Making rotational changes in an armature across all keyframes of an animation.

Support Animation and Rigging
#1

Hello All. I’ve recently been working hard to get several animations from Mixamo.com working on some meshes created in Blender. The animations import just fine, but it turns out a simple biped “walk” animation which was originally created for a normally proportioned skinny human needs a little tweaking for my mesh needs which is a heavy-set monster. Notably, when the arm swings during the walk cycle, my monster has a wide girth to his lower body, so the arms swing right through the sides of his wide body.

I want to simply rotate the shoulder bone out a little in front view but otherwise keep the animation of the walk cycle the same. I figured I could just adjust the IPO curve corresponding to the rotational axis of each shoulder bone, but when I shift the curve (in my case the Y rotation) I find that the bone rotates along other axes and the result is not what I expected. Upon closer inspection I realized there are 4 parameters for bone rotation (instead of 3) and I’m quickly learning that it has something to do with this Quaternion coordinate system?

Does anyone have a suggestion for me to pursue? I could certainly step through all 350 keyframes of this animation and rotate the arm by the same amount each pose (R then Y then -20) but that’s not very efficient and I can’t believe there’s not a more elegant solution?

#2

There shouldn’t be keyframes for that bone on every frame. If there is, I would suggest going through and deleting the unecessary keys. If it’s a walk cycle, it also doesn’t need to be 350 frames long unless there are a couple varied cycles in there. You could cut it down to 1 cycle. Then you’d probably only be looking at manually changing the rotation in 10-20 keys.

You could also just add another bone (or empty) and parent the shoulder to it and rotate the new bone however much you need.

#3

Thank you so much for the response. I think I might have used a bad example with the walk cycle. I guess in more general terms I was asking if there was a way in Blender to globally change the angle of an armature bone across all keyframes using the IPO editor. When I’ve tried to, but the Quaternion curves are really confounding versus the simple Rotate X,Y,Z that’s used in the viewports.

#4

Sorry, meant to reply sooner to this. From what I have seen with quaternion rotations, if you rotate a bone on the x-axis, both the x and w ipo/f-curves change. So I would think, rotate the bone you want to, key it’s rot, and see how much the curve changes in the x (or y or z) and w. then move the curves accordingly…

Randy