Computational Conformal Geometry: Theories and Applications
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ComputationalComputationalComputational ConformalConformalConformal Geometry:Geometry:Geometry: TheoriesTheoriesTheories andandand ApplicationsApplicationsApplications XianfengXianfeng GuGu,, Shing Shing-Tung-Tung Yau Yau UFL,UFL, HarvardHarvard UniversityUniversity AnAnAn importantimportantimportant goalgoalgoal ofofof classicalclassicalclassical geometrygeometrygeometry isisis tototo givegivegive aaa descriptiondescriptiondescription ofofof geometricgeometricgeometric figuresfiguresfigures thatthatthat wewewe seeseesee ininin nature.nature.nature. HighHighHigh powerpowerpower computercomputercomputer computationcomputationcomputation andandand threethreethree dimensiondimensiondimension cameracameracamera allowsallowsallows ususus tototo applyapplyapply classicalclassicalclassical andandand modernmodernmodern geometricgeometricgeometric technologytechnologytechnology tototo realrealreal featuresfeaturesfeatures ofofof objectsobjectsobjects thatthatthat wewewe seeseesee ininin daydayday tototo daydayday life.life.life. ForForFor aaa givengivengiven surfacesurfacesurface ininin threethreethree space,space,space, ititit isisis importantimportantimportant tototo realizerealizerealize thatthatthat theretherethere areareare severalseveralseveral geometricgeometricgeometric structuresstructuresstructures thatthatthat areareare inheritinheritinherit ininin theirtheirtheir description.description.description. TheTheThe mostmostmost importantimportantimportant oneoneone isisis thethethe conformalconformalconformal structure.structure.structure. TheTheThe constructionconstructionconstruction ofofof conformalconformalconformal structurestructurestructure bybyby computercomputercomputer computationcomputationcomputation immediatelyimmediatelyimmediately allowsallowsallows ususus tototo applyapplyapply modernmodernmodern andandand wellwellwell developeddevelopeddeveloped techniquetechniquetechnique ofofof complexcomplexcomplex analysisanalysisanalysis andandand algebricalgebricalgebric geometrygeometrygeometry tototo bebebe broughtbroughtbrought intointointo graphicgraphicgraphic realization.realization.realization. TheTheThe basicbasicbasic techniquetechniquetechnique involvesinvolvesinvolves solvingsolvingsolving nonlinearnonlinearnonlinear andandand linearlinearlinear differentialdifferentialdifferential equations.equations.equations. thethethe differentialdifferentialdifferential equationsequationsequations areareare relatedrelatedrelated tototo questionsquestionsquestions ofofof isometricisometricisometric embeddingembeddingembedding ofofof surfaces,surfaces,surfaces, whichwhichwhich isisis aaa difficultdifficultdifficult subject.subject.subject. TheTheThe equationsequationsequations cancancan bebebe ellipticellipticelliptic ,,, hyperbolichyperbolichyperbolic ororor mixedmixedmixed type.type.type. ThereThereThere areareare equationsequationsequations relatedrelatedrelated tototo movementmovementmovement ofofof surfacessurfacessurfaces wherewherewhere motionsmotionsmotions drivendrivendriven bybyby curvaturecurvaturecurvature areareare important.important.important. InInIn orderorderorder tototo bebebe efficientefficientefficient ininin datadatadata compressioncompressioncompression andandand signalsignalsignal processingprocessingprocessing forforfor geometricgeometricgeometric figures.figures.figures. AlgebraicAlgebraicAlgebraic geometrygeometrygeometry isisis ananan importantimportantimportant tool.tool.tool. OutlineOutlineOutline IntroductionIntroductionIntroduction MotivationMotivationMotivation SolutionSolutionSolution ApplicationsApplicationsApplications GeometricGeometricGeometric databasedatabasedatabase indexingindexingindexing ExpressionExpressionExpression animation,animation,animation, skinskinskin deformationdeformationdeformation SummarySummarySummary Definition:Definition:Definition: ConformalConformalConformal MappingMappingMapping ScalingScaling firstfirst fundamentalfundamental fromfrom AngleAngle preservingpreserving SimilaritiesSimilarities inin thethe smallsmall φ → = λφ * ~ : M 1 M 2 , g ij g ij M1 M2 IntroductionIntroductionIntroduction SurfaceSurfaceSurface ParametrizationParametrizationParametrizationisis is aaa processprocessprocess tototo mapmapmap aaa surfacesurfacesurface tototo aaa regionregionregion ofofof thethethe plane.plane.plane. MotivationMotivationMotivation MotivationMotivationMotivation TextureTextureTexture MappingMappingMapping GeometryGeometryGeometry RemeshingRemeshingRemeshing GeometryGeometryGeometry MatchingMatchingMatching MedicalMedicalMedical ImagingImagingImaging GeometryGeometryGeometry CompressionCompressionCompression TextureTextureTexture MappingMappingMapping –––NondistortionNondistortion