“The moral of this story is that random numbers should not be generated with a method chosen at random.”
–Donald Knuth, The Art of Computer Programming, Volume II

We use a lot of random numbers in procedural generation. You’d think that it’d be pretty easy to get some good ones. Just grab whatever random generator and get to work on making fun stuff. But some random generators are better than others, and how the random generator is seeded and used makes a big difference in the results you get out of it.

Rune Skovbo Johansen has written an article on generating repeatable random numbers, with a visual look at how to get good randomness. Check it out:

http://blog.runevision.com/2015/01/primer-on-repeatable-random-numbers.html