Вообще, вопрос интересный, на сайте самого террагена есть ссылка
Вот дословно:
I wrote two little programs that help to reproduce the camera (camerapath,lookatpath) (from Campath) in 3D Studi Max. The first one called CamPath2txts which creates two TXT files from a TGS file (which was created by Campath). The second one is a maxscript (TerraCamera) that reproduces the camera (using this two TXT files) in Max. It creates a TargetCamera with the same positions and movements as the camera had in Campath. And it creates the target's positions and movements as well. It's very useful to merge Terragen animations with Max! I hope it'll be as useful for many others as for me!
I made the camera import in one maxscript. It's a Utility script, called TerraCamera01. From the selected file ("Select .tgs file") creates the camera.("Create Camera") I hope you'll like this one!
You can download these utilities for free. Please note that these utilities are not written by Planetside Software, and we disclaim all responsibility to them
Вот где я это нарыл: http://www.planetside.co.uk/terragen/maxint.shtml