Dynamically simulated characters are difficult to control because they are underactuated—they have no direct control over their global position and orientation. In order to succeed, control policies must look ahead to determine stabilizing actions, but such planning is complicated by frequent ground contacts that produce a discontinuous search space. This paper introduces a locomotion system that generates high-quality animation of agile movements using nonlinear controllers that plan through such contact changes. We demonstrate the general applicability of this approach by emulating walking and running motions in rigid-body simulations. Then we consolidate these controllers under a higher-level planner that interactively controls the character's direction.


Contact-aware Nonlinear Control of Dynamic Characters
U. Muico, Y. Lee, J. Popović, Z. Popović
ACM Transactions on Graphics (SIGGRAPH 2009)

Demonstration video - Overview
4.5 min, 35 MB, H.264

Demonstration video - Real-time interactive controller
3 min, 10 MB, H.264

Demonstration video - From rest to run
11 sec, 2 MB, H.264

Demonstration video - Walking backwards
23 sec, 2.7 MB, H.264