Calvin ✨

So breath of the wild packs roughness into that blue channel. The logic here is they don't use AO, and unless a metalness map is needed, they just use two maps... albedo and normal (normal X, normal Y, roughness). Okay...

So if you are using PBR, you still need an Ambient Occlusion channel. So rather than pack roughness into the normal blue channel, it makes sense to put the AO channel in there- because material variants will change the albedo, metal and roughness but never the ao.

So, if we do that, we can pack roughness into the alpha of the albedo- store this as linear, and do the gamma for the albedo in the shader. That means only two texture samples for the majority of environmental maps- wood, dirt, mud, stone, leaves etc.

So thats a huge improvement when you are always hitting your 16 sample limit on blended materials. However, here is where my crazy train is headed... what if we can cram metallic into that too?

PBR materials are either metallic or dielectric. The metallic map is therefore mostly black and white, with the grey pixels used for anti-aliasing and dialetric grime on metal surfaces. What if instead of using a whole channel for that, we use part of the roughness?

So, say of 256 bit, 16 is enough for metal. If you remap roughness to 240 bits, you can cram metal into the 16 above that. In other words, deducting 240 and saturating the roughness channel gives you metal.

So that's just two maps. Albedo (roughness/metallic) Normal (normal x, normal y, ambient occlusion) Thoughts?