PDA

View Full Version : Original System Negative Dice Pools

Maat Mons
2018-09-01, 12:19 PM
Has anyone done something like this? You've got your dice pool, with each die having a 50% chance of success. You can get bonuses or penalties to your dice pool, for various reasons. But the trick is, dice pool values of zero or negative dice aren't automatic failure.

Instead, if the numbers would say you roll no dice, you roll two dice. If the numbers say you would roll -1 dice, you roll 3 dice. And each -1 after that is another +1.

The trick is, when you're rolling the "negative" dice pools, you only succeed if every single die you roll is a success. So more dice is worse.

I was originally going to present this same idea a different way, which I'll spoiler here.
I'm not that well-versed in dice pool games. So it's possible some system already does this. It's also possible there's an inherent flaw in the idea I'm not seeing.

Everything involves rolling some number of dice. We'll say d6's. And each die has a 50-50 shot at being a success or failure. We'll say 4-6 succeeds, 1-3 fails.

The baseline is 1 die. If your attribute is equal to the difficulty of the roll, that 1 die is all you roll.

If your attribute is higher than the difficulty, you roll that baseline 1 die, plus and extra die for each point by which your attribute exceed the difficulty. If at least one of them is a success, the whole roll is a success.

If your attribute is lower than the difficulty, you roll that baseline 1 die, plus and extra die for each point by which the difficulty exceeds your attribute. In order for the roll to succeed, every single die must be a success.

So, what do people think?

Morphic tide
2018-09-01, 11:16 PM
The behavior you're looking for is accomplished by roll-under with decreasing dice pools as you progress. It's very atypical, as, among other things, people expect numbers to go up over time. However, there's advantages in using roll-under and decreasing dice pools. One of the biggest is that you have the dice rolling take less time as the game progresses, due to lower numbers of dice rolled, which is extremely helpful as other things go up. For example, if you have an increasing number of attacks, or turns contain more actions, you need the dice pools to go down to get the time sink workable. It's also delightfully swingy, as the average goes down linearly, as do the maximums and minimums, but the odds away from the average get more likely as the pool size goes down.

Some thoughts are to have dice size be the main subject of debuffs, as you have a reliable range of six points to work with (d2/coin, d4, d6, d8, d10 and d12), as this provides a useful range of change (the average would lower by 1 per die for each size, while the six-point-scale means it's decently broad) and offers a bit of room for tradeoffs to exploit the way dice work, while also having a negligible change in time spent rolling. As the average changes by one per die for each step, losing one die, but going up one step, is an advantage if the number of dice after the reduction is more than half the die size. This is unlikely to arise outside the lower levels, but that's exactly where abrupt improvements are needed. Makes for a good Rage mechanic, too.

Knaight
2018-09-03, 02:08 PM
I've got something similar for the current game that I've been working on for a while now (on and off for about a year). Instead of needing all successes though your skills work as a threshold for how many failures you can absorb and still succeed, and the number of dice you roll is determined by the difficulty of a task you're attempting.

The dice being based on the difference in attribute and difficulty with the possibility for both good and bad pools is a bit of a different approach, but I can at least say that I've tested it enough to know that you can flip dice pools my way, and looking at your way it seems entirely functional. Both have some of the same requirements too - difficulty must be known ahead of time, which can be seen as either an advantage or a disadvantage.

Your method also seems like it would be pretty elegant for opposed rolls, though you'll want to clarify how success/success and failure/failure cases work there.

Maat Mons
2018-09-03, 03:39 PM
Actually, I designed this to replace opposed rolls.

I was starting with something along the lines of WoD, where most things are opposed rolls using dice pools. But I was trying to figure out a way to have only one party do the rolling. In fact, I was considering a "players roll all the dice" thing.

I read in a different thread, someone suggested a player could roll dice of two different colors. One set would be good dice, based on the player's skill level. The other set would be bad dice, based on the enemy's skill level. "Successes" on the bad dice would actually be penalties, and would negate successes on the good dice. So, basically, an opposed roll, but the player has to roll for both himself and the enemy.

One problem I had with this was, I don't think the player should ever be rooting against "success" on dice he's rolling. Also, I king of figured, instead of adding bad dice, why not just roll fewer good dice? The average would work out the same, generally.

