I have mixed two textures together using black and white values from a noise texture which is connected to a color ramp. How can I apply a displacement map on a plane so that either the texture "A" or "B" is the limiting factor that determines which parts are affected by the displacement modifier within a plane? I want to use a mask layer to adjust the intensity of the displacement with a noise texture, but at the same time limit it to only some parts of the texture combination.
I have applied a rough displacement on my scene which covers the whole plane, but I'm asking this beacuse I want to add some fine details with two (displacement) modifiers. I know you can assign vertex groups to mark off the affected area, but in my case that's not possible, for you can't see any textures in a vertex select mode and it forces you to select them randomly.
There's a link below to give you a better idea about the problem. Areas which I want to add some extra displacement to are marked as red.
Link: https://drive.google.com/file/d/0B4NHszZHPR_1OVFEWEt2UkdON28/view?pli=1