Most general purpose approaches to shape representation have been developed outside the field of robotics. The study of ``Solid Modelling'' has application not only to robotics, but to computer aided design and drafting, and also computer graphics.
Solid modelling techniques have developed with growing sophistication in CAD methods, which have progressed from a simple description of lines and points in an image, to description of three dimensional objects in terms of ``wireframes'' (the edges and vertices of the three dimensional shape), to boundary representation, which describes the surfaces of an object, and constructive solid geometry, which describes solid shapes in terms of primitive solid components. The remainder of this section discusses each of these categories of representation technique.
Computer aided drafting was first done by specifying a set of co-ordinates of lines and points in a format which could be stored, edited, and used to make copies of the defined drawing. Specifications were either entered numerically, or captured from x-y digitising devices. CAD systems today have generally evolved from this level, but many are still related to manual drafting only in the same way that a word processor is related to a pencil - they remove the tedium involved in copying and editing, and sometimes make data entry more efficient. They do not, however, have any explicit representation of the object being drawn; The internal representation of the drawing is simply a collection of the lines and points which will appear on the page.