A Simple Physics Model to Animate Human Hair Modeled in 2D Strips in Real Time

Abstract

This paper presents a simple Physics model to animate human hair modeled in 2D strips in real time. A major difficulty in animating human hair results from the large number of individual hair strands in a hairstyle. To address this problem, we have presented aframework of human hair modeling based on grouping hair strands into strips. Each hair strip is modeled by one patch of parametric surface. Polygon tessellation and the alpha-mapping using hair textures are then applied. To continue that work, we present a simple Physics model. In particular, a simple dynamic model is adapted and applied to the control point meshes. A set of dynamics equations are defined and solved. The parametric representation of hair strips can handle deformation of any complexity and still appear smooth. Moreover, because the number of control points is much smaller than that of the tessellated triangle vertices, the computation is fast and achieves real time animation. The animation of hair is controlled using event-triggered procedural animation primitives that implement wind, gravity as well as head movement. Inter hair strip collision avoidance is achieved by introducing springs between any two neighboring hair strips. Collision detection and avoidance of hair with other objects is implemented using ellipsoids and reaction constraints.