Efficient and robust skin slide simulation

Skin slide is the deformation effect where the outer surface moves along its tangent directions, caused by the stretching of other skin regions and/or the dynamic motion of the underlying tissues. Such an effect is essential for expressing natural deformations of humans, animals, and tightly-fitting costumes. Previous methods to achieve skin sliding were either manually controlled, or laborious to set up and expensive to compute. We present a novel, automated method to achieve convincing skin sliding with minimal set-up and run-time computation. Our method takes advantage of the recent developments in the elastic body simulations formulated as optimization using Alternating Direction Method of Multipliers (ADMM). This approach, which generalizes position-based and projective dynamics, allows intuitive integration of arbitrary constraints such as collision against the original deforming surface. The collision is accelerated and stabilized by taking advantage of the local nature of the sliding. To accelerate the convergence even further while respecting the artist-driven deformation, we propose a simple method to resume the simulation from the previous local parameterization. Various production results using a Maya deformer implementation of this technique prove its efficiency and competency.