Discusses the use of physics-based models for animating clothes on synthetic actors in motion. In this approach, cloth pieces are first designed with polygonal panels in two dimensions, and are then seamed and attached to the actor's body in three dimensions. After the clothes are created, physical properties are simulated and then clothes are animated according to the actor's motion in a physical environment. The paper describes the physical models used and then addresses several problems encountered. It examines how to constrain the elements of deformable objects which are either seamed together or attached to rigid moving objects. It also describes a new approach to the problem of handling collisions among the cloth elements themselves, or between a cloth element and a rigid object like the human body. Finally, the paper discusses how to reduce the number of parameters for improving the interface between the animator and the physics-based model