8

1246 Chapter 9: Sur face Modeling
for production rendering, by default the software
adjusts the tessellation of adjoining surfaces to
match each other, in terms of the number of faces
along the edges. The Merge parameter controls
how this is done. If Merge is z ero, adjoining faces
are unchanged. Increasing the value of Merge
increases the distance the software uses to ca lculate
how edges should match, g uaranteeing no gaps
between the surfaces when they are rendered.
Default=0.0.
In most cases, you don’t need to adjust Merge. If
rendering shows gaps b etween nearly adjoining
faces, increase Merge to eliminate them.
Technically,theMergevalueis0.1percentofthe
diagonal of the object’s bounding box. In other
words, a Merge value of 1.0 (higher than necessary
for most purposes) is 0.1 percent of the length
of the diagonal. Because Merge is based on the
object’s dimensions, you can scale the NURBS
model without affecting the Merge setting.
Advanced Par ameter s—Click to display the
Advanced Surface A pproximation dialog (page
1–1246)
. The parameters in this dialog apply to
the Spatial, Curvature, and Spatial and Curvature
approximation methods.
Cle ar S u rf ace Le v e l —(App ears only for top-level
surfaces.) Clears all surface approximation
settings assigned to individual surface sub-objects.
When you click this button, all surface-specific
approximations are lost, and Lock to Top Level is
on for surface sub-objects.
Advanced S ur f ace Approx imation
Dia log
Modify panel > Select a NURBS surface object or
surface sub-object. > Surface Approximation rollout >
Tessellation Method group box > Turn off Lock to Top
Level > Advanced Parameters button
Selec t an editab le m esh object. > Modify panel > S urface
Properties rollout > Advanced Parameters button
This dialog sets parameters that control the
tessellation used in the Spatial, Curvature, and
Spatial and Curvature approximation methods.
Interf ace
Subdivision Style
Chooses the method used to subdivide the surface:
Gri d—Subdivides the surface using a regular grid.
Tree—(T he default.) Subdivides the surface using
abinarytree.
Delaunay —Subdivides the surface using nearly
equilateral t riangles.