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Is there a way to edit bone roll on an armature with existing animations, such that the animation data is automatically recalculated for the new bone roll? I.E. the keyframes/fcurves are updated so that the final, visual animation does not break with the modified bone roll.

There seems to be colloquial knowledge that the general answer is "no". Yet, animation is a series of well-defined transformations, so, surely, there must be some way to automatically recalculate the posing to preserve the animation?

Specifically, I am working with a rig that does not use any kind of IK. I imagine that a solution for rigs using IK constraints would be vastly more challenging, if not actually impossible. In this case, that is not what I'm looking for.

In my particular situation, here is an excerpt of an armature I am working with:

Demo of the problem:
The armature has a single-frame animation. The arm is posed in a gripping position. This visual animation (and all others) should be preserved after modifying the bone roll of any and all bones in the armature.
1. The initially selected bone in the demo has a roll of 137 degrees.
2. I want to change it to 50 degrees.
3. Changing the bone roll to 50 degrees in edit mode, however, breaks all animations. This can be easily observed with the included animation. After changing the bone roll, and returning to Pose Mode, the bone does not rotate the same way it did before. Thus, the arm mesh rotates differently, breaking the animation.

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  • $\begingroup$ Related blender.stackexchange.com/a/165753/15543 As usual recommend uploading blend, quantify current and desired roll. $\endgroup$
    – batFINGER
    Mar 14, 2020 at 10:41
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    $\begingroup$ @batFINGER Sure thing, I've cut out a section of the armature for demo purposes. I have to ask though, and, please forgive me, but what's the reasoning behind specifying a list of specific "before -> after" changes? I'm looking for a general-purpose & automated solution, since I need to change the bone roll of several armatures, over 200 bones in total. I certainly don't want to ask for a list of specific fixes, that doesn't help future readers of this question who aren't using the exact armature that I'm using. And it would be excruciating to do 200 similar transformations by hand... $\endgroup$ Mar 14, 2020 at 19:09

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