I'm trying to understand how the new Principled Shader in 2.79 works, so I can make a video tutorial on it.
I get most of it, but a few things have me confused, and there currently isn't much documentation for it.
Since most dielectric materials have an IOR of 1.45, is the default 0.5 value for Specular the correct value?
What does "Sheen" actually do? I've read that it provides an "additional grazing" component useful for fabric. But what does it actually do? Is it adding an additional white fresnel component for the color channel?
Why is Sheen Tint 0.5 by default? Just looks odd since most values are 0, yet this is 0.5. Just curious since it doesn't do anything until Sheen is turned on anyway.
Why does it use Roughness for the specularity, but Gloss for the Clearcoat? Their only difference is that they are opposites of each other, so it requires extra mental effort to think before changing it. Is there a reason for this that I'm missing?
What are some practical situations where you would want a different clearcoat normal? I can only think of situations where you'd want a smooth clearcoat, like metallic paint or carbon fiber. Is there any other reason for wanting bump on a clearcoat?