500 Million and Counting: Hair Rendering on Ratatouille

David Ryu


Featuring plush rats, well-groomed humans, and a colony of rodents numbering a thousand strong, Ratatouille had shots where the original scene descriptions contained many hundreds of millions of hairs. To make these shots renderable, we developed many new technologies to optimize our RenderMan-based hair rendering pipeline, including caching to speed up runtime sculpting, a technique for optimizing bounding boxes for RiProcedurals, and a smooth level-of-detail system incorporating depth-of- eld and motion blur. These techniques resulted in an order of magnitude reduction in hair rendering time and memory compared to the already optimized pipeline used previously in Pixar films.

Available as Pixar Technical Memo #07-09