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Near-Optimal Character Animation with Continuous Control

Adrien Treuille, Yongjoon Lee, Zoran Popovic

SIGGRAPHAcademic251 citesMotion Synthesis

Low-dimensional basis representation over motion capture enables automatic computation of near-optimal real-time character controllers.

Abstract

This paper presents a method for real-time interactive character animation that automatically computes near-optimal controllers from a corpus of motion capture data and a desired task. A motion engine blends sequences of precaptured clips while preventing foot-skate without inverse kinematics, and a control policy selects clip sequences using a compact value function represented as a linear combination of basis functions, learned via a linear programming approach to approximate dynamic programming. Because the value functions for many animation tasks are smooth, very few basis functions are needed, yielding controllers with low memory overhead that respond fluidly to continuous user control and environmental constraints. The authors introduce switchability and separability to mitigate dimensionality, and demonstrate navigation, spinning navigation, and fixed and moving obstacle avoidance, the latter enabling simple crowd simulations.

How to read this

Category
Method: data-driven near-optimal character controllers
Contributions
  • Automatic computation of near-optimal real-time controllers from a motion-capture corpus and a desired task.
  • A motion engine that blends precaptured clips and prevents foot-skate without inverse kinematics.
  • A control policy using a compact value function as a linear combination of basis functions, learned via a linear-programming approximation to dynamic programming, plus switchability and separability to manage dimensionality.
Context
Builds on motion-graph style clip-sequencing (Kovar et al.'s Motion Graphs) and frames clip selection as approximate dynamic programming over a low-dimensional value-function basis.Builds on: Motion Graphs
Correctness
Demonstrated on navigation, spinning navigation, and fixed and moving obstacle avoidance (extending to simple crowds); the compactness argument rests on the value functions being smooth for these tasks, so tasks with non-smooth objectives may need more basis functions.
Clarity
Accessible in motivation but reinforcement-learning-flavored; a first pass conveys the basis-function value-function idea, a second pass for the LP approximation and the switchability/separability constructs.
How to read it
First pass for the problem framing and the motion-engine/policy split; second pass on the value-function approximation and dimensionality tricks if you work on learned controllers.

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