Animation data doesnt properly transfer between armatures

Question

When trying to copy graph editor keyframes from an animated armature and pasting them to a different un-animated armiture ive run into a problem that has absolutley stumped me. Ive created a seperate blend file from the scene I was originally working on to try to isolate the problem.

As you can see when the animation data from rig1 is pasted to rig2, all of the data is identical but the individual bones in rig2 are somehow not rotated properly. You can see that both armatures are in the same quaternion rotation mode. I isolated a single femur bone out of both rigs to see if I could learn anything.

As you can see the bones in the "rotated femur collection" are roughly the same. Unfortunatly this simple rotation data is not somehow contained in the animation data of the individual bones when theyre all parented together in the armature. In other words I cant seem to replicate this simple transformation change using the graph editor and even if i could it wouldnt be worth it to manually modify the rotation of every individual bone.

My goal is to quickly and successfully copy and paste graph editor data from one armature to the other and obviously have the animation look the same.

As far as I can tell, all the bone and object data properties and other relavent settings are identical.

Ive also tried tranfering the data with CTRL+L link animation data, no dice.

I will include some screen shots of the armatures that obviously look different even with the exact same data along with the bones I isolated. I tried to include the blend file as that would be the best way to see the problem but the file was too big. In the last screenshot you can see the two armatures on the left, the two femur bones in the middle and the femur bone pair with one bone rotated -145 degrees on the z axis in euler mode and .301 w rotation + -.954 z rotation in quaterion mode.

TL;DR I cant figure why the animation data wont properly transfer from one armature to an other.

Answer 1

There are two main problems to deal with when transferring one animation from one rig to another: one is the differences between rest poses, the other is the differences between axis of rotations (in Blender workflows mainly due to "Bone roll" differences).

You should turn on "Axes display" in the armature Viewport Display options, to check if your bones share the same orientations and bone roll, as two bones can look equal (same Y orientation), but they can have completely different X and Z directions.

If you can, you should change the bone roll of your target armature in edit mode, in order to align theese rotations between the two armatures; if not, you have to perform a "Retargeting" operation, which will take into account theese differences and calculate new animation curve values, in order to obtain the same movements on the target rig.