Bone to Bone Rotation Copy Constraint not working as expected

I’m trying something very very simple but cannot get it to work. I’ve even tested in a blank .blend file and get the same broken result.

All I want to do is copy the rotation from one bone to another bone in a separate armature. What I’m actually doing is trying to copy bone rotation information from a bvh bone to my eyeball bone (super simple). I’m using “copy rotation” in constraints but getting all sorts of crazy results that make no sense at all. I’m so frustrated I could punch Blender in the face right now if it had one.

I created a scratch blend file with two simple objects. I gave them each a bone and parented the object to the bone (using Ctrl P) so the bone moves the object. Everything works fine. I then used that same copy rotation constraint and sure enough… crazy results that make no sense. I’ve tried the “transformation” constraint and that doesn’t seem to do anything at all. I’m so confused. This should be dirt simple. If I use that constraint from object to object (no bones) it works fine.

Can someone test this for me and tell me if it’s a bug or if Blender is just stupid? I’m using 2.74 on a PC if that helps any.

I spent over an hour messing with this not realizing that there are TWO different constraint systems! One is for objects and one is for bones. That is super confusing. :frowning: