I wish I had sample assets to share how to reproduce this issue, but I don’t just yet… Here is what is happening:
- We have a bunch of models that are sharing the same skeleton
- For one of these skeleton meshes, let’s call it SkelMesh Foo, it has a joint hierarchy not used in any of the other skeleton mesh models
- We made big changes to the unique joint hierarchy in SkelMesh Foo
- I re-imported SkelMesh Foo and received this error:
FAILED TO MERGE BONES:
This could happen if significant hierarchical change has been made - ie inserting bone between nodes
Would you like to regenerate Skeleton from this mesh?
WARNING: THIS WILL REQUIRE RECOMPRESS ALL ANIMATION DATA AND POTENTIALLY INVALIDATE
There are 5 options: Yes, No, Yes All, No All, Cancel
Result: If I pick “Yes All”, the skeleton reverts and only contains the bones from SkelMesh Foo
Expected Result: The skeleton would contain the bones from all the SkelMeshes that reference it
Note: At this point, if I go open a SkelMesh that was also bound to the Skeleton, I get this message:
The Skeleton Core_Skeleton, is missing bones that SkeletalMesh Bar needs. They will be added now. Please save the Skeleton!
If I click “OK”, the unique bones from SkelMesh Bar are merged into Core_Skeleton, but none of the animations against the skeleton work.