Thumbs rotated wrong for Auto-Rig Pro - after retarget to Mixamo animation. How to fix?

Question

Please help, Ty. I searched “Auto-Rig Pro” thumb = no results. Also searched Youtube.

Problem: I rigged my character using Auto-Rig Pro. (Idk if it's IK hands, no one taught me.)

Q1: When I retarget my rig to a Mixamo animation – my thumbs are rotated wrong. What is the issue? I don't want to manually reanimate my thumbs because I have 20 Mixamo animations to do.

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Stats:

Blender 3

Auto-Rig Pro 3.65.39

Year 2022: people should have this addon by now (searched old answers saying people dont have this).

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Steps:

1. Blender 3 > Rigged my character mesh using Auto-Rig Pro, in T pose (“Rig 2”). Thumbs seem to have 3 thumb bones (rings). Mixamo anim has 4 thumb bones (but one is a tip bone at end of finger/thumb, unused?). --

2. I downloaded an Idle animation from Mixamo, using their girl bot character. Saved with and without skin to test both (see their thumbs).

3. Imported skinless Mixamo animation (“Rig 1”) into Blender using Better FBX Importer. I tried the checkmarks for “Optimize For Blender” = on/off, doesnt seem to make a difference.

4. Automatic Bone Orientation is On. Fix Bone Poses is off. Idk if this matters because after Importing the Mixamo animation – their thumbs look correct. It's my rig retarget that fails later.

5. Blender > ARP plugin tab: Select Rig 1 > Redefine Rest pose. T pose activates, Check Preserve > Apply. (After Apply, Rig 1 resets to its default animation pose – which I think is normal.)

6. ARP plugin tab: Select Mixamo as Rig 1. Select my rig as Rig 2 > Build Bone List.

7. Source Bones = 3 Mixamo Thumbs (Rig 1) auto match to my 3 thumb bones (Rig 2)

8. Select Root bone > Set as Root.

9. Did not click Auto Scale (doesnt seem to fix anything, or makes Rig 1 skel too small).

10. ARP > “Re-target” (apply Rig 1 anim to Rig 2). (Rig 2 is in T pose.)

11. Animation gets applied = Rig 2 goes to Pose animation. But Thumbs are rotated wrong. What is the issue? --

12. Tried importing another Mixamo animation (Slow Run) > Apply = thumbs still rotated wrong on Rig 2.

13. Do not want to use Mixamo's rigger because the point of me using Blender to rig, is Mixamos rig window is too small = imprecise joint pins. But IF I import this Character to Mixamo and rig > thumbs do rotate correctly (but animation problems with the thigh/crotch = mesh warp that only ARP is fixing).

14. For step 11, what is the correct way to Rotate the Thumb and apply that rotation to all Keyframes? [I found a vid how to do this, but lost the name. And not sure if I'm doing it correctly (how to set Linear/curve animations?): If the animation is making the thumb move from A to B – instead of staying in the same relative location to the palm... then how do I correctly rotate all the keyframes of the A-B Thumb animation – but merely change its starting Rotation (so it still cycles from A to B – but now at a different starting Rot)?]

Questions repeat:

Q1: at # 11: When I retarget my rig to a Mixamo animation – my thumbs are rotated wrong. What is the issue?

Q2: at #14 above.

Q3: I see people import Mixamo animations (Rig 1), which import at 0,0,0 axis. Then they move Rig 1 on X axis – so it doesnt block the view of their character (Rig 2). How do I do this??

I tried G X – move. But when I click play, the Rig auto jumps back to 0,0,0 – blocking my view. I tried to Apply Transform after moving Rig 2 – but it ruins the arms (location offset) of the retargetting animation on Rig 2.

Answer 1

Q1: In ARP there's a tool called "Interactive Tweaks" which is useful to correct this kind of problems, but it works only on Euler rotations, so you'll have to set thumbs to euler rot in order to use it.

ARP Documentation

Q2: In the Graph Editor you can select all control points of a channel (i.e. X rot of thumb_01 bone: select the channel and press Shift H to isolate it) and press G Y to move all curve introducing an offset which will preserve the relative rotation modifiyng its start (and end) position. Again its easier to edit curves in Euler rot mode, but you can try the adjustment even with quaternions (better if you understand how quaternion math works).

Another method is to add an addittive layer of animation, using NLA, so that you add an offset rot to the bones where needed.

Q3: After importing a Mixamo FBX you can select its armature in object mode and move, rotate and scale it (always in object mode) as you like: the animation will be preserved. Don't apply anything and be sure that you don't have animation record button enabled, so not to set any keyframe on the rig while in object mode.