ABSTRACT
In most computer-based architectural practices, 3-D CAD models are defined in terms of polygon meshes, sometimes referred to as boundary representations (B-Reps), since the points that define the polygons describe the boundaries or surfaces of objects. The characteristics of many if not most architectural models is that they are often composed of planar surfaces. Many architects still work with what are referred to as 2½-D models, in which the plan is central, and in which 3-D objects are formed by extruding 2-D polygons.
