Hi Brian,

re:
> Can the MoI properties of tangents and derivatives, etc., of a curve be used to investigate the
> rotation frame(s) of the spiral target curve?

Not quite, the rotation of a sweep frame is another thing, look up "Bishop Frame" for references.

Bishop, R. L. "There is more than one way to frame a curve.",
American Mathematical Monthly (1975) pp. 245-251

The intrinsic "Frenet frame" of the curve formed by the tangent and curvature vectors does not work well using it for sweep frame rotation.

- Michael

Hi Brian,

re:
> Using a center axis does not seem to make any difference to the Flow, as far as I can tell.

For me it does, I get the red result from the original setup, and the blue result from one
where I moved the base line to run down the center of the object:



- Michael

Thank you Michael.
(I added an edit to indicate that my statement was false, re non-center axis base curve.)

-Brian
(I have heard about Bishop frames. Will have to study Bishop frames for spiral... I guess Flow must use them internally.)

Hi Brian, yes curve-to-curve Flow uses the Bishop frames that is also used by Sweep.

I would like to add a way to control the start normal on the base and the start normal on the target curve.

- Michael

Thanks Michael, Brian indeed the centreline is AOK I though I tried that early in the experiments cycle the ol keep it simple stupid method always wins.

Alex.