One problem I had to work out though, was what to do if the enemy's skill was higher than the players. That would result in a dice pool of zero or negative size. So I started with a different approach. Instead of an opposed roll, only the person with the higher dice pool rolls, and they take a penalty to the size of their dice pool equal to the size of the dice pool the other guy would have rolled.

This still had a few problems. For one thing, I wanted who rolls in what situation to be consistent. So I went back to the good dice/bad dice thing, but with the revision that good dice and bad dice cancel out on 1-1 basis, so you either only roll good dice, or you only roll bad dice. This still had the problem that I didn't want players to ever view "success" as a bad thing. But then I realized that if success and failure on each die was a 50/50 thing, I could just flip them around without altering the probability. So instead of "player makes the enemy's roll, enemy succeeds if there's at least one success," it could be "player makes his own roll, it fails if there's at least one failure."

Also, there was still the question of what to do in the case that the player and enemy were equally matched on skill. I figured that should be 50/50, and I was already going to have each die be 50/50, so the player could just roll one die. Of course, if you're rolling one die for tied scores, you shouldn't also be rolling just one die for a difference of 1 point. So I figured I'd give +1 die to the pool for all the non-tied cases.

Once I had this idea worked out, I noticed that I could arbitrarily change who's doing the rolling, and the odds of any given outcome would be exactly the same. So I could go by the general rule "attacker rolls the dice," or instead "player rolls the dice," and it would have no mechanical effect.

The last thing I figured I needed to do have a way to resolve things that weren't opposed. I decided I could just assign any such roll a "difficulty," and treat that as if it were the enemy's skill level. And then I decided to generalize, and just say that every roll has a "difficulty," and rolls that are, in some fashion, resisted by another person use that person's skill level to set the difficulty.

Knaight
2018-09-03, 04:34 PM
That would also work just fine - opposed skill and difficulty map to each other fairly well - and that being the impetus for the overall design makes a lot of sense.

Chas Kramer
2018-09-07, 09:31 AM
Maat mons, I really like your idea of defining a system to get rid of opposed rolls. I also have been struggling with this.

However (if I got your idea correctly), consider the following.
Assume a 50% probability of success on a roll (it is basically like flipping a coin). The probability of success on a roll with 2 dice is then 25% (1/2 * 1/2 = 1/4). On a 3 dice roll, it will be 1/8.

As you can see, the global possibility of success decreases pretty quickly, as soon as you start adding dice. And imagine when the success threshold on a single die is not 50% (or 4-6 on a die), but less (5-6).
On three-dice rolls, probability of success would be 1/27. I think this system would be too "harsh".

But again, I also have been struggling with the problem of finding an elegant and effective rolling system, which would be ESPECIALLY good for PBP. In my opinion, a good PBP rolling system should
- minimize the overall number of rolls necessary
- allow a single party (players or storytellers) to roll independently and have all the necessary results to progress with the scene
- Contain in itself enough "hints" to role-play a "contrast scene" . I mean, success/fail information does not help much. But if you have a set of successes and fails, it easier to translate this into a story. For example in a fight, you could assume every success is a hit you score, and every fail a hit you take, and invent a fight choreography to justify that
- Obviously, have satisfying statistical properties

I still couldn't come up with anything decent though:smallannoyed:

Composer99
2018-09-07, 10:56 AM
Maat mons, I really like your idea of defining a system to get rid of opposed rolls. I also have been struggling with this.

However (if I got your idea correctly), consider the following.
Assume a 50% probability of success on a roll (it is basically like flipping a coin). The probability of success on a roll with 2 dice is then 25% (1/2 * 1/2 = 1/4). On a 3 dice roll, it will be 1/8.

As you can see, the global possibility of success decreases pretty quickly, as soon as you start adding dice. And imagine when the success threshold on a single die is not 50% (or 4-6 on a die), but less (5-6).
On three-dice rolls, probability of success would be 1/27. I think this system would be too "harsh".

I still couldn't come up with anything decent though:smallannoyed:

That's true if you have to earn a success on both dice (e.g. if you are rolling a "negative" dice pool).

