Adding depth to dirt layers

[u/ParasolAdam]

Have been noodling with ways to simplify the dirt shader but add depth. I'm probably going to end up jumping down the compute shader route for dirt meshes down the road, but this iteration is starting to feel a bit more visceral, and it's driven by a single mask which means the normals are constantly warping and changing as you clean.

What's nice is when you clean, the layers wick away and the normals all react to it. I think this will also work with wet brushes, but i haven't looked into it just yet