Hpl3 is in the vision.

[Statyk]

A majority of all the maps are .daes, not just terrain. =P

I haven't gotten into the tools yet but in most engines, you can use heightmaps to generate terrain. So if you have a model you made in a 3D software, you can put a gradient on it in a way and set a top-view camera to render a heightmap you can use.
EDIT: Checked the wiki documentation for hpl3 and it does but it seems to use the texture continuously on DX11 cards, so if you dont have DX11, there could be problems. Interesting...