Feature Request: add "twist" parameter to swept surfaces

[VikingScientist]

I would like to see a "twist" parameter to all functions in the class Go::SweepSurfaceCreator which allows rotational and linear swept surfaces to twirl around during the sweeping operation.

For an example use case see https://youtu.be/3_VydFQmtZ8?t=6m43s

[VikingScientist]

It has come to my attention when thinking of this that you cannot create the twisted torus geometry (see video in OP) exactly, even when using rational splines. This is due to the fact that the circular sweep is not angle parametrized, and hence any twisting of the curves would suffer the same fate. It is the same problem that arrives when trying to create a NURBS helix.

I would however like to see a twisting parameter, even if it is only an approximation. My guess is that one would like to keep rational representation and circular exactness in the sweeping direction and not in the twisting direction.