Percentiles

[Finarvyn]

I found a quote from Greg Svenson on the COMEBACK INN forum and replied there, yet no one else seems to have found it interesting (or, at least no one has replied) so I'm re-posting it here along with my reply.

You can find the entire conversaion here:
blackmoor.mystara.net/forums/viewtopic.php?f=45&t=8436

---------------

When I was rolling for specific percentages in the early days, I generally used three d6s with a specific set of outcomes (between 3 and 18) whose combined probability of coming up matched the desired percentage result. John Snider had a little chart that showed what numbers to roll would provide a specific percentage result. Does that make sense?

Yes it does, because I used to do much the same thing for d20 rolls using 3d6.

d20 ... Percent ... Numbers to roll on 3d6
20 ... 5% ... 3,6
19 ... 10% ... 3,8
18 ... 15% ... 3,6,8
17 ... 20% ... 4,7,9
16 ... 25% ... 3,4,6,7,9
15 ... 30% ... 3,4,7,8,9
14 ... 35% ... 4,8,9,10
13 ... 40% ... 4,6,8,9,10
12 ... 45% ... 4,5,7,8,9,10
11 ... 50% ... 3,4,5,6,7,8,9,10
10 ... 55% ... 3,4,5,6,7,8,9,10,15,18
9 ... 60% ... 3,4,5,6,7,8,9,10,13,18
8 ... 65% ... 3,4,5,6,7,8,9,10,13,15,18
7 ... 70% ... 3,4,5,6,7,8,9,10,12,14,17
6 ... 75% ... 3,4,5,6,7,8,9,10,12,14,15,17,18
5 ... 80% ... 3,4,5,6,7,8,9,10,12,13,14,17,18
4 ... 85% ... 3,4,5,6,7,8,9,10,11,12,13,17
3 ... 90% ... 3,4,5,6,7,8,9,10,11,12,13,15,17
2 ... 95% ... 3,4,5,6,7,8,9,10,11,12,13,14,16,17,18

[waysoftheearth]

That looks way too hard for me


FWIW, you can roll 1-20 with exactly 5% chance of any result with 3d6 like this:

First d6 yields 0 (odds) or 10 (evens).
Second d6 yields 0 (odds) or 5 (evens).
Third d6 yeilds 1-5; reroll if you get a 6.

Painting these outcomes onto the die faces makes it easier too

[mindcontrolsquid]

If the percentile results are in increments of five anyway, why is there the need for percentile results when a 20-sided die will do the same thing? Is the system meant for times when a 20-sided die would be unavailable or unusable for some reason? Or is there something I'm missing?

[Stormcrow]

Nov 20, 2015 6:53:30 GMT -6 mindcontrolsquid said:

Is the system meant for times when a 20-sided die would be unavailable or unusable for some reason?

Yes. Back in the early days polyhedral dice weren't so easy to come by. A table of conversions to six-sided dice is one way to overcome that problem, and would be a more familiar method to wargamers than waysoftheearth's method.

Using that table isn't hard. Roll three dice, then look at the line with the required percentage. If the total of your roll is on that line, you succeed.

[mindcontrolsquid]

I always thought that the way it was done in the old days was that you would use two ten-sided die each numbered 1-9 and 0, and use them for each digit of a number from 1-20. I guess I was mistaken; I do know that there was a lot of experimentation when it came to dice in the old days, and percentages were just one of the methods used. There's a great article on early dice usage here. (I suspect that many of the posters here have already read it, though...)

Edit: This article from the same blog is relevant too, I think.

[Finarvyn]

Nov 20, 2015 6:25:51 GMT -6 waysoftheearth said:

That looks way too hard for me

Agreed. I was just posting something that seemed to match what Dave did back in the pre-poly days. I haven't used a chart like this in years and am not sure that I would want to use one now, but it does make a d6-only option for folks who want to use d20 tables.

[Stormcrow]

Nov 20, 2015 10:38:27 GMT -6 mindcontrolsquid said:

I always thought that the way it was done in the old days was that you would use two ten-sided die each numbered 1-9 and 0, and use them for each digit of a number from 1-20.

When polyhedral dice first became widely available, there were no ten-sided dice. Most or all twenty-sided dice were numbered 0 to 9, twice (0 is read as 10). You would color each set of numbers differently, or they'd come with special marks on one set of numbers, which meant "add 10 to this number." If you needed a d20, that's what you did. If you needed a d10, you just read the number and ignored the color/mark.

