GR1 Single Span Further Information...

Applying the Single-Span Rule

One way to get into the habit of using single-span curves is to use the Edit Point method for creating curves:

Edit Point method for creating Single-Span curves

If you prefer to use the CV creation method, you can use the Progressive Degree setting which automatically increases the Degree instead of the Spans as you place additional CV positions. Setting the maximum Curve Degree to 7 allows up to 8 CVs.

CV method for creating Single-Span curves

Breaking the Rule

Some of the most useful surface tools, like Freeform Blend or Surface Fillet will often produce multi-span surfaces. During concept and development work, these are usually good enough for design iterations.

Where Single-Span is used in the design process

Continuity & Degree on Single-Span (Bezier)

A single-span curve or surface will always remain smooth and continuous, regardless of the Degree:

A single-span curve is smooth regardless of the degree

Continuity & Degree on Multi-Span

Continuity breaks can occur between spans, but the effect is reduced with higher Degree. The following examples are all 3-Span curves, but with different Degree:

A multi-span curve is smoother with higher degrees

The internal continuity between spans is directly related to the Degree (shown below). So if you need to use multi-span curves or surfaces, choosing higher Degrees will make the result more smooth.

Degree Internal Continuity
1 - G0
2 - G1
3 - G2
4 - G3
5 - G4
6 - G5
7 - G6

A good example is a Curve → Circle with different Degrees:

Example of degree affecting smoothness on multi-span circles