"Why don't war-games use 20 sided dice???" Topic

I'll use whatever the game system calls for, but I don't really like d20s for ergonomic reasons: they seem to roll too far and are not that easy to read.

Phil Dutre
See this excellent explanation by Lou Zocchi: YouTube link

Thanks for posting that. Very informative. And hilarious.

Old D&D player, I love all the polyhedral dice!

If the 5% increments of a D20 fit the mechanics of the game, then use them!

That being said, I prefer a D10 for a decent amount of increments that still tends to roll in a limited amount of table space. Only go up to a D20 if a D10 is just proving to be insufficient.

And how does that make Monopoly a luck-based game?

I'm saying it does not. Likewise Cluedo.

You're right. I misread your post. My apologies.

D10's are also easier to convert to percentages on the fly if you are kind of dense like me :-)

Because I don't believe the game designers can really be that precise to nail down the probabilities to within ±5%.

Also, I don't like the roll of D20s unless you have felt, dice cups, dice towers or dice trays, which I never do.

Game designers might not be able to nail down a 5% modifier, but if you look at American Kriegspiel, published right after the ACW which is based on the Prussian one, the author does throw out a lot of percentage point variables. He's got some 14% and 16% variables, actually. I'm sure those aren't written in stone, but I find it interesting that he puts them in there. One which I recall off the top of my head is that troops leaning their weapons on a fence post are 15% more accurate than if they were not. That would be a +3 modifier on a d20, which is not the same as +1 or +2 on a d10.

Geesh !! What seems to be missed in much of the discussion above is that combat resolutions is ALWAYS a three step process.

STEP ONE: roll a die to get a random result

STEP TWO: Either add a modifier to the die roll to add in the effect of the tactical situation OR CHANGE the "to-hit" or "effects table table row"

STEP THREE: consult a table which maps the die roll to the table top result.

The choice of type and number of die, controls the number of "bins" (possible die roll results) and their relative size. THIS IS THE MOST IMPORTANT PART. THE RELATIONSHIP BETWEEN THE SIZE OF THE BINS AND THE SIZE OF THE "TACTICIAL DIE ROLL MODIFIERS" IS WHERE THE QUALITY OF THE GAME RESIDES.

Is it a simple situation or are there a LOT of considerations that have to be considered? It is important to know if there are a lot of small stuff going on (hint: use a multi-sided die so the small stuff can be factored in but doesn't "count" the same as big stuff)

The game-designer opinion controls the number and relative size of the effect of the tactical modifiers that are applied. Should elite unit charging count the same as a poor/fair/good/excellent defensive position? How many pips on the die correction for each?

The next layer is how the results table is constructed. IF you have a very limited number of bins. you have a difficulty in that it is DIFFICULT to be fair in taking account of small effect variables (which add a lot of flavor to the rules) and big effect variables. You really shouldn't allow them both the SAME affect in creating disaster or happiness. Also, because (with few, small sided dice) there is always a giant difference between the percentials to gradate from one pip number to a different one, you will have trouble in properly weighting effects= they all start to have the same effect. So the trumpet player picking his nose has to be a +1, while an uphill charge against a barricade become similar.

My suggestion: Use a D20 and put the details in the 5% modifiers and the results table.

I do agree with a lot of the comments on the poor-roll-ability of d20s- they do tend to go everywhere, and lead to a high number of leans compared to d6.

If I did a d20 system I would base it on a to-hit-formation system, with penalties or bonus for range. AK makes the good point that the most important factor determining casualties inflicted is the density of targets in the fire-beaten zone. The number of casualties would be based on how much greater or lesser than the target number the dice roll is. AK says that a unit in column will take 16x as many casualties in a given period of time, at a given range, than skirmishers under the same weight of fire. I think that's a nice starting point. AK is based on breach loaders, so you have to adjust for the weapons, shooting positions (which are listed) and the like. But the basic stuff is still there. That said, combat in AK gives radically different results than most war-games. It's a lot deadlier. To the author, it's casualties over time that make the difference, not total casualties.

"troops leaning their weapons on a fence post are 15% more accurate than if they were not. That would be a +3 modifier on a d20, which is not the same as +1 or +2 on a d10."

Er … I don't think it would. If the troops in question are only hitting, say, 5% of the time to start with – which I think would be generous – then a 15% improvement on that is less than 1% of the total outcomes.

Chris

Bloody Big BATTLES!
link
bloodybigbattles.blogspot.co.uk

What I found quite funny some years ago was when, as an exercise in teaching myself how to do drop-down menus and stuff in Excel, I converted all the firing tables from an Arab-Israeli rule set to a spreadsheet.

Despite endless percentage die rolls for this that and the other thing, all you needed to know was that the chances of a hit started at 10%, and went up by 20% for each subsequent round your tank fired at the same target.

When I started, all we had were six sided dice and we liked it. It was good enough for us then, and it's good enough today.

2 x D6 give something approximating a normal distribution. One 12-sided dice would not. I like anything that eliminates outliers.

If you have a D20 ie 5% steps there is a temptation for the rules designer to find things that might deserve a 5% bonus/penalty.

So you end up with a long list of things to consider, perhaps tactical factors or morale considerations, to tally for your computations.

The list will probably be too long to memorise so all computations require studying the rules and play will be slow.

I played rules like this all through the 80s.

(and d20s are hard to read across the table, don't sit flat on the table and roll off the table)

David F Brown

My favorite die are / is a D12 followed by D20. All the games I play of late use 2 or more D6 or D10's. Go figure!

We use a D20 as it allows 1 roll in some cases where 2 rolls were needed before. Less wasted time and less "junk" on the table". As to the significance of 5% vs about 16%. Where for instance multiple firing events are part of the model the 5% is compounded and allows for changes of significance that if done with a D6 is too bigger change.

