A New Algorithm for Controlled Randomness

I don’t know if this problem has a proper name, but in game development you usually don’t want truly random numbers. I’ve seen the solution named a “pseudo random distribution” but “pseudo random” already has a different meaning outside of game design, so I will just call it controlled randomness for this blog post.

The description of the problem is this: An enemy is supposed to drop a crucial item 50% of the time. Players fight this enemy over and over again, and after fighting the enemy ten times the item still hasn’t dropped. They think the game is broken. Or an attack is supposed to succeed 90% of the time but misses three times in a row. Players will think the game is broken.

In this blog post I want to expand that problem to the situation where you not only have two choices (success or fail) but many choices. For example you want to create traffic on a road and spawn a bunch of random cars without having the same car too many times. The problem was already partially solved for the success/fail case, and in this blog post I will improve on that solution and present the solution for the case where there are many choices.

I will also allow you to control exactly how random or non-random you want the result to be. If you’re fine with a 90% success chance to fail three times in a row in certain situations, but want it to be more reliable in other situations, you will be able to tweak that with a number.

Read the rest of this entry »