What is wrong with Mixamo thumb rotation and how to fix?

Report · Oct 16, 2022

Can someone please tell me what is wrong with the Mixamo anim thumb rotation, and how to fix in Blender?

I am using Auto Rig Pro in Blender 3, to retarget Mixamo animations (which I downloaded using their Bot character mesh for reference).

#1 First I downloaded their Bot character in Tpose. And lined up the Mixamo armature underneth my Armature (also in Tpose, but my thumbs are rotated different).

So I rotated my thumb bone angles to match Mixamo thumbs. (After this pic, I also twisted my Thumb bones in Edit mode, so all twist the same - while still being at the same angle of Mixamo bones in Y and Z view.)

Rotated Thumbs to match Mixamo Rest pose.png

#2 (The only question is what do I do for the Thumb Twist in Edit mode - do my twists need to be the same as Mixamo twists for retargets to work? If yes, then what is the exact degrees that Mixamo twists its Thumb1 vs Thumb 2 and 3?)

#3 (And in Blender > Edit mode, do I need to Control + A = Apply the new Thumb rotations of my arma before doing retargeting? Or does exiting Edit mode, lock in the Rots?)

#4 Doing these steps are not enough > when I import a Mixamo animation (not in Tpose) and retarget - my Thumb3 (tip) is rotated (not twisted) wrong:

Mixamo retarget is wrong - Rotated Thumbs crooked.png

#5 (vs #6) Looking at the Mixamo arma, I see the visual problem: When I put the Mixamo animation in Rest pose – the thumbs are rotated straight and no twist.

Mixamo rest pose has thumbs straight.png

#6 But when in Pose mode, the Mixamo Thumb2 and 3 are twisted differently than Thumb1.

Mixamo Anim pose has thumbs crooked.png

(This has ruined my workflow for 4 months because I keep having to re-key animations after I retarget. I'd rather change the Mixamo thumb-rotation keyframe. But I dont know how.)

#7 So why is Mixamo's Thumb rots/twists different in Rest vs Pose mode????

#8 And How do I normalize the thumb rots? Do I do it in Pose mode or Edit mode?

(If I click the Mixamo armature > go to Edit mode > it jumps to the Rest pose where the thumbs are already straight. Thus I cannot untwist the Pose rotations.)

#9 [On the Mixamo animation Armature] - Do I need to Control + A = Apply Rotations of bones before retarget, for the twists to neutralize? If yes, when/where do I do this, in Edit or Pose mode? And with the armature in REST or Pose?

Please help, thank you.