Hello ,
I just want to confirm, when you're applying the materials to the model, is this in Rhino or in Twinmotion?
I'm afraid I won't be of much help for Rhino, but if you're applying the materials after importing your model into Twinmotion, you have to make sure the model is imported with the Keep Hierarchy option instead of Collapse All or Collapse by Material.
If you have Collapse by Material enabled, then all objects that share the same material when they are imported are treated as a single object, so if you have the same glass material for all your windows, then when you replace the glass material, it will replace it across the whole model.
With Keep Hierarchy, each object in Rhino is imported into Twinmotion as is, so you can modify each individual object independently/ This will let you modify each window and apply a different material toe each one.
Best,
Raghib
Best,
Raghib