first of all im sorry maybe i sound like an idiot asking this im quite new on this PBR thingy and just wondering how do most people bake a fake hole on their low poly ?? i mean albedo/diffuse map shouldn't contain any shadow information ,right ?
Best way I've seen is color it black in the albedo, make it 100% rough in the smoothness mask, and 0% metal. That should prevent any light or specular getting to it. It's a fake hole - it's only going to look SO good. :)
Yes, entirely metal with black albedo makes more sense. 0% metal will be 4% reflective. Metal value of 1 and albedo value of 0 and then the gloss/roughness doesn't matter. Though either way will work fine.
I find making it entirely metal, entirely rough, and black diffuse works best. If it's 0% metal, you'll still get a little specular. But setting it to metal will use the black diffuse as the specular, and it'll just be a void.