quite a long time ago I played an interesting game. I eventually noticed what was going on but it looked good. When I entered this certain texture the skybox changed so that the horizon was closer and if there had been no trees on the map at the time it would have looked like I was in a prairie of nothing with trees all around me. The skybox had trees drawn onto it. But instead of a prairie there were several trees, but not a large amount. the effect was that I was running throught a deep forest with seemingly no end but infact there were far fewer trees, as it was simply an illusion.