Tuesday, June 21, 2011

Probability the dice of life

Bad puns aside in table top gaming there is always a want or need for randomization and quite a few methods for randomization have been used for our polyhedron chunks of plastic. Every system has their own special name for what they're doing but more often than not you can compare it to something that's been done before. As no official name exists for any of these I'll just be pulling names out of thin air to get the point across.

The Basic Roll

Even had to pull out the bold and size change for this but I digress. The basic roll is the tried and true RPG odds generator of choice. Can function on as little as one die and is typically the same for all characters and non playing characters. The most basic idea is you roll a die or a few dice add them together, modify it with some number from somewhere, and compare them to a number to see if it's higher or lower to see if you succeed. Doesn't matter if it's a single nerdy 20 sided die or three standard 6 sided dice the basic mechanic is the same. It's good for fast rolls and for players to know the odds of success, especially if it's percentile and they're trying to roll lower than some attribute generated. I called it the basic roll as a lot of systems love this D&D, d20 systems, Basic role play, and Dark Heresy come to mind. There is one that tweaks this idea but still follows the basic mechanics and that is Legend of the 5 rings and possibly 7 seas. They use a system of Roll and Keep where you roll a number of dice like everyone else but then you pick a few from that. Typically the dice kept are the highest amount but allows an interesting function with a variable number of dice rolled.  There is a lot of probability things I could get into about the difference in amount of dice rolled and the horrible results when there is a differnce between two but I think I'll save that for another day as I have a story with that.

The Dice Pool
Dice pools are different than the basic roll for a two reasons. One the amount of dice rolled can greatly vary between players. Two each die rolled in the pool is counted as it's own roll, the dice are not added up like in the basic roll. Typically when you roll a dice pool you are given a target number, this number being lower than the number of sides of the dice used. If you have 10 sided dice you can't have a target number of 11 as it is impossible. From there you tally up the number of dice rolled that meet or beat that number and that is your amount of "successes" you tell that to the person running the game and they will tell you if you succeeded or not. Typically this is a little less insane than rolling numbers and adding them together thus letting the guy rolling 2 for fighting keep up with the guy rolling 4 for fighting though the 4 dice pool is still doing more. I used to love dice pool systems mostly for the mystery behind them. I can do some basic probability and get the odds behind the basic roll systems (besides Roll and keep) and have no idea what is happening in a dice pool. This quickly turned to crap when I started running my own games and realized I have little clue behind the monster I'd make up or the what amount of successes needed for a challenge would be too easy or too hard for my group. It's still usable I just like having a little more knowledge of my gaming mechanics now. For the most part White Wolf games all use some for of dice pool, I also know of Burning Wheel using one too.

Match Systems
Frankly I have no good name for these systems. They're usually some weird combination of the first 2 but have mechanics that separate them. There are only two I know of for this, Frame work (of Cthulhutech) and One Roll Engine. They both have a variable amount of dice rolled but instead of looking for a target number or adding them all together they look for a pattern of some sort in the dice. Both use matching as one combination, Frame Work will take straights of 3 or more dice or the highest one giving it the nick name of dice poker. From there they differ Framework just adds what it finds together as it's output number and O.R.E. uses the number rolled and how many that were found for it's various aspects. These are the most difficult systems to use, there is no quick glance at them to get a number or amount of successes and there can be a lot of "missing" in these systems if you don't get matches which leads to frustration. Now O.R.E. does a lot for it's single roll; it tries to get hit location, damage, and initiative all from one roll which is interesting but takes a lot of explanation to even get people used to it.

And that's the lowdown of how funny looking dice work in pen and paper games. Partway through this I realized that maybe I should have given a rundown of how pen and paper games work but this subject is more interesting to me at least.


  1. Dice are a weird thing.

    I haven't got the head for doing this on such a meta level, you're right about how dice pools and match systems can really match up. Match systems especially since luck can cause a large pool to get terrible, unworkable results, and a small pool very high results now and then. Generally you simply add more for more desired success to be inclined. Still its no sure bet.

  2. Actually dice pools a bit better than matching, typically the target number is around the 50% mark for most tasks. Only in older white wolf games and Burning wheel was that variable though still more likely to "succeed" than the wildly varying matches.

  3. this post like perfectly covers a unit in my finite class.

  4. And this is why I don't play p&p

  5. It's not that bad once you get used to it.