I'm trying to make a logarithmic curve with a rotating cross-section.
I have created a curve object following the instructions at How to create this kind of spiral tube?, giving me the curve shown below, which has an elliptical cross-section that increases in size along the length of the curve.
However, as well as the size of the ellipse increasing along the curve, I would like it to twist, giving a 'corkscrewing' final result that will superficially resemble fusilli pasta.
It seems like this should be a simple thing to do, but I can't see a way to do it. Can anybody help?

(source: dur.ac.uk)
