Maintaining the PBR workflow

jordank95

I’ve been doing game art for a while now, but it occurred to me, other than texturing in Substance Painter and Designer and making sure my blacks don’t go below 30 RGB and my whites don’t go above 240 RGB, I’m not sure what else I need to be doing to make sure I’m staying within PBR specs. 

For things like foliage, I’ll make sure I am using the correct green color according to PBR charts, but so many other colors and spec/roughness values vary that I find those charts to be pretty vague. 

I’ve read that Marmoset PBR guide a hundred times, and while I understand the whole PBR pipeline in general (thanks to that page), I’m not sure what else I should be doing when creating textures in Painter/Designer to make sure I’m staying within PBR. Are there values I need to be checking in my histogram?

Any tips would be great. Thanks

Eric Chadwick

One crucial aspect a lot of artists struggle with is gamma color space vs. linear. Both are used in the same PBR material, depending on the input. Took me a bit of head-scratching to get it.

Another key concept, understanding Metalness. It's  not a reflection control, don't use it to make glass "better" or surfaces shinier. I see this a lot in people new to PBR.

Get familiar with channel packing. Dig into BRDFs. Learn about texture compression.

Understanding each of the controls will help you understand when to bend the rules, or when to break them, for best effect. And how to troubleshoot bugs. 

poopipe

The reason charts of roughness values vary is that you're defining an average roughness value for a pixel and that value will depend how large an area of a surface the pixel defines. 
Eg. Sandpaper is quite shiny if you look very closely but if you step a few paces back it looks much rougher cos the lumpy surface bounces light all over the place - the BRDF in a shader models this sort of thing based on the roughness value so depending on texel density you'll need a different value.
Basically, you need to eyeball it in context. 

Specular colour will be dependent on whether the Shader expects linear or sRGB values.  The standard workflows (ue4, substance) expect color maps in sRGB and maths maps (normal, roughness etc..) in linear but as Eric says above you do need to know what you're dealing with.
You generally need to make science based decisions with specular - it's not just a colour, it affects how light interacts with the surface in other ways - everything Eric said about metallic applies to specular (they're both part of the specular calculations in your Shader)