All-Frequency Rendering of Dynamic, Spatially-Varying Reflectance

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.

In  ACM Transactions on Graphics

Publisher  Association for Computing Machinery, Inc.
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