Perhaps a little subtle from this distance
... but if you look down in the valleys you'll see a grey smudge consisting of 3 fakestone layers mapped via a World Machine flow map. Note the alluvial fans near the lake at the top of the image.
Bottom - smallest rocks, widest distribution
Middle - larger rocks, narrower distribution
Top - largest rocks, low density, narrowest distribution
Further changes to the mapping will include slope restrictions and a fractal breakup to randomise the density a little further. The fake stone shaders are then combined with the masks for plant population density shaders to ensure that trees and grass are not placed on top of the rocks.
I've finally done a rough story board for my animation to give me a clearer focus on just what I need to add to this TGD. I have another render going with an imporved base rock surface (this render has just the fractal detail applied to the terrain) after which I'll move in a bit closer to the valley floor for another check.
As a static shot, this angle loses some of the sense of scale as the peak is lost in the ridge line and there is nothing to indicate how close the camera is to the peak... but in an animation there will be the previous frames to provide the reference.
