If you have mudbox it's real easy (if you know it). Make a sculpt on a subdivided plane, add another simple plane (which will lie underneath it, go to maps... extract vdisp map. Select the simple plane as target (I added both and deleted one), the sculpt as the other, set to world, give it a name and extract as tif or exr. In TG3 set color of image map to 'is linear', set size. Apply vector displacement 1/1/1, and you basically got it.
I think I had to rotate vector -90 and switch blue and green channels... yes.
