No, as I said it is Terragen output format. Terragen makes awesome landscapes for scenery, fly-by animations, etc., and CAN be used to create terrain for AH, but it will require work (work you could avoid by simply ignoring this post).
Terragen is FREE for personal use. Commercial users include the CroTeam (Serious Sam: Second Encounter), Max Ink Cafe (Playstation 2 games), EA Sports (Formula 1 2000: PS 2 again), and others.
http://www.planetside.co.uk/terragen/