Yeah, I'm just saying that way to have a solid basis - everything that's driven by (bounced) ambient light will tint to match the sky without having to bake 10 different settings. Of course the option's still open to have time-specific textures if you want to take the time.
imo if VRAM is a problem, halving texture resolution of separate ao+illumination maps (which ends up 1/4 as large each so 1/2 the texture space vs. just removing one of them) is better than having them in one compromise texture. But I don't know how many textures you have planned for the whole track.
You mentioned that 'local AO' crease texture - I think that's more likely to suffer from being half-resolution than a regular AO map (the only time AO looks bad is if it's so low-res that the unwrap is blurred over neighboring islands of UV)
Spintires focuses a lot on nighttime lighting and has an interesting strategy - there's a couple textures set to global coordinates, one color and one normals, that says what direction the light hits the ground plane and how bright it is. It's obviously only an approximation of how light would hit objects in motion (ie. vehicles) since it's 2d, but it looks good for only needing an extra low res texture over the whole map. I didn't really follow how they use it to cast shadows or if that's just done based on 'hero' light sources getting shadowmaps.
I don't think Racer can use it as-is because car and track textures are loaded separately, but it's an interesting idea... eg. replace a fixed ambient with a texture lookup based on the car's current coordinates.
Yeah that is a good point on splitting textures and making them smaller. As long as you do good 2nd UV channels and pack the parts well you should still get most of the visual benefits of the results with fairly moderate texture sizes.
Yeah, I think the cavity map resolution should be quite high, along the lines of the normal map resolution really.
I've put AO into the normal map alpha here for now with my PBR because it's the best place for it probably, given the similarity in detail types.
Thinking along those lines though, the blue normal map channel is kinda spare as object space are always pointing 'forwards'... so perhaps cavity could be stored there... though the blue channel already looks a bit cavity like to begin with.
As a quick fudge to get something closer to cavity from AO maps here, for multiplying against ambient spec, I've just done clamp(bumpCol.a * 1.75,0,1)
The multiply factor being a bit of a fudge but tending to bring out only the crevice type details more.
I've also been thinking that with this shader and custom LDR cubes you could at least do some water, with say an animated normal map uv coords (or mix of normal maps), and bake in reflections of surroundings a bit.
OK it won't be omni-functional, and ideally you'd use the fancy mirror surface shader that Ruud implemented (kinda) but for now I bet we can get some pretty nice looking water too.
I'm gonna have a play over the next few evenings to see how nice I can get a lake looking using these approaches!
That Spin Tyres approach sounds interesting. So the ambient lighting term is just a LUT from a terrain texture. Quite smart I suppose. I guess a special shader just shoots a ray in -Y and checks the colour it hits and then passes it to the ambient value?!
Hmmm
Dave
