mhaze - you can actually get a full copy of Realflow for $99! It's an educational version, so all they ask is that you don't use it commercially - but yes I appreciate that some of these techniques are not accessible to Terragen users, I did this more in the spirit that Terragen is being increasingly aimed at the the professional community as well as hobbyists and to explore how that could be realised.
Dune, I think you mean the waterfall particles from Realflow? I split the particles into a few passes - main body, splash, foam etc - these are just contain the information about the position and velocity of the particle and have to be rendered in a compatible 3d app like Maya - they were about 12GB added together. These can't be rendered in Terragen so have to be composited over. To get the reflection in the water of the mesh I made a mesh of the particle volume in Realflow and, imported that into Maya. Took the rendered element of the particles from the comp and projected that onto the mesh object and brought it into Terragen. As it wasn't directly visible in the Terragen render it didn't have to be very hi-rez.
