texture mapping by model pelting and blending deva ramanan hao zhang
TRANSCRIPT
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Texture Mapping by Model Pelting and Blending
Deva Ramanan
Hao Zhang
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Texture mapping• Improve surface appearance
– Versatile: image map, displacement map, reflection map …
– Relative small amount of computation
(from Pixar shutterbug image series)
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Texture mapping (contd.)• Requires “good” parameterization
– Minimize distortion– Appears to be seamless
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Subdivision surfaces
• One single mesh for any topology– Multiple NURBS patches
– Maintain smoothness (static and animated)
• (u,v)-parameterization – Tensor product B-Spline patches
– Shapes of arbitrary topology
• Cf. “Character animation” (SS98)(SS98)
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Texture mapping on subdivision surfaces
• 3D Solid Textures
• Multiple local textures– Blend overlapping regions at the seam
• Goals (again):– Minimize distortion– Seam blending
http://graphics.eecs.wsu.edu/apst/
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Texture coordinates
• Linear interpolation [Stam98]– texture coords as local (u,v) parameterization– yields C1 interior and C0 cross-boundary
• Catmull-Clark on scalar field– position (x,y,z) position+texture (x,y,z,s,t)– subdivide in 5D– yields C2 interior and C1 on extra-ordinary
points– needs texture coordinates on M0
(SS98)
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Texture mapping analogy: The pelt
• Initial control mesh ~ rubber sheet– Stretch mesh to form a pelt– Paint texture on the pelt
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Pelting: The Cut
• Cut: User specified connected tree of edges
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Pelting: Implementation
• Approximate rubber sheet by a spring-mass system
• Distortion measure:– Elastic energy– Scale invariance
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Simulate a spring-mass system
• System evolves so as to minimize energy
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Blending Texture: Approach• Split M0 into 2 overlapping regions:
-Uo: Pelt Region
-U1: Patch Region
• Use blend functions b0() & b1() along overlapping regions
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Example Patch
C0 + C1 + C2 + C3= patch region
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Review: Domain of Control
• 2D Cubic B Splines:
• Catmull/Clark surfaces:
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PA B C D
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Blend Function• Pelt, Patch, and Overlapping Regions
surrounding the Cut
• b1= cubic B-spline
• b0 = 1 - b1
C0 C1 C2 C3 C4
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Results: Cool Pictures!
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Evaluation• Pelting:
– Novel 3D Spring Mass implementation eliminates “buckling” [Maillot et al 93]
• Seam blending:– Painted textures
• Weaknesses:– Tiled/tesselated pattern– low polygon count meshes
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Conclusion
• Ultimate goal:– Minimum distortion– texture coordinate control
http://www.tfe.umu.se/courses/systemteknik/Multimed2/