Can multiple bones influence another bone at once?

Question

Note my screenshot - what I'm trying to accomplish is that when any of the outer "arms" move, the center, vertical bone moves along with it, basically in an IK relationship - tilting based on the moving arm. However, I'm only aware of how to do any IK stuff by using parental relationships. Since bones can only have one parent, I'm not sure how to accomplish what I wanted.

I tried adding multiple "Copy Transform" constraints from the arm bones to the center bone, but it seems like the constraints just execute in order and whichever one is last overwrites the others.

Answer 1

I understand that you've got yourself something you're happy with. If it's working for you, that's all that matters. However, I suspect you'll find that using Child-ofs to do this is not ideal. Those 8 child-of constraints are not equal: they are evaluated in order, from top to bottom. Still, it may be good enough for your purposes.

A better solution here would be an armature constraint. This works very similarly to weighting meshes, but rather than using multiple bones to move a vertex, it uses multiple bones to move a bone (or object.) With the armature constraint, you can weight your central bone equally to each of your 8 arms (1/8 = 0.125, so that's the individual weights) and the central bone will move with each evenly.

Answer 2

The short answer here is: yes you can. It turns out my initial instinct of "parenting" was the correct one, but indeed the typical parenting implementation only allows for a 1:1 relationship.

Thankfully there's a solve for this, the Child Of Constraint. I simply added 8 Child Ofs to the center bone, and used TheLabCat's advice of adjusting their influence down a bit for a more realistic look (though it still works with an influence of 1.000 on all parents, for the record).

Check out the screenshot below where multiple arm movements are each applying separate, additive tilts to my center bone.