I have some questions about PBR
polycounter lvl 3
So the current project I'm working on, in UE4, has encouraged me to rethink everything I know about PBR as I'm needing to create dynamic assets that work in the blackness of space as well as well lit hangars.
Some basic questions,
1. Should lighting be built around PBR or PBR around lighting?
For instance, is there only one way to convey 'gold' or will those values vary depending on your lighting set-up? Let's say I make an environment, set up the lighting, then throw in a gold material texture from Substance and it doesn't look gold, it goes really pale or really shiny, do I tweak the material to match my lighting or the other way around?
2. Similar to the first question, are Substance's materials pretty much perfect, or were they just built for their own viewport?
3. Would a good way to start lighting be to bring in some of Substance's materials in to my UE4 scene then work around that?
4. Do I HAVE to use metalness on metal? Or is that entirely relative?
I've seen some people very rarely use metalic values, even on metal, only to highlight glossy areas, or edge wear (metal showing through paint,) keeping the rest purely controlled with the roughness.
5. What does the albedo do on metalness maps?
I heard that once a value is metal, it uses the albedo as 'power' and doesn't look at it as color anymore. Does that mean anything that's metal shouldn't have a very colorful diffuse value? Should it be black and white with a hint of color? There are lots of metals which have some color to them, like copper.
6. I heard you have to untick sRGB in UE4 when bringing in Substance materials? What does that mean and why?
Some basic questions,
1. Should lighting be built around PBR or PBR around lighting?
For instance, is there only one way to convey 'gold' or will those values vary depending on your lighting set-up? Let's say I make an environment, set up the lighting, then throw in a gold material texture from Substance and it doesn't look gold, it goes really pale or really shiny, do I tweak the material to match my lighting or the other way around?
2. Similar to the first question, are Substance's materials pretty much perfect, or were they just built for their own viewport?
3. Would a good way to start lighting be to bring in some of Substance's materials in to my UE4 scene then work around that?
4. Do I HAVE to use metalness on metal? Or is that entirely relative?
I've seen some people very rarely use metalic values, even on metal, only to highlight glossy areas, or edge wear (metal showing through paint,) keeping the rest purely controlled with the roughness.
5. What does the albedo do on metalness maps?
I heard that once a value is metal, it uses the albedo as 'power' and doesn't look at it as color anymore. Does that mean anything that's metal shouldn't have a very colorful diffuse value? Should it be black and white with a hint of color? There are lots of metals which have some color to them, like copper.
6. I heard you have to untick sRGB in UE4 when bringing in Substance materials? What does that mean and why?
Replies
2 - Substance mats should look as good in UE4, but, again, this will depend on your UE4 lighting set-up.
3 - Yes, this would be a perfectly good approach for your project considering it is set in a non-Earth environment. Or you could load a custom HDRI into Substance to simulate your project's lighting.
4 - It is advised to use metalness as part of the PBR workflow, but is entirely up to you. Once you know the rules you can break them. Again: 'if it looks good, it is good' But not using metal on metal shaders will give dielectric reflections which will essentially make the shader a non-metal. The metalness parameter is an essential aspect of the PBR workflow and should be used for 'correct' results. Using a metalness map as a mask to show metal through chipped paint is a perfect example of this, and the reason for its use is plainly obvious.
5 - Albedo(from the Latin: reflected light) is not a diffuse map in the traditional sense. A metal doesn't have a colour so the albedo is used as the reflection value, i.e: gold, copper, brass, etc. Or a greayscale value for non-tinted metals such as Iron, steel, aluminium, etc.
6 - sRGB is essentially a toggle to gamma/de-gamma images, both RGB and greyscale, and is related to linear colour space. This is an in-depth topic and should definitely be studied to understand why we all should be working this way. Unticking sRGB is to prevent 'double-gamma'. Greyscale maps need to be in linear colour space.
Also, something to bear in mind is that it's good practice to keep your albedo values between around .15 and .85
The reason for this is that an overly bright/dark value will either be blown out under intense lighting(which multiplies the value) or show as unnaturally dark in deep shadow.
In your case, however, your scene is set in space so you will definitely need to use some artistic licence. Because your lighting will not be atmospherically filtered(as on Earth) you would have areas of extreme lighting/shadow contrast.