it would be really nice if someone could point me to a fast-running function that could pick a random number with a lognormal probability.
the idea i have would work (it doesn't have to be terribly precise), but would probably be pretty slow. (i'm guessing around 100 calculations on average.)
first, i'd evaluate the distribution on several evenly-spaced intervals to get a trapezoidal estimate of the area of each segment, assign each segment an interval between 0 and 1 proportional to its length, and choose a random float with (float) rand()/RAND_MAZ. that would select the segment...i'd be more likely to land near the middle than in the tail. then i would choose another random float within that segment.