点云模型阴影线条画的绘制 (1)

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1、山东大学硕士学位论文ABSTRACTWiththedevelopmentofcomputergraphics，it’Sgettingmoreandmoreattentionthatusingpointcloudgeometryasthedepictionof3Dmodelsincomputer．Ononeside，it’Sveryeasytoacquirepointcloud．Onanotherside，comparedtomeshmodels，thestorageforpointcloudmodelsismuchsmal

2、ler．Nowadays，theareasthatstudypointcloudrangefromreconstruction，renderingandapplication．Pointcloudhasbeenahotarea．Line．artdrawingofhatchingisakindofstyleofnon—photorealisticrenderingwhichusesdifferentkindofhatchingtoexpresstheshape，textureandintensityonthesurfaceo

3、fa3Dmodel．Thedirectionsofhatchingexpresstheshapeofthesurface．Thewidthanddensityofhatchingexpressintensityonthesurface．Differentstylesofhatchingexpressthetextureonthesurface．Line-artdrawingofhatchingiswidelyusedincartoons，illustrationsfortechniqueliterature，designs

4、ketchofindustryandarchitectureandrepairmanual．Tillnow,therearealreadymanymethodStorendertheline—artdrawingofhatchingformeshandsmoothsurface，butthereisnointegrityworktorendertheline—artdrawingofhatchingforpointcloudgeometry．ExitingmethodsCanbedividedtothreecatalogs

5、．Oneisimage-spacebased．First，geta2Dimageofthemodelundercertainviewpoint．Thenrendertheline—artdrawingofhatchinginthe2Dimage．Anotherisobject-spacebasedwhichdirectlyuses3Dmodeltorenderthedrawing．Thelastoneishybrid，whichusesboth3Dmodeland2Dimagetorender．Onthewhole，the

6、rearethreestepstofinishahatchingdrawing：(1)Findthesilhouetteofthemodel．(2)Computeadirectionfieldonthesurfacethatexpressestheshapeofsurface．(3)Discoverareasofsingle-hatchingandcross—hatchingonthesurfaceaccordingtointensity．Thentracestreamlinesinthedirectionfieldoft

7、hoseareastorenderhatching．Differentmethoddiffersinthosethreesteps．Basedontheexistingwork，thispaperstudiedtheworktorenderline—artdrawingofhatchingforpointcloudgeometrysystematically．ThemethodforIII山东大学硕士学位论文renderingforpointcloudissimilar、jvitllmesh．However,because

8、ofthediscretepropertyofpointcloud，thespecificprocessofeachstepdiffersgreatlywithmesh．Themethodusedinthispaperishybrid．Operationsaremainlyinobjectspacewh