What is the maximum and minimum value for roughness to be physically accurate? Because I’ve heard that a material can not be 100% reflective because it bounces 100% of the light back. I’m also assuming that material can’t be 100% rough but I might be wrong on that. I know a lot of people say that it doesn’t matter but every little bit helps to make a material more realistic. I only ask this question because I have been tampering with the roughness map to get it to what I want with the gamma node so I’m afraid that the minimum value for roughness is like .1 or something. But would fixing this issue include darkening the diffuse if it gets close to the value of 0? If so by how much?
A material can be both 0% and 100% rough afaik. We divide into specular, diffuse, and volumetric effects for calculation and convenience of approximation. The fresnel equation basically determines if a ray bounces specularly back out (at angle defined by surface normal and roughness) or if it enters the medium. A rougher surface has a greater chance of absorbing the ray (fresnel gets darker). Think of throwing stones on flat water or rough seas.
Unless it’s a polished metal surface, it won’t reflect 100% of light back. Fresnel determines what gets reflected and what enters, and albedo defines which colors that enters are not absorbed but exists again. Use albedo cheat sheets to see how bright your diffuse part needs to be. Snow is about the whitest we have, and even that is not 100% white.
But real life is a bit more complicated - real life doesn’t care about fresnel, fresnel was invented to describe real life observations. Diffuse doesn’t really exist. It’s all volumetric, but tracing a ray through internals of medium, well, we all know how long that can take (try rendering smoke). So we use diffuse instead because it’s a much faster approximation. “Recently” diffuse has becoming a bit more advanced, doing exit IOR darkening, and I believe we only have that in Principled. The effect of this I think is less than using O-N for rougher surfaces (Principled combines these).
Don’t get too strung up in numbers. Recreate what you observe, and learn to observe.
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Thank you for explaining this to me! I’ll try not to get too much into the numbers 