Custom attribute with morph targets not working?

Hi!

I have a rig in Maya where blendshapes are used in animations, and want to make sure the animated blendshapes work in UE5.3. Aka, that the curves for the blendshape values are baked and imported correctly. Right now the rig has one skinned body mesh and three separate skinned modular meshes.

I’ve connected the values of the blendshapes to custom attributes in the rig’s root joint - and when exporting this to UE the animations work well for the body mesh but not the other skinned meshes. I can see that the curves themselves are imported correctly (and Maya shows that they have values during the animation), but the curves don’t seem to be associated with the morph targets at all. The skinned meshes all have working morph targets so that’s not the issue either - it’s the connection that seems to be missing.

Does anyone have any idea of how to solve this?