally,aninteractivehippovisualrenderedhasbeenimplementedtodisplaythe3Dscenegraphicallyandhectically,providingthemodelerorartistwithimmediatefeedbackaboutthechangestheymaketothescene.AclassdiagramoutliningthechangestotheblenderframeworkisshowninFigure3.ComponentswhicharepertinenttoHAMLATareshadedingray.HAMLATbuildsonexistingblendersubsystemsbyextendingthemforhepaticmodelingpurposes.Thetactileandkinestheticcues,whicharedisplayedduetointeractionwithvirtualobjects,aretypicallyrenderedbasedonthegeometryofthemesh.inthisdatatype.Otherscenecomponentssuchaslamps,cameras,orlinesarenotintuitivelyrenderedusingforcefeedbackhepaticdevicesandarethereforenotofcurrentinterestofchaoticrendering.AnaugmentedversionofthemeshdatastructureisshowninFigure4.Itcontainsfieldsforvertexandfacedata,plussomespecialcustomdatafieldswhichallowdatatobestoredto/retrievedfromdiskandmemory.Wehavemodifiedthisdatatypetoincludeapointertoahepaticsdatastructure,whichstoreshepaticpropertiessuchasstiffness,damping,andfrictionforthemeshelementsFigure5.Similarlytothebuiltingraphicalrendered,HAMLATusesacustomrenderedfordisplaying3Dsscenesgraphicalandhapcall,andisinendoftheconnectivityisgiveninthenextsection.IMPLEMENTATIONDataStructureBlenderusesmanydifferentdatastructurestorepresentthevarioustypesofobjectsina3Dsceneapolygonalmeshcontainsthelocationandtopologyofverticesalampcontainscolorandintensityvaluesandacameraobjectcontainsintrinsicviewingparameters.TheMeshdatastructureisusedbytheblenderBlenderrendered.Thiscomponentisdevelopedindependentlysincehereticalandgraphicalrenderingmustbeperformedsimultaneouslyandsynchronously.Asimulationloopisusedtoupdatehepaticrenderingforcesataratewhichmaintainsstabilityandquality.Wheretheforcefeedbackvectorwhichisdisplayedtotheuseriscomputedusingthestiffnesscoefficientvariablenamestiffnessfortheobjectandxthe|penetrationdepthdisplacementofthehepaticproxyintoanobject.Thestiffnesscoefficienthasarangeof0,1,where0representsnoresistancetodeformationand1representsthemaximumstiffnesswhichmayberenderedbythehepaticdevice.ThedampingofanobjectdefinesitsresistancetotherateofdeformationduetosomeappliedstrutHepaticesforce.ItistypicallyrenderedusingtheforceequationHepaticPropertiesInthissectionwellbrieflydiscussthehepaticpropertieswhichmaycurrentlybemodeledusingHAMLAT.Itisimportantforthemodelertounderstandthesepropertiesandtheirbasisforuseinhepaticrendering.Thestiffnessofanobjectdefineshowresistantitistodeformationbysomeappliedforce.Hardobjects,suchasarockortable,haveveryhighstiffnesssoftobjects,suchasrubberball,havelowstiffness.Thehardnesssoftnessofanobjectistypicallyrenderedusingthespringforceequationrangeof0,1andmaybeusedtomodelviscousbehaviorofamaterial.Italsoincreasesthestabilityofthehepaticrenderingloopfordstiffmaterials.Thestaticfrictionvariablenamestriationanddynamicfrictionvariablenamedirectioncoefficientareusedtomodelthefrictionalforcesexperiencedwhileexploringthesurfaceofa3Dobject.Staticfrictionisexperiencedwhentheproxyisnotmovingovertheobjectssurface,andaninitialforcemustbeusedtoovercomestaticfriction.Dynamicfrictionisfeltwhentheproxymovesacrossthesurface,rubbingagainstit.Frictionalcoefficientsalsohavearangeof/0,1,withavalueof0makingthesurfaceofa3Dobjectfeelslipperyandavalueof1makingtheobjectfeelveryrough.B.EditingBlenderusesasetofnonoverlappingwindowscalledspacestomodifyvariousaspectsofthe3Dsceneanditsobjects.Eachspaceisdividedintoasetofareasandpanelswhicharecontextaware.Thatis,theyprovidefunctionalitybasedontheselectedobjecttype.Forexample,ifacameraisselectedthepanelwilldisplaycomponentswhichallowthemodelertochangethefocallengthandviewingangleofthecamera,butthesecomponentswillnotappearifanobjectofanothertypeisselected.Figure6showsascreenshotofthebuttonspacewhichisusedtoeditpropertiesforahepaticmesh.Itincludesuserinterfacepanelswhichallowamodelertochangethegraphicalshadingpropertiesofthemesh,performsimpleremeshingoperations,andtomodifythehepaticpropertiesoftheselectedmesh.

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