3 D Object Modeling

Every computer-rendered image requires three essential components: a 3D scene description, one or more sources of light, and a description of the camera or eye viewing the scene. The scene description is typically composed of one or more models, or 3D structures. Typically we think of a model as a stand-alone part, e.g. a pencil or a tree, and the scene as the assembly of these parts into a complete 3D environment. This attitude re ects the most common procedure for building up a 3D scene: one builds many models, and then assembles them. Each model contains two descriptions: a mathematical representation of the structure of the shape, and a recipe for guring out how that shape would look if illuminated. Let us examine these descriptions in turn.