Animation Retargeting Challenges | Thomas Claiborne | 02/14/2025

The Problem

During the initial setup of our team's Unreal Engine 5.2 project, I encountered a significant challenge while implementing character animations. After successfully setting up our base player character with WASD movement and mouse look controls, I hit a roadblock when trying to integrate a third-party animation pack into our character's Animation Blueprint (ABP). The core issue was a skeleton mismatch between our base player model and the purchased animation set. This mismatch meant that simply dropping in the animations wouldn't work - they needed to be properly retargeted to our character's skeleton structure.

For anyone who's worked on a game project, having broken or misaligned animations can completely break player immersion and make the game feel unpolished. In our case, this was particularly critical since fluid character movement is central to our game's core mechanics.

The Solution

The solution to this problem involved several steps and some key learnings about UE5's animation retargeting system. Initially, I attempted to create a retargeting solution from scratch, but quickly discovered I needed IK (Inverse Kinematics) rigs for both skeletons - our base player's skeleton and the animation pack's skeleton. The animation pack didn't include its IK rig, which initially seemed like a major blocker.

After researching the issue, I discovered a valuable resource that ships with Unreal Engine: the UE4 mannequin pack comes with a pre-configured UE4 -> UE5 retargeter and IK rig for the UE4 mannequin. This was a game-changer because the animation pack we purchased used the same skeleton structure as the UE4 mannequin.

By leveraging these existing tools, I was able to:

1. Import the UE4 mannequin's IK rig
2. Use it as a base for retargeting our animation set
3. Successfully export all animations properly mapped to our player skeleton
4. Implement them in our movement Blend Space

The end result was smooth, 8-directional character movement that properly blended between animations. This solution not only fixed our immediate animation issues but also established a pipeline for integrating future animation sets into our project.

For other developers facing similar challenges, I'd recommend checking if your animation packs use standard skeleton structures (like the UE4 mannequin) before attempting to create custom retargeting solutions from scratch. The built-in tools in Unreal Engine can save significant development time if leveraged properly.