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Model Predictive Control with a Visuomotor System for Physics-based Character Animation

Haegwang Eom, Daseong Han, Joseph S Shin, Junyong Noh

TOGWeta FX34 citesMotion Synthesis

Physics-based character animation using model predictive control paired with a visuomotor perception system for reactive locomotion.

Abstract

This article presents a Model Predictive Control framework with a visuomotor system that synthesizes eye and head movements coupled with physics-based full-body motions while placing visual attention on objects of importance in the environment. As the engine of this framework, we propose a visuomotor system based on human visual perception and full-body dynamics with contacts. Relying on partial observations with uncertainty from a simulated visual sensor, an optimal control problem for this system leads to a Partially Observable Markov Decision Process, which is difficult to deal with. We approximate it as a deterministic belief Markov Decision Process for effective control. To obtain a solution for the problem efficiently, we adopt differential dynamic programming, which is a powerful scheme to find a locally optimal control policy for nonlinear system dynamics. Guided by a reference skeletal motion without any a priori gaze information, our system produces realistic eye and head movements together with full-body motions for various tasks such as catching a thrown ball, walking on stepping stones, balancing after being pushed, and avoiding moving obstacles.

How to read this

Category
Method: model predictive control with a visuomotor system for physics-based animation
Contributions
  • An MPC framework that synthesizes coupled eye, head, and physics-based full-body motion while attending to important objects.
  • A visuomotor system based on human visual perception and full-body dynamics with contacts, using partial, uncertain observations from a simulated visual sensor.
  • A tractable formulation that approximates the resulting POMDP as a deterministic belief MDP and solves it with differential dynamic programming.
Context
Sits in the physics-based control lineage exemplified by Peng et al.'s DeepMimic, adding a perception-driven gaze-and-body coupling rather than relying on a priori gaze data.Builds on: DeepMimic: Example-Guided Deep Reinforcement Learning of Physics-Based Character Skills
Correctness
Demonstrated on tasks such as catching a thrown ball, walking on stepping stones, balancing after a push, and avoiding moving obstacles; results rely on the belief-MDP approximation and DDP finding a locally optimal policy, so behavior is local and task-guided by a reference skeletal motion.
Clarity
Mathematically dense; a first pass conveys the perceive-then-control loop, but the POMDP approximation and DDP need a careful second pass.
How to read it
Focus first on how visual attention feeds the controller and what the reference motion provides; a second pass on the belief-MDP and DDP formulation is needed to follow or reproduce the control.

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