No IDtech is for the RAGE game , the RAGE Engine is the Rockstar Game Engine ....
Oops, my mistake :sweat:
Actually the RAGE engine that you say is nothing special is the one used for fre roaming in Red dead redemption that runs solely on consolles ... here you can see a video how it workks in a Skyrimish environment ...
http://www.youtube.com/watch?v=edmTtBnHmV0
I am adding it to the RAGE engine link ....
I never played Red Dead Redemption, but I have played GTAIV and there are some very noticeable differences between GTAIV and Oblivion, despite the games being sandbox games.
GTAIV barely keep track of the game world stuff, if cause a huge mass destruction and return a minute later, any sign of mass destruction is gone. Oblivion (and probably Skyrim too) keeps track track of everything and it take 3 ingame days until corpses are being removed from the game world. The Assasin's Creed games have the same issue, the game forgets everything and "resets" the game world even if you just revisit it a few minutes later. Infact, the modern TES games are pretty much the only Sandbox games that do not do this.
All NPCs in GTAIV are pretty much just random people generated by the game walking the streets, while all the NPCs in Oblivion (and probably Skyrim too) are unique and the game keeps track of all those NPCs (their location, what they do and so on) at all times.
In GTAIV you're only able to walk into a few selected buildings, while in Oblivion (and probably Skyrim too) you can walk into them all.
If you start a quest in GTAIV, you're pretty much locked into that quest until you finish it or die. You can't do anything else, you can't start a new quest while doing a quest.
So the RAGE engine (or at least GTAIV) take huge shortcuts into handling the game world, as it decides to keep track of
far less stuff.