The "Bloodybacks" rules mechanism

The recent versions of my Bloodybacks AWI rules use a very specific die rolling mechanism and I thought it might be of use or interest to include a bit more information on the probabilities associated with this.

In version 9 of the rules, this "136=123" mechanism has only been retained for unit activation.




1. Activation rolls

I'll start with a look at the version of the system that deals with unit activation (and which was also used to resolve shooting in Bloodybacks 8)

The essence of the system is to roll a "hand" of six dice. I use d12s. The hand can be reduced or increased in size. Each of the dice rolled needs to score a "to succeed" number or under. The number of successes are totalled and this is translated into a number of orders, hits or whatever the outcome measure may be.  Let's describe them as "hits" for now. This translation as based on a triangle meaning that one success gives one hit, three successes are needed for two hits and six or more successes for three hits. With a larger hand of dice ten successes would produce four hits and so on, however there is a practical limit to the sensible size of the hand of dice I find.

Mechanisms such as this permit the game designer to control the range of possible outcomes. In this case it is zero to three. This level of control can be very helpful. As an example, I find this a preferable method of determining results in order systems such as seen in Warmaster or Black Powder as it tends to result in fewer absolute failures and better engagement for the players.

Below I present a series of tables that show the range of outcomes for various numbers of d12s and "to succeed" values. These were determined by creating a model within an Excel spreadsheet that simulated 10,000 hands of dice being rolled, so they are not absolute but give a fair impression of the expected probabilities. Where a value of 0% is indicated, this is a possible outcome but very unlikely. 


To succeed = 1
3d12 4d12 5d12 6d12 7d12 8d12
zero hits 76% 70% 64% 59% 54% 49%
one hit 23% 30% 36% 41% 45% 48%
two hits 0% 0% 0% 0% 0% 0%
three hits Not possible 0% 0% 0%

To succeed = 2 or less
3d12 4d12 5d12 6d12 7d12 8d12
zero hits 58% 48% 40% 34% 28% 23%
one hit 42% 51% 57% 61% 62% 63%
two hits 0% 1% 3% 6% 10% 14%
three hits Not possible 0% 0% 0%

To succeed = 3 or less
3d12 4d12 5d12 6d12 7d12 8d12
zero hits 43% 32% 25% 18% 14% 10%
one hit 56% 63% 65% 65% 63% 58%
two hits 1% 5% 10% 17% 24% 31%
three hits Not possible 0% 0% 0%

To succeed = 4 or less
3d12 4d12 5d12 6d12 7d12 8d12
zero hits 30% 20% 13% 9% 6% 4%
one hit 67% 69% 66% 59% 51% 43%
two hits 4% 11% 11% 32% 42% 51%
three hits Not possible 0% 1% 2%

To succeed = 5 or less
3d12 4d12 5d12 6d12 7d12 8d12
zero hits 20% 11% 7% 4% 2% 1%
one hit 73% 69% 59% 48% 36% 27%
two hits 7% 20% 35% 48% 59% 65%
three hits Not possible 0% 2% 6%

To succeed = 6 or less
3d12 4d12 5d12 6d12 7d12 8d12
zero hits 13% 7% 3% 2% 1% 0%
one hit 75% 63% 47% 33% 22% 14%
two hits 12% 31% 49% 63% 71% 72%
three hits Not possible 1% 6% 14%

To succeed = 7 or less
3d12 4d12 5d12 6d12 7d12 8d12
zero hits 7% 3% 1% 1% 0% 0%
one hit 73% 52% 33% 20% 11% 6%
two hits 20% 45% 65% 76% 75% 66%
three hits Not possible 4% 13% 28%

To succeed = 8 or less
3d12 4d12 5d12 6d12 7d12 8d12
zero hits 4% 1% 0% 0% 0% 0%
one hit 67% 39% 21% 10% 4% 2%
two hits 29% 59% 79% 81% 70% 51%
three hits Not possible 9% 26% 47%

To succeed = 9 or less
3d12 4d12 5d12 6d12 7d12 8d12
zero hits 1% 0% 0% 0% 0% 0%
one hit 56% 25% 10% 4% 1% 1%
two hits 43% 74% 90% 78% 54% 32%
three hits Not possible 18% 45% 68%

To succeed = 10 or less
3d12 4d12 5d12 6d12 7d12 8d12
zero hits 1% 0% 0% 0% 0% 0%
one hit 42% 13% 4% 1% 0% 0%
two hits 57% 87% 96% 66% 33% 14%
three hits Not possible 33% 67% 86%

To succeed = 11 or less
3d12 4d12 5d12 6d12 7d12 8d12
zero hits 0% 0% 0% 0% 0% 0%
one hit 23% 4% 1% 0% 0% 0%
two hits 77% 96% 99% 41% 11% 2%
three hits Not possible 59% 89% 98%

2. Melee rolls


The mechanism for resolving melee also involves a hand of 6 d12. In version 8 of Bloodybacks there was no modifier to the number of dice rolled and results were calculated in the same "136=123" way as activation and shooting. The attacker again has a "to succeed" number starting at a basic 6 which is modified upwards in the attacker's favour or downwards in the defender's favour. As with the other mechanism this constrains the range of possible outcomes while adjusting the probability of each. The following table demonstrates this:



Outcome
Major win Minor win Draw Minor loss Major loss
Attacker loss: 0 1 2 2 3
Defender loss: 3 2 2 1 0
To succeed #:
1 0% 0% 1% 40% 59%
2 or less 0% 1% 5% 60% 34%
3 or less 0% 4% 13% 65% 18%
4 or less 0% 10% 21% 60% 9%
5 or less 0% 20% 29% 47% 4%
6 or less 1-2% 33% 31% 33% 1-2%
7 or less 4% 47% 29% 20% 0%
8 or less 9% 60% 21% 10% 0%
9 or less 18% 65% 13% 4% 0%
10 or less 34% 60% 5% 1% 0%
11 or less 59% 40% 1% 0% 0%







As with the previous tables, probabilities were estimated from a model created in Excel to simulate around 10,000 hands of dice being rolled. Probabilities of "0%" actually represent unlikely but still possible outcomes.

I hope that at least someone finds this interesting and possibly useful in your own games design projects.

Comments

  1. Probability is at the heart of gaming; we often refer to luck, when we mean a likely, or unlikely outcome. You have laid out very clearly the statistical outcomes based on variable factors eg number, type and frequency of rolls and made. This is a most useful resource for others who ponder on the number of d6, 8 10, 12 or 20 they should be throwing to manage a degree of realism in their gaming endeavours. Thank you Steve.

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