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.

One-line summary: Radiosity caching speeds up distribution ray traced global illumination by more than 30 times in production shots.

Published as: Pixar Technical Memo #12-06. Pixar, July 2012.

Download the tech memo here: paper.pdf.

Videos of interactive global illumination and interactive ray-traced subsurface scattering here: globillum.m4v and subsurf.m4v.

SIGGRAPH 2012 talk here: sig12talk.

Back to Per's publication page.