Ex modder, Zones only ferret and will someday release a game
On forum: 02/20/2010
1) There are some extensions which are unstable, but they can be disabled easily.
2) Well, there is a function which returns the distance to the nearest level terrain/alife object, but its only available for the actor. Basically, it returns the number you get from enabling crosshair distance in the hud options. Somehow, I don't think this is what you are after.
See here for the complete xrGame extensions: http://pastebin.com/EZ1Aauj5
IMPORTANT! Fetching error logs! - http://sdk.stalker-game.com/en/index.php?title=Crash-log
My first STALKER story: The Job (Updated 11/6/11)