Major - Migrated assets from UE5 lose their inter asset references

[Lars_Thomsen]

Migrating assets from UE5 that reference each other, results in those references being lost. It seems to affect all inter asset references. Parent materials, material functions, and material parameter collection references are lost. Same with texture references.

An example material made in UE5:

The same material in UEFN after migration:

Looking into the asset files. The cause of this could be the different paths used for the content folder. “/Game/” in UE asset paths should perhaps be replaced with what makes the content root of the targeted UEFN project during migration, due to the plugin nature of UEFN projects structure.

Here are some paths found in a migrated material referencing a material function immediately after migration:
/Game/Migration/MigrationTestMaterial
/Game/Migration/MigrationTestMaterialFunction

Saving the material fixes the material assets own path but drops all other paths(MaterialImport is the name of the UEFN project):
/MaterialImport/Migration/MigrationTestMaterial

Hooking the references back up in the material fixes the other path:
/MaterialImport/Migration/MigrationTestMaterial
/MaterialImport/Migration/MigrationTestMaterialFunction

I should mention that moving assets from one UEFN project to another likewise breaks all inter asset references. Probably for similar reasons.

[Cardin ([JOGO]Cardin)]

Some additional findings of my own ;

All of this happens regardless of if the migration consolidates into the “migrated” folder or moves across clean. When all references are repaired manually the assets work as they did prior to migration.

Meshs default to “WorldGridMaterial” -

Restoring the correct material references automatically restores missing LOD sections -

Material references missing their parent reference -

Material Functions lose their reference -

Fixing the material function reference does not restore the node links -

Texture Parameters lose their references -

[HalcyonKnight96]

Hi @Lars_Thomsen @Cardin thanks for the information on this issue. We’ve taken a note and when the team gets back from break we’ll find some time to investigate. Thanks!

[Cardin ([JOGO]Cardin)]

I happened to be showing the migration process to a colleague today and this issue does not affect him at all and everything migrates smoothly.

I am currently investigating the difference in conditions that causes this and will post back if I find anything.

[Cardin ([JOGO]Cardin)]

This migration issue is fixed for me in UE5.1, anybody else having this issue, try updating UE.

This seems quite random as there is nothing mentioning it in the UE5 changelog.
I sure am happy it is working again though

[HalcyonKnight96]

Great to hear @Cardin! Thanks for following up!

[yojj47]

For others who come across this and are unfamiliar with migrating content from UE, you can refer to this! Migrating Assets | Unreal Engine 4.27 Documentation