Help for tricky Armature needed.


I need to twist a mesh, then bend it to a circle and then "un"twist it without opening the circle.

It was easy to twist and bend, but the untwisting is hard, I hope not impossible.

Here is a image illustrating the question, 1 base mesh, 2 twisted, 3 bened to circle, 4 untwisted circle (faked here):

I guess my problem is that the Quaterions are always global. Maybe some Python script is needed to calculate local rotations and express it in global Quaternions wxyz. But My Math is much to bad…

Oh and it has to work in the gameengine…
A testfile is here:

Any ideas highly welcome!


Not even a “Impossible” statement? :-?

At first I thought you could just rotate the bone on their local axis, but this didn’t work for obvious reasons (it would twist the circle out of shape)

I was trying to solve it the other day using copy loc constraint to replace the parenting between bones but it kept twisting but this gave a problem when going from the linear shape to the cirlce shape. Though that could “probably” be fixed by using more keyframes. Anyway, I tohught you had given up or found a solution yourself, but as I see this is not the case, I’ll retry my hand at it tonight and upload the file, even if it’s just a partial solution.


No I did not gave up! :o

I would be very happy to see any *.blend nearer to a solution.

Currently I am experimenting with a inverse Kinematic Solver Constraint.

Maybe this is a good direction, but more tomorrow… enough work for today.


The only part that is not working properly is the untwisting part at the end, and only because I didn’t do it by step like I did with the folding.

Is that enough or you need explanations on how I did it? It’s nothing much more then what I said in the other post.

Hopefully that should help you a bit.


maybe a texture trick can do? you’d need an animated texture sequence that simulates the twist, so you don’t have to bother with tricky bone quaternions… :wink:

Solmax: Impossible, you need to see the deformation on the mesh itself.

Theeth: Wow, looks really good. I will now try with my approx. 3 times more komplex modell. THANKS!


Oh I forgot…

Theeth: the small extra bones are only visual markers? I could not figure out any extra use?!

EDIT: Stupid me! :wink: Forget the above sentence…


Just one more thing. Unless you want to manually correct each bone IPO for overshooting, you should switch their interpolation mode to Linear by selecting all the channel in the action window and hitting Tkey.