Editing Curve CV Sub-Objects

This topic describes the controls for CV sub-objects that lie on curves. A rollout labeled CV contains the CV sub-object controls for NURBS models. In addition to the CV rollout described here, the Curve CV sub-object level displays the Soft Selection rollout.

In you can edit the CVs in CV curves on surfaces as you edit other kinds of curve CVs. You can transform CVs in CV curves on surfaces, but you can't move the CVs off the surface. Using the Curve CV sub-object level is an alternative to editing these CVs by using the Edit Curve on Surface dialog.

Procedures

To transform curve CV sub-objects:

  1. At the Curve CV sub-object level, select one or more CVs.

    The sub-object selection tools are the same as for other kinds of sub-objects. You can also use the H key while the Keyboard Shortcut Override toggle is on. See Sub-Object Selection.

    The Selection group box, described under "Interface" later in this topic, provides some additional options for selecting CV sub-objects.

  2. Activate (Select And Move) or another transform and then drag in a viewport to transform the selection.

    The shape of the model changes as you interactively transform the CVs.

    Rotate and Scale are useful only when you've selected multiple CVs.

Tips

To use the keyboard to select curve CV sub-objects:

    You can select curve CV sub-objects using the Ctrl key and the arrow keys. The arrows traverse the sub-objects in the order they were created. To do so, follow these steps:

  1. Turn on (Keyboard Shortcut Override Toggle).
  2. Click or drag to select CVs.
  3. Hold down Ctrl and use the arrow keys to move among the CV sub-objects.

    For CVs on curves, the arrow keys traverse the CV selection along the length of the curve. The arrow keys don’t move between curve sub-objects.

You can also use the H keyboard shortcut (while the Keyboard Shortcut Override Toggle button is on) to display a dialog and select CVs by name. Ctrl+H displays only the names of CVs directly beneath the mouse cursor.

To remove a CV from a curve:

  1. Select a CV.
  2. Click Delete.

    Keyboard shortcut: Delete

    The CV is deleted and the shape of the curve is updated.

    Note: A CV curve must have at least one more CV than the degree of the curve.

To add a CV to a curve:

  1. Turn on Refine.
  2. Click the curve where you want to add the CV.

    A CV is added at the location you clicked. Neighboring CVs move away from the new CV in order to preserve the original curvature.

To add CVs and extend the length of a curve:

  1. Click to turn on Extend.
  2. Move the mouse over a CV curve. The curve is highlighted in blue, and one of the curve's ends displays a box to show where the curve will be extended.
  3. Drag from the highlighted end CV, and then release the mouse button.

    New CVs are added beyond the original length of the curve.

To fuse two CVs:

  1. Turn on Fuse.
  2. Click a CV without releasing the mouse button. Drag to another CV, and then release the mouse button.

    The first CV you choose acquires the position of the second CV, and becomes dependent to it. If the first CV has an animation controller, the controller is discarded. If the second CV has an animation controller, the first CV acquires it too.

    Fused CVs display in purple by default.

To unfuse fused CVs:

  1. Select the fused CV.
  2. Click Unfuse.

    Now you can move and edit the two CVs independently.

To transform a region:

  1. Using sub-object selection, select one or more CVs for the center of transformation.
  2. Turn on Soft Selection.
  3. Transform the CV.

    A region around the selected CV is transformed accordingly.

Move is the most common transform to use. Rotate and Scale can be used with a non-local transform center.

Tip: If Soft Selection appears not to be working, the Falloff value might be too small for the size of your surface. On the Soft Selection rollout, increase the value of Falloff so it encompasses other points or CVs.

Interface

In addition to the CV rollout described here, the Curve CV sub-object level also displays the Soft Selection rollout.

Selection group

Curve sub-object selection controls

Single CV

(The default.) When on, you can select individual CVs by clicking, or groups of CVs by dragging a region.

All CVs

When on, clicking or dragging selects all the CVs in the curve.

Name

Shows either "No CVs selected", "Multiple CVs selected", or "CurveName(index)", where "CurveName" is the name of the CV's parent curve, and "index" is the CV's U location along the length of the curve. You can't edit the Name field to customize the names of CVs.

If CVs are fused, the Name field shows the name of the first CV.

Weight

Adjusts the weight of the selected CVs. You can use a CV's weight to adjust the CV's effect on the curve. Increasing the weight pulls the curve toward the CV. Decreasing the weight relaxes the curve away from the CV.

Increasing weight is a way to harden a curve; that is, to sharpen its curvature at a particular location.

By default, the weight is 1.0 for the CVs of NURBS objects that you create on the Create panel or the NURBS sub-object creation rollouts. The weight of CVs in geometry that you convert to NURBS can vary, depending on the object's original shape.

You can change the weight when multiple CVs are selected. Using the Weight field or spinner while multiple CVs are selected assigns all of them the value you choose. Because weights are relative to each other (rational), using the Weight control when all CVs are selected has no visible effect.

Hide

Click to hide the currently selected CVs.

Unhide All

Click to unhide all hidden CVs.

Fuse

Fuses a CV to another CV. (You can't fuse a CV to a point, or vice versa.) This is one way to connect two curves. It is also a way to change the shape of curves.

Fusing CVs does not combine the two CV sub-objects. They are connected but remain distinct sub-objects that you can unfuse later.

Fused CVs behave as a single CV until you unfuse them. Fused CVs behave similar to a single point, but the property of multiplicity for coincident CVs also applies. (See NURBS Concepts and CV Curve.) The fused CVs have proportionally more influence on the curve. The curve can become sharper in the fused CVs' vicinity, or even angular if more than two CVs are fused together.

Fused CVs are displayed in a distinct color. The default is purple. (You can change this color using the Colors panel of the Customize User Interface dialog.)

Unfuse

Unfuses the fused CVs.

Refine

Refines the curve by adding CVs.

Warning: When you add CVs with Refine, you lose the animation controllers for all CVs on the curve.

As you move the mouse over the CV curve, a preview of the CVs that will be added, and their locations, is displayed in blue.

Tip: It is a good idea to reparameterize after you have added CVs to a curve by refining. See Editing Curve Sub-Objects.
Delete

Deletes the selected CVs.

Insert

Inserts CVs into the curve. Click Insert and then click the curve where you want to insert the new CV. Inserting CVs is similar to refining with CVs, except that other CVs in the curve do not move. This means that the shape of the curve changes when you insert.

Inserting CVs does not remove animation from the curve, as refining does.

Tip: It is a good idea to reparameterize after you have added CVs to a curve by inserting. See Editing Curve Sub-Objects.
Extend

Extends a CV curve. Drag from the end of a curve to add a new CV and extend the curve.

Warning: When you add points with Extend, you lose the animation controllers for all points on the curve.
Remove Animation

Removes animation controllers from the selected CVs.

Display Lattice

When on, displays the control lattice that surrounds CV curves. When off, the control lattice isn't shown in viewports. Default=on.

CVs Selected

This text field shows how many CVs are currently selected.

Parent topic: Creating and Editing NURBS Sub-Objects