【Unreal Engine】UE5.4 Animation Retargeting: IK Rig and IK Retargeter Setup

Animation Retargeting Overview

In game development using Unreal Engine (UE), "animation retargeting"—reusing animations between different character models—is an essential technique. However, UE5's previous workflow was a major barrier, especially for beginners.

To perform retargeting, you had to manually create IK Rig assets for both source and target skeletons, then create an IK Retargeter asset to associate them—a cumbersome 3-step process. This effort was a major obstacle when incorporating high-quality animations purchased from asset stores into projects.

However, Unreal Engine 5.4 dramatically evolved this workflow. This article explains the complete picture of new animation retargeting features introduced in UE5.4, thoroughly guiding beginners to intermediate users through the new era workflow that approaches "one-click" liberation from cumbersome setup.

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Changes in UE5.4

The most important change in UE5.4's evolved animation retargeting (formerly IK Retargeter) is that pre-creating IK Rig and IK Retargeter assets is no longer required.

Previously, the following 3 assets had to be manually created and configured for each retarget:

1. Source IK Rig: IK setup for the source skeleton
2. Target IK Rig: IK setup for the target skeleton
3. IK Retargeter: Mapping and settings between the above two IK Rigs

In UE5.4, when executing retargeting, these assets are auto-generated internally with automatic bone mapping. This lets developers specify just "from which skeleton to which skeleton" and immediately execute retargeting.

Feature	UE5.3 and Earlier (Old Workflow)	UE5.4+ (New Workflow)
IK Rig Assets	Manual creation/setup required	Auto-generated, not required
IK Retargeter Asset	Manual creation/setup required	Auto-generated, not required
Bone Mapping	Manual verification/adjustment required	Mostly automatic
Execution Steps	Execute from IK Retargeter after creating 3 assets	Execute directly from animation asset

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Retargeting Execution Steps

Retargeting in UE5.4 has become surprisingly simple. Here we explain steps for the most common "applying source animation to target skeleton."

Step 1: Start Retargeting

First, right-click the source animation asset you want to retarget (e.g., ThirdPersonRun) in the Content Browser.

Select [Retarget Animation] from the menu.

Step 2: Select Target Skeletal Mesh

In the displayed dialog box, select the target skeletal mesh with the target skeleton (e.g., SK_MyCustomCharacter).

💡 Point: In previous versions you selected an IK Retargeter asset, but in UE5.4 you directly specify the target skeletal mesh. At this point, the system internally auto-sets up the necessary IK Rig and IK Retargeter.

Step 3: Select and Export Animations

After selecting the target, retarget candidate animations are listed. Usually, the right-clicked animation is already selected.

1. Verify the animation you want to retarget is selected.
2. Click the [Export] button at the bottom.

Step 4: Save Location Settings and Completion

Finally, set the destination folder and filename prefix for the new retargeted animation asset.

• Destination Folder: Specify any folder.
• Prefix: Auto-assigned prefix (e.g., RTG_).

Click [Retarget] to generate the new retargeted animation asset in the specified folder.

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Fine-Tuning After Retargeting

Auto-retargeting is very powerful, but between characters with different body types or bone structures, slight pose misalignments can occur from differences in limb length, etc.

Common Mistakes and Best Practices

Issue	Common Mistake	Best Practice
Pose Misalignment	Using retarget result as-is	Edit the auto-generated IK Retargeter
Root Motion	Root Motion not applying correctly	Check root bone transformation type in IK Retargeter, verify source/target root bone names match, also check Animation Sequence's Root Motion settings
Body Type Difference	Retargeting while ignoring skeleton proportions	Make source and target retarget poses match as much as possible before retargeting

Best Practice: Editing IK Retargeter

The auto-generated IK Retargeter in UE5.4's new feature is an internally auto-generated asset, and its location and UI display may vary by editor version and project settings. Access it through these steps for detailed adjustment using the traditional IK Retargeter editor.

1. Double-click the retargeted animation asset to open it.
2. Click the [Open IK Retargeter] button in the asset editor toolbar.

This opens the auto-generated IK Retargeter asset, allowing bone transformation settings (translation, rotation) and retarget pose fine-tuning. Hand/foot IK goal settings and disabling specific bone translations are adjusted here especially.

Blueprint Runtime Adjustment Example

Adjusting specific bone offsets in the Animation Blueprint after retargeting can improve character grounding feel at runtime.

For example, if feet sink into the ground after retargeting, use Transform (Modify) Bone node to slightly adjust the ankle bone.

// In Animation Blueprint's Anim Graph

// Using Transform (Modify) Bone node
//    - Target Bone: foot_l (left foot bone name)
//    - Translation Mode: Add to Existing
//    - Translation Space: Component Space
//    - Translation: +2.0 on Z-axis (lift slightly)

// Note: Two Bone IK is effective for foot IK control,
// but Transform (Modify) Bone is more direct for retarget-specific issues

Placing this node in the animation graph enables dynamic fine-tuning of retargeted animation poses to match character body type.

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Key Points for Retargeting Utilization

Unreal Engine 5.4's animation retargeting evolution dramatically improves the animation workflow.

• Simplified Setup: Manual IK Rig and IK Retargeter creation is no longer required, making retargeting a near "one-click" experience.
• Time Savings: Eliminating cumbersome initial setup dramatically reduces time spent on animation trial and error.
• Maintained Flexibility: Auto-generated IK Retargeters can always be edited in the traditional IK Retargeter editor, maintaining advanced customizability.

💡 Auto-Retarget Limitations

UE5.4's auto-retarget is very powerful, but when source and target bone hierarchy differences are large (e.g., retargeting a four-legged creature to humanoid), auto-mapping can break down. In such cases, you need to manually create IK Rigs and configure custom bone chain settings as before.

With this new feature, animation development in Unreal Engine has progressed to a more intuitive and efficient next stage. Please update to UE5.4 and experience this new workflow.