Tutorial: Fog Made Easy (depending on whether you paid attention in math)

Fog can be explained in a graph. The X-axis is your distance from camera and the Y-axis is fog density. Linear fog is simply a curve with a slope of x, meaning that for every x unit away from the camera, your fog is 1 unit denser. exponential fog is a curve, like x^2 or x^3. you get way denser fog with this option.

Z-start and Z-end is basically how far away from the camera the fog starts and ends. So again, if your fog starts at say, 1000, then up until 1000 units away from the camera, your fog density will be 0. Then at 1000 units away, your fog density will start to increase until your Z-end. Now say your Z-end was at 5000. This means that at 5000 units away from the camera, your fog will be at its maximum density, and you can't see past it. Depending on how close or far your Z starts and ends are, the rate at which fog will increase will be faster or slower. If the Z start and end is far apart, like say, 100 to 5000, then you'll have a very gradual increase in fog density. If they're closer together, like 100 to 200, then you'll have a very sudden increase in fog density, with almost no inbetween values.

Thanks, that makes a lot of sense, guess i payed attention in math