8
964 Chapter 9: Surface Modeling
When the check box is off, the software computes
the surface normals from the smoothing groups
of the mesh object to w hich the patch object is
converted before rendering. These normals are not
accurate, especially with a low View/Render Steps
setting. When the check box is on, the software
computes true patch normals directly from the
patch surfaces, which can generate more accurate
shading.
In the illustration below, a sphere was converted
to Editable Patch format, and then a vertex was
moved toward the center and rotated. The sphere
onthelefthasUseTruePatchNormalsturnedoff,
and the one on t he right has it turned on. In both
cases, View Steps was set to 8.
A patch sphere with Use True Patch Normals off (left) and
on (right).
Miscellaneous group
Patch S mooth—Adjusts the tangent handles of
selected vertices to smooth the surface of the patch
object.
Patch Smooth sets the handles to absolute
positions based on the patch object geometry;
repeated applications have no effect.
A patch box before smoothing (left) and after using Patch
Smooth on the top vertices (right)
Sur face Properties rollout
Edit Vertex Colors group
Use these controls to assig n t he color, illumination
color (shading), and alpha (transparency) values
of selected vertices.
Co lor—Click the color swatch to change the color
of selected vertices.
Illumination—Click the color swatch to change the
illumination color of selected vertices. This lets
you change the color of shadows without changing
the vertex colors.
Alpha—Lets you assign an alpha (transparency)
value to selected vertices.