ABSTRACT
In creating models of objects for use in computer animation and visualization programs the most popular and versatile approach is to build them from a large number of very simple primitive planar polygons. Highly successful professional 3D animation programs and most computer games use this approach. It would be quite impractical to build polygonated models by entering lists of facets and vertex positions on a keyboard. In all useful programs the computer provides pre-built collections of flat triangular or rectangular polygons to represent primitive shapes such as cylinders, spheres and torii. It is rarely sufficient to limit the modeling process to a simple combination of primitive shapes and therefore application programs must provide a wide variety of algorithmic procedures to help the user combine and manipulate the basic shapes as well as creating other more complex ones.
