After a few attempts, i came across some cliff texture that i really like.
The texture originates from here, so it's GPL.

















I agree. In fact, there are two sides of the problem. One is the fluffiness of cliff texture spreading that makes some passable areas look unpassable. This problem is code-related and not rockies-specific, but cliff decals could solve it as well. The other side of the problem is that on rockies tileset gravel and cliff seem to be a bit too similar. I don't think the whole texture pack needs rework (it's very beautiful!), but probably just a slight touch is needed to make those two textures more distinguishable.I just want to mention that the solution could locate in code but not in textures. The "fade" range should be much shorter than we have now.

