Next on my idea list is a render of a cenote. If you are unfamiliar with the term just google it. Basically it is a relatively deep cavern with water inside with an abundant vegetation growing all around it. Obviously, I could do that with crater shader but I'll have to apply displacement shader so that it doesn't look so smooth and unnaturally round. However...
What should I put into the "function" box? ??? I don't really know whether I should create some winding node network here or will just a heightfield do (say, as a displacement map/pattern)? Help me out here.
Looks like you need either a vector displacement map, or an inverse big fake stone, or a displacement down and then a compute tarrain and a redirect under a certain height.....
Before getting complicated, a power fractal feeding the Rim Shader input of the crater can do quite a bit.