Nondistortion GeometryGeometryGeometry RemeshingRemeshingRemeshing ChangeChangeChange irregularirregularirregular connectivityconnectivityconnectivity tototo regularregularregular oneoneone WithWithWith accurateaccurateaccurate reconstructedreconstructedreconstructed normalnormalnormal ConstructConstructConstruct conformalconformalconformal geometrygeometrygeometry imageimageimage ProposedProposed inin SIGGRAPHSIGGRAPH 20022002 (with(with StevenSteven GortlerGortlerand and HuguesHuguesHoppe) Hoppe) UseUse regularregular gridsgrids toto samplesample eacheach chartchart UnifyUnify imageimage andand geometrygeometry GeometricGeometricGeometric matchingmatchingmatching ParameterizeParameterizeParameterize surfacessurfacessurfaces tototo aaa canonicalcanonicalcanonical domaindomaindomain MatchMatchMatch featuresfeaturesfeatures bybyby parameterparameterparameter DependsDependsDepends ononon geometrygeometrygeometry continuouslycontinuouslycontinuously demo BrainBrainBrain ConformalConformalConformal MappingMappingMapping thth Alzheimer’sAlzheimer’s DiseaseDisease (AD)(AD) waswas asas thethe 88 leadingleading causecause ofof deathdeath inin U.S.U.S. forfor 1999;1999; itit costscosts U.S.U.S. societysociety $100$100 billionbillion perper yearyear 11.. SchizophreniaSchizophrenia affectsaffects 0.20.2-2%-2% ofof thethe worldwidworldwid population;population; itit costscosts $32.5$32.5 billionbillion perper yearyear inin U.S.U.S. 22 BrainBrain conformalconformal mappingmapping cancan bebe usedused toto thethe diagnosisdiagnosis ofof ADAD andand Schizophrenia,Schizophrenia, brainbrain developmentdevelopment study,study, andand surgerysurgery mapping.mapping. OurOur conformalconformal mappingmapping waswas demonstrateddemonstrated toto bebe aa stablestable solutionsolution andand superiorsuperior thanthan otherother methodsmethods andand isis expectedexpected toto becomebecome aa standardstandard inin thisthis filefile inin thethe future.future. 1Alzheimer’s Disease Statistics. 2Statistic from Brain Facts. GrowthGrowthGrowth patternspatternspatterns ininin thethethe developingdevelopingdeveloping humanhumanhuman brainbrainbrain ** *Thompson et.al Growth patterns in the developing brain detected by using continuum mechanical tensor maps, Nature, 2000. GeometryGeometryGeometry MatchingMatchingMatching-brain--brainbrain mappingmappingmapping ConformalConformalConformal brainbrainbrain mappingmappingmapping demo GeometricGeometricGeometric MatchingMatchingMatching-brain--brainbrain mappingmappingmapping MinimizeMinimizeMinimize L2L2L2 normnormnorm underunderunder MobiusMobiusMobius transformationtransformationtransformation LeastLeastLeast squaresquaresquare problemproblemproblem demo GeometryGeometryGeometry CompressionCompressionCompression SphericalSphericalSpherical harmonicharmonicharmonic functionsfunctionsfunctions SpectrumSpectrumSpectrum compressioncompressioncompression SolutionSolutionSolution OutlineOutlineOutline TheoreticTheoreticTheoretic backgroundbackgroundbackground GenusGenusGenus zerozerozero closedclosedclosed surfacessurfacessurfaces NonzeroNonzeroNonzero genusgenusgenus closedclosedclosed surfacessurfacessurfaces SurfacesSurfacesSurfaces withwithwith boundariesboundariesboundaries SummarySummarySummary TheoreticTheoreticTheoretic backgroundbackgroundbackground –––RiemannRiemann Riemann surfacesurfacesurface ForForFor genusgenusgenus zerozerozero closedclosedclosed surfaces,surfaces,surfaces, aaa mappingmappingmapping isisis conformalconformalconformal ififif andandand onlyonlyonly ififif ititit isisis harmonic.harmonic.harmonic. HodgeHodgeHodge theory:theory:theory: EachEachEach cohomologycohomologycohomologyclassclass class hashashas aaa uniqueuniqueunique harmonicharmonicharmonic oneoneone-form--formform representative.representative.representative. AbelAbelAbel-Jacobi--JacobiJacobi theory:theory: theory: TheTheThe dimensiondimensiondimension ofofof holomorphicholomorphicholomorphicdifferentialdifferential differential groupgroupgroup isisis 222 timestimestimes genus.genus.genus. TheoreticTheoreticTheoretic background:background:background: StructuresStructuresStructures ononon meshmeshmesh TopologicalTopological structurestructure SimplicialSimplicialcomplex complex HomologyHomology groupgroup GeometricGeometric structurestructure EmbeddedEmbedded inin thethe EuclideanEuclidean Space,inducedSpace,induced metricmetric Curvature,Curvature, geodesicsgeodesics ConformalConformal StructureStructure (Novel(Novel viewview toto surfaces)surfaces) RiemannRiemann surfacessurfaces HolomorphicHolomorphicdifferentials differentials NovelNovelNovel viewviewview TreatTreat surfacessurfaces asas RiemannianRiemannian surfacessurfaces ConformalConformal mappingsmappings ConformalConformal invariantsinvariants ConformalConformal automorphismautomorphism