Chapter 9. Subdiv Surfaces

Subdivision surface modelingalso known as subdiv modeling or sub-Dscombines NURBS and polygons and has two modeling modes: standard and polygon. In polygon mode, you can use all of the polygon tools on the surface. In standard mode, you work primarily with vertices, which act similarly to NURBS control vertices (CVs). But subdiv surfaces in standard mode also have edges and faces, similar to a polygon. Standard mode gives you the unique capability of moving between display levelsthat is, different levels of detail. This allows you to move back and forth between low and high levels of detail on an object (Figure 9.1).

Figure 9.1. This odd creature is called a Huffer. It was designed by Roy Miles and modeled by Andrew Britt using subdivision surfaces. Left, polygon mode; right, standard mode with vertices visible; top, standard mode with no components visible.

In polygon mode, you see the edges of a polygon shape surrounding a smooth surface, which is the subdiv surface. In this mode, all of the components are the same as in any other polygon.

Standard mode includes a different set of components, which can be manipulated at different display levels. Note that subdiv surfaces, like NURBS surfaces, have smoothness levels of rough, medium, and fine that can be activated by the , , and keys, respectively (Figure 9.2). However, these should not be confused with display levels, which actually make the surface more complex.

Figure 9.2. These are two copies of a subdivision cylinder. The one on the left is at display level-0, and the one on the right is at display level-1.