8
CV Sur face 1105
The Generate Mapping Coordinates control is
present on the Modify panel. It is at the Surface
sub-object level.
Flip Normals—Turn on to reverse the direction of
the surface norma ls.
The Flip Normals control is present on the Modify
panel. It is at the Surface sub-object level.
When you modify a point surface, a rollout lets
you change its
surface approximation settings
(page 1–1241)
.
CV Surf ace
Create panel > G e ometry > NURBS Surfaces > CV Surf
Createmenu>NURBS>CVSurface
TheCVsinacontrollatticeshapethesurfaceitdefines.
CV surfaces are
NURBS surfaces (page 1–1102)
controlled by control vertices (
CVs (page
3–1020)
). The CVs don’t lie on the surface. They
define a
control lattice (page 3–1017)
that encloses
the surface. Each CV has a weight that you ca n
adjust to change the shape of the surface.
Because an initial NURBS surface is meant to
be edited, the surface creation parameters
do
not appear
on the Modify panel. In this respect,
NURBS surface objects are different from other
objects. The Modify panel provides other ways to
change the values you set in the Create panel.
Procedure
To create a CV surface:
1.
Go to the Create panel.
2. Tu r n on Ge ome tr y, and cho ose NUR BS
Surfaces from the drop-down list.
3. Turn on CV Surf.
4. In a viewport, drag to specify the area of the
planar seg ment.
5. Adjust the surface’s creation parameters.
Note: When you edit a CV surface you can add
or move CVs so that more than one CV is at
thesamelocation(orclosetoit)toincrease
the influence of the CVs in that region of the
surface. Two coincident CVs sharpen the
curvature. Three coincident CVs create an
angular peak in the surface. This technique c an
help you shape the surface. However, if you
later move the CVs individually, you lose this
effect. (You can also obtain the influence of
multiple CVs by
fusing (page 3–1040)
CVs.)
Interf ace
Thecreationparametersarethesameforboth
pointsurfacesandCVsurfaces,exceptthatthe
labels indicate which kind of basic NURBS surface
you are creating.
Keyboard Entry rollout
The Keyboard Entry rollout lets you create a
CVsurfacebytyping. UsetheTABkeytomove
between the controls on this rollout. To click the
Create button from the keyboard, press ENTER
while the button is active.