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Iso-charts: Stretch-Driven Parameterization via Nonlinear Dimension Reduction Kun Zhou, John Snyder, Baining Guo, Harry Shum presented at SGP, June 2004
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Goals of Mesh Parameterization Large Charts Low Distortion
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Stretch-Driven Parameterization l Advantages n measures distortion properly for texturing apps l Disadvantages n requires nonlinear optimization (slow!) n provides no help in forming charts –resort to simple heuristics like planarity or compactness l Solution: apply Isomap (NDR technique) n stretch and Isomap related: both preserve lengths n eigenanalysis rather than nonlinear optimization n provides: –good initial guess for stretch optimization –good chartification heuristic via “spectral clustering” l Advantages n measures distortion properly for texturing apps l Disadvantages n requires nonlinear optimization (slow!) n provides no help in forming charts –resort to simple heuristics like planarity or compactness l Solution: apply Isomap (NDR technique) n stretch and Isomap related: both preserve lengths n eigenanalysis rather than nonlinear optimization n provides: –good initial guess for stretch optimization –good chartification heuristic via “spectral clustering”
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IsoMapIsoMap Data points in high dimensional space [Tenenbaum et al, 2000] Data points in low dimensional space Neighborhood graph
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Surface Spectral Analysis Geodesic Distance Distortion (GDD)
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Surface Spectral Analysis 1. Construct matrix of squared geodesic distances D N
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Surface Spectral Analysis 2. Perform eigenanalysis on D N to get embedding coords y i
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Isomap → low stretch (take first two coords) IsoMap, L 2 = 1.04, 2s IsoMap+Optimization, L 2 = 1.03, 6s [stretch, Sander01], L 2 = 1.04, 222s [stretch, Sander02], L 2 = 1.03, 39s
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Isomap → good charts (spectral clustering) Analysis Clustering
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ResultsResults 19 charts, L 2 =1.03, running time 98s, 97k faces
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ResultsResults 38 charts, L 2 =1.07, running time 287s, 150k faces
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ResultsResults 23 charts, L 2 =1.06, running time 162s, 112k faces
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ResultsResults 11 charts, L 2 =1.01, running time 4s, 10k faces
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Remeshing Comparison Original model [Sander03], 79.5dBIso-chart, 82.9dB
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Texture Synthesis Results
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