in 3D games the game worlds are split in to chunks, and only the few closest to the player are rendered and there logic processed. Am I right?
only for shooters.
sims will tend to simulate or model (at least to some degree), the entire game world (or its pertinent impacts on gameplay) at all times.
red barron II and red barron 3D simulated every aircraft aloft on the western front in ww1, you could fly over no-man's land from switzerland to the channel and engage in any dogfight you came across. its not hard, moving units and making them fire and take damage is easy and fast, modeling estimated result thereof for a far off battle is even easier and faster. the trick is you just draw whats nearby.
silent hunter 4 models every ship in the pacific during ww2 down to the last sampan!
3d shooters evolved from 2d side view shooters: one screen per level, you can jump, and shoot. hence the level based design, with level maps, entry and exit points, spawn points, power ups, save points, hard coded design with zero replayability, hostiles that don't chase you across levels cause they only run the logic for one level at a time, etc. oh - and don't forget the best thing ever invented by level based designed games: load screens between levels!
the sim i'm working on now, Caveman (a caveperson simulator), models a randomly generated persistent modifiable 2500x2500 mile game world with no level based stuff. its all driven by random encounters. only shelters and caverns have "spawn points" for npcs or animals (monsters). so caverns are like a shooter level, and the rest of the game is a seamless open world simulation. the result is, its more of a virtual paleo-world than it is a fps/rpg or person sim. and NO in-game load screens! and no, it doesn't take 5 years to load, like silent hunter! <g>. about 20 seconds at program start is it. not bad for a game as big a skyrim. the trick is heavy reuse of assets and procedurally generated content. as opposed to tons of hand edited level maps.