a visibility algorithm for hybrid geometry- and image-based modeling and rendering

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1、AVisibilityAlgorithmforHybridGeometry-andImage-BasedModelingandRenderingThomasA.FunkhouserPrincetonUniversityAbstractHybridgeometry-andimage-basedmodelingandrenderingsystemsusephotographstakenofareal-worldenvironmentandmappedontothesurfacesofa3Dmodeltoachievep

2、hotoreal-ismandvisualcomplexityinsyntheticimagesrenderedfromarbitraryviewpoints.Aprimarychallengeinthesesystemsistodevelopalgorithmsthatmapthepixelsofeachphotographefficientlyontotheappropriatesurfacesofa3Dmodel,aclassicalvisiblesurfacedetermina-tionproblem.Thi

3、spaperdescribesanobject-spacealgorithmforcomputingavisibilitymapforasetofpolygonsforagivencameraviewpoint.Thealgorithmtracespyramidalbeamsfromeachcameraviewpointthroughaspatialdatastructurerepresentingapolyhedralconvexdecompositionofspacecontainingcell,face,ed

4、ge,andvertexadjacencies.Beamintersectionsarecomputedonlyforthepolygonalfacesontheboundaryofeachtraversedcell,andthusthealgorithmisoutput-sensitive.Thealgorithmalsosupportsefficientdeterminationofsilhouetteedges,whichallowsanimage-basedmodelingandrenderingsystem

5、toavoidmappingpixelsalongedgeswhosecolorsaretheresultofaveragingoverseveraldisjointsurfaces.Resultsreportedforseveral3Dmodelsindicatethemethodiswell-suitedforlarge,densely-occludedvirtualenvironments,suchasbuildinginteriors.1IntroductionHybridgeometry-andimage

6、-basedrendering(GIBR)methodsareusefulforsynthesizingphoto-realisticimagesofreal-lifeenvironments(e.g.,buildingsandcities).Ratherthanmodelinggeo-metricdetailsandsimulatingglobalilluminationeffects,asintraditionalcomputergraphics,onlyacoarselydetailed3Dmodelisco

7、nstructed,andphotographsaretakenfromadiscretesetofviewpointswithintheenvironment.Thecalibratedphotographicimagesaremappedontothesur-facesofthe3Dmodeltoconstructarepresentationofthevisualappearanceofgeometricdetailsandcomplexilluminationeffectsoneachsurface.The

8、n,novelimagescanberenderedforarbi-traryviewpointsduringaninteractivevisualizationsessionbyreconstructionfromthesehybrid1geometry-andimage-basedrepresentations.Thismethodallowsphoto