Automatic rigging for animation characters with 3D silhouette

Animating an articulated 3D character requires the specification of its interior skeleton structure which defines how the skin surface is deformed during animation. Currently this task is to a large extent accomplished manually, which consumes a large amount of animators' time. This paper presents an automatic rigging method making use of a new geometry entity called the 3D silhouette. The first step is to extract a coarse 3D curve skeleton and some skeletal joints of a character. This curve skeleton is then refined with a perpendicular silhouette. According to the connectivity of the skeletal joints, the hierarchical animation skeleton is finally constructed. By avoiding complicated computation such as voxelization and pruning, this method is simple and efficient, much faster than existing methods. It proves very useful for quick animation production, with applications including games design and prototype graphical systems. Copyright © 2009 John Wiley & Sons, Ltd. Generating animation skeleton of a hand model with our method: (a) Original mode, (b) Primary 3D silhouette, (c) 3D medial axis of hand through constrained Delaunay triangulation, (d) Decomposition result, (e) Curve skeleton and key skeleton points, (f) Animation skeleton.