Better Collisions and Faster Cloth for Pixar's Coco

David Eberle


Among the many technical challenges of Pixar's Coco was the need to handle cloth simulation for a densely populated city of skeleton characters. Skeletons posed new challenges to the collision algorithms of our in-house cloth system, Fizt. Continuous collision detection and response is an obvious solution to handling fast motion of thin geometry, but it presents us with a serious problem. In our production pipeline, geometry often starts in intersection. Animation also frequently causes kinematic surfaces to pinch the cloth between them and drive the cloth through itself. We present a solution for robustly allowing intersection recovery while employing standard continuous detection techniques. Coco also demanded more cloth than any previous Pixar film. To keep up with demand, Fizt needed to run much faster. We share our techniques for gaining performance in linear system assembly and solution, which should be applicable to most implicit solvers.

Paper (PDF)