The thing I've done most over the past year is change the dice mechanics of my game. I've gone from 2d10, to opposing 2d10, to 2d20s and now 4d6s. Each had their merit and each their limitations. I've built a list of five points that I see as ideal dice mechanics.
Talking dice mechanics can be touchy so before some of you get all fired up please note that these are "ideal" dice mechanics. They don't exist. They are goals to seek given the reasons I lay down below.
The more possible outcomes a die roll has the more precision it holds. Precision is like bit rate in digital media, the more bits you have the more information you can contain in it. This allows one die roll to represent more information about the event. It also allows you to add more modifiers for different things without going off the chart.
Precision also has to do with how the distribution curve behaves. If steps are all equal it can become hard to add small increments to the odds of an event succeeding. I've found distributions with long tails to be helpful when modeling events with small odds.
Ease of Use
Ease of use refers to how simple the dice operation is. Are we just comparing values? Are we counting? Adding or subtracting? We can get some really interesting probability curves out of dice, but if these are hard to calculate they will slow down game. Thus operations such as counting and comparing are quicker than adding or subtracting and these in turn are much faster than multiplying and dividing.
This is the hardest restriction of all. As they say, there is no free lunch. The more interesting dice mechanics are also more complicated. Nothing beats reading a single number, but that's a flat distribution that as we'll see goes against "correctness" below. When you roll many dice things get interesting, but adding is one step further from reading. Getting more precision and correctness goes against the interest of ease of use.
Fortunately it seems there is a middle ground. In my experience very simple die rolls that excel in their ease of use may have complications later on due to lack of precision or correctness. Once again there is no free lunch. It's my belief based on my experience that those simpler dice mechanics may end up requiring more modifiers and tables to achieve the same precision and correctness than a slightly more complex die roll that provides greater precision and correctness out of the box.
A side note to keep in mind is dice type. Although polyhedral dice are common nowadays, d6 are even more common. Selecting d6 over d10 also adds ease of use, just as using d20 does so over using d34.
Correctness refers to how well the selected dice mechanism satisfies our intuitive expectations of an outcome so as to not create frustration. The average and variance must fall within what we normally expect. If there is too much variance, that is outliner values that lead to extreme results (too much success or failure), then we begin to fee let down and even frustrated.
Another trait of correctness refers to character progression. The selected dice mechanics must correspond to our expectations as the character improves. A well trained character should not only better, but also more consistent than an untrained one. Success should group around a center value and the character should suffer less unexpected failures.
This refers to the ability of the dice mechanics to hide the result from the player even when all modifiers are known by the player. This allows the player to roll all required dice with her own hand and add all modifiers, but still not know the outcome unless the GM reveals his. Such a feature allows the GM to keep the outcome of certain actions hidden from the players, outcomes which could certainly alter the decision making process of the player. For example knowing the outcome of a disable trap may change the way the player opens a chest or if she even opens it. I'm aware that there are many out there who would claim that the player should be able to filter this out on her own and not metagame, and while it is true, it is not a skill held by anyone. An even for a skilled player like that the game changes and becomes more thrilling.
This is a nice feature that may bother some players. The good thing is that it is easily removed by everyone rolling in the open.
Die rolls should be able to stack or group in a way that many characters cooperating on a task can gain a benefit from teamwork.This mechanism should not only allow the simple addition of all the team members, but must also comply with the correctness attribute. That is, if characters of various skill levels are involved the average and variance must reflect that of the members, adding the higher skills of the better trained while also increasing variance due to the lower skills of the less trained.
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