Creating NURBS curves

NURBS (Non-Uniform Rational B-Splines) are used to create curves in 3D space. They can also be used as defining objects for extrusions along a path.

NURBS curves can be created using the NURBS Curve tool and one of two modes. Specify the NURBS curve degree prior to clicking a mode. The Push/Pull mode is available in 3D views for instantly extruding the NURBS curve after creation.

Mode	Description
Interpolation Point	Creates a NURBS curve by interpolation point
Control Point	Creates a NURBS curve by control point
Push/Pull (3D views only)	Instantly extrudes the NURBS curve after creation; see Push/Pull mode of planar tools
Push/Pull Combine (available with Push/Pull mode)	When the shape to be extruded is drawn on the face of a solid object, combines the two objects into a single solid addition or solid subtraction; when this submode is disabled, the new extrude remains a separate object, and the existing solid object remains unchanged
NURBS Curve Degree Setting	Enter the NURBS curve degree; the higher the setting, the more vertices are created

NURBS curves can also be created from planar objects by converting them to NURBS; see Converting to NURBS.

Setting the NURBS curve degree

Mode

Tool

Tool set

Shortcut

NURBS Curve Degree Setting

NURBS Curve

3D Modeling

Shift+7

The curve degree affects the number of vertices created; the higher the degree value, the greater the number of vertices.

To specify the NURBS curve degree:

Click the tool and mode.

Alternatively, double-click the NURBS Curve tool to open the Curve Degree dialog box.

The Curve Degree dialog box opens. Specify the curve degree for the tool to use.

Set the degree value to 1 to create a NURBS curve with linear segments (similar to a 3D polygon). A linear NURBS curve can be used to measure an object from point to point in a 3D view.