Inspired 3D: Constructing the Inspired Character Part 2 (continued from page 1)


Triangles, however, are not defined as NURBS surfaces. They are defined as subdivided triangles, in a similar way that smoothed polygons behave. The ability to tessellate adaptively is reduced.

Maya behaves differently than RenderMan. The geometry can still displace better than any smoothed polygon model, and the areas where quads transition into triangles are treated differently.

These points can be seen as advantages that subdivision surfaces in Maya have over smoothed polygonal models.

Other advantages include the following:

In short, Maya has developed many tools that make subdivision surfaces look attractive. But it must be noted that this entity type is notoriously unstable. Before using this entity type on a production, test it carefully and often. Results attributed to using subdivision surfaces include these:

Figures 19 & 20] A model with no rows of controlling polygons.
[Figures 21 & 22] A single row of control polygons.

Detail
Detailing in polygonal modeling has to be done in combination with a way to preview the results, which is why the smoothing discussion was introduced before the discussion on creating detail. If the resultant model is going to be smoothed using subdivision modeling techniques, then the results of this additional process should be checked whenever a significant amount of work is to be done. When the lips are detailed, check them, when the ear is detailed, check it and so forth.

Detailing usually requires the model to be split along the areas where the model has a topological change. For example, the edge of the lip is not exactly a hardedge. But if the edge of the lip is compared to the side of the cheek, it is significantly sharper.

Creating detail in regions like this requires the process of adding additional rows of polygons along these areas. To create the ridge at the edge of the lip, a row of polygons is created at the edge of the lip; when this single row is subdivided, it becomes two or more rows, adding more definition.

When applying additional rows to create detail, it is important to understand how these rows will affect the final model. Some simple rules can come in handy when these conditions arise. In the examples in Figures 1926, different examples of polygonal smoothing are shown.

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