Greetings, I'm attempting my first hack at using fog (as in Lesson #16), and I can't seem to figure out why changing the values for the fog start and end has no effect. I assumed start and end had to be between [0, 1] but the tutorial has start = 1, and end = 5. If I change the start to 100 and end to 500 (both well behind the rendered cube), I get no change in the appearance of the fog. In fact, I can make them both 0 and it has no effect. Why is this? Thanks.