Many times I have needed surfaces with multiple layers of materials.
- - Rain drops on glass
- Car shader (glossy coat on top of metallic rough surface)
- Screens on devices or appliances
- Graffiti on concrete walls
- Labels on objects/machines
- Ink/pencil on paper
- Explosion decals on a surface
While technically these could be accomplished with a Mix Material node, sometimes you need multiple layers that are physically stacked. Sometimes I can accomplish this by duplicating the mesh and expanding the surfaces
just barely and apply a separate material for this, but this is not a good solution, especially for multiple layers. Imagine if I had a wall to put a ton of posters/graffiti/decals to place on it. Would I need another Mix Material with each one and have a huge chain of them? Not elegant.
In real life many surfaces have layers of thin materials on them. I think this is the correct (and physically based solution) to this problem.
