Lathe Surface

A lathe surface is generated from a curve sub-object. It is similar to a surface created with the Lathe modifier. The advantage is that a lathe sub-object is part of the NURBS model, so you can use it to construct other curve and surface sub-objects.

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

Surface created by lathing a curve

Procedures

To create a lathe surface:

The NURBS object must contain at least one curve.

In the NURBS toolbox, turn on (Create Lathe Surface).
Click the curve to lathe.
The lathe surface rotates about the NURBS model's local Y axis. The initial lathe amount is 360 degrees. A gizmo (yellow by default) indicates the axis of the lathe. Transforming the lathe surface's gizmo changes the shape of the lathe, and lets you lathe around an axis that isn't aligned with a local coordinate axis.

The Flip Normals control lets you flip the surface normals at creation time. (After creation, you can flip normals using controls on the Surface Common rollout.)
Adjust the lathe parameters.

Interface

While a lathe sub-object is selected, a rollout with the lathe parameters is displayed at the bottom of the Modify panel.

Lathe Surface rollout (creation time)

Degrees: Sets the angle of rotation. At 360 degrees (the default), the surface completely surrounds the axis. At lower values, the surface is a partial rotation.

A partial lathe (degrees=225)

Direction group

X, Y, and Z: Choose the axis of rotation. Default=Y.

X, Y, and Z rotations of the same curve

Align group

These buttons position the axis of rotation relative to the curve.

Min: (The default.) Locates the lathe axis at the curve's negative local X-axis boundary.
Center: Locates the lathe axis at the curve's center.
Max: Locates the lathe axis at the curve's positive local X-axis boundary.

Min, Center, and Max lathes of the same curve

Start Point

Adjusts the position of the curve's start point. This can help eliminate unwanted twists or "buckles" in the surface.

This control is disabled if the curve is not a closed curve.

The start point is displayed as a blue circle.

Flip Normals

Lets you flip the surface normals at creation time. (After creation, you can flip normals using controls on the Surface Common rollout.)

Cap

When on, two surfaces are generated to close the ends of the lathe. While they are present, the cap surfaces are maintained so they match the dimensions of the lathe surface. The lathe must be a 360-degree lathe.

The Cap checkbox appears only on the creation rollout. If you want to remove the caps later, simply select them as surface sub-objects and delete them. Think of lathe capping as a workflow shortcut rather than a property (or parameter) of lathe surfaces.

To flip the normal of a lathe cap, select it as a Surface sub-object and use the Flip Normals toggle on the Surface Common rollout.

Adding a cap to a partial lathe

Lathe Surface rollout (modification time)

Degrees: Sets the angle of rotation. At 360 degrees (the default), the surface completely surrounds the axis. At lower values, the surface is a partial rotation.