within an object) With this, one can create a translucent material with a smooth surface and with a milky look. The final refraction roughness has to be calculated using the surface roughness and the refraction roughness because those two are correlated for refractions. If a ray hits a rough surface of a translucent material, it is scattered while entering the surface. Then it is scattered further within the object. The calculation I'm using is the following: RefrRoughnessFinal = 1.0 - (1.0 - Roughness) * (1.0 - RefrRoughness)