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Matching 3D Models With Shape Distributions. Robert Osada, Tom Funkhouser Bernard Chazelle, and David Dobkin Princeton University. Shape Similarity. Determine similarity between 3D shapes. Computer Graphics. Computer Vision. Computational Biology. [Insulin, PDB]. [Caltech].
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Matching 3D Models With Shape Distributions Robert Osada, Tom Funkhouser Bernard Chazelle, and David Dobkin Princeton University
Shape Similarity • Determine similarity between 3D shapes ComputerGraphics ComputerVision Computational Biology [Insulin, PDB] [Caltech]
Previous Work in 2D • Shape representations • Fourier analysis [Arbter90] • Turning function [Arkin91] • Size function [Uras95] • Metrics for comparing curves • Hausdorff • Fréchet • Bottleneck • etc.
Previous Work in 3D • High-level representations • Generalized cylinders [Binford71] • Medial axis [Bardinet00] • Skeletons [Bloomenthal99] • Statistical • Moments [Reeves45, Prokop92] • Crease angle [Besl94] • Shells decomposition around centroid [Ankerst99] • Extended Gaussian Images [Horn84] • etc.
Desired Properties • Match global properties of shape • Invariance • Rotation, translation, scale, mirror • Robustness • Noise, cracks, insertions and deletions • Practicality • Concise representation • Efficient comparison • Working with degenerate models
Our Approach • Shape distributions • Concise shape descriptor • Common parameterization • Function of random points Random sampling Parameterization ShapeDistribution 3D Model
Our Approach Parameterization Shape Function SimilarityMeasure Parameterization 3D Model Shape Distribution
Issues • Which shape function? • How to compare shape distributions? Parameterization SimilarityMeasure Parameterization
Issues • Which shape function? • How to compare shape distributions? Parameterization SimilarityMeasure Parameterization
Which Shape Function? • Computationally simple options (~ 1s) • Based on random points • Angles, distances, areas, volumes A3 D1 D2 D3 D4 [Ankerst99]
Shape Function – D2 • Distance between two random points on surface Line Segment Circle Triangle Cube Cylinder Sphere Two adjacent spheres Two spheres moving apart
Which Shape Function? • Sneak preview
Shape Function – Key Questions • Invariant? • Rotation, translation, mirror (not scale) • Robust? • Noise, cracks, insertions and deletions • Descriptive?
Issues • Which shape function? • How to compare shape distributions? Parameterization SimilarityMeasure Parameterization
Comparison • Normalize for scale • Compare shape distributions Parameterization Parameterization
Normalization for Scale max mean search
Compare shape distributions • Computationally simple options (~ .1ms) • Ln norms of densities (PDF) orcumulative densities (CDF) • More complex options • Earth mover’s distance, Bhattacharyaa distance. PDF CDF
Experimental Results • Goal is to address the following: • Is the method robust? • How well does it classify? PDF L1 L2 L CDF L1 L2 L A3 D1 D2D3 D4 Max Mean Search
Robustness Experiment • 10 Models Car Chair Human Missile Mug Phone Plane Skateboard Sub Table
Robustness Experiment • 6 Transforms • Rotate, scale, mirror, noise, delete, insert • Total of 70 models 1% Noise 5% Deletion
Robustness Results • Resulting distributions stable 7 Missiles 7 Mugs Probability Distance
Classification Experiment • 133 Models categorized into25 Groups • Large variety • within a group • among groups 4 Mugs 6 Cars 3 Boats
5 Animals 4 Balls 2 Belts 3 Blimps 3 Boats 6 Cars 8 Chairs 3 Claws 4 Helicopters 11 Humans 3 Lamps 3 Lightnings 6 Missiles 4 Mugs 4 Openbooks Classification Results
Classification Results Probability Distance
Line Segment Circle 5 Animals 4 Balls 2 Belts 3 Blimps 3 Boats Triangle Cube 6 Cars 8 Chairs 3 Claws 4 Helicopters 11 Humans Cylinder Sphere Two adjacent spheres Two spheres moving apart 3 Lamps 3 Lightnings 6 Missiles 4 Mugs 4 Openbooks Classification Results
Query NearestNeighbor 1stTier 2ndTier Results … Classification Results • Avoid bias due to varying group sizes
Classification Results • Similarity matrix • Nearest Neighbor • 1st Tier • 2nd Tier • Blocks • Tanks • Mugs • Humans • Airplanes • Boats
Comparison to Moments • Method • Align 1st moments (translation) • Align 2nd moments (rotation and scale) • Compare using remaining moments (L2)
Conclusion – Properties • Match global properties of shape • Invariance • Rotation, translation, scale, mirror • Robustness • Noise, cracks, insertions and deletions • Practicality • Concise representation • Efficient comparison • Works for degenerate models
Conclusion – Key Ideas • Sampling gives common parameterization • Simplifies comparison • Comparing distributions is fast and easy • Avoids registration, correspondence, etc. • Simple shape functions are discriminating • Method suitable as preclassifier
Future Work • Use a larger and more controlled database • Combine shape distributions with other classifiers into a working shape-based retrieval system
Thank you • Sloan Foundation • NSF