9

Creating NURBS Curves from Splines 1115
2-Sided in the Render Scene dialog to see both
sides of the extruded or lathed surface. To see both
sidesinviewports,turnonForce2-Sidedinthe
View por t Configuration dialog.
By default, an object with Extrude or Lathe
collapses to an editable mesh (page 1–996) object.
To have Extrude or Lathe output collapse to a
NURBS object, change the setting to NURBS in the
Output group box of the Ext rude or L athe rollout,
and then collapse the modifier stack (page 3–760).
Cr e a t in g N U RBS Cu rv e s f rom
Splines
Select Spline object. > Modify panel > Right-click the
spline name. > Convert To: NURBS
Splines become NURBS cur ves that then become NURBS
surfaces.
Yo u c a n t u r n a spline (page 1–266) into a NURBS
object formed of CV curves (page 1–1106) .Once
converted, you can no longer edit the spline shape
parametrically, but you can edit it as a NURBS
object, moving CVs and so on.
When you convert a spline circle (page 1–273)
to a NURBS curve, the direction of the curve is
reversed. Th is f acilitates using the curve to trim a
surface: if the direction weren’t reversed, usually
the circle would trim outward instead of inward.
Procedure
To turn a spline into NUR BS cur v es:
1.
Create the spline.
2. Go to the Modify panel.
3. In the stack display, r ig ht-click the name of the
spline.
4. On the pop-up m enu, choose Convert To:
NURBS.
ThesplineisconvertedtooneormoreCV
curves.
Smoothly curved splines, such as circles and
arcs, convert to a single CV curve.
Splineswithsharpangles,suchasrectangles
and stars, convert to multiple CV curves whose
endpointsareattheanglesintheoriginal
spline. These endpoints are fused except for the
initial CV in the spline (for a star, the initial
segment is unfused at both ends).
"Sharp angles" doesn’t apply to smooth splines
to which you have given angles by changing
vertex tangents using the Edit Spline (page
1–680) mo difier. These st ill convert to a single
NURBS curve.