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Old 06-12-2020, 10:03 AM   #1
Nightharrow
 
Join Date: May 2020
Default Playing With Different Dice

I'm curious what the background is for choosing 3d6. I have been talking with my group and we are considering going to 2d10 as we feel it will allow more granularity with bonuses/skill levels. Obviously we have our reasons for this, but I am more interested in hearing why the 3d6 distribution was chosen.

Please feel free to use as much technical language as you wish in the reply, half the group has advanced engineering degrees, so if I don't understand I can just get one of them to explain it to me...lol
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Old 06-12-2020, 10:17 AM   #2
Turhan's Bey Company
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Default Re: Playing With Different Dice

IIRC, one of the big reasons for choosing six-sided dice is that everybody has six-sided dice. When GURPS was first published back in 1986, stores selling RPGs and RPG accessories like polyhedral dice (which didn't usually include d10s at the time anyway; most dice were based on the platonic solids: d4, d6, d8, d12, and d20, which could be pressed into service to give 0 to 9 results) weren't as common as they are now, when there are more dedicated game stores and even comic book stores tend to have a corner devoted to games and are likely to carry polyhedral dice. d6s, on the other hand, are ubiquitous. You could get them at any reasonably well-stocked store with a toy or games section, or just raid a Monopoly or Yatzee set. It was a pragmatic decision rather than a subtle determination of how to handle probabilities.
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Old 06-12-2020, 10:51 AM   #3
Stormcrow
 
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Default Re: Playing With Different Dice

Another reason is that three dice produce a better bell curve than two.

And GURPS stats were largely compatible with D&D's 3d6 ability scores.
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Old 06-12-2020, 11:04 AM   #4
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Default Re: Playing With Different Dice

3d6 also makes the extremes less common that 2d10. A '3' and '18' both have a 1/216 chance of occurring on 3d6, while a '3' has a 2/100 chance of occurring on 2d10 and '18' has a 3/10 chance of occurring on 2d10. If you want a greater range of probabilities, 3d6 is better than 2d10.
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Old 06-12-2020, 12:10 PM   #5
Nightharrow
 
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Default Re: Playing With Different Dice

Quote:
Originally Posted by Turhan's Bey Company View Post
IIRC, one of the big reasons for choosing six-sided dice is that everybody has six-sided dice... It was a pragmatic decision rather than a subtle determination of how to handle probabilities.
I thought something like this might be a significant contributor. Just seemed like there could be room to change on more recent additions, but maybe not. I know there can be some outspoken sub groups (I'm looking at you magician hobiests).

It just seems like the granularity (number of possible numbers that can be rolled) as well as the smaller jumps in success probabilities for each +1 to skill/ability would be more desirable to me. I also have a preference for the likelihood of of rare events to be skewed towards more likely in my fantasy, but I can see that being more of a subjective personal preference.
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Old 06-12-2020, 12:17 PM   #6
Nightharrow
 
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Default Re: Playing With Different Dice

Quote:
Originally Posted by Stormcrow View Post
Another reason is that three dice produce a better bell curve than two.
Yeah, I have personally found it to be undesirable. I kind of like the middle ground (2d) from the equal probability 1d and the bell of the 3d. I found this as a helpful visual aid for my players...

https://anydice.com/articles/three-basic-distributions/
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Old 06-12-2020, 01:17 PM   #7
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Default Re: Playing With Different Dice

I've played Big Eyes Small Mouth, which uses 2d6. If you do that, the smallest chance of an extreme result (a critical or fumble) is 1/36, or about 2.8%. With 3d6, as in GURPS, the smallest chance is 1/216, or about 0.5%. I prefer the smaller chance; with 2d6, "extreme" events come up more often than I like in a single session, and to avoid excess weirdness they need to be given more restrained interpretations.

With 2d10, the chance is exactly 1%, which is much more acceptable than 2.8%. But it's still not as good, from my viewpoint, as 3d6, and also I do prefer the bell curve to the sawtooth.
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Old 06-12-2020, 01:18 PM   #8
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Default Re: Playing With Different Dice

I wrote a couple articles on alternatives to d6 on my website GURPSLand. Polyhedral GURPS goes into detail about replacing the d6 with various polyhedrons while Cards as Dice discusses using a deck of cards as dice (which could be useful in situations where flat surfaces for rolling dice aren't handy). Both have details on the different bell curves that you get and compare them to d6 bell curves.
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Old 06-12-2020, 02:26 PM   #9
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Default Re: Playing With Different Dice

Add +4 to all stats and go with 3d8.
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Old 06-12-2020, 02:41 PM   #10
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Default Re: Playing With Different Dice

I go the other way and really like 4dF ;)
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