Hi Colin, thanks for reporting this - it is definitely a bug with sweep.

It's triggered specifically by a 6 loop helix (or I suppose any multiple of 6 like 12, 18, 24, etc..).

What happens is the sweep is doing one phase of work checking for things at 7 different stations along the rail, like 0, 1/6, 1/3, 1/2, 2/3, 5/6, 1 - and it gets messed up if the profiles at all of these stations are all completely lined up with one another in one straight line.

I should be able to fix it up, but I'm kind of worried about altering the way sweep does its calculations just immediately before the v1 release. I think that to be safe (to make sure there aren't adverse side effects from changing it), I should probably wait to apply this fix a little bit later instead.

There is a workaround you can use to make sweep work for this case of a 6 / 12 / 18 / 24 loop helix: select the triangle and use Transform / Array / Curve, and then select the helix as the path curve. Set Rotation: Flat (this is the same kind of thing as Twist in sweep), and set the Item count to some number that will distribute some profiles in such a way that they are not completely lined up vertically, for example Item count = 5. That will give you this:



Now select all those 5 triangles and then do Sweep - it should now work with the profiles arranged like this, or basically with any kind of non-single-column vertically stacked arrangement.

Thanks for posting the example file! I have saved that off and put a note on my todo list to implement the fix a bit later.

- Michael