Terraman has released an update to their software, which now supports Arnold Stand-Ins and Vector Displacement.
If you are a Maya user, there is an awesome new pipeline script that will allow for communications between your world-building apps and the software. With it, unify terrains when importing them into another app like Terragen or World Machine! Terraman just updated recently with this update.
The script now offers support for terrain tiling, OBJ meshes and Arnold Stand-Ins as well. It also exports camera animation in a variety of formats to make it easy on you! World Machine is a world building tool that lets users Procedurally generate very realistic environments while Terragen does something similar with its landscapes generator tools.