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Estimating Specular Roughness and Anisotropy from Second Order Spherical Gradient Illumination
Author(s) -
Ghosh Abhijeet,
Chen Tongbo,
Peers Pieter,
Wilson Cyrus A.,
Debevec Paul
Publication year - 2009
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/j.1467-8659.2009.01493.x
Subject(s) - specular reflection , tangent , isotropy , surface finish , bidirectional reflectance distribution function , specular highlight , anisotropy , point (geometry) , surface roughness , surface (topology) , tangent space , optics , computer science , geometry , materials science , mathematics , physics , reflectivity , composite material
This paper presents a novel method for estimating specular roughness and tangent vectors, per surface point, from polarized second order spherical gradient illumination patterns. We demonstrate that for isotropic BRDFs, only three second order spherical gradients are sufficient to robustly estimate spatially varying specular roughness. For anisotropic BRDFs, an additional two measurements yield specular roughness and tangent vectors per surface point. We verify our approach with different illumination configurations which project both discrete and continuous fields of gradient illumination. Our technique provides a direct estimate of the per‐pixel specular roughness and thus does not require off‐line numerical optimization that is typical for the measure‐and‐fit approach to classical BRDF modeling.