Generating Avoidance Motion Using Motion Graph

Abstract

We propose a method of generating avoidance motions. We use a motion graph to generate continuous motions, including both avoidance and other kinds of motions. In the combat of real humans, trained fighters avoid an attack with minimal movement. To realize such avoidance motion, we developed criteria to find an appropriate path (series of edges) in the motion graph. The characters are expected to move their body by only a minimal distance to avoid an attack. We introduced attack, body and avoidance space–time volumes to evaluate this criterion. Each candidate path is evaluated according to the distance between attack and body volumes and the overlap between attack and avoidance volumes. We also introduced a method to control the execution speeds of edges, and thus adjust the timing of avoidance motions. Moreover, to find a path in real time, we developed methods to facilitate the searching process such as the use of grid-based indices to look up candidate paths and GPU-based quick collision detection to cull candidate paths. We tested our approach on an application in which a character avoids incoming balls controlled by a user and demonstrated the effectiveness of our approach.