Jiaping Wang, Peiran Ren, Minmin Gong, John Snyder, and Baining Guo
1 December 2009
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.
|Published in||ACM Transactions on Graphics|
|Publisher||Association for Computing Machinery, Inc.|
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