Occlusion culling - James McAndrew Environment

To make the game runs well and there is a little lag as possible form the environment sense, i have been looking into occlusion culling, which is basically when the camera isn't looking at something it isn't being rendered.

When the camera is looking at meshing and objects, whatever it maybe. that mesh is see by the camera and is rendered as should be. However all the stuff behind the camera is un-rendered and invisible.