Physics based cloth simulation

This thesis presents a technique to simulate the movement and draping of fabric in an animation qualitatively. Cloth simulation with fabric characteristics has been a frequently visited topic in computer graphics. Most cloth animation systems allow users to simulate different types of fabrics by providing controls over the parameters which determine fabric characteristics. However, given a real fabric it is still unknown how an animator can specify its fabric characteristics without having expensive measurement equipment and expertise to incorporate characteristics into the system. This is unfortunate since in many cases that is what an animator intends to do. Fabric characteristics include elasticity, friction property, viscosity, reflectance property, texture, etc. Among these properties, we present a method by which an animator can incorporate fabric elasticity into a cloth system. We first identify core parameters to represent a fabric, while the fabric is allowed to be anisotropic (i.e. having different elastic properties along weaving directions). We then present a method to approximate those core parameters. Using those core parameters we build a governing equation of cloth based on the finite element method. Given a governing equation of cloth, we simulate cloth using implicit integration. Furthermore we present a new collision resolution scheme for cloth collisions. Our concern is to find dynamically convincing collision resolutions for any kinds of cloth collisions. Given a set of non-colliding current particle positions and another set of suggested next particle positions, our collision resolution method finds appropriate noncolliding next positions and velocities of particles. Cloth collision resolution is a case of deformable N-body collision resolutions. To resolve collisions, we solve a system of linear equations derived from the collision relationships. A system of linear equations is built using a scheme adapted from the simultaneous resolution method for rigid N-body collisions. For the special case where we can find cyclic relationships in collisions, we solve a system of linear inequalities derived from the collision relationships