Multiresolution Radiosity Caching for Efficient Preview and Final Quality Global Illumination in Movies

Per H. Christensen, George Harker, Jonathan Shade, Brenden Schubert, Dana Batali

Abstract:

We present a multiresolution radiosity caching method that allows global illumination to be computed efficiently in a single pass in complex CG movie production scenes.

For distribution ray tracing in production scenes, the bottleneck is the time spent evaluating complex shaders at the ray hit points. We speed up this shader evaluation time for global illumination by separating out the view-independent component and caching its result --- the radiosity. Our cache contains three resolutions of the radiosity; the resolution used for a given ray is selected using the ray's differential. The resulting single-pass global illumination method is fast and flexible enough to be used in movie production, both for interactive lighting design and final rendering. It is currently being used in production at several studios.

The multiresolution cache is also used to store shader opacity results for faster ray-traced shadows, ambient occlusion and volume extinction, and to store irradiance for efficient ray-traced subsurface scattering.

Paper (PDF)

Additional materials: [siggraphtalk.pdf], [subsurf.m4v], [globillum.m4v], [siggraphslides.pdf]

Available as Pixar Technical Memo #12-06