“Better Collisions and Faster Cloth for Pixar’s Coco” by Eberle

  • ©David (Dave) Eberle

  • ©David (Dave) Eberle

  • ©David (Dave) Eberle

Conference:


Entry Number: 08

Title:

    Better Collisions and Faster Cloth for Pixar's Coco

Presenter(s):



Abstract:


    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.

References:


    D. Baraff and A. Witkin. 1998. Large Steps in Cloth Simulation. In Proceedings of the 25th Annual Conference on Computer Graphics and Interactive Techniques (SIGGRAPH ’98). ACM, 12.
    D. Baraff and A. Witkin. 2003. Untangling Cloth. In ACM SIGGRAPH 2003 Papers (SIGGRAPH ’03). ACM, 9.
    R. Bridson, R. Fedkiw, and J. Anderson. 2002. Robust Treatment of Collisions, Contact and Friction for Cloth Animation. In Proceedings of the 29th Annual Conference on Computer Graphics and Interactive Techniques (SIGGRAPH ’02). ACM, 594–603.
    T. Brochu, E. Edwards, and R. Bridson. 2012. Efficient Geometrically Exact Continuous Collision Detection. ACM Trans. Graph. 31, 4, Article 96 (2012), 7 pages. S. Curtis, R. Tamstorf, and D. Manocha. 2008. Fast Collision Detection for Deformable Models Using Representative-triangles. In Proceedings of the 2008 Symposium on Interactive 3D Graphics and Games (I3D ’08). ACM, 9.
    X. Provot. 1995. Collision and self-collision handling in cloth model dedicated to design garment. Graphics Interface (1995), 12.
    R. Tamstorf, T. Jones, and S. McCormick. 2015. Smoothed Aggregation Multigrid for Cloth Simulation. ACM Trans. Graph. 34, 6, Article 245 (2015), 13 pages. M. Tang, R. Tong, Z. Wang, and D. Manocha. 2014. Fast and Exact Continuous Collision Detection with Bernstein Sign Classification. ACM Trans. Graph. 33, 6, Article 186 (2014), 8 pages.
    H. Wang. 2014. Defending Continuous Collision Detection Against Errors. ACM Trans. Graph. 33, 4, Article 122 (2014), 10 pages.

Keyword(s):



Acknowledgements:


    Thanks to Theodore Kim and Andrew Butts for their valuable feed back on this abstract, Hayley Iben for her support in this endeavor, and the Coco Sim/Tailoring team for their outstanding work.


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