A Hybrid Iterative Solver for Robustly Capturing Coulomb Friction in Hair Dynamics

Gilles Daviet (1) , Florence Bertails-Descoubes (1) , Laurence Boissieux (2, 3)

1 BIPOP - Modelling, Simulation, Control and Optimization of Non-Smooth Dynamical Systems
2 Inria Grenoble - Rhône-Alpes
3 SED [Grenoble] - Service Expérimentation et Développement

Dry friction between hair fibers plays a major role in the collective hair dynamic behavior as it accounts for typical nonsmooth features such as stick-slip instabilities. However, due the challenges posed by the modeling of nonsmooth friction, previous mechanical models for hair either neglect friction or use an approximate smooth friction model, thus losing important visual features. In this paper we present a new generic robust solver for capturing Coulomb friction in large assemblies of tightly packed fibers such as hair. Our method is based on an iterative algorithm where each single contact problem is efficiently and robustly solved by introducing a hybrid strategy that combines a new zero-finding formulation of (exact) Coulomb friction together with an analytical solver as a fail-safe. Our global solver turns out to be very robust and highly scalable as it can handle up to a few thousand densely packed fibers subject to tens of thousands frictional contacts at a reasonable computational cost. It can be conveniently combined to any fiber model with various rest shapes, from smooth to curly. Our results, visually validated against real hair motions, depict typical hair collective effects and greatly enhance the realism of standard hair simulators.

Mots clés: Hair simulation; hair contacts; Coulomb friction

Domaines: Synthèse d'image et réalité virtuelle [cs.GR]

Gilles Daviet, Florence Bertails-Descoubes, Laurence Boissieux. A Hybrid Iterative Solver for Robustly Capturing Coulomb Friction in Hair Dynamics. ACM Transactions on Graphics, 2011, Proceedings of SIGGRAPH Asia 2011, 30 (6), pp.139:1--139:12. ⟨10.1145/2070781.2024173⟩. ⟨hal-00647497⟩