A computer system for simulating human facial expression

Computer simulation of human facial expression requires an interactive ability to create arbitrary face models and to control the simulated expression on those models. The system described in this paper provides interactive facilities for attaching muscles and wrinkle lines to arbitrary rectangular face meshes and then for simulating the contractions of those muscles. The system is divided into two modules: the Expression Editor and the Muscle and Wrinkle Editor. The Expression Editor system uses the Facial Action Coding System notation (FACS) to control facial expression at a very high level. The FACS notation is a compact and intuitive way of describing facial expression since it encodes the visual effect of muscle contraction and abstracts out the low level details of facial physiology. The Muscle and Wrinkle Editor is used to establish the correspondence between the high level FACS encoding and the low level muscular action of the face. A new skin model is described which more accurately simulates the extended area effects of large facial muscles. Structural analysis techniques are used to solve the resulting elasticity equations efficiently. Several mechanisms for reducing computation time are described.