
	Eg 2: SUBD Fit Points

Figure 214 shows the SUBD surface generated from the network shown above. Overall its not looking too bad but, on closer inspection, some areas seem to show odd kinks that you wouldn't expect or want.

Note: New in CySlice v3.2 is the Auto Fit Points preference. When enabled, fit points are automatically added to problem areas and the initial surface builds are free of a lot of the artifacts described below. See the Optional Code: Auto Fit Points section for more details.

Figure 214. Default Surface

Figure 215 shows a detail of the eye area; the arrows point to a few obvious kinks and creases.

Figure 215. Close-up of Eye

Arrow number 1, pointing into the corner of the eye, shows one very common cause of kinks. The problem here is the large change in grid spacing from the area around the eye to the more detailed grid in the corner of the eye. One solution would be to add more shape or division points to the area surrounding the eye to force more even grid spacings. The draw-back to this method is that you are probably adding more detail where you don't need it, and the final control hull will be much heavier than you want.

The arrows numbered 2 highlight another common cause for artifacts in the surface. This particular problem has already been described in the Creating SUBD Patches chapter, and always occurs along resolution change boundaries.

You can see from the control hull (right side of image) how the control points in these problem areas are pulled out in exaggerated ways. The best solution is to add fit points to change the fitting methods used.

Figure 216. Close-up of Eye and Fit Points

Figure 216 shows the same area of network, but this time with green fit points added. You can see an immediate improvement in the surface quality.

Figure 217. Close-up of Eye and More Fit Points

Figure 217 shows the final result, with a scattering or more green and white fit points. Although the addition of fit points can improve the SUBD surface smoothness, keep in mind that its relaxing the fit requirements, and so the resulting surface isn't following the underlying polymesh as accurately. This often isn't such a big deal though, as a less exaggerated control hull can be more important when it comes to animation, and any error is picked up in displacement maps.

Remember: Hit Rebuild after adding fit points if you want to see how they affect the control hull and fitted surface.

Half Completed, Then Mirror Copy

Figure 218. Half Completed, Then Mirror Copy

Figure 218 shows the completed half, and the templated mirror merged with the original. Normally with NURBS networks, you would define all the texture mapping information before templating the half. But with SUBDs the mapping is defined after the surface is complete. This is because the UVs have to be calculated for the entire surface at once.