Constraint bone to two parent bones

Hi there blender artists.

What I am trying to achieve is that when the jaw drop down, the bone on the side of the mouth follow it just half the way, and jet be able to be animated.

On other softwares like 3ds max or Maya, I could achieve this by assigning two parent constraints with half influence on it. I have already tried to assign those two parent/child constraints to the bone, and it works quite well when the rest of the body don’t move, but when the spine or the head bone is rotated in any direction, the side mouth bone starts to get an incremental offset.
This is what I try to achieve:

This is the unexpected result I try to fix:

I have tried also removing the head bone as a parent on the armature hierarchy.

Any thoughts on this?

Thanks in advance guys

A couple of ways to do this, one would be to use a copy location constraint targeting the jaw bone, see attached .blend file.

Obviously, this isn’t ideal since once constrained the bone is moved from it’s rest position. 2 other ideals that come to mind would be using the action constraint or the transformation constraint. Actually, re-looking at your pictures, I think instead of constraining the corner mouth bones to the jaw bone, I’d constrain them to the midLowLip bone instead (that’s assuming the midLowLip bone is a child of the jaw bone.

Anyway, more than one way to do it, but I don’t think I’d be looking at the child of constraint for this case.



example.blend (278 KB)

First of all, I really appreciate the fast response you gave Randy and the valuable info and file you give me.

I proved the file you send but it wasn’t quite what I was looking for, but it gave me some new ideas on how to tackle this rig. In the end I made this setup:
Once the corner mouth left was in the correct position, I duplicate it (named “cornerRef.l” and then set its parent to the jaw, so it follow perfectly the movement of the jaw.
Then added a Location constraint to the original corner left bone, and set the influence to half. That give me exactly what I wanted. That the corner mouth always follow just half the way the movement of the jaw.

Thanks man.