Multicurve Trimmed Surface

A multicurve trimmed surface is an existing surface trimmed by multiple curves that form a loop.

Select a NURBS object. > Modify panel > Create Surfaces rollout > Dependent Surfaces group box > Multi-Trim
Select a NURBS object. > Modify panel > NURBS toolbox > (Create a Multicurve Trimmed Surface)

Creating a multicurve trimmed surface

When you create a multicurve trimmed surface, you create only one trimmed hole. If you want to create multiple holes, first create holes in the surface using other techniques, and as the final step create the multicurve trim.

You can't trim across the edge between two surfaces, or across a "seam" where a surface touches itself, as at the back of a spherical surface created by converting a Sphere primitive.

Procedures

To create a multicurve trim:

The NURBS object must contain a surface with curves on it that create a closed loop.

Create a loop out of multiple curve sub-objects.
At the Curve CV or Point sub-object level, use Fuse to connect the ends of the curves.
The curves must form a single closed loop, or completely traverse the surface.
Project the curves onto the surface by creating a normal or vector projected curve for each curve in the loop.
Tip: You can also use CV or point curve on surface for these curves.
In the NURBS toolbox, turn on (Create A Multicurve Trimmed Surface).
Click the surface to trim, then click each of the curves in the loop. Right-click to end creation.
The Trim list shows the names of the curves you select. Flip Trim inverts the direction of trimming. Flip Normals lets you flip the surface normals at creation time. (After you have created the surface, you can flip normals using controls on the Surface Common rollout.)

Interface

While a multicurve trimmed sub-object is selected, a rollout with the multicurve trim parameters appears. This rollout appears only when one multicurve trimmed sub-object is selected. It isn’t possible to edit more than one multicurve trimmed object at a time, so unlike some other NURBS sub-objects, the rollout doesn’t appear when multiple multicurve trimmed sub-objects are selected.

Tip: When you edit a multicurve trimmed sub-object, close the Surface Common rollout to see the Multicurve Trim Surface rollout more easily.

Multicurve Trimmed Surface rollout (creation time)

Trim Curves: This list shows the names of the curves used to trim the surface. You can select a curve by clicking its name. Viewports display the selected curve in blue.
Insert: (Disabled.)
Remove: Removes a curve from the list. Select the curve in the list, and then click Remove.
Replace: (Disabled.)
Flip Trim: Reverses the direction of the trim.
Flip Normals: Turn on to reverse the direction of the trimmed surface's normals.

Multicurve Trimmed Surface rollout (modification time)

Trim Curves

This list shows the names of the curves used to trim the surface. You can select a curve by clicking its name. Viewports display the selected curve in blue.

Insert

Adds a curve to the Trim Curves list. Click to turn on Insert, then click the curve. The curve is inserted before the selected curve. To insert a curve at the end, first highlight the "----End-----" marker in the list.

Remove

Removes a curve from the list. Select the curve in the list, and then click Remove.

Edit Curves

Lets you edit the currently selected curve without switching to another sub-object level. Click to turn on Edit Curve. The points or CVs of the curve are displayed, as well as the control lattice if the curve is a CV curve. You can now transform or otherwise change the points or CVs as if you were at the Point or Curve CV sub-object level. To finish editing the curve, click to turn off Edit Curves.

Don't edit the curve so you break the loop. If you do, the surface goes into an error condition.

Replace

Lets you replace the selected curve. Select a curve in the list, click this button, and then select the new curve.

Flip Trim

Reverses the direction of the trim.

Along with Edit Curves, the Insert, Remove, and Replace buttons let you alter the curves that trim the surface. While you are making changes, the surface will go into an error condition (orange display by default) until the curves you are working on once again form a closed loop.