Representation of Articulable, Quasi-Rigid, Three-Dimensional Objects

Many three-dimensional objects consist of quasi-rigid pieces connected at articulable joints. The choice of a suitable three-dimensional representation for such objects, for example, the human body, is considered with respect to properties required during movement of the jointed segments. We discuss the coordinate systems involved, representation of the surface of the object, and maintenance of proper segment orientation during movement. Generalization to more complex forms is discussed.