Silhouette Clipping Silhouette Clipping Pedro V. Sander Pedro V. Sander Xianfeng Gu Xianfeng Gu Steven J. Gortler Steven J. Gortler Harvard University Harvard University Hugues H. Hoppe Hugues H. Hoppe John M. Snyder John M. Snyder Microsoft Research Microsoft Research
Silhouette Clipping. Pedro V. Sander Xianfeng Gu Steven J. Gortler Harvard University. Hugues H. Hoppe John M. Snyder Microsoft Research. poor silhouette. + texture/bump map. Mesh simplification. original mesh. coarse mesh. Silhouette clipping. original mesh. coarse mesh. - PowerPoint PPT Presentation
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Silhouette ClippingSilhouette Clipping
Pedro V. SanderPedro V. SanderXianfeng GuXianfeng Gu
Steven J. GortlerSteven J. Gortler
Harvard UniversityHarvard University
Hugues H. HoppeHugues H. HoppeJohn M. SnyderJohn M. Snyder
Microsoft ResearchMicrosoft Research
Mesh simplificationMesh simplification
original meshoriginal mesh+ texture/bump map+ texture/bump map
poorpoorsilhouettesilhouette
coarse meshcoarse mesh
silhouette clippedsilhouette clipped
Silhouette clippingSilhouette clipping
original meshoriginal mesh coarse meshcoarse mesh+ texture/bump map+ texture/bump map
silhouette clippedsilhouette clipped
Silhouette clippingSilhouette clipping
original meshoriginal mesh coarse meshcoarse mesh+ texture/bump map+ texture/bump map
Silhouette clipping demoSilhouette clipping demo
normal maporiginal mesh
rendered
coarse mesh
OverviewOverview
[Soucy et al 96][Soucy et al 96][Cignoni et al 98][Cignoni et al 98][Cohen et al 98][Cohen et al 98]
Given mesh, create coarse mesh that encloses it.Given mesh, create coarse mesh that encloses it.
Original meshOriginal mesh Coarse hullCoarse hull
Progressive hullProgressive hull
Progressive mesh sequenceProgressive mesh sequence Every mesh encloses all finer meshes.Every mesh encloses all finer meshes.
Edge collapseEdge collapse
Perform greedy sequence of collapses.Perform greedy sequence of collapses. Ensure new mesh encloses old mesh:Ensure new mesh encloses old mesh:
Linear programming problem Linear programming problem
M i M
i-1
Linear programming (2D)Linear programming (2D)
Linear programming (2D)Linear programming (2D)
Linear programming (2D)Linear programming (2D)
Linear programming (2D)Linear programming (2D)
Linear programming (2D)Linear programming (2D)
Linear programming (2D)Linear programming (2D)
Linear programming (2D)Linear programming (2D)
new vertexnew vertexpositionposition
Progressive hull demoProgressive hull demo
Texture creationTexture creation
normal maporiginal mesh
rendered
coarse hull
[Cignoni et al 98][Cignoni et al 98][Soucy et al 96][Soucy et al 96]
Texture creationTexture creation
closest-pointclosest-point[Cignoni et al 98][Cignoni et al 98]
vertex normalsvertex normals
normal-shootingnormal-shootingOursOurs
originaloriginalcoarsecoarse
Silhouette extractionSilhouette extraction
Given mesh and viewpoint, return edges on silhouette.Given mesh and viewpoint, return edges on silhouette.
What is a silhouette edge?What is a silhouette edge?
Edge is on silhouette iff Edge is on silhouette iff oneone adjacent adjacent triangle faces towards viewpoint:triangle faces towards viewpoint:
not silhouettenot silhouette silhouettesilhouette
Related schemesRelated schemes Brute force: Brute force: O(edges)O(edges)
but O(edges on silhouette) but O(edges on silhouette) O( O(edges) !edges) ! [Markosian et al 97][Markosian et al 97]
probabilisticprobabilistic [Gooch et al 99] [Gooch et al 99]
assumes orthographic viewassumes orthographic view [Barequet et al 99] [Hertzmann & Zorin 00][Barequet et al 99] [Hertzmann & Zorin 00]
dual-space formulation dual-space formulation
[Kumar et al 96] [Johannsen & Carter 98] [Kumar et al 96] [Johannsen & Carter 98] backface cullingbackface culling
Ours: optimized hierarchy of anchored conesOurs: optimized hierarchy of anchored cones extracts 3,500 sil edges of 10,000 edges at 250 fpsextracts 3,500 sil edges of 10,000 edges at 250 fps
Hierarchical cullingHierarchical culling
Each node contains:Each node contains: cluster of mesh edgescluster of mesh edges spatial culling primitivespatial culling primitive
Hierarchical cullingHierarchical culling
Each node contains:Each node contains: cluster of mesh edgescluster of mesh edges spatial culling primitivespatial culling primitive
Spatial culling primitiveSpatial culling primitiveGiven cluster of edges,Given cluster of edges,
check if there are no silhouette edges.check if there are no silhouette edges.
True if adjacent triangles are True if adjacent triangles are all front-facing or all back-facing.all front-facing or all back-facing.
Spatial culling primitiveSpatial culling primitiveGiven cluster of edges,Given cluster of edges,
check if there are no silhouette edges.check if there are no silhouette edges.
True if adjacent triangles are True if adjacent triangles are all front-facingall front-facing or all back-facing. or all back-facing.
Spatial culling primitiveSpatial culling primitiveGiven cluster of edges,Given cluster of edges,
check if there are no silhouette edges.check if there are no silhouette edges.
True if adjacent triangles are True if adjacent triangles are all front-facingall front-facing or or all back-facingall back-facing..
Anchored cone primitiveAnchored cone primitive
front-facingcone
back-facingcone
Anchored cone primitiveAnchored cone primitive
Calculate central axisCalculate central axisGilbert’s algorithmGilbert’s algorithm
Algorithm inspired by Algorithm inspired by concave polygon-filling algorithmconcave polygon-filling algorithm..
Silhouette edges organized in hash table.Silhouette edges organized in hash table. Each contour drawn as fan of triangles:Each contour drawn as fan of triangles: