Spline

A spline is a smooth, flowing curve that passes through the points you click. Use it for shapes that are not made of straight lines and circles: the outline of a surf handplane, a guitar body, a curved chair back, a leaf-shaped tray.

How to use it#

1. In a sketch, click Spline, or press S.
2. Click the points the curve should pass through. The curve shows as you go.
3. To close the curve into a loop, click the first point again (after at least three points). The pointer says Close the curve.
4. To stop with an open curve, double-click, or press Esc.
5. Press Esc again to go back to Select, then drag the points to reshape the curve.

A closed spline is a closed shape by itself. An open spline needs other lines joined to its ends to make a closed shape: for example, a curved top joined to straight sides and a base. Every point snaps to points and lines, like the ends of a line do.

Making it exact#

The points of a spline are ordinary sketch points, so you can:

• Dimension them: click two points (the origin counts as one) and type the distance between them.
• Constrain them: Symmetric puts two points the same distance either side of a centre line, and Fix (⚓) pins a point where it is.

Tips#

• A few well-placed points give a smoother curve than lots of points.
• For a symmetric shape, draw half the outline and mirror it across a construction centre line. When you change the original half, the copy follows.
• To take a point out of the curve, select it and press Delete. If too few points are left, the whole curve goes.
• A spline can be the path for a Sweep.

If it does not work#

• Trim does nothing to the spline: Trim only works on lines, arcs and circles. Drag the spline's end point instead.