Retargeting UE4 weapon animations to MetaHumans accurately

Development Character & Animation
1

Hi everyone,

We’re currently using UE 5.7.2 and still working with the UE4 mannequin skeleton. We have around 1,000 custom animations authored for it and want to move to MetaHumans in the future without losing that animation library.

Almost all of these are weapon animations involving the fingers, hands and arms. Accurate positioning is essential for weapon grips, reloads and interactions between both hands. Getting something that looks roughly similar isn’t enough.

I’ve spent a long time looking for a working solution and have followed numerous guides. Many give conflicting instructions, and none have produced the results we need so far.

I’ve been testing UE4-to-UE5 retargeting with RTG_UE4Manny_UE5Manny, including adjustments to the IK setup and Pin Bones. However, the hand positions already visibly differ from the source in the retargeter preview, and the hand IK isn’t transferring as expected.

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Has anyone successfully transferred precise weapon animations from the UE4 skeleton to MetaHumans?

I’m particularly looking for guidance on:

  • The correct retargeting workflow for UE 5.7.2.
  • Preserving hand placement, finger poses and the relationship between both hands.
  • Correctly handling ik_hand_l, ik_hand_r and ik_hand_gun.

A working example or a current step-by-step guide would be extremely helpful. With this many animations, we’re looking for a repeatable workflow for the entire library.

Thanks for any help!

2

Hello!

This looks like a huge animation library to transition and so I completely understand why you need such precise and repeatable workflows in this situation.
The process of retargeting weapon animations (especially reloading and two-handed holds) to the MetaHumans can be really complex because of the difference in proportions and the way MetaHumans rely on their skeletal hierarchy.

Before I provide a solution, I’d like to ask a couple of questions beforehand so that I can provide the steps that would suit you the best

  1. Are you intending to retarget the animations via the IK Retargeter window or do you want to implement Runtime IK Retargeting inside your Animation Blueprints?

  2. Are your weapon animations using custom IK socket bones/virtual bones attached to the UE4 skeleton (like an extra weapon root bone) or strictly relying on standard ik_hand_l and ik_hand_r?

  3. And finally regarding MetaHuman, do you retarget the animations directly to the MetaHuman Body Skeleton or is UE5 Manny/Quinn an intermediate?

Once I know a bit more about how you’ve got those IK chains and bones set up, I think we can pinpoint exactly why the hand IK isn’t transferring properly in your preview and get this sorted out for you!

3

Hey,

here are some answers:

  1. We intended to retarget tem via the Retargeter and not on runtime.
  2. No custom IK bones
  3. We have wanted to use UE5 Skeleton as a basis.
4

Hi @PolygonArt_WEN

Thanks for clarifying. As you are using the default IK Retargeter within UE 5.7.2 and have not been adding any custom IK Bones, the hand drifting/incorrect finger poses are typically due to the settings applied to the bone translation mode, root scaling and Hand IK Retargeting node in your Animation Blueprints.

When retargeting around 1000 weapon animations from a UE4 skeleton configuration to the UE5/MetaHuman baseline/proportions, the arms will often appear stretched or incorrectly placed due to the difference in shoulder width and arm length between MetaHuman/UE5 and the classic UE4 Mannequin.

Here is a step-by-step workflow and troubleshooting approach you can test to lock those hands back onto the weapon accurately:

Adjust Retarget Chain Settings and Translation Mode

  • Open your IK Retargeter asset, select your character chain mapping, and check the Translation Mode for your arms and hands.
    Setting spine and arm chains to RBF Interpolate or tweaking Static Offset values can prevent the arms from overextending or collapsing inward toward the chest
    Verification: Preview the reload animation inside the Retargeter window, the hands should track closer to the source mesh’s relative gun grip position without detaching.

Enable and Configure the Hand IK Retargeting Node

  • In your characters Animation Blueprint, ensure you are utilizing the Hand IK Retargeting node (or Retarget Pose from Mesh node depending on your setup).
    This dynamically adjusts the left hand to stick to the weapon socket even if limb lengths differ between skeletons.
    Verification: Play the animation in-engine, the supporting hand should lock securely onto the weapon barrel or grip instead of floating in empty space

Fine-Tune Target Root and Height Offsets

  • In the Asset Settings of your Retargeter, adjust the Root Motion Scale and Height Offset parameters if your MetaHumans are sitting slightly lower or higher relative to the original UE4 animation floor plane.
    Verification: Feet and hips remain planted correctly on the ground plane without weapon clipping through the torso or floating above the hands.

Epic Documentation: IK Rig Retargeting

Video: How to Hold Weapons Properly in Unreal Engine 5

Hope this helps a bit! Let me know how it goes.