It is our opinion that a D10 was better, D12 even better, D20 better still. Above D20, say D30 and above the returns diminish and its probably a bit too fine and readability becomes more of an issue.

While not perfect you can approximate a bell curve on 1 D20. Above 6 D6 the results are a very flat middle and extremes are very remote. So remote in my opinion that they are not worth it. 6 D6 thrown to get dice 1 on each is a 1 in 7776 to me not a useful value.

I have often wondered the same thing.
With a D10, each result is a 10% variation in the odds, IMO for closer accuracy, the D20 brings each result to 5%.
Where a D6, each is roughly a 16.6% variation.

Over the yrs I have written a few of my own game rules and have often gone with D10's.

Death in the Dark Continent uses d20s for firing (one per base)
Dead Man's Hand uses d20 for firing
General Quarters 3 uses d12 for firing a pair of guns, and d20 for odd guns.

So there are quite a few rules which use them.

The main downside is that they roll too well; you really need to roll them in a box or they end up on the floor to be batted under the furniture by one of the cats.

What an argument! I support increased use of Average dice (2,3,3,4,4,5) at least in terms of regular/trained troops, and 'wild' 6-sided dice for irregulars. Er, that's it. :-)

The game I play most, Infinity, rolls a small handful of d20s in opposed rolls.

Despite using d20s, the core game modifiers are multiples of 3, and max out at +-12.

The d20 allows you to have a greater variety of initial chances of success than a d6 does. OK, let's roll back to our classic GW games: I have a ballistic skill of 3, I hit on 4+. On a d20, that could be a BS of 9 to 11 or 12.

But I wouldn't want to roll more than 6 d20s.

D20 allow you to minimise the number of die to throw and speed the game up. That is in addition to any othet gains. Is there any other practical version? D6 are for kids and gamling. ;-)/

Some rules do.

I just use a D12, divide by 2, and round the fractions up. Easy, what?

d20 lacks the granularity you can get with 2d6.

D6 are easier to read. And more plentiful to buy.

One advantage of using d20 is that you can use the d20 system. Its not necessarily the fastest or most elegant, but its widely known, easy to pick up for those who already are familiar, and is readily taught to those who are not.

Could you explain further, please? Twenty possible results (from a single roll of a single D20) seems more granular than eleven possible results (from a single roll of two D6, used in the usual additive way).

Does a D20 have 20 results, or 20 sides, yielding 10 results?

Does a D20 have 20 results, or 20 sides, yielding 10 results?

Either or both, depending on how they're marked.

We did back in the 1970s when d20 were easier to find than d10.

D6 are only for real men

Could you explain further, please? Twenty possible results (from a single roll of a single D20) seems more granular than eleven possible results (from a single roll of two D6, used in the usual additive way).

First, using 2d6 isn't limited to d6+d6. Opposed rolls, d6-d6 or d6>d6 or d6>=d6, are very common in wargame mechanics. "Best of" and "worst of" mechanisms are not unfamiliar. So 2d6 can, at the outset mean half a dozen things.

d6+d6, as opposed to d20, has a discrete triangular (NOT a "bell curve"!) distribution. So there are 36 outcomes, more than 20. Moreover, d20 has twenty options, each 5% probability. Rolling a "2" on 2d6 has 1/36 chance, or ~2.8% – more granular than d20's 5%.

"Doubles" is a concept with 2d6, but not with d20. This opens up additional granularity with mechanics and dynamism. A simple example is "critical hits". Having a fixed number (natural 20) on a d20 to be a critical hit, is again a static 5% (or integral multiple) chance. Doubles being a critical hit integrates the 1/6 chance of doubles with the graded scale of probability for hitting (all doubles are not a subset of the number you need to hit).

And that is just one example of the use of doubles.

Likewise, rerolling criteria are much more robust with two random number generators than one (again, a fixed set of integral multiples of 5%). One reroll leads to a 216 section state space, or 1296 for rerolling both.

<quote>d6+d6, as opposed to d20, has a discrete triangular (NOT a "bell curve"!) distribution. So there are 36 outcomes, more than 20. Moreover, d20 has twenty options, each 5% probability. Rolling a "2" on 2d6 has 1/36 chance, or ~2.8% – more granular than d20's 5%.</quote>

@etotheipi

Slight revision, while there are 36 combinations with 2d6, there are 11 actual outcomes for the sum. For example, you can roll a 1 and a 2, or a 2 and a 1, but the result is still 3 for your sum. For most games, it's the sum that's important, not the number of combinations.

While the granularity is greater at the two ends, i.e., rolling a 2 or a 12, the granularity is much less towards the middle, that is rolling a 6 has a 13.89% chance, much less than any single possible outcome on a d20

For most games, it's the sum that's important, not the number of combinations.

Not sure that's true for most or even a plurality. Again, opposed rolls are extremely common.

Even with summing, while there are only 11 outcomes, the probability space includes the individual and combined probabilities giving the options for

2.78%, 5.56%, 8.33%, 11.11%, 13.89%, 16.67%, 19.44%, 22.22%, 25.00%, 27.78%, 30.56%, 33.33%, 36.11%, 38.89%, 41.67%, 44.44%, 47.22%, 50.00%, 52.78%, 58.33%, 61.11%, 63.89%, 66.67%, 69.44%, 72.22%, 75.00%, 77.78%, 80.56%, 83.33%, 86.11%, 91.67%, 94.44%, 97.22%, 100%

thirty-four combinations. The d20 only has 20 multiples of five, no matter how you combine outcomes, since each is even probability.

What is important is not the value of the roll you are getting, but the odds of getting that value.

the biggest problem with 2d6 is that a +/-1 variable doesn't have the same value across all the roles. +1 on an 11 adds 2.8%, a +1 on a 10 add 5.6%