Displacement only on Shader?

[ejgodwin]

Hopefully this hasn't been answered somewhere ... I wasn't sure what key words to search for.

I have a snow shader over some mountains, and I want to add a bit of texturing to it. I like the effect of the first attached image, which looks like the result of either wind or snow slides (or both). The problem I'm having is that any displacement I attach to the Surface Layer snow shader ends up altering the underlying terrain as well, which of course I don't want. I got close with the (2nd) attached render, but out of sheer luck: if you look close, you'll see sharp cut-offs at the edge of the snow, which is the result of the underlying terrain being altered a little. I used "Favor depressions", so I don't know if that makes any difference.

Is there a way to apply displacement only to a shader?

Thanks.

[Dune]

The problem of course is that the planet only consists of one infinitely thin layer, there is no snow layer 'on top' of the rock layer, they meet eachother. As soon as you apply some of these sharp edged displacements to the 'snow area', you're bound to get some in the rocks, and it takes some precise work to get the edges clean of artifacts. The edges are hard, and as soon as you use the snow 'mask' to displace the ridges, you get a hard breakoff of that displacement where it hits the rock.
Unless you use two planets (or an extra sphere), where one takes the mountain with (billowy) rock, the other the slightly altered fractals for the snow. Worth a try maybe.