@Friidilinen, I understand what you are going for now. Thanks for the screen shots as they are very helpful.
What you want to do is separate the mesh that holds the net from the mesh that represents the frame. You also don’t need that much resolution in the net mesh… it could be a quad and work just as well. The reason for this is that glTF can assign materials based on mesh but not face. So only one material can be assigned to any mesh. This is a good way to think of your material breaks as they will be assigned to a different mesh in your outliner. In this case you will have two meshes and two materials in your scene.
I am going to assume that since you are using Maya that you are using the Babylon.js exporter for Maya: github[dot]com/BabylonJS/Exporters. so you will want to use Arnold materials for your meshes. Docs for this can be found at doc[dot]babylonjs[dot]com/extensions/Exporters/Maya_to_glTF. You will create two materials and just point the basecolor, metallic, roughness, normal, etc. to the same files on disk.
Once you have the file exported, you can then check the file in the Babylon.js sandbox at sandbox[dot]babylonjs[dot]com where you can just drag and drop your glTF files (if you export as a glb just drag that file, otherwise you will want to select the glTF file, the bin file, and all texture files and drag/drop the group of files in the sandbox window). You can also drag/drop an hdr equirectangular HDRI onto the sandbox to test out different lighting as well.
Sorry for the not-really-a-link-links. I haven’t posted enough on this forum to be able to post links yet. Let me know if you have more questions.