This topic describes the controls for CV sub-objects that lie on surfaces. 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.
Transforming CVs changes the shape of the surface.
To transform surface CV sub-objects:
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 button is on. See Sub-Object Selection.
The Selection group box, described under "Interface" later in this topic, provides additional options for selecting CV sub-objects.
(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.
The Lock Selection Set button is useful when you transform NURBS CV sub-objects. You can make a selection in one viewport,
click Lock Selection Set (or press the Spacebar), and then transform the selection in a different viewport.
To Shift+clone surface sub-objects:
The Sub-Object Clone Options dialog appears. This dialog provides various ways to clone the surfaces, some of which reduce relational dependencies to improve performance.
To use the keyboard to select surface CV sub-objects:
You can select surface 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:
(Keyboard Shortcut Override Toggle).
Click or drag to select CVs.
For CVs on surfaces, the left and right arrow keys traverse the U dimension of a surface, while the up and down arrow keys traverse the V dimension of the surface. The arrow keys don’t move between surface 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.
Select a row, column, or a row and column.
A row, a column, or both are added close to the point where you clicked the surface. Neighboring CVs move away from the new CVs in order to preserve the surface’s original curvature.
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.
Move is the most common transform to use. Rotate and Scale can be used with a non-local transform center.
In addition to the CV rollout described here, the Surface CV sub-object level also displays the Soft Selection rollout.
Surface CV sub-object selection controls
Single CV
Row of CVs
Column of CVs
Row and Column of CVs
All CVsShows either "No CVs selected", "Multiple CVs selected", or "SurfaceName(uIndex,vIndex)", where "SurfaceName" is the name of the CV's parent surface, and "uIndex,vIndex" is the CV's UV location on the surface. 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.
Adjusts the weight of the selected CVs. You can use a CV's weight to adjust the CV's effect on the surface. Increasing the weight pulls the surface toward the CV. Decreasing the weight relaxes the surface away from the CV.
Increasing weight is a way to harden a surface: 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.
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 surfaces. It is also a way to change the shape of surfaces.
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, which 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.)
These buttons constrain CV motion. They are enabled when you select one or more CVs. When you finish dragging the CV selection, the active constraint button turns off.
These buttons delete CVs from the surface. Select one or more CVs, and then click Row, Col., or Both.
You can't delete surface CVs if the deletion would give the surface fewer than four rows or fewer than four columns. Aside from that restriction, these buttons delete all rows, columns, or rows and columns that contain selected CVs. This means that you can't delete after you make a selection using the Row and Column or All selection buttons: that would imply deleting the entire CV surface.
These buttons are unavailable unless the deletion is possible.
These buttons refine the surface by adding CVs. As you move the mouse over the surface, a preview of the CVs that will be added, and their locations, is displayed in blue.
Adds both a row and a column of CVs to the surface.
These buttons insert CVs into the curve. Click to turn on one of these buttons and then click the surface where you want to insert the new CVs. Inserting CVs is similar to refining with CVs, except that other CVs in the surface do not move. This means that the shape of the surface can change when you insert.
Inserting CVs does not remove animation from the surface the way refining does.
Inserts both a row and a column of CVs into the surface.
When on, displays the control lattice that surrounds CV surfaces. When off, the control lattice isn't shown in viewports. Default=on.
Modify panel 
