I discovered all that on WBandD
http://66.7.210.142/~virtualh/VHLbase/VHL_Front_Page.htmvery interesting ..
It remembers me all the years I spent on Duke Nukem Editor ,
then on UNreal , then trying to convert Unreal into vrml without succes LOL
But the guy succeed

one of my old complains about all that LOL
http://closed.forumactif.com/3d-gallery-f26/halflife-unreal-etc-t2292.htm