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Siggraph Course Mesh Parameterization: Theory and Practice Barycentric Mappings.

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Presentation on theme: "Siggraph Course Mesh Parameterization: Theory and Practice Barycentric Mappings."— Presentation transcript:

1 Siggraph Course Mesh Parameterization: Theory and Practice Barycentric Mappings

2 Triangle Mesh Parameterization triangle mesh – vertices – triangles parameter mesh – parameter points – parameter triangles parameterization – piecewise linear map

3 The Spring Model replace edges by springs fix boundary vertices relaxation process energy of spring between and : – spring constant – spring length total energy

4 Energy Minimization interior vertices ’s neighbours overall spring energy partial derivative

5 Energy Minimization minimum of spring energy for all interior points is a convex combination of its neighbors with weights

6 The Linear System separation of variables unknown parameter points fixed linear system

7 The Linear System solve system twice for and coordinates of interior parameter points matrix is – sparse – diagonally dominant – nonsingular as long as all

8 Choice of Weights uniform spring constants –, chordal spring constants –, no fold-overs for convex boundary no linear reproduction – planar meshes are distorted

9 Choice of Weights suppose is a planar mesh specify weights such that barycentric coordinates of then solving reproduces

10 Barycentric Coordinates Wachspress coordinates discrete harmonic coordinates mean value coordinates normalization

11 fold-overs for negative coordinates – affine combinations, numerically unstable if mean value coordinates guaranteed to be positive Example – Pyramid Wachspressdiscrete harmonicmean value

12 The Boundary Mapping chordal parameterization around convex shape – circle – rectangle projection into least squares plane – may lead to fold-overs


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