8

1146 Chapter 9: Sur face Modeling
Rigid sur faces reduce the amount of memory
used by the NURBS model. Making sur faces r igid
improves performance, especially for large and
complex models.
When a surface is rigid, you can’t see its points
or CVs when you are at the P oint or Surface CV
sub-object levels. If the model has no nonrigid
surfaces and no point curves, the Point and Surface
CV sub-object levels aren’t available at all.
To make a surface no longer rig id, click Make
Point or Make Independent. Editing the surface
with Break, Join, and so on also makes it no longer
rigid.
Mak e Loft—Displays a Make Loft dia log (page
1–1235)
to convert the surface sub-object to a
(dependent) U loft or UV loft surface. Can also
change the dimension used to construct a U loft
surface.
Youcan’tuseMakeLoftifthesurfacesub-object
is in an error condition.
Tip: Make Loft creates a loft with uniformly spaced
curves. To make a loft with adaptively spaced iso
cur ves, m anually create the curves and then loft
themwithUIsoLines,VIsoLines,orUandV
Iso Lines.
Mak e Point—Displays a Make Point dialog (page
1–1236)
to con v ert any kind of surface to a point
surface. You can also use Make Point to change
thenumberofrowsandcolumnsifthesurfaceis
already a point surface.
Convert Surface—Click to display the Convert
Surface dialog (page 1–1228)
.Thisdialogprovides
ageneralwaytoconvertasurfacetoadifferent
type of surface. You can convert between lofts,
point ("fit") surfaces, and CV surfaces. The dialog
also lets you adjust a number of other surface
parameters.
Mak e Independent—Disabled if the surface is
independent. If the surface is dep endent, clicking
this button makes it independent.
Wa rni ng: When you make a surface independent, you
lose the animation controllers for all objects that depend
on it in turn.
Remove Animation—
Removes animation
controllers from the selected sur faces.
Detach—Detaches the selected surface sub-object
from the NURBS model, making it a new top-level
NURBS sur face object (page 1–1102) .The Detach
dialog (page 1–1230)
is displayed, which lets you
name the new surface. The new object is no longer
part of the original NURBS model.
To create a new top-level N URBS surface that is a
copy of the selected surface, turn on Copy before
you click Detach.
Co py—When on, clicking Detach creates a copy of
the selected sur face instead of detaching it from
the NURBS model. Default=off.
Renderable—When on, the surface renders. Turn
offtomakethesurfaceinvisibleinrenderings.
Default=on.
Display Normals—When on, the normal for each
selected sur face is displayed. There is
one normal
per surface sub-object. The nor mal is displayed at
the surface’s UV origin, so displaying normals can
help you see how materials will be mapped. On
the other hand, the norm al can be hard to see if
you are zoomed out. Default=off.
Flip Normals—Turn on to reverse the direction of
the surface normals. Default=off.
Tip: TheFlipNormalscontrolisusefulforviewing
a surface that is mostly concave or mostly convex.
With more complicated NURBS surfaces, you
often want to render both sides of the surface.
Turn on Force 2-Sided in the
Render Scene dialog
(page 3–2)
toseebothsidesofthesurface.Tosee
both sides of the surfaces in viewports, turn on