Corruption of Custom UV's Datasmith 4.23


We’re having some serious issues with UE4.23 with Datasmith and custom lightmaps. We’re experienced in using datasmith and have only recently encountered issues. Although they’ve now become critical i’d say we first noticed this behaviour on some objects in 4.22.

In short if we create custom lighmaps in 3DS Max they don’t seem to make it across to UE (sporadically on some objects but not others), what’s odd is the lightmap density preview in the editor appears to display the correct maps (can’t be 100% sure but they look clean) however if you look in the mesh editor they’re an overlapping mess and they bake as such. What’s particularly annoying is because the maps look clean in the preview we would have to open every single mesh to check if they have an issue.

See images below.

Wondering if anyone else has experienced the same thing and/or if they have a fix.

Just to clarify we’re changing lightmap coordinate index post export.