Efficient Elasticity for Character Skinning with Contact and Collisions

How to read this

Category

Method: a near-interactive physics-based skinning algorithm (corotational elasticity)

Contributions

• A one-point quadrature discretization of corotational elasticity over a uniform hexahedral lattice with a stabilization scheme suppressing hourglass modes, needing only one polar decomposition per cell
• A matrix-free indefiniteness correction enforcing element stiffness positive-definiteness, enabling efficient CG solves for quasistatics and implicit dynamics
• A multigrid solver (with a Full Approximation Scheme nonlinear variant) and a branch-free vectorized SVD scaling to hundreds of thousands of DOFs, handling body/self-collisions and soft constraints

Context

Production soft-tissue character skinning at Disney, building on the corotational-elasticity and FEM simulation lineage and pushing it toward interactive rates via lattice discretization and multigrid.

Correctness

Demonstrated in a production character-skinning pipeline with collision and constraint handling; a reader should note the method assumes a uniform hexahedral embedding lattice and relies on the stabilization to control nullspace modes, so behavior depends on lattice resolution and the penalty-based collision response.

Clarity

Dense numerical-methods paper; a first pass conveys the system design and goals, but a second pass is needed to follow the quadrature, stabilization and multigrid formulation.

How to read it

First pass for the overall pipeline and why one-point quadrature plus stabilization matters; do a careful second pass on the discretization, the indefiniteness correction, and the multigrid/FAS solver if you intend to implement or evaluate it.