Leg Mesh Twist after retarget bones correctly with source BVH rig


Yes I am asking for help again on “twisted mesh” on re-targeted rig.
The source rig is a BVH file (created from VRM tool) and re-targeted rig (imported with MMD addon to Blender). I am using Blender 2.92.
Attached is my final results file.

I had “aligned retarget rig bones” same as the source rig bones" using retarget tool (keemap)
The animation transfer from source to retarget rigs works fine.

However b’cos I align retarget rig to source rig, the retarget rig that has a mesh … both its legs mesh get twisted.

I have attempted the following but failed.

  1. In pose mode, try to correct bones rotation to ensure the mesh is ok … but this will result in the animation transfer get distorted.
  2. In edit mode, try to correct the bones rotation … but this does not work at all.

The problem is X, Z is about 45 degree difference between the source rig (BVH) that has the animation, and the re-target rig (MMD rig). I tried using Mixamo rig … same problem; that is able to transfer the animation nicely after align the bones, but the legs mesh also get twisted.

So question is, how do you ensure the mesh don’t get twisted?
Or is that is some not possible … that source to retarget rigs only works with bones? and not the mesh in Blender? or in general in any other tool?

Hope someone can advise so I know if I should give up the idea of “retargeting” to a rig with mesh that differs in bone alignment with the source rig.

Hi Again,
Any help please ?

Just so I got myself clear on this problem …
Trying to align bones rotation between source and retarget rig to allow smooth “transfer of animation”.

However, when I try to align bones (rotating bones) on
A. source bones either on Edit or Pose mode, the animation get distorted.
B. retarget bones, either on Edit or Pose mode, the mesh of retarget rig get twisted

So what’s the best approach to avoid either distorted animation or twisted mesh when attempting
to copy animation from source rig to retarget rig?
The issues that I’'d experienced is mostly around the legs and sometimes on both legs and hands.

The rig I used are bvh bones (source) to either Mimamo rig, MMD rig or VRM rig … all faces the same problem on “twisted mesh (legs, hands or both)” if I want the animation transfer to be perfect. Need a manual fix but how?


Hi again,
Any help or advise please?

Did not get any respond …
Well I tried to investigate further and come to the following conclusion.
If the bones of source rig and target rig (with mesh) are not in the same /matching axis direction then the results is either
a) distorted animation … if adjusting bones (either in Edit or Pose mode) rotation to match source against target rig
b) twisted mesh … if adjusting bones (either in Edit or Pose mode0 rotation to match target against source rig.

So there is no perfect solution. In either situation …
(a) will require to adjust animation to avoid distorted animation (using graphic editor) …
(b) re attached mesh to target bones after animation data transfer from source to target … this can be kept ot a minimal if only have twisted legs or hands or both generally speaking.

This appears to be the case in either using bone renaming, bone matching (even with paid version of auto rig tool).

Hopefully someone can come up with “better” approach , best advise is to find closely matching sourcea and target rigs with same bone rotation/matching axis.

If anyone disagree to this findings, would appreciate your views.