Wednesday, January 25, 2012

Dice Descriptions

I've been spending some time programming over the last few days, delving into Android development as a way to teach myself Java. As my first project I'm building a dice roller. Originally I was going to use the same text descriptions for rolls that I use on my web based dice roller, but after implementing them I decided I could do better. I'm trying to cover as many rolling mechanics as possible, so I thought I would throw out the roll definitions here and see what other folks thought.

Traditional dice: XdY
Roll X dice with Y sides, sum their values. Y can also be F, indicating Fudge dice, or %, shorthand for d100.

Dice pool: XpY
Roll X dice with Y sides, treating each die as an individual result. As with traditional dice, Y can be F or %.

These can be appended to the base descriptors above. N below is a numeric value.

  • +-N - A numeric modifier to the roll. The value is added to or subtracted from the final total for traditional dice, or applied to each die in a dice pool.
  • EN - Exploding dice. Any dice roll greater than or equal to N generates another die roll. In traditional rolls the result is added to the total. In a dice pool it is added to the original exploding die's result.
  • LN - Drop the lowest N rolls. The classic example is D&D character generation using the roll four six-sided and drop the lowest method, which would be written as: 4d6L1.
  • HN - Drop the highest N rolls. Not sure if any game would make use of this. I guess you could make some very lame D&D characters with 4d6H1.
  • SN - Count successes. For traditional dice, a total result greater than or equal to N is a success. For a dice pool each die greater than or equal to N is a success.
  • FN - Count failures.  For traditional dice, a total result less than or equal to N is a failure. For a dice pool each die less than or equal to N is a failure.

Some things I think I'm missing, but I'm not sure if they're useful.

  • Imploding dice - rolls below a certain value generate an additional roll that's subtracted from the first.
  • Savage Worlds - Wild Dice. I don't play Savage Worlds, can someone throw me a clue?
  • Exploding dice that don't continue to explode.

I'm sure there are a bunch of methods I've forgotten or ignored. Anyone know of a concise list of RPG dice mechanics published anywhere?


  1. Interesting.
    --I suppose more folks would need to use these in a standard fashion for them to catch on.

  2. I seem to recall someone had developed a dice grammar, but can't seem to find a link to anything useful in that regard. From what I recall it was a bit too complex for my purposes.

    I'm aiming for easy to type and full-featured enough to support most games. The standard XdY+Z should support most D&D type rolls, and XpY with success and failure indications should cover most dice pool games.

  3. Wild Dice:

    Wild Cards (i.e., Player characters and significant non-player characters) get to roll a second die in addition to the regular trait die for a task (an extra d6 known as a "Wild Die"). As with normal dice, this roll may "Ace", i.e., re-roll and add the result if the result is the highest possible one for that die type (if the additional roll "Aces", roll again and add, etc.)

    The Wild Card uses the higher of the two rolls (trait die or Wild Die) to determine the actual result of the roll.

    Alas, the drawback is that if snake eyes should be rolled (a "1" on both the trait and the wild die) then a critical failure occurs...

  4. Thanks Del! I think I had that right in my head, except for the snake eyes critical failure results. The explanation is much appreciated!


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