The Clear Coat Shading Model can be used to better simulate multilayer materials that have a thin translucent layer of film over the surface of the Material.
In addition to this, the Clear Coat Shading Model can also be used with either metal or nonmetal surfaces. In fact, it was specifically designed to model this second class of smooth colored films
over a non-colored metal. Some examples of Clear Coat Materials include acrylic or lacquer clear coats, and colored films over metals such as soda cans or car paint.
The Clear Coat Shading Model opens up two new Material inputs on the Main Material node.
Clear Coat: Amount of clear coat layer, 0 acts like the standard shading model, 1 is the full clear coat model. This is useful for masking.
Clear Coat Roughness: Roughness for the clear coat layer. Our approximation is accurate for small values. Very rough clear coat layers are supported but will not be very accurate compared to their real world counterparts.