Eg 2: SUBD Surfacing

This example shows a polymesh being fitted with a SUBD surface, as well as the setup of default and imported texturing. Because polymesh preparation, point placement, curve drawing and patch creation are the same for SUBDs and NURBS, we'll only quickly go over those parts of the process. These stages are described in more detail in the previous chapter.

Figure 209. Network Layout

Figure 209 shows three progressing snapshots of the network layout used in this example. Note that only one half is built initially; it will be mirrored later on. Also note that only a low detail decimated polymesh is used to fit the surface to. The full detail original polymesh is used later on when defining and calculating texture maps.

Figure 210. Close-up of 4-to-2

Figure 210 shows a close-up view of the network under the ear; note the 4-to-2 change in patch dimensions. This ensures that only quads (four sided polygons) are used in the final SUBD control hull.

Figure 211. Close-up of 6-to-3

Figure 211 shows what happens at a 6-to-3 change in resolution; triangles have to be used. Yes, the Catmull-Clark subdivision scheme does support triangles in the control hull, but the resulting surface exhibits subtle rippling in these areas. Many people like to avoid triangles wherever possible, and by taking care with network construction and patch dimensions, it is entirely possible to produce quad only control hulls.

Figure 212. Close-up of 3-sided Patch

The left side of Figure 212 shows a three-sided patch, commonly used when building NURBS surfaces. However, this approach should be avoided when building SUBBS, as triangles and high valence vertexes will be produced, and some modelers/renderers have valence limits.

The right side of Figure 212 shows the recommended approach when fitting SUBD surfaces. A normal 4-sided patch is created, and low valence quads are all that's produced.

Figure 213. Half Head Network

The half head network shown in Figure 213 uses the above methods, and has a maximum valence of 6, no triangles and 568 quads.