Keywords: UE4, FBX, Skeletal Mesh, Animation, Multiple roots found

Attentions

Skinning Method

UE4 doesn’t support Dual Quaternion of Maya, Skinning Method must be set as Classic Linear.

Import SkeletalMesh using existed Skeleton

Check Skeletal Mesh and select existed Skeleton.

When pop a tip window:

FAILED TO MERGE BONES:
This could happen if significant hierarchical changes have been made
e.g. inserting a bone between nodes.
Would you like to regenerate the Skeleton from this mesh?
WARNING: This may invalidate or require recompression of animation data.

This means that the hierarchical structure of bones in FBX doesn’t match the source skeleton.

Solution 1st (Maya):
Hierarchical Structure of Skinned Mesh in FBX for Unreal

Solution 2nd (Blender):
Import FBX into Blender, select root, then hold down Shift, then select mesh, and export FBX.

Reference: How to export & import Skeletal Mesh between Blender and Unreal

Issues

Duplicate bone name found (‘XXX’). Each bone must have a unique name

Issue:
When Import FBX into UE4, there’s error log:

Multiple roots found 
Error, Could not import MinigunPlaceholderSkel.
Duplicate bone name found ('MinigunPlaceholderSkel'). Each bone must have a unique name.

Possible Causes:

  • The Group name is the same as the Mesh name or Bone name.
  • There’s no Group out of Mesh and Bones.

Solution:

  • Change Group name that isn’t the same as Mesh name or Bone name.
  • Create a Group and put Mesh and Bone under it.
Mesh contains XXXX bone as root but animation doesn’t contain the root track

Error on importing animation asset (FBX):

FBXImport: Error: Mesh contains XXXX bone as root but animation doesn't contain the root track.
Import failed.
FBXImport: Error: Import failed.

Caused by:
The name of top node in Outliner (the top node can be a Joint, or a Group) wasn’t the same between skeletal mesh and animation sequence.

Solution:
Make sure the name of top node in both skeletal mesh and animation sequence are the same.
Group name in skeletal mesh:

root joint name in animation sequence:

When names of top node are the same, then you can name the chind node as what you want. e.g. you can name the child node which under root node as AAAA

Attention:
The top node in Outliner would became as a bone when it was imported in Unreal.

Seams on mesh (small piece deleted)

Uncheck Remove Degenerates:

Docs

How to import animated FBX assets

How to Import Animated FBX Assets in Unreal Engine | Twinmotion to Unreal Engine Tutorial
https://www.youtube.com/watch?v=0sFeAyf1E54

How to import mesh with textures and materials from Blender, Maya or 3DsMax

Export Alembic Animations to Unreal Engine the correct way (WITH MATERIALS)
https://www.youtube.com/watch?v=b_FvqQyyYFk

这世上所有事都不能感同身受，只能报以温柔。