Representations and Operations in the ICEM Systems

Abstract

CAD/CAM systems are computer programs which help to describe geometric objects of the real world. The description is called a model of the real world object. Geometric objects in the model consist of building blocks which can be classified as wireframe, surfaces and solids for one-dimensional, two-dimensional and three-dimensional objects, respectively. Mathematical notions are used to represent the geometric objects in a way so that the description data can be stored in a computer. It is important for designers of CAD/CAM systems to decide which representations are to be used, since this choice will decide which objects of the real world can be modeled by the system. It is clear that most objects of the real world can only be represented in an approximate way. This is not only true because computers store data in a finite number of bits. Elementary elements, like lines, arcs, cylinders, boxes, spheres, etc., represent the appropriate real world object “exactly”, i. e. up to the possibilities a computer has for such a representation. An outer car body will, in most cases, not be represented by elementary elements but by socalled free-form elements which only approximate, however close, the real world object.