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Iso-charts: Stretch-Driven ParameterizationIso-charts: Stretch-Driven Parameterizationvia Nonlinear Dimension Reductionvia Nonlinear Dimension Reduction
Iso-charts: Stretch-Driven ParameterizationIso-charts: Stretch-Driven Parameterizationvia Nonlinear Dimension Reductionvia Nonlinear Dimension Reduction
Kun Zhou, John Snyder, Baining Guo, Harry ShumKun Zhou, John Snyder, Baining Guo, Harry ShumKun Zhou, John Snyder, Baining Guo, Harry ShumKun Zhou, John Snyder, Baining Guo, Harry Shum
presented at SGP, June 2004presented at SGP, June 2004
Goals of Mesh ParameterizationGoals of Mesh ParameterizationGoals of Mesh ParameterizationGoals of Mesh Parameterization
Large Charts Low Distortion
Stretch-Driven ParameterizationStretch-Driven ParameterizationStretch-Driven ParameterizationStretch-Driven Parameterization AdvantagesAdvantages
measures distortion properly for texturing appsmeasures distortion properly for texturing apps
DisadvantagesDisadvantages requires nonlinear optimization (slow!)requires nonlinear optimization (slow!) provides no help in forming chartsprovides no help in forming charts
– resort to simple heuristics like planarity or compactnessresort to simple heuristics like planarity or compactness
Solution: apply Solution: apply IsomapIsomap (NDR technique) (NDR technique) stretch and Isomap related: both preserve lengthsstretch and Isomap related: both preserve lengths eigenanalysis rather than nonlinear optimizationeigenanalysis rather than nonlinear optimization provides:provides:
– good initial guess for stretch optimizationgood initial guess for stretch optimization
– good chartification heuristic via “spectral clustering”good chartification heuristic via “spectral clustering”
AdvantagesAdvantages measures distortion properly for texturing appsmeasures distortion properly for texturing apps
DisadvantagesDisadvantages requires nonlinear optimization (slow!)requires nonlinear optimization (slow!) provides no help in forming chartsprovides no help in forming charts
– resort to simple heuristics like planarity or compactnessresort to simple heuristics like planarity or compactness
Solution: apply Solution: apply IsomapIsomap (NDR technique) (NDR technique) stretch and Isomap related: both preserve lengthsstretch and Isomap related: both preserve lengths eigenanalysis rather than nonlinear optimizationeigenanalysis rather than nonlinear optimization provides:provides:
– good initial guess for stretch optimizationgood initial guess for stretch optimization
– good chartification heuristic via “spectral clustering”good chartification heuristic via “spectral clustering”
IsoMapIsoMapIsoMapIsoMap
Data points in highdimensional space
[Tenenbaum et al, 2000]
Data points in lowdimensional space
Neighborhoodgraph
Surface Spectral AnalysisSurface Spectral AnalysisSurface Spectral AnalysisSurface Spectral Analysis
12d
Nd2
Nd1
1x
2x
Nx
N
i
N
j
ijji d1 1
2)||(||min yy
Geodesic Distance Distortion (GDD)
2y
Ny
1y
Surface Spectral AnalysisSurface Spectral AnalysisSurface Spectral AnalysisSurface Spectral Analysis
222
21
22
222
221
21
212
211
NNNN
N
N
N
ddd
ddd
ddd
D
1. Construct matrix of squared geodesic distances 1. Construct matrix of squared geodesic distances DDNN
12d
Nd2
Nd1
1x
2x
Nx
Surface Spectral AnalysisSurface Spectral AnalysisSurface Spectral AnalysisSurface Spectral Analysis
2. Perform eigenanalysis on 2. Perform eigenanalysis on DDNN to getto get embedding coords embedding coords yyii
Tnn
T
T
N
v
v
v
yyy
22
11
21
|||
|||
12d
Nd2
Nd1
1x
2x
Nx
Isomap → low stretch (take first two coords)Isomap → low stretch (take first two coords)Isomap → low stretch (take first two coords)Isomap → low stretch (take first two coords)
IsoMap, L2 = 1.04, 2s IsoMap+Optimization, L2 = 1.03, 6s
[stretch, Sander01], L2 = 1.04, 222s [stretch, Sander02], L2 = 1.03, 39s
Isomap → good charts (spectral clustering)Isomap → good charts (spectral clustering)Isomap → good charts (spectral clustering)Isomap → good charts (spectral clustering)
Analysis
Clustering
Remeshing ComparisonRemeshing ComparisonRemeshing ComparisonRemeshing Comparison
Original model [Sander03], 79.5dB Iso-chart, 82.9dB