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Extracting Microfacet‐based BRDF Parameters from Arbitrary Materials with Power Iterations
Author(s) -
Dupuy Jonathan,
Heitz Eric,
Iehl JeanClaude,
Poulin Pierre,
Ostromoukhov Victor
Publication year - 2015
Publication title -
computer graphics forum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.578
H-Index - 120
eISSN - 1467-8659
pISSN - 0167-7055
DOI - 10.1111/cgf.12675
Subject(s) - bidirectional reflectance distribution function , eigenvalues and eigenvectors , computer science , algorithm , surface finish , anisotropy , nonlinear system , texture mapping , mathematical optimization , mathematics , computer vision , optics , reflectivity , physics , materials science , quantum mechanics , composite material
Abstract We introduce a novel fitting procedure that takes as input an arbitrary material, possibly anisotropic, and automatically converts it to a microfacet BRDF. Our algorithm is based on the property that the distribution of microfacets may be retrieved by solving an eigenvector problem that is built solely from backscattering samples. We show that the eigenvector associated to the largest eigenvalue is always the only solution to this problem, and compute it using the power iteration method. This approach is straightforward to implement, much faster to compute, and considerably more robust than solutions based on nonlinear optimizations. In addition, we provide simple conversion procedures of our fits into both Beckmann and GGX roughness parameters, and discuss the advantages of microfacet slope space to make our fits editable. We apply our method to measured materials from two large databases that include anisotropic materials, and demonstrate the benefits of spatially varying roughness on texture mapped geometric models.