8

Ruled Surface 1195
Automatic Cur ve Att achment
When you create a ruled surface, you can select
curves that are not a lready sub-objects of the ac tive
NURBS model. You can select another curve or
spline Splines object in the scene. When you select
that curve, it attaches to the current object as if you
hadusedthe
Attach button (page 1–1121) .
Wa rni ng: If the curve you attach is a sub-object of
anotherNURBSmodel,theentiremodel(thatis,the
curve’sparentNURBSobject)isattachedaswell.
Asyoumovethemouseoveracurvethatisnot
part of the active NURBS object, the cursor
changes shape to indicate that you can pick the
cur ve, but the curve is not highlig hted in blue.
Procedure
To create a r uled surface:
1.
In a NURBS object that contains at least
two curves, turn on Ruled.
2. Drag from one curve to the other .
You can also click first one curve, then the other.
A dependent surface is generated, using the
twocurvesasthesurface’soppositeedges.
The perpendicular edges are generated
automatically.
The Flip Normals control lets you flip the
surface normals at creation time. (After
creation, yo
u can flip normals using controls on
the Surface Common rollout.)
Interf ace
WhenyouturnontheRuledbutton,andwhilea
ruled surface sub-object is selected, a rollout with
the ruled surface parameters is displayed at the
bottom of the Modify panel.
Ruled Surf rollout (creation time)
Flip B eginning and Flip End—Flip one of the curve
directions used to construct the ruled surface.
A ruled surface is created using the directions
of the parent curves. If the two parents have
opposing directions, the ruled surface can be
shaped like a bow tie. To correct the situation,
use Flip Beginning or Flip End to construct the
ruled surface using a direction opposite the
corresponding p arent curve’s direction. These
controls eliminate the need to reverse the curve.
Start Point 1 and Star t Point 2—Adjust the position
of the start point at the two curves that specify
the r uled surface. Adjusting the star t points can
help eliminate unwanted twists or " buckles" in the
surface.
These spinners are disabled if the edges or curves
are not closed.
While you’re adjusting start points, a dotted
blue line is displayed between them, to show the
alignment. The surface is not displayed, so it
doesn’t slow down adjustment. When you release
the mouse button, the surface reappears.
Flip Normals—Turn on to reverse the direction of
the ruled surface’s normals.