its called multimap nm detail in the editor. transparency is also delivered through the diffuse alpha channel. its used for cars, buildings, water surface, chrome metallic etc. windows don't require second material when using this multimap shader. best way to see this shader in action. is to looks at black cat county road surface and compare it to say Barcelona`s. then look at highlands buildings. then check out the bull statue at the redbull ring.
its not just transparency you want for windows. its a mix reflection and transparency. and same for a wet track too. I mean same principle.
Ah ok it sounds like they've got a shader that equates over to the general PBR shaders you'd see elsewhere now (has it always?)
I'm sure last time I looked it still wasn't, but maybe it is now.
So in the case of the building in the OP, I think you could get away with just defining the entire thing as dielectric (or default, or whatever AC supports for spec), then just make the window bits glossy (near 100%) so they reflect the environment sharply. Leave their diffuse colour around what you'd see 'straight on' on an overcast day.
Leave normals blank, or add a slight dip for the windows.
Even with it filling half the vertical screen with a 512px tall texture it'd look 'photoreal' most of the time.
Going OTT on geometry on buildings is pointless unless you're getting really near them at low speeds. Better to just consider the silhoutte profile as you drive near it, and add detail for that, then throw the rest in normal maps where you can get much higher frequency detail kinda 'for free' vs adding geometry, you can then bake in complex geometry forms easily (Quixel type approach), get nicer shading (on normal maps high frequency detail vs actual geometry which small details don't get nicely self-shadowed)
Dave
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