I want away of limiting the amount of screen you can see without resorting to luminosity, or changing the actual view size.

What I want is to be able to set something like view_distance = 3 and have anything outside that range as black. just like the way luminosity and see_in_dark work, but without using them. (why? well so I can use them as well)
This is so that view_distance reflects how far you can see, wereas see_in_dark is how far you can see at night or in dark places. i want both =p