Another quick update. I have been working on adding craters to the procedural moon. I implemented a Voronoi diagram shader in HLSL and then I tweak it with quite a few different parameters to generate conical pits that are distorted slightly with fBm noise.
I tried for quite a while to get rims around the edges of the craters, but I couldn't get it to work. I tried using a colormap to alter the Voronoi results, but I was having issues with the it. I will continue to tinker around with it because I think having rims would add quite a bit.
Interesting fact: If I add even more fBm noise to the crater distortions, it forms pretty cool canyons: