My buildings looks like they are plopped onto the road and what I would like is a buildup of grit and grime and the only way I can think of doing it is to use decals.
Is there other options that I should be considering?
Hi Frankie,
I’ll be the first to say I’m not a strong materials guy, but wouldn’t some possible vertex painting work well in this case? Paint in some areas you want to have more dirt and grime? I’m assuming you’re using mostly tiling textures and not unique UVs for each mesh, which is what I would do as well.
I’m just throwing out an idea. I’ve not setup a lot of material stuff so I can’t say for certain, but maybe where I’d start. I’d be curious any other thoughts on this as well from some material masters out there! 
Tim
Hay Tim
Yeah I looked at vertex paint and my first impression is it’s going to be a lot of work to get the kind of material splash I’m looking for with the same degree as an AO. Seems to me though that it would be a no brainer to bootstrap a grim and grit parameter to AO that a grit material can be blended in with the AO effect.
Decals seems to be the simple route but I’m also considering adding a skirt along the bottom of the wall and ground and applying the grit mater to it instead.
You could also lerp the dirt in with a mask texture…
Vertex Painting is certainly the way I’d do it. It’s a long-old setup process though, so I’d find some vertex paint materials somewhere.
Eat3D Has a good one IIRC, but you’ll have to adapt it somewhat for PBR.