# Weighting behavior based on bone angle?

Hello everybody.

I didn’t find a better title.
I don’t know if what I am looking for exists or not.
And english is not my native language, so I hope my message won’t hurt your eyes too much.
Note also that it’s pretty late (4:05 am here) and that I won’t be able to answer before tomorrow evening.
Finally, note that I am a beginner with blender. I am a computer scientist with knowledge about 3D rendering, but a complete noob with blender.

That being said.
I am doing some rigging/weight painting on a character.
However, this character has clothes. A skirt, for example.
I can weight paint the clothes, to make it move with the bones.
However, I would like to have an asymetric behavior, based on whether the leg is going forward or going backward.
If you have troubles to understand it with a skirt, think about a cloak/a cape. It should only deform when the leg is behind the torso (what I mean by “going backward”) not when the leg is in front of it.

A way to achieve this would be to have behavior based on the bone’s angle.
It doable in a shader. I mean : a vertex shader can take the weighting given by the vertex and multiply it by something else, like a formula using the bone angle.
Technically, it’s doable. At least it seems doable.

I know that it would not replace a real phyic on the tissues.

So my question(s) is (are):
1/ is it doable ?
2/ is it doable in blender ?
3/ do you have a tutorial ?
4/ (if you don’t, then) do you have any keyword, so I can do more researches on this topic (I’ll have something to give to google).

Alternatively, I thought about this solution, but I don’t know if it’s doable. It’s just an idea.
Instead of having 1 skeleton on my mesh, I’ll have 2 skeleton. I’ll use one skeleton for movements going forward, and the other skeleton for movements going backward.
But it doesn’t seem solid at all. Like : at all.

Anyway, do you have suggestions ? Answers ? hints ?