Clearcoat IBL attenuation inconsistant between doc and code

[kai-z99]

Documentation for clearcoat IBL says:

iblSpecular *= sq(1.0 - Fc)

while in surface_light_indirect.fs we have

Fr *= attenuation; (not squared)

where
float attenuation = 1.0 - Fc;

For both importance sampling and split sum path

[romainguy]

The document you are referring to describes Filament's lighting and material model at a certain point in time and does not necessarily accurately represents the current state of the engine. It remains however a perfectly valid reference on how to implement a PBR system. Removing the square attenuation was done after energy conservation was added. This extra term was already trying to account for it.

[romainguy]

What I'm basically saying is that the squaring of the specular attenuation with a clear coat layer should just be removed from the documentation.