8

1086 Chapter 9: Sur face Modeling
Sub-Object Selection
When you work with NURBS models, you often
work with sub-objects. While you are at the
sub-object level, you use the usual select ion
techniques, such as clicking, drag ging a region,
or holding down CTRL, to choose one or more
sub-objects.
YoucanalsoselectNURBSpoint,curve,and
surface sub-objects by name. Turn on the
Key b oard Shortcut Override Toggle (p age 3–912)
on the status bar, go to a NU RBS sub-object
level, and then press the H key . This displays a
select-by-name dialog that lists only sub-objects at
the current level. Choose one or more objects in
the list, and then click Select. You can assign your
own names to NURBS sub-objects (aside from
CVs)thatyouwanttoeditfrequently.
Press CT RL+H to have the Select Sub-Objects
dialog list only sub-objects directly beneath the
mouse cursor.
The H shortcut is also a con venient way to choose
parent objects while you’re creating dependent
sub-objects.
Wo rkflow Tip s
When you work with NURBS, you switch
frequently between the object and sub-object
levels, or from one sub-object level to another.
Keyboardshortcutsandpop-upmenuscanhelp
you do this.
•TheSub-ObjectSelectionToggle
(default=CTRL+B)switchesbetween
object and sub-object levels.
• The Cycle Sub-Object Level shortcut
(default=INSERT)switchesfromone
sub-object level to another.
• Whenyouright-clickinaviewportwhilea
NURBS object is selected and the Modify
panel is active, the quad menu lets you switch
between various levels of the NURBS model:
Top Level, Surface CV Level, Surface Level,
Curve CV Level, Point Level, Curve Level, and
Imports Level.
• The command panel’s right-click popup menu
(available w henever the pan hand is visible)
helpsyounavigatetherolloutsonthecurrent
command panel.
If you have a three-button or wheel mouse,
rolling the wheel scrolls the command panel.
• Sub-object selection sets are p ersistent. If you
go to a different sub-object level, when you
return to the previous level, your selection is
still available. However, refining or inser ting
points or CVs makes the sub-object select ion
sets invalid for that object.
• You can move a sub-object selection set among
sub-objects at the active level of the NURBS
model by holding down CTR L while you press
the arrow keys.
•WhenyouselectsurfaceCVsub-objects
that are "on top of " each other in a 3D view,
sometimes all the selected C Vs fail to highlight.
To fix this, choose Customize >
Viewport
Configuration (page 3–896)
,andturnon
Z-buffer Wireframe Objects.
CV Sub -O bje cts an d P o in t
Sub-Objects
Independent curves and independent surfaces
both come in two varieties: they are either CV
sub-objects or point sub-objects. This topic
describes the differences between the two.
CV Curves an d CV Surfaces
CV curves and CV surfaces have control vertices
(CVs) as do splines. The posit ion of the CVs
controlstheshapeofthecurveorthesurface.
However, unlike spline ver tices, CVs don’t