Tuesday, August 11, 2009

Tools - Dominoes

I was sort of obsessing over dominoes over the weekend. I love the way they are so similar to a six sider, like a d6 exploded, like some tesseract version of a d6.

So, some things I sat down and figured out that I hadn't known before: in a double six set of dominoes there are 28 tiles total. Each number, 0-6, has seven tiles. There are seven doubles.

Because of the way the pips work, there are more occurrences of some numbers than others. I made a little chart of occurrences over pip total.
Hmm, not so much a bell curve as a step pyramid.

So, if you threw all these bones in a bag, what would be the probability of drawing a tile with a particular pip total? Well, keep in mind I'm no math expert, but I calculate to get a tile with only one occurrence would be ~3.6%. To draw a tile with two occurrences would be ~7%. To draw a 4, 5, 7, or 8-- numbers appearing 3 times-- would be ~10.7%. And finally, to draw a 6 would be ~14.3%.

To compare that to the more common six sided die toss, rolling one d6 has an equal chance of getting 1-6 at 16.67%. And the bell curve that results from tossing 2d6 will get you a 6 13.89% of the time.

So, if you find yourself stuck in a vacation cottage with no dice but a set of double six dominoes, even though the number range is so similar, it isn't really possible to simulate six siders. Telling your player to draw a 6 from the bag of dominoes is less than the chance of rolling a 1 on a d6.

If you tell your player to draw any tile with a certain number on the tile-- not the pip total, but one of the sides of the domino-- the chance of success is 25%. Drawing either one or another number, say any tile with a 5 or a 6 on it, would be a 50% chance. The chance of drawing any particular tile, say the 5/6 is ~3.6%.

Again, doesn't seem too useful a range of probabilities to use in play to determine outcomes, but I haven't given up on the shiny bones! I was racking my brains trying to think of a way to use them to produce a simple dungeon generator. I also think they may be a cool way to do a NPC reaction minigame. I'll post more on those two possibilities later.

In the meantime, have you used dominoes in a roleplaying game? Have you heard of them being used?


  1. I never used them as 'dice', but I used to keep a cheap set in my game bag to use as scenery. I'd set them with the long sides being 10', and voila! Instant scenery.

    Verification word: Caterca. The next wizard my players meet will be named Caterca!

  2. Hey, you're right, the set in front of me has tiles exactly 2 inches long. Each half of the tiles could be a room, corridor etc. Great call.

  3. We used them as walls also. The idea of using them for number generation, etc., is genius.