8

1096 Chapter 9: Sur face Modeling
andaddingsub-objectsbyusingrolloutsorthe
NURBS Creation Toolbox (page 1–1085) .
• Sub-objects are either independent or
dependent.
Dependent sub-objects (page
1–1088)
use relational modeling to build
NURBS geometry that is related to other
geometry. However, understand that the
more dependencie s a model has, the slower
interactive performance becomes.
• In general, point curves and surfaces are
slower than CV curves and surfaces. Trims are
the slowest kind of dependency, and texture
surfaces are the slowest kind of dependent
sub-object.
• Ifadependentsub-objectdoesn’tchange
during animation, you can help performance
by making the sub-object independent after
you finish creating it.
•Youcanuse
NSurf S el (p age 1–740) to apply
modifiers to a sub-object selection. However,
beforeyoudosomakesurethatRelational
Stack is on;
Relational Stack (page 1–1118)
is on the General rollout for NURBS models.
Otherwise, NSurf Sel can select only the Surface
and Surface CV sub-object levels.
Conver ting Other Objects to NUR B S
• Remember that you can collapse splines (page
1–261)
to NURBS objects. A spline Shape or a
NURBS curve can b e a good starter object for
aNURBSmodel.
• Shapes with sharp angles collapse to multiple
NURBS cur ves. You can control this before
NURBS conversion by first converting the
Shape to an
editable spline (page 1–284) .
Modifytheeditablesplinesothatallitsvertices
are Bezier or Smooth vertices. Then when you
collapse the spline to a NURBS curve, you
obtain a single c urve.
• If you want a single NURBS curve,
don’t change
vertices to Bezier Corner vertices. These always
convert to a junction between two different
NURBS curves.
•Collapsinga
primitive (page 1–165) into a
NURBSobjectisoneofthequickestwaysto
start building a NURBS model. After collapsing
the primitive, you can select various CVs and
transform them. Other objects you can convert
to NURBS are
prisms (page 1–200) , torus knots
(page 1–184)
, lofts (page 1–347) ,and patch
grids (page 1–980)
.
• You ca n also change the NURBS surface by
applying modifiers. The modifiers act on the
points or CVs of the surface, and not on the
surface itself. After applying the modifiers,
collapse the
modifier stack (page 3–802) .This
removes t he modifiers from the stack without
changing the position of the modified points or
CVs,makingforasimplerandquickermodel.
•AnotherwaytocreateaNURBSsurfaceobject
is to apply a
Lathe (page 1–699) or Extrude
(page 1–671)
modifier to a NURBS curve. Se t
themodifier’sOutputTypetoNURBS,and
then collapse when you’re done adjusting the
parameters.
(TherearealsoNURBSlatheandextrude
surface sub-object ty p es, which you can apply
to curve sub-objects.)
Sho r tcuts, Sna ps, and Us er I nterfa ce T i ps
•Remembertoturnonthe Plug-In Keyboard
Shortcut Toggle (page 3–912)
. While it is on,
youcanusealltheNURBSkeyboardshortcuts.
• One of the most useful NURBS shortcuts is H,
which displays a select-by-name dialog. You
can use H during sub-object creation as well
as sub-object selection. This is handy when
sub-objectsarecrowdedorhardtosee.
AvariantofH is CTR L +H,whichalsodisplays
the select-by-name dialog, but lists only those
NURBS sub-objects beneath the mouse cursor
position.