Circle Options

Periodic Circle

When this option is turned on (check mark) the circles are closed curves, with the first and last span overlapping. (The result corresponds to the circle primitives created in previous versions of the software.)

When this option is turned off (no check mark), the circles are open curves, with only the first and last CV touching. They can be opened by moving those CVs apart. They also use an algorithm that produces better quality circles and the ability to specify a range of degrees (see the following options).

The following options only appear when Periodic is turned on.

Degree

The degree of the NURBS curve. The values range from 1 to 7. The default is 5.

Spans

The number of subdivisions (spans) on the curve.

The default is 12. A workable primitive shape usually has at least 4 subdivisions. It is not usually necessary to use more than 20 subdivisions.

The following options only appear when Periodic is turned off.

Sweep Angle

The degrees of rotation around the center of the circle.

For example, if you enter 180 degrees, Alias creates a half circle.

Degree

Specifies the degree of the circle. The values range from 2 to 7. The default is 5.

Spans

Specifies the number of spans in the circle. The values range from 1 to 14. The default is 1.

Note

The sum of the degree and number of spans for a non-periodic circle cannot exceed 16. When creating rational geometry, as set in Preferences > Construction Options, the Arc Spans option is not available.