About splines

About splines:

A spline is a smooth curve that passes through or near set of control points tha influence the shape of curve.

By default, a spline is a series of blended curve segments of degree 3 (also called cubic) polynomials. These curves are technically called nonuniform rational B-splines (NURBS), but are referred to as splines for simplicity. Cubic splines are the most common, and mimic the splines that are created manually using flexible strips that are shaped by weights at data points.

Understand Control Vertices and Fit Points

You can create or edit splines using either control vertices, or fit points. The spline on the left displays control vertices along acontrol polygon, and the spline on the right displays fit points.

Control vertices

Use the triangular grip on a selected spline to switch between displaying control vertices and displaying fit points. You can use the round and square grips to modify a selected spline.

Fit points

Note: Switching the display from control vertices to fit points automatically changes the selected spline to degree 3. Splines originally created using higher-degree equations will likely change shape as a result.

Create Splines Using Fit Points

When you create splines using fit points, the resulting curve passes through the specified points, and is influenced by the spacing of mathematical knots in the curve. You can choose the spacing of these knots with the knot parameterization option.

Special Cases

You can create a spline with a parabolic shape by specifying a degree 2 spline created with exactly 3 control vertices as shown on the left. Degree 3 splines created with 4 control vertices have the same shape as Bezier curves of degree 3 as shown on the right.

Related Concepts:

Related Task:

Related Reference:

Commands for curved geometric objects.

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