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Chapter 13: Modeling with Polygons and Patches

You use the Smoothing Groups option to assign a subobject to a unique smoothing group. To do this, select
a subobject and click a Smoothing Groups number. The Select By SG button, like the Select By ID button,
opens a dialog box where you can enter a Smoothing Groups number, and all subobjects with that number
are selected. The Clear All button clears all Smoothing Groups number assignments, and the Auto Smooth
button automatically assigns Smoothing Groups numbers based on the angle between faces as set by the
value to the right of the Auto Smooth button.
The Polygon Properties rollout also includes options for setting vertex Color, Illumination, and Alpha values.

Subdivision Surface
Editable Poly objects include an extra rollout called Subdivision Surface that automatically smoothes the
object when enabled. The Subdivision Surface rollout, shown in Figure 13.31, applies a smoothing algo-
rithm known as NURMS, which stands for Non-Uniform Rational MeshSmooth. It produces similar results
to the MSmooth button but offers control over how aggressively the smoothing is applied; the settings can
be different for the viewports and the renderer.

FIGURE 13.31
The Subdivision Surface rollout includes controls for NURMS subdivision.
Cage Selection color
Cage color

To enable NURMS subdivision, you need to enable the Use NURMS Subdivision option. The Smooth Result
option places all polygons into the same smoothing group and applies the MeshSmooth to the entire object.
Applying NURMS with a high Iterations value results in a very dense mesh, but the Isoline Display option
displays a simplified number of edges, making the object easier to work with. The process of smoothing
adds many edges to the object, and the Isoline Display option displays only the isolines. The Show Cage
option makes the surrounding cage visible or invisible. The two color swatches to the right of the Show
Cage option let you set the color of the cage and the selection.
The Iterations value determines how aggressive the smoothing is. The higher the Iterations value, the more
time it takes to compute and the more complex the resulting object. The Smoothness value determines how

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