UV Loft Surface

A UV loft surface is similar to a U loft surface, but has a set of curves in the V dimension as well as in the U dimension. This can give you finer control over the lofted shape, and require fewer curves to achieve the result you want.

Select a NURBS object. > Modify panel > Create Surfaces rollout > Dependent Surfaces group box > UV Loft
Select a NURBS object. > Modify panel > NURBS toolbox > (Create UV Loft Surface)

Using perpendicular curves to create a UV loft surface

If the U and V curves intersect, the UV loft surface interpolates all the curves. If the curves don't intersect, the lofted surface lies somewhere between the U and V curves. In general, UV loft works best if the ends of all the curves in one direction lie on the two end curves in the other direction, as in the illustration. UV loft does not work well if the curves in both directions are closed.

Note: The Make Loft dialog (displayed by the Make Loft button on the Surface Common rollout for surface sub-objects) now lets you convert a surface to a UV loft as well as a U loft. In addition, you can use point curves instead of CV curves for the new loft lattice. If you use point curves for a UV loft, turning on the Fuse Points option guarantees that the U and V curves intersect.

Automatic Curve Attachment

When you create a UV loft, you can select curves that are not already sub-objects of the active NURBS model. You can select another curve or spline object in the scene. When you select that curve, it attaches to the current object as if you had used the Attach button.

Warning: If the curve you attach is a sub-object of another NURBS model, the entire model (that is, the curve's parent NURBS object) is attached as well.

As you move the mouse over a curve that is not part of the active NURBS object, the cursor changes shape to indicate that you can pick the curve, but the curve is not highlighted in blue.

Procedures

To create a UV loft:

Create the curves that outline the surface you want to create.
In the NURBS toolbox, click to turn on (Create UV Loft Surface).
Click each of the curves in the U dimension, then right-click. Click each of the curves in the V dimension, then right-click again to end creation.
As you click curves, their names appear in the lists on the UV Loft Surface creation rollout. The order in which you click the curves can affect the shape of the UV loft surface.

In either dimension, you can click the same curve more than once. This can help you create a closed UV loft.

To create a UV loft with automatic attach (example):

Go to the Create panel and three or more independent CV or point NURBS curves.
Go to the Modify panel. In the NURBS toolbox, click to turn on (Create UV Loft Surface).
Click the curves in the appropriate order for the loft.
3ds Max creates the UV loft. You don't need to collapse the curves to a NURBS surface or Attach them to an existing NURBS model.

As you move the mouse over a curve that is not part of the active NURBS object, the cursor changes shape to indicate that you can pick the curve, but the curve is not highlighted in blue.

Interface

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

Tip: When you edit a UV loft sub-object, close the Surface Common rollout to see the U Loft Surface rollout more easily.

UV Loft Surface rollout (creation time)

U Curves and V Curves

These lists show the names of the curves you click, in the order you click them. You can select a curve by clicking its name in a list. Viewports display the selected curve in blue.

The two buttons above and the four below each list are identical for both lists.

While you create the loft, in either dimension you can click the same curve more than once. This can help you create a closed UV loft.

Arrow Buttons

Use these to change the order of curves in the U Curve or V Curve list. Select a curve in the list, and then use the arrows to move the selection up or down.

Insert

(Disabled.)

Remove

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

Refine

(Disabled.)

Replace

(Disabled.)

Display While Creating

When on, the UV loft surface is displayed while you create it. When off, the loft can be created more quickly. Default=off.

Flip Normals

Reverses the direction of the UV loft's normals.

UV Loft Surface rollout (modification time)

U Curves and V Curves

These lists show the names of the curves you click, in the order you click them. You can select a curve by clicking its name in a list. Viewports display the selected curve in blue.

The two buttons above and the four below each list are identical for both lists.

Arrow Buttons

Use these to change the order of curves in the U Curve or V Curve list. Select a curve in the list, and then use the arrows to move the selection up or down.

Insert

Adds a curve to the U list or V 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 U list or V list. Select the curve in the list, and then click Remove.

Refine

Refines the UV loft surface. Click to turn on Refine, then click an iso curve on the surface. (As you drag the mouse over the surface, the available curves are highlighted.) The curve you click is converted to a CV curve and inserted into the loft and the U Curves or V Curves list. As when you refine a point curve, refining a UV loft can change the curvature of the surface slightly. Once you’ve refined the surface by adding a U curve or V curve, you can use Edit Curves to change the curve.

Replace

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

Display Iso Curves

When set, the UV loft’s iso curves are displayed as well as the U-axis and V-axis curves used to construct the loft. The iso curves are only for display. You can’t use them for surface construction.

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.

When you turn on Edit Curves, all applicable rollouts for the selected curves are displayed, including the Curve Common rollout, the CV or Point rollout (depending on the curve type), and the CV Curve or Point Curve rollout. These rollouts appear beneath the U Loft rollout. They let you edit the loft curves and their points or CVs without having to switch sub-object levels.

Tip: When you edit curves in a UV loft, turning off display of the UV loft itself can make the curves easier to see and improve performance. Use Ctrl+D (while the Keyboard Shortcut Override Toggle button is on) to toggle display of dependent sub-objects, including UV lofts.

The UV loft surface can deviate from the curve if you edit a curve in a UV loft by increasing the weight of the curve CVs. You can work around this by refining the curve at the point where the surface deviates.