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This chapter is from the book

This chapter is from the book

TESSELLATION VERSUS CVs

As we just covered in the previous tip, subdivisions are a necessary parameter to define adequate rounding of NURBS curved surfaces. Many fail to consider, though, that within modeling, the biggest factor affecting render times is subdivisions (tessellation settings) and how they are related to CV count. One can easily magnify the render time by multiple factors if subdivisions are not properly understood. For instance, many surfaces have a flat component where a subdivision of 1 is all that is necessary. Remember that subdivision settings are relative to the span between isoparms, not the length of the surface. Therefore, if isoparms and the corresponding CV count are high, fewer subdivisions are needed. The inverse is true as well—if you have fewer CVs to describe an object (a good goal), then more subdivisions are required. You can see this is a push-pull relationship, and there are no magic numbers to define just how many CVs are necessary. Typically, it is best to rely on setting finer tessellation instead of adding CVs, which will build up the file size. The main point is to understand what your settings accomplish and optimize just to the point of noticeable faceting, as dictated by the proximity of the object. Setting manual subdivisions is a tedious affair, but if you integrate it into your workflow after each element is built and drink a pot of coffee at each sitting, it goes unnoticed.

Figure 3.7Figure 3.7

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