All-Frequency Rendering of Dynamic, Spatially-Varying Reflectance

Jiaping Wang, Peiran Ren, Minmin Gong, John Snyder, and Baining Guo

Abstract

We describe a technique for real-time rendering of dynamic, spatially-varying BRDFs in static scenes with all-frequency shad- ows from environmental and point lights. The 6D SVBRDF is rep- resented with a general microfacet model and spherical lobes fit to its 4D spatially-varying normal distribution function (SVNDF). A sum of spherical Gaussians (SGs) provides an accurate approxima- tion with a small number of lobes. Parametric BRDFs are fit on- the-fly using simple analytic expressions; measured BRDFs are fit as a preprocess using nonlinear optimization. Our BRDF represen- tation is compact, allows detailed textures, is closed under products and rotations, and supports reflectance of arbitrarily high specular- ity. At run-time, SGs representing the NDF are warped to align the half-angle vector to the lighting direction and multiplied by the mi- crofacet shadowing and Fresnel factors. This yields the relevant 2D view slice on-the-fly at each pixel, still represented in the SG basis. We account for macro-scale shadowing using a new, nonlinear vis- ibility representation based on spherical signed distance functions (SSDFs). SSDFs allow per-pixel interpolation of high-frequency visibility without ghosting and can be multiplied by the BRDF and lighting efficiently on the GPU.

Details

Publication typeArticle
Published inACM Transactions on Graphics
PublisherAssociation for Computing Machinery, Inc.
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