1. A method comprising: receiving an animation rig with a plurality of rig parameters, the rig parameters defining a deformation space for an attached surface mesh, the attached surface mesh comprising a plurality of nodes; receiving material stiffness data on a subset of the rig parameters, using the rig and the material stiffness data to influence a physics-based simulation that is constrained by the deformation space of the rig; and generating keyframes on some or all of the parameters as a result of the simulation.