The Ellipsoid Normal Distribution Function
نویسندگان
چکیده
The Ellipsoid NDF is a new normal distribution function (NDF) that we introduce and use in the accompanying paper. It can be used with micro-facet BRDF to model the reflection and refraction of light from surfaces. This new distribution is a generalization of the widely used isotropic GGX/Trowbridge-Reitz distribution. The Ellipsoid model is based on the surface statistics of an arbitrary 3D ellipsoid allowing both anisotropy and rotations of the distribution. This document describes the derivation of the ellipsoid NDF along with a corresponding shadowing/masking term, which is needed for energy conservation, and a low-variance importance sampling strategy that guarantees the sample weights never exceed one.
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