UBC Theses and Dissertations
A physics-based model for wrinkling skin Harrison, Darcy
Wrinkling of human skin significantly affects the realism of computer generated characters. Wrinkles convey emotion and expression, provide clues of age and health, and indicate interaction between the skin and external objects. Wrinkling is caused by compression: an elastic material buckles out-of-plane in order to preserve length and volume. Human skin buckles in a distinctive pattern, characterized by sharp valleys with rounded peaks. Many techniques used in visual effects require artists to directly produce wrinkles through sculpting or painted displacement maps, while automated techniques are generally designed for adding detail to coarse, cloth-like simulations which are usually not consistent with human skin. The layered structure of skin, and the properties of each layer are critical to producing the buckling patterns observed in real life. In this work a simulation of wrinkling skin is developed that is physically based, while also simple enough for use in computer graphics. A novel constitutive model suitable for large compressive strain is derived and applied to a three-layered model of skin, with a thin shell outermost layer (stratum corneum), and volumetric dermis and hypodermis layers. Finally, we present a modified Newton scheme and linear finite elements for simulating equilibrium configurations of skin under compressive strain.
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