8

Surface Approximation 1245
When both Distance and Ang le are 0.0, the
surfaces degenerate and can become flat surfaces.
Curvature mesh of the NURBS teapot
Spatial and Curvature—Combines the spatial
(edge-length) method and the cur vature (distance
and angle) metho ds, using all three values.
The Edge parameter specifies the maximum
length of a triangular face in the tessellation. The
valueisapercentageoftheobject’sbounding
box. Decreasing this value increases accuracy but
increases rendering time. When you set Edge
to 0.0, the effect is equivalent to the Curvature
method.
The Distance parameter specifies how far the
approximation can deviate from the actual
NURBS surface. Distance is a percentage of the
diagonal of each surface’s bounding box. Each
surface in an object is tessellated based on its size,
independently of other surfaces. Scaling a surface
doesn’t change its tessellation. D ecreasing this
value increases accuracy but increases rendering
time. When you set Distance to 0.0, the software
ignores this parameter and uses the Edge and
Angle values to control accuracy.
The Angle parameter specifies the maximum angle
between faces in the approximation. Decreasing
this value increases accuracy but increases
rendering time. When you set Angle to 0.0, the
software ignores this parameter and uses the Edge
and Distance values to control accuracy.
When Distance, Ang le, and Edge are a ll 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,takestheobject’sdistancefromthecamera
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 orthographic views. This
controlisdisabledwhileViewportsisactive.
For the Spatial, Curvature, and Spatial and
Curvature methods, the Distance and Edge values
specify pixels instead of 3ds Max units when
View-Dependent is on.
Note: When View-Dependent is on, tessellat ion
quickly reaches the maximum subdivision limit.
You might want to increase this value to 7 (the
greatest va lue allowed). See the descr ipt ion of
Advanced Parameters, below .
Merge (sub-object sur faces only)—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