What is the correct workflow for importing multiple materials on an object from Cinema 4D?

Hey guys I’m kind of breaking my head over this problem so I’m looking for help.

I’m working on a project where I’m modeling a bunch of buildings with two materials applied to them. One is the base material, one for a window shader.

I made one building with a single selection tag which applies the window shader. The base material doesn’t have a selection tag, so it fills in the rest of the polygons. When I export it as an .FBX it imports just fine and shows two material slots in UE4. Great!

So I used the same workflow for the second building. Base material on the whole mesh, and a selection tag for the windows. However with the second building UE4 shows only one material slot.

Things I tried:

  • Tried making two selection tags, one for the windows and one for all polygons that are not windows.
  • I tried all .FBX versions C4D supports
  • Using different Cinema4D versions to export the .fbx files.
  • Only exporting the part that actually has both materials.
  • Exporting .obj and .abc
  • Triangulating the mesh
  • Importing into UE5 to see if it makes a difference.
  • Googling a bunch of stuff

I’m kind of at my end, so I hope someone can explain me the proper workflow on how to export meshes from Cinema4D with multiple materials. The way I’m doing it seems to randomly not work.

Here are two images that show my C4D file: