GameAnimationSample 5.8 bad retargeting to metahuman

Development Programming & Scripting
, ,
1

I’m using the latest Game Animation Sample in UE 5.8 and I’m running into a persistent wrist/hand rotation issue with MetaHumans.

The problem is very specific:

  • The MetaHuman body retargets correctly overall.

  • Locomotion, jumping, traversal and ragdoll mostly work.

  • However, both hands/wrists appear to keep almost the same downward-facing orientation regardless of the animation.

  • In idle this is easy to miss because the hands naturally point down.

  • During running, jumping, falling or ragdoll, the issue becomes very obvious: the forearms move correctly, but the hands remain bent downward like “hooks”.

  • This also happens on some of the MetaHuman-based visual overrides that ship with the Game Animation Sample, so it does not appear to be caused by my custom MetaHuman.

My setup:

  • I am using the stock SandboxCharacter_Mover.

  • The MetaHuman Body uses:

    • Anim Class = ABP_GenericRetarget

    • Component Tag = RTG_UEFN_to_Metahuman_nrw

  • ABP_GenericRetarget resolves this tag through its IKRetargeter_Map.

  • The retarget asset is RTG_UEFN_to_Metahuman_nrw.

  • Target IK Rig is IK_Metahuman_Retarget.

  • Source IK Rig is IK_UEFN_Mannequin.

What I have already tested:

  1. Verified the source GASP animation itself

    • I inspected the final animated UEFN mannequin/source mesh.

    • The wrists and hands look correct on the source character.

    • So the bad hand rotation does not originate from the GASP locomotion animation.

  2. Tested the same animations directly inside the IK Retargeter

    • When I preview the same run/jump animations inside RTG_UEFN_to_Metahuman_nrw, the MetaHuman target looks correct.

    • The wrists rotate normally in the Retargeter preview.

    • The issue only appears during runtime through ABP_GenericRetarget / Retarget Pose From Mesh.

  3. Disabled MetaHuman Post Process Anim Blueprint

    • Disable Post Process Blueprint = true

    • No change.

  4. Tested Retarget Pose From Mesh source modes

    • Default: Parent Skeletal Mesh Component

    • Also tested Custom Skeletal Mesh Component and explicitly passed the GASP source SkeletalMeshComponent.

    • No change.

  5. Tested visibility/tick settings on the source mesh

    • Source mesh already uses:
      Visibility Based Anim Tick Option = Always Tick Pose and Refresh Bones

    • So this is not caused by hidden source mesh bones not updating.

  6. Disabled runtime IK stage in the Retargeter

    • Disabled Run IK Rig in the Op Stack.

    • The wrist problem remained.

    • So the issue does not seem to come from the IK pass.

  7. Tested FK chain rotation modes

    • Changed LeftArm / RightArm from Interpolated to One to One.

    • No change.

  8. Checked arm retarget chains

    • In IK_Metahuman_Retarget:

      • LeftArm: upperarm_l -> hand_l

      • RightArm: upperarm_r -> hand_r

    • These appear to be mapped correctly.

  9. Tested another retargeter

    • As a test, I changed the Body tag to RTG_UEFN_to_UE4_Mannequin.

    • The body proportions became incorrect, as expected.

    • But interestingly, the hands started following the animation much more correctly.

    • This strongly suggests that the issue is specific to the MetaHuman retarget setup rather than ABP_GenericRetarget itself.

  10. Compared with non-MetaHuman retargeted characters

  • For example, TwinBlast uses its own skeleton but also goes through ABP_GenericRetarget.

  • Its wrists behave correctly.

  • This again suggests that the problem is specific to RTG_UEFN_to_Metahuman_nrw / IK_Metahuman_Retarget.

Current conclusion:

The source pose is correct, the IK Retargeter preview is correct, and the issue appears only when the MetaHuman retarget is evaluated at runtime through Retarget Pose From Mesh.

It looks like hand_l / hand_r rotations are either not being transferred correctly or are being evaluated differently at runtime for the MetaHuman target rig.

Has anyone else reproduced this in UE 5.8 with the current Game Animation Sample?

Is this a known regression in Retarget Pose From Mesh, IK_Metahuman_Retarget, or the new MetaHuman body rig/joint orientations?

Any workaround for correctly preserving hand_l / hand_r rotation at runtime would be appreciated.

image
image570×417 197 KB

image
image356×286 75.1 KB

image
image793×744 61 KB

2

Since the retargeter preview is right and only runtime is wrong, I’d look at what differs between the two rather than the chains:

1. LODs. The preview evaluates LOD0; at runtime the hidden source mesh and the MetaHuman body can sit on different LODs, and MetaHuman body LODs strip twist/helper bones. Test with r.ForceLOD 0 (or ForcedLodModel = 1 on both components). If the hands fix themselves, set the RTG’s LOD threshold / per-component LOD settings accordingly.

2. Retarget pose. Retarget Pose From Mesh uses the retargeter’s current retarget pose for the target. If the MetaHuman retarget pose has wrists rotated (common in _nrw/_tal variants), check it in the Retarget Pose dropdown and compare hand_l orientation with the source A-pose.

3. Something overriding after the retarget: add a Pose Watch on the Retarget Pose From Mesh node and on the Output Pose in ABP_GenericRetarget. If the hand is correct at the node but wrong at output, a later node or the Leader Pose setup on the arms/hands mesh is the culprit.

4. Make sure the visible hands are on the Body mesh, not a separate component leader-posed to the wrong mesh.