Thanks for your positive feedback, guys. I'm quite pleased how this works out, but it can be better (as always). Basically, it's simple (as always); the falling foam is a localized cloud (dense), a max height (distribution shader) as final cloud input, the main cloud is stretched in Y (4), some very hard fractal, and warped by a distribution shader (through a vector displacement shader of course), where Z is bent 20m from the distribution lower end of 0 (base of fall) with fuzzy zone of 30m, so a gradient is there going up towards white. This bends the cloud to the fall.
I dropped the image map (white triangle), projected by camera, as this is easier.
The cloud fractal is also masked by 2 simple shapes; an oval at the bottom of the fall, slightly wider than the fall multiplied by a longer rectangle about the width of the fall, to harden the sides, but not the soft ends above the stream. Very workable.
Oh, and the fall cliff is redirected with a soft distribution shader as well, to get more vertical. The area around the fall area is negatively masked by a soft simple shape, like the default scene. The stream itself is displaced down (normal) from the basic soft terrain through a simple shape (again), to a gully. The same simple shape acts as negative mask for further rocky displacements. With some color adjust shaders in between nodes you can shape the masks however you like (within limits). The basic soft terrain is also fed into a plane (through a default shader to act as opacity mask), so an extra surface is present in the gully (the waterfall and stream). You can build that up with waves, water and foam.
The only problem I encountered here is GISD on the edge between fall plane and planet.
