Vertex Group from part of Material I have a terrain in Blender (see red inset) and in the material node setup for that terrain I have separated an area with certain geometry features (height, orientation). Its the white area in the picture. (Nodes used : Geometry, Mapping, Colorramp) 

My question is if there is a way to select the vertices in the mesh that correspond only to the white area, in order to create a Vertex Group. Now, if I create a vertex group directly from that material it obviously includes de vertices of the black area as well.  

Thanks in advance !
Lynxx





UPDATE

Thanks Serge and Ray for your comments. I think I am closer to the solution but I cant seem to find the last step. 

I have baked the texture and used it as a mask in the Vertex Weight Mix modifier, but I still not clear on how to select only the vertices with a weight of 1 (red ones on the left in the image bellow).

 

When I go into edit mode, to assign vertices, all are selected not only the ones corresponding to the red area. I have even applied a Mask Modifier as show below, to mask the blue area, but again when I go into edit mode the whole mesh appears not only the red part. So I cant select only the red vertices.



Just to clarify, I want to select only the vertices (red part of Weight Paint), to assign them to a new Vertex group, so I can then assign a material to only that part of the mesh. 

Thanks again.
Assigning weight

Add Vertex Weight modifier, create empty vertex group, enable group add and tweak few sliders to get it work.



Selecting vertices

Add Mask modifier and select same group as in Vertex Weight modifier. Also enable all display options to see modifiers working in edit mode (inside green box on screenshot)



Next, you enter edit mode and select everything. Press A twice to toggle selection. It is mandatory to select all NOT by pressing A, use selection tools instead (like border B or circle C) with wireframe view  enabled Z to speed up things a bit. Once you have select everything, assign it to new vertex group.



To check if you done it right, disable viewport visibility of modifiers.