This contextual allows to remove the stress of a tighten spline.

Creation stages / Use:

Select the Untighten... contextual command from a spline.

The BSpline (Bezier spline) can be tight or not. Imagine that a spline is a classical cord (no elasticity along his tangent) going throw prescribed points (clamps). And that you pull or push on the cord. If you pull as much as you can, the cord would take a certain shape. This shape will maximize the cord energy, it means minimize the curvature (= 1 / radius) along the curve. Between two points, the cord will be shaped into a line. Between several non aligned points, the curve will be a tight shape.