Animation Retargeting
Transferring animation between skeletons
Also known as: Retargeting · Animation transfer
Definition
Animation retargeting transfers a clip recorded on one skeleton onto another with different proportions or bone count. The retargeter matches bone names or a manual mapping, then re-calculates the animation to preserve the original intent (foot placement, hand contact) despite skeletal differences. Without retargeting, every character would need its own animation library — with it, one Mixamo run cycle plays on a tall thin character and a short stocky one alike.
In production
UE5 IK Retargeter is the modern standard — it exposes a visual bone-mapping interface with a real-time preview viewport, so animators can watch the retarget correct foot sliding before committing. It works by defining an IK Rig on the source and target skeletons, then chaining matched limbs (root, spine, arm, leg) so the solver preserves ground contact and hand placement even when the target has a longer torso or shorter limbs. Mixamo's retargeting is fully automated — upload a mesh, get an auto-rigged skeleton back — but it produces lower-quality results on stylized rigs with exaggerated proportions, since its heuristics assume roughly human bone ratios. A common pitfall is retargeting between skeletons with different bone counts — without a manual chain mapping, twist bones get ignored and shoulders visibly pop during arm rotations.