Modelling predicament: How to unravel a spiral at one end?

Help! :spin:

So I need to model a spiral that will unravel in a different different direction at one end. Turns out this is a huge pain in the ass - especially since the spiral shaft is not perfectly round, but instead a semicircle. Get the picture?

Had it been a simple spiral I’d have used the screw modifier and been done with it ages ago.
Spent all day on it yesterday and while I’ve learned some new things in the process I have no answers yet.

I tried using a curve and modelling along the curve path with the Bevel & Taper method.
There are two problems with this though. I can’t get a spiral as perfectly shaped as the ones the Screw modifier generates. But most importantly I can’t control the direction in which the semicircle pivots along the curve path.

Any ideas?


So I need to model a spiral that will unravel in a different different direction at one end
What does that mean exactly ?

Imagine a spring that you bend and straighten out at one end.

Here’s a rough sketch that illustrates what needs to happen with this shape.


i have a script to make spiral of many type
let me know if you need it !

but not certain if it still work in latest Bmesh SVN !
but i can always upload one in a file

but you can also make a spiral with the array modifier !

now what do you mean for problem at the end of curve?

also you can control the tilt of the curve with Alt-T for any control point alomg the curve !

can you upload file so we can look at your curve!


Thank you! I just tried editing the tilt and it worked perfectly. You just solved half of my problem!
(And actually it is Ctrl+T)

Now I just need to figure out how to make a bézier curve in the shape of a perfect spiral.

(I’m curious about your script too, could you please send me a link to it?)

Now I just need to figure out how to make a bézier curve in the shape of a perfect spiral.

Have you tried the Mesh-to-Curve option (Alt-C)? You could probably use the spin/screw tools to make a mesh spiral then convert to curve. I think it only works on single-vertex wide paths.

Thanks for the idea!
I tested this, but the curve that is generated is not bézier (there are no handles), it is just a regular curve.
I hit the V key with all verts selected and tried to change the type, but nothing changes. Why might this be?

go to tool panel and change the curve type to bezier !

butnot certain bezier is the bst choice in this case

i would go with poly instead!

or do it with my script so you get a real helix or spiral !


I went to to the Tool panel. I also tried from the Edit Mode Curve menu. I also tried with the keyboard shortcut. But nothing changes. Here’s a screen shot of my test circle, converted from a mesh to a curve. I can’t seem to get bézier handles to show up no matter what I do. You can see that all verts are selected (in orange), and Handle Type is set to Automatic - yet I still just have rigid lines and points.

Going all poly would make it very difficult nearly impossible to pose and maintain a natural-looking curve. Unless I rig an armature. But then I have to choose between a low bone count resulting in a rigid look, and a high bone count with hard-to-manage IK.

Can you please send me that script?

iv’ given the link in earlier post #7 just click on in first post it and it will download

see curves type here

if you V key you can select for each point the type of handles
i guess you can select all verts and then select vector or any other with 2 handles


Thank you, Ricky! That was exactly what I needed to know. Bézier curves are working now.
And thanks for the link. Not sure how I missed it the first time.