Well, staying on topic of SpeedTree, probably you haven't seen this too: It's Houdini too. Quite old, from 2007. Search for Arkadiusz Rekita + Houdini + Avatar.
Holy houdini! I've seen many great rocks and cliffs with vue's procedural but never I saw houdini can do this as well. Thanks for the insight mantragora.
It's a Houdini. No other package can do what you can in it. Not without ton of programming/scripting or ton of plugins that costs double of Houdini FX price. Even Softimage with its ICE covered only portion of what you could do in Houdini. I will not even mention Maya. And remember that there is Houdini Indie version…
I had no idea Houdini could be used in this way... I love that last one. Some of the others look cool but aren't particularly convincing. Does this output polygonal geometry, or is it some kind of voxel thing?