There was this person by the name of Dymytry who made a procedural erosion plugin for MojoWorld some time back but it was never released to the public sad to say. He did a volumetric cloud plugin as well, yet that was made public. Last i heard it was going to be implimented into Houdini but weather it made it into the 11 release is unknown. He figured it out and i am sure he is not the only one. There was an article i had come across a year back about planet wide procedural forests as well but for the life of me i did not save that web page. I think it's just a matter of coming up with some cleaver code more the needing a powerful PC. That wiz kid proved that on a plug-in that is new a few years old.