... though I'm not entirely sure why it's working
I've got a stack of fake stones shaders piped into a network via a surface shader, but some of the stones in shadowed areas look unnaturally dark like there are NaN's in the color values or something:
[attachimg=1]
So I thought I'd try to split the displacement and the color so I could clamp the black values and try to fix it, but the fake stione shaders are contributing both the dsp and color so I thought I'd pipe the output through two merge shaders, each Mix to A set to 0 and Merge Color turned off on one and Merge Displacement turned off on the other (not even sure if that would work!)
When I plugged the color merged only node into my surface layer - it fixed the dark stones:
[attachimg=2]
It's a complete fluke and I don't know why it's fixing that, but I'm not complaining
anyway here's the merge node that is the last node in the tree plugged into the surface layer
[attachimg=3]
[attachimg=4]