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STD: Student's t‐Distribution of Slopes for Microfacet Based BSDFs
Author(s) -
Ribardière M.,
Bringier B.,
Meneveaux D.,
Simonot L.
Publication year - 2017
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.13137
Subject(s) - range (aeronautics) , isotropy , representation (politics) , bidirectional reflectance distribution function , distribution (mathematics) , attenuation , student's t distribution , graphics , function (biology) , anisotropy , mathematics , reflectivity , computer science , mathematical analysis , computer graphics (images) , optics , physics , engineering , volatility (finance) , autoregressive conditional heteroskedasticity , evolutionary biology , politics , political science , law , econometrics , biology , aerospace engineering
This paper focuses on microfacet reflectance models, and more precisely on the definition of a new and more general distribution function, which includes both Beckmann's and GGX distributions widely used in the computer graphics community. Therefore, our model makes use of an additional parameter γ , which controls the distribution function slope and tail height. It actually corresponds to a bivariate Student's t‐distribution in slopes space and it is presented with the associated analytical formulation of the geometric attenuation factor derived from Smith representation. We also provide the analytical derivations for importance sampling isotropic and anisotropic materials. As shown in the results, this new representation offers a finer control of a wide range of materials, while extending the capabilities of fitting parameters with captured data.