There were no ten-sided dice at first because there is no ten-sided regular polyhedron. The only regular polyhedrons, also known as Platonic solids, are the tetrahedron (d4), cube or hexahedron (d6), octahedron (d8), dodecahedron (d12), and icosahedron (d20).

To produce percentile results, you'd roll two ten- or twenty-sided dice, each numbered as a d10. You'd designate one die as the "tens" digit and one die as the "ones" digit. This gives you numbers from 0 to 99 (0 is read as 100).

These days you can buy sets of ten-sided dice where one is numbered 0 to 9 and the other is numbered 00 to 90 by tens. You just add them together, reading a total of 0 as 100.

[mindcontrolsquid]

Thanks for the info, Stormcrow. Dice history is pretty interesting in terms of it being one of the "side-industries" which formed as a result of the advent of tabletop rpgs. And (slightly more on-topic) it does explain to me why polyhedric die varieties worked so well instead of (or in addition to) percentile dice systems. Percentile dice are perhaps more precise and have more granularity, but even today six-siders are far more widely available (and can even be cannibalized from ordinary board games, as I used to do before I had my own dice set) and they and ordinary polyhedric dice seem much more expedient to me.

[waysoftheearth]

The 1973 D&D draft has attack matrix I and II based around percentile numbers (in increments of 5%) rather than numbers 1-20. It goes on to describe how to roll d100 by drawing twice from a deck of playing cards. A time consuming procedure I'm sure!

[cadriel]

Jon Peterson (increment) wrote a lengthy and interesting article on this: How Gaming Got Its Dice. It includes a chart similar to the one above, but for two six-sided dice instead of three.

If you stick strictly to the 3 LBBs, OD&D requires only a d10 (preferably an icosahedron numbered 0-9 twice) and a d6 to play. Multiples make life easier. I have some really beautiful Gamescience dice that Lou Zocchi inked, and have taken to rolling them the way Tim Kask spoke of it recently, where you roll the d10 and d6 at the same time, with 1-3 meaning you read the face value of the d10, and 4-6 indicating that you add 10, so a 4 and 0 makes a 20.

Of course, we now live in times of glorious dice excess. I have dice for every integer from 2 to 12, every even number up to 24, plus 30, 50, 60 and 100 sides.

[Zenopus]

In the comments to that blog post, Jon actually points out that the 3 LBBs refer to the other dice in places. The Monster Reference Table itself requires a d4, d6, d8, d10, d12 and d20 to generate all of the "Number Appearing" ranges.

[cadriel]

Nov 20, 2015 20:33:34 GMT -6 Zenopus said:

In the comments to that blog post, Jon actually points out that the 3 LBBs refer to the other dice in places. The Monster Reference Table itself requires a d4, d6, d8, d10, d12 and d20 to generate all of the "Number Appearing" ranges.

Yeah, I'm aware, although technically those mostly come up in prep. During play you could bring 3d6 and 2d10 and never need to substitute. And someone who only had the "percentage dice" of the early '70s and such six-siders as could be scrounged from board game boxes would be able to simulate d4 (d6 reroll 5/6), d8 (d10 reroll 9,0), d12 (just as the d20 but using two six-siders), and of course the d20. Only the referee needs to roll them, and emulating dice is only really onerous when you have to roll multiples of a type other than d6 or d10. That doesn't happen until Greyhawk changes the monster hit dice type to d8s.

[LouGoncey]

Nov 20, 2015 14:59:28 GMT -6 cadriel said:

Jon Peterson (increment) wrote a lengthy and interesting article on this: How Gaming Got Its Dice. It includes a chart similar to the one above, but for two six-sided dice instead of three.

If you stick strictly to the 3 LBBs, OD&D requires only a d10 (preferably an icosahedron numbered 0-9 twice) and a d6 to play. Multiples make life easier. I have some really beautiful Gamescience dice that Lou Zocchi inked, and have taken to rolling them the way Tim Kask spoke of it recently, where you roll the d10 and d6 at the same time, with 1-3 meaning you read the face value of the d10, and 4-6 indicating that you add 10, so a 4 and 0 makes a 20.

Of course, we now live in times of glorious dice excess. I have dice for every integer from 2 to 12, every even number up to 24, plus 30, 50, 60 and 100 sides.

That is exactly how we rolled our twenty sider for my first three years of gaming. It happened so often, it became the preferred way for my entire group. Of course we ahead red crayons, we where being traditionalist. My next game I may force all players to roll that way -- roll for the Dice God!