Adaptive Radiosity Textures for Bidirectional Ray Tracing

Abstract

We present a rendering method designed to provide accurate, general simulation of global illumination for realistic image synthesis. Separating surface interaction into diffuse plus specular, we compute the specular component on the fly, as in ray tracing, and store the diffuse component (the radiosity) for later-reuse, similar to a radiosity algorithm. Radiosities are stored in adaptive radiosity textures (rexes)1 that record the pattern of light and shadow on every diffuse surface in the scene. They adaptively subdivide themselves to the appropriate level of detail for the picture being made, resolving sharp shadow edges automatically.We use a three-pass, bidirectional ray tracing algorithm that traces rays from both the lights and the eye. The "size pass" records visibility information on diffuse surfaces; the "light pass" progressively traces rays from lights and bright surfaces to deposit photons on diffuse surfaces to construct the radiosity textures; and the "eye pass" traces rays from the eye, collecting light from diffuse surfaces to make a picture.