Animation retargeting solves one of the most common problems in Unreal Engine 5 projects: you have a motion capture animation built for one skeleton, and a character with a different skeleton. Retargeting transfers the animation data so it plays correctly on any compatible humanoid rig — without re-capturing or rebuilding the animation from scratch.
When You Need to Retarget
Every animation in UE5 is bound to a specific skeleton asset. An animation authored for the UE5 Mannequin skeleton (SK_Mannequin) will only play correctly on a character that uses that exact skeleton — or one that has been retargeted to it.
UE5 animation retargeting allows you to apply mocap data from one skeleton to another without losing motion quality or requiring manual cleanup.
You need to retarget when:
- Your character uses a custom skeleton with different bone names or proportions
- You purchased animations for a different skeleton than your character uses
- You want to transfer animations from a MetaHuman to a custom character or vice versa
You do not need to retarget when your animations were built for the UE5 Mannequin and your character uses the same skeleton. MoCap Online's UE5 packs are delivered pre-configured for the UE5 Mannequin skeleton, which eliminates retargeting work for most standard projects.
Understanding IK Rigs and Retarget Chains
Before creating an IK Retargeter, you need IK Rigs for both source and target skeletons. An IK Rig defines the bone chains that the retargeter maps between skeletons — spine chain, left arm chain, right arm chain, left leg chain, right leg chain, and root.
Each chain tells the retargeter which bones correspond to which body segment. A spine chain on the source skeleton maps to the spine chain on the target skeleton, and the retargeter transfers rotation values across the proportion difference between the two. Without well-defined chains, the retargeter cannot determine which bones correspond and the result is broken joint behavior.
The root bone handling is critical for root motion animations. If the root chain is not defined in both IK Rigs and mapped in the retargeter, root motion displacement will not transfer — the retargeted animation will play in place even when the source clip has root displacement.
UE5 IK Retargeter — Step by Step
- Create IK Rigs for both skeletons. In the Content Browser, right-click your source skeleton asset, select Create IK Rig. Repeat for the target skeleton. Define the IK chains (spine, arms, legs) in each rig so UE5 understands how bones correspond.
- Create an IK Retargeter. Right-click in the Content Browser, Animation → IK Retargeter. Set the source IK Rig and target IK Rig.
- Align the retarget pose. In the Retargeter editor, put both characters in a matching T-pose or A-pose. Mismatched rest poses are the most common source of retargeting artifacts — limbs rotating incorrectly or spine deforming under motion.
- Preview and adjust. Select an animation in the Asset Browser and preview it on the target character. Use the Chain Mapping panel to fix any chains that are not retargeting correctly.
- Export retargeted animations. Select the animation sequences in the Asset Browser, right-click, Export Animations. UE5 creates new animation assets bound to the target skeleton.
Batch Retargeting Your Animation Library
Once the IK Retargeter is configured and producing clean results on preview, you can retarget your entire animation library in one operation. In the IK Retargeter's Asset Browser panel, select all animation assets you want to retarget (Ctrl+A to select all), then right-click and choose Export Animations. UE5 processes each clip against the retargeter configuration and creates new Animation Sequence assets bound to the target skeleton.
The batch export preserves clip names and optionally adds a suffix (such as "_Retargeted") to distinguish the new assets from the originals. Set the export destination folder before running the batch to keep your Content Browser organized.
For large libraries (50+ clips), the batch operation is the only practical workflow. Retargeting clips individually would take several minutes per clip. The batch approach processes the full library in a single operation that runs while you continue other work.
Common Retargeting Problems and Fixes
- T-pose on import (before retargeting) — Skeleton mismatch. The animation was built for a different skeleton than the one assigned. Fix: reassign the correct skeleton in the FBX import dialog, or use the IK Retargeter.
- Limbs rotating incorrectly — Rest pose mismatch. Fix: align the retarget pose in the IK Retargeter so both characters are in the same rest position before retargeting.
- Root bone not transferring — Root motion may not be mapped. Fix: ensure the root chain is defined in both IK Rigs and mapped in the Retargeter's Chain Mapping.
- Fingers or extremities deforming — Hand and foot chains may be misconfigured. Fix: check the IK chain definitions for hands and feet; fingers often need separate chains from the main arm chain.
MetaHuman Retargeting
UE5 includes a pre-built IK Retargeter for transferring animations between the UE5 Mannequin and MetaHuman skeletons: RTG_UE5Mannequin_To_MetaHuman, found in the MetaHuman project content. This eliminates the need to build IK Rigs manually when working with MetaHumans.
