Vector occluders: an empirical approximation for rendering global illumination effects in real-time

Abstract

Precomputation has been previously used as a means to get global illumination effects in real-time on consumer hardware of the day. Our work uses Sloan’s 2002 PRT method as a starting point, and builds on it with two new ideas. We first explore an alternative representation for PRT data. “Cpherical harmonics” (CH) are introduced as an alternative to spherical harmonics, by substituting the Chebyshev polynomial in the place of the Legendre polynomial as the orthogonal polynomial in the spherical harmonics definition. We show that CH can be used instead of SH for PRT with near-equivalent performance. “Vector occluders” (VO) are introduced as a novel, precomputed, real-time, empirical technique for adding global illumination effects including shadows, caustics and interreflections to a locally illuminated scene on static geometry. VO encodes PRT data as simple vectors instead of using SH. VO can handle point lights, whereas a standard SH implementation cannot.