Material Functions (landscape)

Hi all,

I’m working on a new landscape material based on Kevin Mitchel landscape tut. (youtube)
He uses materialfunctions for stacking his layers. I’m looking for way to build in some
more parameters to have some more controle. I’m struggeling to get things working.
I have setup my Landscape material and also added in a materialfunction with a

-Rock_Scale UV

I think my ML_Rock material function in setup incorrectly can anybody help out???
Thanks. My parameters are showing up in my Instance_material but don’t have any effect.