Keys-to-Sim: Transferring Hand-Crafted Key-framed Animations to Simulated Figures using Wide Band Stochastic
Trajectory Optimization
Abstract
The vision of fully simulating characters and their environments has the potential to offer rich
interactions between characters and objects in the virtual world. However, this introduces a challenging
problem similar to controlling robotic figures: computing the necessary torques to perform a given task. In
this paper, we address the problem of transferring hand-crafted kinematic motions to a fully simulated
figure, by computing open-loop controls necessary to reproduce the target motion. One key ingredient to
successful control is the mechanical feasibility of the target motion. While several methods have been
successful at replicating human captured motion, there has not yet been a method capable of handling the
case of artist-authored key-framed movements that can violate the laws of physics or go beyond the
mechanical limits of the character. Due to the curse of dimensionality, sampling-based optimization methods
typically restrict the search to a narrow band which limits exploration of feasible motions, resulting in a
failure to reproduce the desired motion when a large deviation is required. In this paper, we solve this
problem by combining a window-based breakdown of the controls on the temporal dimension, together with a
global wide search strategy that keeps locally sub-optimal samples throughout the optimization.