Many controls are common to the various kinds of sub-objects in NURBS models (with the exception of Imports, as previously described). This topic describes these common controls.
One way to alter a NURBS model is to transform its sub-objects. This lets you interactively change the model’s curvature and shape. Transforming points or CVs is especially useful for adjusting the shape of a NURBS curve or surface.
Tips:
There is a Selection area of the rollout for all NURBS sub-objects except Imports. These buttons let you control just which sub-objects to select. They differ depending on the kind of sub-object, and they are described in the sections that follow.
Note: There is no delete modifier for NURBS curves, as there is for splines. There are two NURBS selection modifiers, NCurve Sel and NSurf Sel, described below under "NURBS and Modifiers."
Name: The Name field shows the name of the currently selected sub-object. It is blank if multiple sub-objects are selected.
By default, the name is the name of the sub-object type ("CV," "Point," "CV Curve," "Point Curve," "CV Surf,"or "Point Surf") followed by a sequence number. You can use this field to give the sub-object a name that you choose.
Import sub-objects have a Name field, but no other selection controls.
The selection controls for point and CV sub-objects are the same except for their tool-tip labels.
For Curve CVs, you can choose to select either individual CVs (or groups, by dragging), or all the CVs in the curve at once.
For CV Surfaces, the selection buttons are as follows:
Single CVs: (The default.) When on, you can select individual CVs by clicking, or groups of CVs by dragging a region.
Row of CVs: When on, clicking a CV selects the entire row the CV belongs to. Dragging selects all rows in the region.
Column of CVs: When on, clicking a CV selects the entire column the CV belongs to. Dragging selects all columns in the region.
Row and Column of CVs: When on, clicking a CV selects both the row and column the CV belongs to. Dragging selects all rows and columns in the region.
All CVs: When on, clicking or dragging selects all the CVs in the surface.
Remember that when all CVs are selected, adjusting the rational Weight value has no effect.
Note: Rows and columns are easily visible when the NURBS surface is planar, or nearly so. When the surface has a complicated curvature, rows and columns can be harder to see. The Row, Column, and Row/Column buttons can be especially useful in this situation.
The selection buttons for Curve sub-objects let you select either individual curves, or curves that are connected in space.
Single Curve: Clicking or transforming a curve selects only a single independent curve sub-object.
All Connected Curves: Clicking or transforming a curve selects all curve sub-objects that are connected within the NURBS object. To be connected, two curves must have fused points, or one curve must be a connected dependent (a blend, fillet, or chamfer) of the other.
The selection buttons for Surface sub-objects let you select either individual surfaces, or surfaces that are connected in space.
Single Surface: Selecting a surface selects only that surface sub-object.
All Connected Surfaces: Selecting a surface selects all surface sub-objects that are connected within the NURBS surface object. To be connected, two surfaces must have fused points, or one surface must be a connected dependent (a blend) of the other.
With the CTRL key and the arrow keys, you can select sub-objects by using the keyboard. The arrows traverse the sub-objects. To do so, follow these steps:
Turn on the Plug-In Keyboard Shortcut Toggle.
At the sub-object level, set the selection controls to select a single sub-object.At the Curve and Surface sub-object levels, the left and right arrow keys move forward and backward through individual sub-objects in the order they were created. The up and down arrows are simply equivalent to left and right.
For curves at the Point and CV Curve levels, the arrow keys traverse points or CVs along the length of the curve you selected in step 3. The arrow keys don’t move between curve sub-objects.
For surfaces at the Point and CV Surface levels, 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-objectsthey traverse only the surface you selected in step 3.
The arrow keys don’t traverse individually created points that aren’t part of a curve or surface.
You can hide or unhide NURBS sub-objects as you do 3DS MAX objects. Hidden sub-objects are invisible in viewports. They remain renderable (at the sub-object level, hiding doesn’t affect the renderer). You can’t select hidden sub-objects.
Hide: Click to hide the current sub-object selection.
Unhide All: Click to unhide all hidden sub-objects at the current sub-object level.
You can make a dependent point, curve, or surface sub-object independent.
Caution: When you make an object independent, you lose the animation controllers for all objects that depend on it in turn. When you make point objects independent, you lose the animation controllers for all points on the curve or surface.
You can’t make CV sub-objects independent. CVs are always part of a curve or surface.
You can also use Make Independent to convert a point curve or point surface into a CV curve or CV surface. The original points are deleted from the scenein this respect, using Make Independent on a point curve or surface differs from using it on other kinds of dependent sub-objects.
You can create a new curve or surface object by detaching a curve or surface sub-object from a NURBS model. To do so, select the curve or surface and then click Detach. 3DS MAX displays a dialog to let you enter a name for the new NURBS object (the default name is "Curve" or "Surface" followed by a sequence number). The new object is no longer part of the original NURBS object.
You can also use the Detach button to create a new NURBS object that is a copy of a curve or surface sub-object. To do so, select the curve or surface, and click to turn on Copy before you click Detach. 3DS MAX displays a dialog to let you enter a name for the new object. The original curve or surface sub-object remains part of the NURBS object you were editing, but the copied curve or surface is now a NURBS object of its own.
If you choose Point as the sub-object level, points become visible in viewports. If you choose Curve CV or Surface CV, both the CVs for curves or surfaces and their control lattices become visible.
The sub-object selection tools are the same as for other kinds of 3DS MAX sub-objects. This includes using the "H" key in conjunction with the status bar’s Plug-In Keyboard Shortcut Toggle, as previously described in "Sub-Object Selection."
See the next section, "Selection Controls," for more detail about the selection controls provided in the Modify command panel for different kinds of NURBS sub-objects.
If you choose Imports, then when you select an imported object it is highlighted in shaded viewports as well as wireframe viewports.
The shape of the model changes as you interactively transform the sub-objects.
The sub-object no longer depends on its parent objects, and editing them has no effect on the newly independent sub-object, which retains its shape unless you edit it explicitly.