The Refractor Engine, is a game engine designed by Stockholm-based studio Refraction Games, first developed for the computer game Codename Eagle, which was released in November 1999. Since then, Refraction Games was bought by Digital Illusions CE, and working alongside with the Refraction Games team, designed and developed the Refractor 2 Engine for the famous Battlefield game series for the computer.
This is better than BF3. It is 6 or so years old and better than BF3. That is because of the modding abilities. Even though EA/DICE doesn't give a crap about it now, mod teams are still working on it and make the game even better.