Thanks for info.
But i wanna know: games like Oblivion,GTA,Just Cause,do they use skyboxes(spheres)?I mean the maps are really big.Dont they eat up computer resources?
The size of the maps does not have anything to do with the sky geometry size. You can have a map that's a few kilometers in diameter, but still have the sky geometry to fit inside a one-cubic-foot cube.
The trick is in the fact that the camera does not move around in the sky scene, even if it does move in the "real" scene. It does rotate, yes, but is never translated out of the center.