If you have a 50% chance of success on one die, and are rolling two dice, and you succeed as long as at least one die succeeds, your chance of success is instead 1 - (1/2)^2 = 75%, and it gets better as you get to roll more dice.

Maat Mons: I think this dice-rolling system for skill/combat/anything resolution is simple and elegant. There are, it seems to me, only two corner cases that need sorting out: when you have to roll 0 dice, and when you have to roll -1 dice.

Knaight
2018-09-07, 10:29 PM
B]Maat Mons:[/B] I think this dice-rolling system for skill/combat/anything resolution is simple and elegant. There are, it seems to me, only two corner cases that need sorting out: when you have to roll 0 dice, and when you have to roll -1 dice.

Those corner cases don't exist - the 0 modifier case is 1 die, and the -1 modifier case 2 that must both succeed. It's basically a y=|x|+1 curve for number of dice, where x is the difference in skill.

Composer99
2018-09-08, 11:54 AM
Maat Mons: I think this dice-rolling system for skill/combat/anything resolution is simple and elegant. There are, it seems to me, only two corner cases that need sorting out: when you have to roll 0 dice, and when you have to roll -1 dice.

Those corner cases don't exist - the 0 modifier case is 1 die, and the -1 modifier case 2 that must both succeed. It's basically a y=|x|+1 curve for number of dice, where x is the difference in skill.

Ah, gotcha, thanks. That's what I get for not reading through the thread a second time before replying.

GaelofDarkness
2018-09-08, 11:16 PM
I really like the symmetry and simplicity of this idea - a lot.

I think it's lacking a little in the kind of granularity I tend to prefer (probability of success jumps from 25% to 50% to 75% per point assuming a 50/50 success threshold around the base line as Chas Kramer noted, and I don't like that probability to jump by more than about 10-12% per point) - though that depends on the kind of game you're running, obviously, and I could see this working really well for the right kind of game.

You could have a little more granularity by having the 0 modifier case require you to roll say 3 or 5 dice and need 2 or 3 successes (equivalently fail should you roll 2 or 3 failures) respectively (you can do this for any odd number of dice btw). For each step in the positive direction, you roll one extra die and don't need more successes (equivalently you can absorb one more failure). For each step in the negative direction, you roll one extra die but also need an extra success (equivalently you can absorb only the same number of failures). It means the probability of success jumps by a little less but it does requires more rolling and counting - and that does ruin the simplicity even if it maintains the symmetry.

Maat Mons
2018-09-09, 02:40 AM
Hmm... So for rolls where you have advantage, it's "third times a charm," and for rolls where you have disadvantage, it's "three strikes and you're out." ... I might be able to work with that.

Though it still jumps from 50% to about 65% when you add the first extra die. And I don't know if going higher than 5 dice as a baseline is going to wind up being too many.

GaelofDarkness
2018-09-09, 11:17 AM
Hmm... So for rolls where you have advantage, it's "third times a charm," and for rolls where you have disadvantage, it's "three strikes and you're out." ... I might be able to work with that.

Though it still jumps from 50% to about 65% when you add the first extra die. And I don't know if going higher than 5 dice as a baseline is going to wind up being too many.

Yeah, the probability of success/failure is still more of a leap than I personally would prefer - but that's just me and my preference is 100% arbitrary - but the jump is a bit more restrained and stuff like that can be worth considering. Also, I wouldn't go higher than 5 dice. The size of the jump will decrease more gradually the more dice you add and it would quickly become tiresome to roll like 7 or 9+ dice every time looking for 4 or 5 successes/failures. It'd slow things down too much.

Knaight
2018-09-09, 05:31 PM
Though it still jumps from 50% to about 65% when you add the first extra die. And I don't know if going higher than 5 dice as a baseline is going to wind up being too many.

It's a coarse scale, but that's hardly a problem. For instance Fudge and Fate both see about a 20% success jump when going from skill equal to difficulty to skill off by 1 from difficulty (+19.75, -23.46), with gaps that narrow as you go further away. This makes a lot of sense, as going from just good enough to notably better really does improve things more than the second such increment, and a similar thing applies to getting worse.