Modeling Animals with Bones, Muscles, and Skin

A new approach to animal modeling and animation using simulated individual bones and muscles, soft tissues, and skin is described. Bones and muscles (made of combinations of ellipsoids) can be generated automatically from a tree structure and joint geometry or designed interactively. Together with soft tissue, these provide the underlying anatomy. A polygonal skin mesh is automatically generated to form a smooth covering. Muscles stretch across joints, and their orientations, sizes, and shapes change during joint motion. The skin mesh automatically adjusts to changes in position due to the eeect of neighboring skin points and anchor points associated with the underlying anatomy. Much of the process is automated; parameters may be be adjusted, and components can be added and removed. Manipulation and animation occur at comfortable interactive speeds on graphics workstations.