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Consolidation of Unorganized Point Clouds for Surface Reconstruction. Hui Huang 1 Dan Li 1 Hao Zhang 2 Uri Ascher 1 Daniel Cohen-Or 3 1 University of British Columbia 2 Simon Fraser University 3 Tel-Aviv University. Raw Scan Data.
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Consolidation of Unorganized Point Clouds for Surface Reconstruction Hui Huang1 Dan Li1 Hao Zhang2 Uri Ascher1 Daniel Cohen-Or3 1 University of British Columbia 2 Simon Fraser University 3 Tel-Aviv University
Surface Reconstruction • Delaunay techniques • [Amenta & Bern 1998], Power-crust [Amenda et al. 2001], Cocone [Dey & Giesen 2001], [Cazals & Giesen 2006] …… • Approximate reconstructions • [Hoppe et al. 1992], RBF [Carr et al. 2001], Poisson [Kazhdan et al. 2006] ……
Difficulties • Direct surface reconstruction may fail on challenging datasets • Normals are crucial for surface reconstruction • noise • outliers • close-by surface sheets • missing normal information • not always available • not always reliable
Unsigned Directions by PCA Thick cloud Non-uniform distribution Close-by surface sheets
Normal Consistency • [Hoppe et al. 1992] • Based on angles between unsigned normals • May produce errors on close-by surface sheets
Point Cloud Consolidation Input Output Input Output Unorganized Noisy Thick Outliers Non-uniform Un-oriented Consolidated Clean Thin Outlier-free Uniform Oriented
Contributions To consolidate point clouds: • Weighted locally optimal projection operator (WLOP) • Robust normal estimation
Locally Optimal Projection LOP operator [Lipman et al. 2007] defines a point set by a fixed point iteration where, for each point x, given the current iterate, the next iterate is to minimize The repulsion function here is
New Repulsion Function • More locally regular point distribution
New Repulsion Function • Better convergence behavior
Non-uniformity The first term of LOP, an L1 median, tends to follow the trend of non-uniformity if input is highly non-uniform. σ = 0.18 σ = 0.24 LOP (old η) LOP (new η) Raw scan
Improved Weighted LOP Define the weighted local densities for each point in the input set and projection set as Then the projection becomes
Raw Scan LOP (old η) LOP (new η) WLOP WLOP vs. LOP • More globally regular point distribution σ = 0.18 σ = 0.24 σ = 0.09
WLOP vs. LOP • Better convergence
Select a source Propagate Detect thin surface features Normal flipping Normal Propagation
Source Selection
Limitation: cannot distinguish between flat and concave Thin Features and Normal Flipping Outside the convex hull Remedy: normal flipping
PCA OPCA Propagate Corrector Loop Orientation-aware PCA Predictor
One Example Without flip After correction Noisy input Traditional result With flip
Up-sampling Raw scan Without consolidation With consolidation
Surface Generation RBF LOP WLOP RBF
RBF Poisson
Traditional Our NormFet+AMLS+Cocone [Dey et al.]
Traditional Without iteration With OPCA
Sparse set Front-culling Back-culling Poisson surface
Future Work • Theoretical guarantee for the correctness of normal estimation under sampling • Rigorous theoretical analysis of the predictor-corrector iteration • Better handling of missing data • Recovery and enhancement of sharp features
Acknowledgements Federico Ponchio Anonymous Reviewers AIM@SHAPE NSERC (No. 84306 and No. 611370) The Israel Science Foundation
Point-Consolidation APIis available http://people.cs.ubc.ca/~hhzhiyan/consolidation.html