How does subdivision surface modeling differ form other forms of modeling (such as NURBS)?
There are really only two basic methods of modeling; polygonal modeling and spline based modeling. Subdivision modeling is a form of Polygon modeling. Other forms of polygon modeling include MetaNurbs (àla LightWave and trueSpace), Metaballs, and Metashapes (àla Amorphium). All of these basically rely on the direct manipulation of an objects geometry as if sculpting something in clay. There are no true curves in polygon modeling because the models are made up of, well… polygons. That is to say curves are simply approximated by a series of short straight lines connecting vertices. Because of this polygon modeling is not a good choice for the highly accurate modeling needed for machining manufactured parts. It is however, ideal for organic modeling. It is also good for modeling man made items that do not require precise curves. Splines (àla sPatch) and NURBS (àla Rhino and Amapi) on the other hand are a method of modeling that uses true curves to define a shape. The curve is then swept
