8

1112 Chapter 9: Sur face Modeling
Draw I n A ll Viewports —
Lets you use any viewpor t
whileyouaredrawingthecurve.Thisisoneway
to create a 3D curve. When off, you must finish
drawing the curve in the view port where you
began it. Default=on.
WhileDrawInAllViewportsison,youcanalso
use
snaps (page 2–38) in any viewport.
CV Cu rve
Create pa nel > Shapes button > NURBS Curves > CV
Curve button
Create menu > NURBS > CV Curve
CV curves are NURBS curves (p age 1–1107)
controlled by control vertices ( CVs (page
3–1020)
).TheCVsdon’tlieonthecurve.They
define a
control lattice (page 3–1017) that encloses
the curve. Each CV has a weight that you can
adjust to change the curve.
Whileyou’recreatingaCVcurveyoucanclick
to create more than one CV at the same location
(or close to it), increasing the influence of the
CVsinthatregionofthecurve. Creatingtwo
coincidentCVssharpensthecurvature.Creating
three coincident CVs creates an angular corner
in the curve. This technique can help you shape
the curve; however, if you later move t he CVs
individually, you lose this effect. (You can also
obtain the influence of multiple CVs by
fusing
(page 3–1040)
CVs.)
ACVcurvecanbethebasisofafull
NURBS
model (page 3–1074)
.
CVs shape the control lattice th at defines the curve.
Drawing T hree-Dimensional Curves
When you create a CV cur ve, you can dr aw it in
threedimensions.Therearetwowaystodothis:
• Draw In All Viewports: This toggle lets you use
any viewport to draw the curve, enabling you
to draw three dimensionally.
• Using CTRL to drag CVs: While you draw a
cur ve, you can use the CTRL key to drag a CV
off of the construction plane.
With the C TRL key method, further mouse
movement lifts the latest CV off the construction
plane. There are two ways to use CTRL:
• Click-drag.IfyouholddownCTRLandalso
hold down the mouse button, you can drag to
change the height of the CV. The CV’s location
is set when you release t he mouse button.
This method is probably more intuitive.
• Click-click. If you CTRL+click and then release
the mouse button, the height changes as you
dragthemouse.Clickingthemouseasecond
time sets the CV’s location.
This method is less prone to repetitive stress
injury.
WhileyouareoffsettingtheCV,areddotted
lineisdrawnbetweentheoriginalCVonthe
construction plane and the actual CV offset