Sketcher CreatePeriodicBSplineByInterpolation

Description
This tool creates a periodic B-spline curve passing through given points. See this page for more info about B-splines.

Usage

 * 1) Press the  button.
 * 2) Create a series of points by clicking in the 3D view. While the command is active, the created points are connected with straight lines.
 * 3) Optionally press  before terminating the input to define the multiplicity of the knot at the last defined point (note that this may not always be respected; see limitations for details).
 * 4) Optionally press  before terminating the input to delete the last created control point.
 * 5) Right-click to terminate the input and generate the curve.
 * 6) Depending on preferences, the tool may remain active to trace a new curve. Right-click again to exit the command.
 * After a B-spline is created, it is possible to define the weight of the control points by changing the radii of the weight circles. The equality constraints on the circles need to be deleted first. The radius constraint is arbitrary, the weight of the control points will be defined by the relative radii of the circles. It works similar to gravity: the bigger a circle is in relation to the others, the more the curve will be attracted to the control point.
 * The visibility of the control polygon, the curvature comb, the degree and the knot multiplicity can be toggled on/off from the B-spline tools toolbar.
 * Check out the other tools in the B-spline tools toolbar for more B-spline editing tools.

Limitations

 * The resultant curve is no different than the curve defined through control points. So all limitations of a periodic B-spline apply.
 * The B-splines created are always cubic (i.e. with degree 3).
 * The defined multiplicity may not always be respected
 * For a periodic spline, the first knot (coincident with last) always has a multiplicity of 2.
 * If the points just before and just after have multiplicities >=3, the piece between these two is fully continuous, and this (middle) point will only be constrained with point-on-object. If a knot is needed, consider using the insert knot tool.