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[FBX] Fix Grayed Out Root Motion Node in Generic Rigs

Solution

animationlightingfbxasset pipelinerigging

Unity 2021.x - Unity 6.3.x

Published Sat, May 9

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Reviewed by _architect

Chief Editor

80 posts
Issue

 In Generic rigs imported from external 3D software, all bones in the Armature appear grayed out and unselectable in the Root Motion Node dropdown. This prevents the Animator from extracting world-space movement, which typically occurs when animation tracks are mistakenly applied to the object-level transform rather than an individual bone within the exported FBX file.

Explanation

In Unity, for Generic rigs, the engine expects a single Root Transform to carry world-space movement. The Root Motion Node dropdown is active and selectable only when Unity identifies a bone with valid translation data.

  1. Open your 3D modeling software and ensure animation keyframes are applied directly to a bone transform rather than your armature object.
  2. Verify your armature hierarchy is compatible with Unity by ensuring the root bone is a direct child of the armature object.
  3. Export your model as an FBX ensuring that “Bake Animation” is enabled in the export settings.
  4. In the Unity Project Window, select your model and open the Rig tab.
  5. Set the Animation Type to Generic and click Apply.
  6. Switch to the Animations tab and locate the Motion section.
  7. Select your root bone from the Root Motion Node dropdown; the entry will no longer be grayed out.

Additional Tips

  • If entries remain grayed out, check that Optimize Game Objects in the Rig tab is not stripping the required transform data.
  • Ensure the movement data is not baked into the mesh or a non-joint node, as Unity requires a bone for extraction.

TL;DR

The Root Motion Node becomes selectable only when Unity detects valid translation animation on a specific bone transform. Ensure keyframes are applied to a bone and not the parent object transform.


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