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Re: theoretical pbr question, how does energy conservation work?
alright i read those links, so here is my visaulisation to make sure i understand; 1. specular 2. angle of the specular reflection, based on the glossiness of the surface. if its wide its more spread out and thus weaker (energy conservation) 3. diffuse different materials have different amounts of specular reflections and… -
Re: theoretical pbr question, how does energy conservation work?
The concept of energy conservation states that a given surface can not reflect more than 100% of the light that hits it. This is logical and physically grounded in reality, how could something reflect more than 100% of the light that hits it? It would have to generate photons of its own to do such a thing. So, if you have… -
Re: theoretical pbr question, how does energy conservation work?
".... is this correct?" Yep. "if so, the maps we use in a pbr workflow would be, diffuse; the colour of the light after it bounced around underneath the surface gloss: the angle of specular reflections (microsurface) metalness: amount of specular vs diffuse is this also correct?" A PBR system doesn't have a specific set of… -
theoretical pbr question, how does energy conservation work?
so im trying to understand pbr, and make it relatable to the real world, and im stuck on the energy conservation theory. it says, the how much reflective light a material has, is directly proportional to how little diffuse light it has. so a highly reflective material has a darker diffuse, and a non reflective have… -
Re: theoretical pbr question, how does energy conservation work?
""The reflection on a shiny white ball is much less bright than the reflection on a shiny black ball." can be rather confusing. Both a white and black rubber ball have the same specular reflection intensity, but differing diffuse reflection intensities." so the total light output is lower for the black ball? same spec,… -
Re: theoretical pbr question, how does energy conservation work?
aright i think i got it now! thanks eq and the others! follow up question: a big difference with the pbr workflow is that you cant pick the diffuse values yourself anymore you have to base it somewhat on scanned data and such. why? if i paint a wall in real life, i get to pick whatever diffuse i want right? why is this not… -
Re: theoretical pbr question, how does energy conservation work?
It's a misconception that you can't pick your diffuse/albedo value in a PBR system. Diffuse values will vary heavily for insulators depending on what color a material is. If you find a measured diffuse value for say, red paint, that doesn't you have to use that value for every type of paint, obviously blue paint or black… -
Re: theoretical pbr question, how does energy conservation work?
Semantics, albedo is basically a synonym for base color, albedo essentially means the measured reflectance value of something, which could, on a more esoteric level, mean specifically diffuse albedo or specular albedo. The reason the base color/albedo map stores both diffuse and specular content in UE4 is because they use… -
Re: theoretical pbr question, how does energy conservation work?
The reflection on a shiny white ball is much less bright than the reflection on a shiny black ball. They are receiving the same lighting. The white ball is reflecting most of that light from its indirect bounces (diffuse), and little from its direct bounces (reflection). It's bouncing the sum of what it receives (minus a… -
Re: theoretical pbr question, how does energy conservation work?
Another interesting tidbit, if you have two balls, and you paint one with a glossy white paint, and the other with a glossy black paint, and looked at each of them, you might quite reasonably assume the black one was more reflective. It's not though, the diffuse is simply darker, while the specular reflectivity is the same…
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