9
1078 Chapter 9: Surface Modeling
The After quantity updates dynamically as you
change the s etting with the spinner.
Apply—Applies the settings to the current
selection, retaining them if you then make another
selection.
OK —Applies the settings to the current selection
and closes the dialog.
Cancel—Closes the dialog w ithout applying the
settings to the current selection. Does not reverse
previous uses of Apply.
NUR B S
Fountain crea ted as a NURBS mo d el
3dsMaxprovidesNURBSsurfacesandcurves.
NURBS stands for Non-Uniform Rational
B-Splines.NURBShavebecomeanindustry
standard for designing and modeling surfaces.
They are especially suited for modeling surfaces
with complicated curves. The tools for modeling
with NURBS do not require an understanding
of the mathematics that produces these objects.
NURBS are popular because they are easy
to manipulate interactively, and because the
algorithms that create them are both efficient and
numerically stable.
You can also model surfaces using polygonal
meshes or patches. Compared to NURBS surfaces,
meshes and patches have these shortcomings:
• Using polygons can make it more difficult to
create complicated curved surfaces.
• Because meshes are faceted, facets appear at the
edge of rendered objects. You must have a large
number of small faces to render a smoothly
cur ved edge.
NURBS surfaces, on the other hand, are
analy tically generated. They are more efficient to
calculate, and you can render a NURBS sur face
that appears to be seam less. (A rendered NURBS
surface is actually approximated by polygons,
but the NURBS approximation can be very fine
grained.)
NURBS Models: Objects and Sub-Objects ( page
1–1078)
NURBS and Modifiers (page 1–1089)
NURBS and Anim ation (page 1–1091)
NURBS Concepts (page 1–1091)
Working with NURB S
Models
Like Shape (page 1–262) objects, a NURBS
model can be an assemblage of multiple NURBS
sub-objects. For example, a NURBS object might
contain two surfaces that are separate in space.
NURBS curves and NURBS surfaces are controlled
by either point or control vertex (CV) sub-objects.
Points and CVs behave somewhat like the vertices
of spline objects, but t here are differences.
The parent object in a NURBS model is either a
NURBS sur face or a NURBS curve. Sub-objects
canbeanyoftheobjectslistedhere. ANURBS