To use it: import your animation for the UE5 Mannequin skeleton, then open the pre-built retargeter, add the animation to the Asset Browser, and export retargeted. The exported clip plays on any MetaHuman character without additional configuration.
For retargeting in the other direction (MetaHuman animations to a custom character), create custom IK Rigs for both the MetaHuman skeleton and the target skeleton, then build a Retargeter connecting them. See our MetaHuman mocap guide for the full workflow.
Retargeting Best Practices
Build IK Rigs once per skeleton, not per animation. The IK Rig is a reusable asset — set it up correctly once and it applies to every animation you ever retarget to or from that skeleton.
Keep the original animation assets separate from the retargeted copies. Retargeted animations are derived assets. If you update the original or the retargeter configuration, you need to re-export. A clear folder structure (source animations in one folder, retargeted copies in another) prevents confusion when updating.
Avoid retargeting when possible by purchasing packs built for your engine's native skeleton. MoCap Online's Unreal Engine animation packs are built for the UE5 Mannequin skeleton — zero retargeting work for standard UE5 projects. See the complete UE5 mocap import guide for the full pipeline from FBX import to Animation Blueprint.
UE5 IK Rig Advanced Setup: Chain Mapping, Proportional Correction, and Root Motion Handling
The IK Rig setup quality determines the ceiling for what the IK Retargeter can produce. A minimal IK Rig — just a root bone and full-body IK chain without dedicated limb chains — retargets body position but not limb proportion compensation. For characters with significantly different limb lengths from the source mannequin, this produces correct joint rotation data mapped to wrong endpoint positions: the arms reach the same rotational extreme as the source but do not reach the same spatial point in world space. Adding explicit limb chains (each arm, each leg) to the IK Rig enables the retargeter to apply proportional compensation, stretching or compressing the limb chain to match the source character's spatial reach while preserving the rotation data. This is the step most IK Rig tutorials omit that most matters for non-standard body proportions.
Root motion handling in the IK Retargeter requires attention when the source and target characters have different height scales. UE5's retargeter applies a global scale factor based on the ratio between the source and target skeleton root bone heights, which correctly scales locomotion speed for characters taller or shorter than the source mannequin. The issue arises with hybrid pipelines where some animations have root motion and others are in-place — if the scale factor is applied to in-place animations, it has no effect, but if the retargeter is configured for a scaled root motion pipeline and an in-place clip is retargeted through it, the displacement calculation produces incorrect values. Maintain separate retarget asset configurations for root motion and in-place clip sets, or use the per-animation retarget settings to override the scale behavior on a clip-by-clip basis for edge cases.
After retargeting, validate results at three canonical test poses before deploying to the Animation Blueprint: the neutral idle, the maximum locomotion frame (highest velocity frame in a run cycle), and a contact frame from a combat animation. The idle validates reference pose alignment; the maximum locomotion frame validates root motion scale and limb endpoint positions at peak extension; the contact frame validates that impact moments — sword swings, punch contacts — maintain the spatial relationship between the attacking limb and the target point. A retarget that passes all three tests performs correctly across the full animation set. A retarget that passes the idle but fails at peak extension needs proportional compensation refinement in the IK Rig chain setup. Documenting these three test results for each retarget asset gives the team a reference for evaluating whether future skeleton changes break the retarget.
Retargeting MoCap Packs to MetaHuman: Workflow and Known Limitations
MetaHuman characters in Unreal Engine 5 use a skeleton compatible with the UE5 Mannequin hierarchy but with additional facial bones and a slightly modified hand chain. Retargeting standard MoCap Online animation packs — built for the UE5 Mannequin skeleton — to MetaHuman characters requires an IK Retargeter asset configured from the UE5 Mannequin as the source and the MetaHuman body skeleton as the target. The body animation transfers correctly for all major joint regions. The limitation is the MetaHuman's additional hand bones: the MetaHuman hand chain includes metacarpal bones that the standard UE5 Mannequin lacks. Finger animation retargets to the MetaHuman's proximal finger joints correctly, but the metacarpal rotation stays at its bind pose.
For most game animation use cases — grips, holds, combat stances — this is visually acceptable. For close-camera finger articulation in cutscenes, the metacarpal gap may need manual correction per clip. MetaHuman body animation retargeting for locomotion and combat works reliably without any manual adjustment beyond the IK Retargeter setup. The proportion difference between the standard UE5 Mannequin and a MetaHuman body is minimal, which means the IK chain adjustments needed for non-standard characters are not required here. Creating one IK Retargeter asset per character with the Mannequin as source enables bulk retargeting of entire Unreal Engine animation packs in a single operation.