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1244 Chapter 9: Surface Modeling
software ignores this parameter and uses the Edge
and Distance values to control accuracy.
When Distance, Angle, and Edge are all 0.0, the
surfaces degenerate and can become flat surfaces.
Spatial and Curvature mesh of the NURBS teapot
V i ew-Dependent—(for the Renderer only) When
on, takes the object’s distance from the camera
into account while calculating tessellation. This
can improve rendering time by not generating
fine-grained tessellations for objects in the distance
of the rendered scene. The view-dependent effect
works only when you render camera or perspective
views. It doesn’t work in orthogr aphic views. This
controlisdisabledwhileViewportsisactive.
For the Spatial, Curvature, and Spatial and
Curvature m ethods, t he Distance and Edge values
specify pixels instead of 3ds Max units when
View-Dependent is on.
Note: When View-Dependent is on, tessellation
quickly reaches the maximum subdivision limit.
You might want to increase this value to 7 (the
greatest value allowed). See the description of
Advanced Parameters, below .
Mer ge (s ub-obj ect su rf a ces onl y )—Controls the
tessellation of surface sub-objects whose edges
are joined or very nearly joined. When input
to a modifier (such as Mesh Select) requires a
mesh, and when NURBS surfaces are tessellated
for production rendering, by default the software
adjusts t he tessellation of adjoining surfaces to
match each other, in terms of the number of faces
along the edges. The Merge parameter con trols
howthisisdone.IfMergeiszero,adjoiningfaces
are unchanged. Increasing the value of Merge
increases the distance the software uses to c alculate
how edges should match, guaranteeing no gaps
between t he surfaces when they are rendered.
Default=0.0.
In most cases, you don’t need to adjust Merge. If
rendering shows gaps between 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 mo st 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 Parameters—Click to display the
Advanced Surface Approximation dialog (page
1–1245). The parameters in this dialog apply to
the Spatial, Curvature, and Spatial and Curvature
approxima tion methods.
Cle ar Surf ace Le v e l—(Appears 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.