I need to find a suitable mechanic for rolling open-ended rolls using D20 and D10. Currently, the mechanic I use is as follows:
A] D20 Result
1 :Go to B
2-19 :Stop
20 :Go to C
B] D20 Result
1-10 :Stop, result is 1
11-19 :Stop, subtract 10, subtract from prior result (-1 to -9)
20 :Result is -10, go to D
C] D20 Result
1-10 :Stop, result is 20
11-19 :Stop, subtract 10, add to prior result (21 to 29)
20 :Result is 30, go to E
D] Repeat B
E] Repeat C
In other words, if the first roll is 1 or 20 roll again. If the second or subsequent roll is 1-10 stop rolling. If the second or subsequent roll is 11-19 then add/subtract 1-9 from the first roll and stop rolling. If the second or subsequent rolls is 20 then add/subtract 10 and roll again.
The problem with this method is that extreme rolls become very rare. Does anyone know of a better open-ended system that centers on the numbers 1-20? Thanks very much for any suggestions.
Brian Koppi
chikoppi@pipeline.com
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How about this:
1) Roll d20.
* If you roll 1-5, keep this total and roll again, subtracting the "tens"
digit of the second roll from your total.
* If you roll 16-20, keep this total and roll again, adding the "tens"
digit of the second roll to your total.
If on the second roll you get 1-5 or 16-20, add/subtract the "tens" digit
and roll again. Repeat as necessary.
John Harper http://www.shootingiron.com/feng
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At 2:57 PM -0500 8/16/99, John Harper wrote:
>1) Roll d20.
>
>* If you roll 1-5, keep this total and roll again, subtracting the "tens"
>digit of the second roll from your total.
>
>* If you roll 16-20, keep this total and roll again, adding the "tens"
>digit of the second roll to your total.
>
>If on the second roll you get 1-5 or 16-20, add/subtract the "tens" digit
>and roll again. Repeat as necessary.
Ah, I like it! So, if I'm not mistaken (I'm terrible with statistics, so I probably am), the percentage spread looks something like this:
Etc.
-19 through -10 : 0.3125%
-9 through 5 : 1.25%
6 through 15 : 5%
16 through 25: 1.25%
26 through 36 : 0.3125%
Etc.
Brian Koppi
chikoppi@pipeline.com
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In favor of ease in reading dice during play, I took John Harper's model and altered it slightly. Does the following open-end mechanic raise a red flag for anyone? Thanks to all for helping me straighten out this kink in my system.
Roll D20
If 1-2 then [A]
If 3-18 stop
If 19-20 then [B]
[A] Roll D20
If 1-10 result equals -1 to -10
If 11-18 stop
If 19-20 repeat [A] and subtract 10 from result
[B] Roll D20
If 1-10 result equals 21 to 30
If 11-18 stop
If 19-20 repeat [A] and add 10 to result
(11-20) : 0.025%
(1-10) : 0.1%
1-2 : 2.25%
3-18 : 5%
19-20 : 2.25%
21-30 : 0.1%
31-40 : 0.025%
Brian Koppi
chikoppi@pipeline.com
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...How about: On the 1 or 20, roll a d10 and a d20. If the d20 is 11 or more, stop without modifying the base score further else modify the base score by the amount rolled on the d20 (downward when the original was 1, upward if the original was 20). If the score on the d10 is greater than the score on the d20, repeat else stop. Discussion: I'm not sure whether mathematically, the extreme scores become a lot more likely. The modified spread becomes interesting because the more the score is modified by the d20 roll, the less likely you are to be able to repeat and add more. If you really like extremes, you could instead say that whatever was rolled on the d20 modifies the base score before determining whether to repeat. chikoppi@pipeline.com wrote: > > I need to find a suitable mechanic for rolling open-ended rolls using D20 and D10. Currently, the mechanic I use is as follows: > > A] D20 Result > 1 :Go to B > 2-19 :Stop > 20 :Go to C > B] D20 Result > 1-10 :Stop, result is 1 > 11-19 :Stop, subtract 10, subtract from prior result (-1 to -9) > 20 :Result is -10, go to D > C] D20 Result > 1-10 :Stop, result is 20 > 11-19 :Stop, subtract 10, add to prior result (21 to 29) > 20 :Result is 30, go to E > D] Repeat B > E] Repeat C > > In other words, if the first roll is 1 or 20 roll again. If the second or subsequent roll is 1-10 stop rolling. If the second or subsequent roll is 11-19 then add/subtract 1-9 from the first roll and stop rolling. If the second or subsequent rolls is 20 then add/subtract 10 and roll again. > > The problem with this method is that extreme rolls become very rare. Does anyone know of a better open-ended system that centers on the numbers 1-20? Thanks very much for any suggestions. > > Brian Koppi > chikoppi@pipeline.com > ---------------------------------------------------------------- > To unsubscribe, send mail to gmast-off@phoenyx.net. > GMAST Home Page: http://www.phoenyx.net/gmast/ ---------------------------------------------------------------- To unsubscribe, send mail to gmast-off@phoenyx.net. GMAST Home Page: http://www.phoenyx.net/gmast/
> Ah, I like it! So, if I'm not mistaken (I'm terrible with statistics,
so I probably am), the percentage spread looks something like this:
[percentages snipped]
Er... I have no idea. I suck at statistics, too. But I'm glad you like my
method. If only Mike Harvey were here.. why we'd have an accurate
probability curve for this thing in no time. Mike! Mike! Where are ya?
John Harper http://www.shootingiron.com/feng
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