MIRALab Copyright © Information 1998 A Dynamic Wrinkle Model in Facial Animation and Skin Aging Yin Wu, Nadia Magnenat Thalmann MIRALab, University of Geneva Daniel Thalmann Computer Graphics Lab, EPFL Abstract This paper describes a dynamic model to simulate expressive wrinkles in 3D facial animation and skin aging. A skin surface is defined that can slide over an underlying layer, which constrains the surface by a spring force that simulates the connective fat tissue between them. Muscle masks are constructed to characterize the muscular contractions that provide the facial movement. Skin deformation is simulated through an elastic process assembled with visco and plastic units. By adjusting parameters for this physically based model, distinctive wrinkles for different faces can be generated. Keywords: Physically Based Model, Elasticity, Plastic Unit, Visco Unit, Expressive Wrinkles, Facial Animation, Skin Aging. 1. Introduction Human face modeling and animation is a very complex task because of the physical structure of the face and the dynamics involving the psychological and behavioral aspects. Thus, a realistic facial animation is rather difficult. However, a lot of successful research has been done in this area (Parke 10,11 , Platt and Badler 12 , Waters 17 , Magnenat-Thalmann et al. 9 , Terzopoulos and Waters 13 ). Three classes of models have been developed for facial animation: interpolation, parametric and muscle action model, each based on a specific method of defining facial actions. They can be also classified as geometrical models or physically based models, according to the way of simulating the behaviors of facial components. The purely geometrical facial models ignore many complexities of human facial tissue. It is difficult to mimic many of the subtleties of facial tissue deformation such as wrinkles during animation. This suggests using a physically based approach. Up to now, little has been done to simulate the aging process. It is a quite cumbersome process which is related to the change of physical structure and biological composition in body tissues. Aging signs appear over the whole body, and one major visible sign is the change of the skin, as it is the outmost layer of human body. In this paper, we consider the change of the facial skin due to aging.