i modelled the mesh. any idea?
Would you be okay with providing the problem mesh? You can just attach it here if that is okay.
I performed a test by making a mesh with multiple material IDs applied and confirmed no issues after importing to the engine. The issue may be with the mesh itself or with the settings used to import.
Key things to look out for:
- Properly laid out UVs
- X-Form is reset on mesh
- Verify that the polygon faces are actually assigned a material ID number
Hope that helps!