PBR workflow. When should you use Metallic vs reflectance?
polycounter lvl 9
I'll be learning the PBR workflow today, and that question stumped me. When should use either map and where it is appropriate? How does it differ? For example what if I have a metallic map and I wanted it to have colored reflectance in some areas?
Replies
For example, UE4 is metalness only, Cryengine is full reflectivity, Unity is whatever shader you use.
If you're concerned about being able to colour your reflective values wherever you like, then you should absolutely use reflectance. Metalness is a much quicker workflow though, and generally speaking it's easier to learn as an artist.
What I was trying to mean in my previous post is what if I use a Metalness map, but some small areas of the object require some color in its reflection? Would I just add more color to the Albedo to try and get that point across?
I haven't seen any workflow videos of someone actually pbr texturing in regular photoshop. I have read the Marmo tutorial and checked out the the Cerberus model provided by Andrew on polycount.
due to energy conservation, the diffuse is multiplied by 1 - metalness. so as you try to tint the specular, the diffuse will become darker. at the same time, the specular will only be tinted by the original diffuse colour, you couldn't have say, a green diffuse and a yellow specular.
your best bet is to ask the client which workflow they use, and if possible could you have the compiled shader to use on your end.
failing that, i have written a unity shader that does metalness or reflectivity. (well, two shaders, one for each workflow). I'll be releasing those soon.
Its specific to Toolbag, but most of the concepts are pretty universal and it explains the metalness vs spec map thing.
Is this correct?
People really should stop using term albedo, as it really means pure color without any fakes, and I say good luck, making good looking prop without any faked lighting
Albedo is a very technically correct term, these days you should not be faking any lighting, provided you have decent shaders/lighting systems.
I've been really struggling figuring out metalness, because it feels incredibly confining to me; but I think it's just because I misunderstand the way it works.
In Toolbag 2, yes, though adjusting the albedo for non-metals doesn't actually affect reflectivity (just apparent reflectiveness). Adjusting the gloss value does affect reflectivity indirectly, due to energy conservation.
Other engines may have both a metalness and base reflectivity input though (but this gets sort of messy).
Yeah, and in that case you probably want a special-case newton's rings shader, you can't really get that look with just a standard colored spec map either.
I have, and I still fake lighting. We are just not yet on film level, and we won't be for foreseeable future.
The only difference is how much lighting you should fake. Now, it's about faking smaller details
I'm sure there will be hacks as long as we're simulating the real-world. Even "film" level is garbage compared to reality. It's all just layers of hacks. But you shouldn't be baking much lighting - certainly not compared to the diffuse of old.
I had a look at this
So it looks like to get the colored specular I was talking about, you can add color to the roughness? I thought the roughness had to be grey scale.
I was also wondering, how did quixel find the values for each material? Where can us artists find values for each material like that?
There is one : http://www.polycount.com/forum/showthread.php?t=124683
They don't find them, they scan them with this monster.
All the roughness values (which are labelled "Microsurface") do seem to be greyscale.
The R in the image stands for Reflectivity, and those are colored.
So my real question is, can I make any material accurate only using a metallic map workflow?
longer answer: although almost all dielectric materials fall into the reflective range of 0.02 - 0.04, there are some extreme cases that don't. and because the metalness workflow puts all dielectrics at reflectivity 0.04 that means that you will have some materials that are never 100% physically accurate.
that said, the difference between values of that range is almost imperceptible to most people.
I wonder does anyone really use reflectance workflow nowdays? I mean in actual game?
As of physically accurate materials I think neither of them are . The idea of PBR is all around microsurface while most of natural materials are very grainy and its surface irregularity is not micro at all.
Normal map resolution is typically not enough to reproduce not so micro surface bumps . Thus such basic thing as asphalt is very tricky actually and needs a lot of special tricks and workarounds . I have to see yet a real looking asphalt highlight in a game. Same with a snow or sand, or grass and so on.
Both of workflows are good for man made objects really
yes. but its rare
i would love to have it on more projects
having control over the color of reflections besides using metalness is so much nicer for stylized stuff
If you're using glTF format there's an extension for colored specular KHR_materials_specular or you can use the older but still valid extension KHR_materials_pbrSpecularGlossiness.