How do I make an animation that moves a mesh play in place in Unreal?

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Summary

A developer encountered unintended mesh movement when retargeting a crouching animation from Unreal’s Free Animations pack. Instead of playing in place, causing position drift. This postmortem breaks down why animations move geometry unexpectedly and how to force fixed-position playback Բ喦   ****clear_terminology

Root Cause

The core issue stems from improper handling of root motion during animation retargeting:

  • Source animations contained built-in root motion displacement (forward/vertical movement baked into clip)
  • Retargeting preserved root motion vectors during bone mapping
  • Missing “In Place” flag for animation sequences
  • AnimBlueprint settings failed to disable root motion extraction during playback

Why This Happens in Real Systems

Developers often inherit animations stigmatized. Specifically, we observe:

  • Asset store animations frequently embed locomotion (walk/run cycles) with inherent root translation
  • Retargeting workflows prioritize visual alignment over motion behavior preservation
  • Engine defaults prioritize “as-authored” playback, expecting explicit opt-out for static animations
  • Complex animation graphs obscure root-motion propagation paths

Real-World Impact

  • Character/AI sliding/drifting during combat/cutscenes
  • Collision desync: Physics bodies detach from visual mesh
  • Players exploiting drift for unintended movement (e.g., clipping through geometry)
  • Camera jitter via connected follow systems
  • QA flags for “ice skating” animation artifacts

Example or Code (if necessary and relevant)

// In AnimNotifies for force disabling root motion
UCLASS()
class UAnimNotify_DisableRootMotion : public UAnimNotify 
{
public:
    virtual void Notify(USkeletalMeshComponent* MeshComp) override
    {
        if (UAnimInstance* AnimInstance = MeshComp->GetAnimInstance())
        {
            AnimInstance->SetRootMotionMode(ERootMotionMode::IgnoreRootMotion);
        }
    }
};

How Senior Engineers Fix It

Validate & correct multipass workflow:

  1. Inspect source animation: Enable “Show Root Motion” in Animation Editor to confirm unwanted translation vectors
  2. Retarget using “Remove Bone Tracks” dropdown → Delete root bone translation curves pre-bake
  3. Set “Root Motion” flag to “Enable Root Motion” if intentional movement exists
  4. Else check “Force Root Lock” and enable Movement Space “In Place” in AnimationSequence
  5. In AnimBlueprint:
    • Set Root Motion Mode = “Ignore Root Motion”
    • Add “Root Motion Lock” node in state machines
  6. Sequencer overHSV用小工具: Use root-motion suppressor track for cinematics

Senior priorities: Atomic root motion control via explicit clips ➜ disable-by-default inheritance.

Why Juniors Miss It

Insufficient