9

1094 Chapter 9: Surface Modeling
You can also thin k of a point curve or surface as
dependent on its points. You can use the Convert
Curve button to convert a point curve or surface to
the CV form, or vice versa.
NUR B S T ips a nd Techni ques
These topics contain suggestions on how to work
with NURBS. They include t ips collected from
various NURBS mo deling users.
How to Make Objects with NURBS Modeling (page
1–1094)
How to Fix NUR BS Objects (page 1–1098)
How to Improve Performance (page 1–1099)
Animat ion, Textures, and Rendering (page 1–1099)
How to M ak e Objects with NUR B S
Modeling
These are tips on using NURBS to create models.
Objects and S ub-Objects
• In 3ds Max, a NURBS model is a single,
top-level NURBS object (page 1–1078) that can
contain a var iety of sub-objects. Get in the
habit of creating a single object at the top level,
then going imm ediately to the Modify panel
andaddingsub-objectsbyusingrolloutsorthe
NURBS Creation Toolbox (page 1–1083).
• Sub-objects are either independent or
dependent. Dependent sub-objects (page
1–1087) use relational modeling to build
NURBS geometry that is related to other
geometry. However, understand that the
more dependencies a mo del has, the slower
interactive performance becomes.
• In general, point curves and surfaces are
slower than CV cur ves and surfaces. Trims are
the slowest kind of dependency, and texture
surfaces are the slowest kind of dependent
sub-object.
• If a dependent sub-object doesn’t change
during animation, you can help performance
by making the sub-object independent after
you finish creating it.
•YoucanuseNSurf Sel (page 1–747) to apply
modifiers to a sub-object select ion. However,
beforeyoudosomakesurethatRelational
Stack is on; Relational Stack (page 1–1116) is
on the General rollout for NURBS models.
Otherwise, NSurf Sel can select only the Surface
and Surface CV sub-object levels.
Conver ti ng O ther Obj ects to NU RBS
•Rememberthatyoucancollapsesplines (page
1–266) to NURBS objects. A spline Shape or a
NURBS curve can be a go od st arter object for
aNURBSmodel.
• Shapes with sharp angles collapse to multiple
NURBS curves. You can control this before
NURBS conversion by first converting the
Shape to an editable spline (page 1–289).
Modif y the editable spline so that all its vertices
are Bezier or Smooth vertices. Then when you
collapsethesplinetoaNURBScurve,you
obtain a single curve.
• If you want a single NURBS curve, don’t change
vertices to Bezier Corner vertices. These a lways
convert to a junction b etween two different
NURBS curves.
•Collapsingaprimitive (page 1–170) into a
NURBSobjectisoneofthequickestwaysto
start building a NURBS model. After collapsing
the primitive, you can select various CVs and
transform them. Other objec ts you can convert
to NURBS are prisms (page 1–205), torus knots