Clip and Invert Splines

The "clip" operation of a spline is not removing the points defining the spline. Instead, it is equivalent to defining a linear transformation on the spline coordinate \(u\) as follows:

\(\boldsymbol{C}_{clipped}(u) = \boldsymbol{C}(\alpha _{0} (1 - u) + \alpha _{1} u)\)

\(\boldsymbol{C}_{clipped}(0) = \boldsymbol{C}(\alpha _{0})\) and \(\boldsymbol{C}_{clipped}(1) = \boldsymbol{C}(\alpha _{1})\) indicate that the new spline is defined by the \(\alpha _{0} \le u \le \alpha _{1}\) region of the original spline.

As it is simply a linear transformation, spline inversion can also be defined the same way:

\(\boldsymbol{C}_{inv}(u) = \boldsymbol{C}(1 - u)\)

Clip by Length

API: clip_spline

GUI: Splines > Clip spline or Ctrl+K → Ctrl+X

This method clips the selected spline at both ends by the given lengths. Local properties of the clipped spline will be discarded, while global properties will not.

Spline Clipper

GUI: Splines > Open spline clipper

For precise clipping, you can use the spline clipper widget. This widget synchronizes the clipping lengths and the projections of the spline edges. "Clip here" will call clip_spline internally.

Invert Splines

API: invert_spline

GUI: Splines > Orientation > Invert spline

This method inverts the selected spline. This operation does not discard the local properties. They will be inverted as well.