Group motion editing

Abstract

Animating a crowd of characters is an important problem in computer graphics. The latest techniques enable highly realistic group motions to be produced in feature animation films and video games. However, interactive methods have not emerged yet for editing the existing group motion of multiple characters. We present an approach to editing group motion as a whole while maintaining its neighborhood formation and individual moving trajectories in the original animation as much as possible. The user can deform a group motion by pinning or dragging individuals. Multiple group motions can be stitched or merged to form a longer or larger group motion while avoiding collisions. These editing operations rely on a novel graph structure, in which vertices represent positions of individuals at specific frames and edges encode neighborhood formations and moving trajectories. We employ a shape-manipulation technique to minimize the distortion of relative arrangements among adjacent vertices while editing the graph structure. The usefulness and flexibility of our approach is demonstrated through examples in which the user creates and edits complex crowd animations interactively using a collection of group motion clips.