Okay, no I never did do a tutorial on how to use TerraGen I'm afraid. I do seem to remember a very old tutorial that was put out back in 2007 or so by someone here at the GoW, but the wiki has been revamped and I can't find it.
So a little bit of research on my part:
I downloaded TerraGen 3 free version and took a look. There is no way to export a 3D mesh from it that I can find. It's for rendering portraits mostly. I do not know about TerraGen 2, and there is no free version to use.
However, they still have what they call TerraGen Classic, which was version 0.9. It's free, and you can export a mesh from whatever you create in it. Here is a link to download it:
http://planetside.co.uk/terragen-classic-windows-downloadAnd here is how I used to do it:
Create the terrain you want in TerraGen Classic:
In the "Landscape" box is a button that says "Export", click on it and another window will open:
change the dropdown box to "Lightwave 3D Object", then click on "Select File and Save" and save the file.
Now I do not know about the newer versions of Blender. But I was able to open up and import the Lightwave file in the old Blender 2.49:
If nothing else you can import it in this old version of Blender, and then save it as a blend file and open it up in a newer version of Blender, or you can export it as a 3D object that Max can open up.
TerraGen Classic is what I had used in the past for Ages like Camp Bravo. Hope this helped.