1、TRANSFORMATIONOFGEOMETRYINFORMATIONBASEDONFACEHIERARCHYBETWEENCADSYSTEMANDVIRTUALASSEMBLYENVIRONMENTAbstract/Traditionalassemblydependsonmock-ups/butcreationofthesemock-upsistime-consumingandlabor-consuming/ThedevelopmentofVAbasedonvirtualreality(VR)providesusalow-costandrapidmethodforassembly/VRiso
2、fthreecharacteristics/immersion/interactionandimagination/WithVRtechnology/geometrymodelsandtolerance(orerrors)valuesareinputtedintocomputerafterpartsaredesigned/Equipments/toolsandhumanmodelareunitedinVEtoanalyzeandevaluateassemblyperformance/Unqualifiedstructureisthencorrected/assemblyscenarioisop
3、timizedandbestassemblyplanisselectedtoassurethesuccessofactualassembly/Afterallthesesteps/actualassemblyisimplemented/Thereforeproductdevelopmentcycleisshortenedandproductdevelopmentcostisdecreased/Keywords/virtualassembly/virtualenvironment/datatransformation/geometryAlthoughCADmodelcanbetransferre
4、dintoVE/thesemodelsareofonlytheconceptofbodyandnotofthatofface/Thewholeassemblyorsinglepartcanbeselected/butfacesofpartscannotbeselected/Howeverfaceisanimportantconceptinassembly/anditsfunctionsareasfollows/(1)orientationofpailsorassemblybodies；(2)constraintdefinition；(3)jointdefinition；(4)definitio
5、nofshapetoleranceandpositiontolerance；(5)definitionofprecisionandroughness；(6)physicalinformationdefinition(e/g/colorandmaterialetc/)etc/Withouttheconceptofface/theconceptofassemblybecomesvagueandVAsystemisalsoreducedtoasimplesimulationsystem/SoitisfarfromrequirementwhenVAisofonlytheconceptofbodies/
6、SoconceptoffaceisneededtobecreatedwhilecreatingVRdocument/ThesurfacesofCADmodelcanbediscretizedtoaggregateofpolygontessellationsortriangletessellationsthroughdatetransformationinterfaceofCADsystem/ThenthesetessellationsinformationiswrittenintoVRdocument/UsingtessellationsinformationprovidedbyVRdocum
7、ent/VRsystemwilldrawallthetessellationstocreateVRobject/Apartcanberegardedasaggregateoffaces/andafacecanberegardedasthatoftessellationsinCADsystem/ThereexistsacorrespondingrelationshipbetweenbodiesandtessellationsinVE/andalltessellationscanformthewholeVRobject/andinthiswaytheinformationofbodiesareco
8、nstructedinVE/ButtheredoesntexistcorrespondingrelationshipbetweenfacesandtessellationsinVE/whichconsequentlyresultsinloseoffacesinformation/Inordertocreatetheinformationoffaces/correspondingrelationshipbetweenfacesandtessellationsisneededtobecreatedinVE/ThetechnologyofforwarddevelopmentofCADsysteman
9、dColorRecognitionandTransformationMethod(CRTM)areusedtocreatecorrespondingrelationshipamongfaces/colorsandtessellationsbymeansofcreatinglinkedlistoffacesandlinkedlistoftessellations/InCADsystem/eachfaceofCADmodelingispaintedwithdifferentcolorinvirtueofforwarddevelopmentofCADsystem/Accordingly/tessel
10、lationsofthesamecolorbelongtothesameface/andthencorrespondingrelationshipbetweenfacesandtessellationsiscreatedbyconstructinglinkedlistoffacesandlinkedlistoftessellations/Inthisway/facesinformationiscreated/InVEoperationsonfaceswillbetransformedtooperationsontessellations/thustheconceptoffaceisbuilta
11、ndgeometryinformationisreconstructedonthebasisofit/InordertorealizeCRTM/Pro/Engineer(Pro/E)isselectedasplatformofassemblymodeling/WorldToolKit(WTK)isselectedasplatformofVAdevelopment/andvisualC+isselectedasplatformofapplicationdevelopment/VRdocumentinterfaces(e/g/NFP/3DS/WRL/DXFandSLPetc/)areusedtot
12、ransfergeometryinformationfromanyotherkindofmodelingsoftwaretoWTK/AlthoughWTKsupportsmanyVRdocumentformat/onlyWRLformatandSLPformatcanbeusedtotransfergeometryinformationfromPro/EtoVE/Inactualapplication/WRLformathasthefollowinglimitationsinWTKenvironment/1）Geometryinformationcantbepickedup/soWTKcann
13、otmodifycolorsandtexturesetc/ofvirtualobjects/2)WTKcannotcarryoutzoomoperationonvirtualobjects/3)PrecisionofcollisiondetectionforvirtualobjectislowfortheinformationofpolygonsofvirtualobjectscantbepickedupinVE/Consequently/SLPformatwrittenintextformat/anotherformatofVRdocumentisused/Fig/1showsthecrea
14、tionprocessofVRdocument/PartscolorsaremodifiedbymeansofPro/DevelopmoduleofPro/E/Mixingcolorismadeofthreecolors/red(r)/green(g)andblue(b)/Settingdifferentvalueofr/gandbtoeachface/facesofdifferentcolorsarecreated/Inordertodistinguishtwofaces/one-increasing-another-decreasing-paintingmethodisused/Ifthe
15、valueofrandgincrease/thenthevalueofbshoulddecreaseaccordingly/andtheextentofincreaseanddecreaseshouldbedifferent/Thusfacesareeasytodistinguishbecauseofbigdifferenceofeachfacescolor/Afterpaintingcolor/VRdocumentofSLPiscreatedthroughPro/InterfacemoduleofPro/E/Withoperationsonallpartsofassemblybody/cor
16、respondingVRdocumentswillbecreated/VRdocumentprovidesustessellationsinformation/normalsinformationandcolorsinformationetc/Inordertocreatethecorrespondingrelationshipbetweenfacesandtessellations/twostructuresoflinkedlistareneeded/i/e//linkedlistoffacesandlinkedlistoftessellations/Linkedlistsoffacesin
17、cludethefollowinginformation/numberoffaces/nameoffaces/coloroffacesandlinkedlistoftessellations/Afacescolorcorrespondstothelinkedlistoftessellationsofthisface/Thefunctionoflinkedlistoftessellationsistostoretessellationsofthesamecolor/ByreadingSLPdocumentinturn/informationoffacesandtessellationsispic
18、kedupandstoredtolinkedlistoffacesandlinkedlistoftessellationsrespectively/Correspondingrelationshipbetweenfacesandtessellationsisbuiltthroughthemedia-colorsoffacesandtessellations/InVE/afaceisselectedbyhighlightingallthetessellationscorrespondingtotheface/Firstly/currentactivetriangletessellationisp
19、ickedupthroughWTscreen_pickpolyfunction/andnumberofcurrentactivetriangletessellationispickedupbymeansofWTpoly_getidfunction/Thenthefaceincludingthenumberofthetessellationcanbeobtainedbymeansofsearchinglinkedlistoffacesandlinkedlistoftessellations/Whenallthetessellationsofafacetakethesameoperations/thefacewilltakethesameoperation/Forexample/whenallthetessellationsofafacearehighlighted/allthepartsofthefacesarehighlighted/andthenthefaceisselectedinvisualeffectInthisway/geometryinformationisreconstructedbasedonfacehierarchy/
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