As with a low voltage electric cable, the negative line has a stripe along it’s length. I was trying to twist it just for interest. The curve isn’t overly complicated, but it’s the child mesh that would show the result.
Thanks, I’ll look at the modifier, see if I can work it out.
You’re looking for the curve’s ‘Tilt’. You can change this manually for each control point by pressing Ctrl T or modifying the Tilt value in the properties (N) panel.
Personally, to get a nice smooth twist, I use this little code snippet:
curve = bpy.context.active_object
rotation = 0.5
for i, point in enumerate(curve.data.splines.points):
point.tilt = i*rotation
To use it, copy/paste into the text editor, select the curve you’d like to use it on, and press Alt P with your cursor in the text window to run it. It helps if your control points are evenly spaced, or close to it.