sweeping with no twisting

Dear Professor @geuzaine,

I'm Alessandro a PhD student and I'm currently using Gmsh for research purposes, in particular for Finite Element Analysis. First of all I want to thank you for the great job you're doing developing Gmsh, a powerful and lightweight software.

I need to model and then mesh a thread screw. The thread is generated by sweeping a triangle along a helix, similarly to what you've done in the demo 'pipe.geo'.

I've drawn the triangle and the helix and then performed the sweep. Unfortunately it doesn't work for me since the triangle is twisted while being swept all the way along the helix. I've noticed a similar behavior for the sweep generated by the square in the demo "pipe.geo".

Is there any command in Gmsh to prevent such twisting? Because my goal is to get a sweep of the triangle without twisting it along the helix.

Would you be so kind to helping me solving this issue?

Thank you.