RPG Percentile Mechanics



  • We have a huge core of tabletop and other RPG gamers here. Does anyone have much experience with percentile dice systems? Particularly i'm wondering if there is one out there that considers the stats of two opponents to determine the percentage.


  • Politics

    Not that I know of.

    But percentiles would be cool if they could fuck with each other. Like, if I have a 60% in ATTACK and you have a 20% in DEFEND, then my roll is at 40%, etc.

    The real problem with percentiles is that they... are limited to 100%. So you would have to find other ways to figure things out.

    Fact is, multiple dice will always have more dice tricks, which is more evocative of stuff. Anyway, digression.



  • @Coin
    I think that's how the Cthulu percentages work, you take yours, sub theirs and you have your target.

    I'm fiddling with some theorycrafting and was looking at a stat vs. stat determines the percentage of success (so someone with equivalent stats, attacking someone with equivalent stats, has a 50% chance at 0 total; then each +/- increases or decreases the success level) method, and trying to just theorycraft.



  • @Coin That gave me a weird idea, though, for something regarding extended tasks and potentially also team mechanics.

    Percentile could prove interesting for multiple days/hours/etc. work -- roll with any mods, add up; this gives you 'how far you get on that task'. If you hit 100%, you made it. If not, you still have something. Could use the skill rating or whatever for the number of times you can roll.

    What could be additionally useful with something like that would be for team mechanics; if someone else wants/needs to complete the task later, they may end up with a negative mod (for picking up where someone else left off/not necessarily knowing how the other party was going about it/etc.) but they would only need to fill the gap between wherever the first party left off and 100%. Teams working together could potentially just pool the rolls somehow, 'many hands make light work' and such.


  • Politics

    @surreality said in RPG Percentile Mechanics:

    @Coin That gave me a weird idea, though, for something regarding extended tasks and potentially also team mechanics.

    Percentile could prove interesting for multiple days/hours/etc. work -- roll with any mods, add up; this gives you 'how far you get on that task'. If you hit 100%, you made it. If not, you still have something. Could use the skill rating or whatever for the number of times you can roll.

    What could be additionally useful with something like that would be for team mechanics; if someone else wants/needs to complete the task later, they may end up with a negative mod (for picking up where someone else left off/not necessarily knowing how the other party was going about it/etc.) but they would only need to fill the gap between wherever the first party left off and 100%. Teams working together could potentially just pool the rolls somehow, 'many hands make light work' and such.

    Extended tasks in CofD actually already does this, sort of, ever since GMC. You can pick a project up again if you have a certain percentage of it done, IIRC.



  • @Coin It does, yeah, but it isn't using percentile to accomplish it though.


  • Pitcrew

    @surreality said in RPG Percentile Mechanics:

    @Coin That gave me a weird idea, though, for something regarding extended tasks and potentially also team mechanics.

    Percentile could prove interesting for multiple days/hours/etc. work -- roll with any mods, add up; this gives you 'how far you get on that task'. If you hit 100%, you made it. If not, you still have something. Could use the skill rating or whatever for the number of times you can roll.

    that is the part of the RoleMaster mechanics, granted a lot of the rest is hard to get through but I liked that part of it. In general I preferred the scaled down RM mechanics found in MERP (Middle Earth Role Playing, long out of print) to the full ones found in RM itself, but yeah it is all percentile in nature.
    Rolemaster itself is still in print and supported.


  • Coder

    This reminds me of a couple system ideas I've been working on instead of trying to convert a table top system to an unrelated environment.

    My first idea was to have dice cancel each other out, like if person 1 has 8 dice to attack and person 2 has 5 dice to defend then person 1 has only 3 dice to roll on attack against person 2 in normal situations.

    My second idea was using d6's where your 'dodge' skill (or equivalent) would determine the target number to being hit. So if you had a 5 dodge skill then they'd need to roll 5's and 6's to hit on a d6. The only problem with this is having 1 in a skill was useless so I changed it so that you had to roll /higher/ than the skill. Still doesn't fix the problem of a 1 skill being pretty much crap. Still toying around with this idea as it's clearly not ready and needs modification.

    The third idea I had was to go with a percentile based system where each point in stat + skill combinations equated to 10% chance to succeed, which was reduced by environmental factors, and your opponents defense stat + skill combinations. So if you had a 4 skill + a 3 attribute you'd have a base 70% chance for success. If the target had 3 skill + 3 attribute it'd be reduced to a base of 10%.

    The problem with this is that it'd drag out combats to an insane degree for equally skilled combatants so this too needs further tweaking.

    The other way to use percentile is to just have a chart. A few games back in the day were percentile based and used a chart to determine whether or not you hit or missed based on the weapon, range, and skill of the shooter. This can work, but if you start using a chart, and then start getting into the minutiae of it based on range, environment, cover, etc it's a lot of charts and math which some people do not enjoy.

    Which is why I am leaning on a static TN 5 on a d6 for my new system with counteracting dice pools reducing to a minimum of 1. This works for both hit and damage so there is a variety of ways to defend, dodge, or armor, and both are equally effective over all.


  • Pitcrew

    @Lithium Two ways to fix your second system. Either go for 'equal or over' and have everyone -start- with Dodge 1 (the simplest solution) and buy it up from there, or go with 'over' and allow the dice to explode. If you roll a 6, you add on an additional d6-1, giving you a result from 7-11.

    My problem with 1d100 is that it's much more random than anything involving multiple dice. It's such a wide array of possible results, with none of them being more likely than any other. This makes a single die roll very susceptible to swingyness, as someone with a really high skill can roll a 99 just as easily as they can a 01 and still whiff. With a bell curve from multiple dice, these outlier events are less likely and you get more consistent results.

    I know I've banged the 1d100=random=bad drum before, and it's a personal pet peeve of mine, so I'll leave it at that.


  • Pitcrew

    @Seraphim73
    It all depends on what you want out of the system and taste.
    For me it is a lot about what I am trying to represent in a campaign. In games where I want a feel of real world gritty-ness or a noir-ish tone I go for systems with a Bell curve it helps keep things grounded as extremes of both good and bad are rare and helps set tone.
    For a Superhero or high action game like a space opera I would go with one dice to role be it a percentile or d20 because of the randomness it gives a mechanical feel that anything can happen and might. I think this adds to the over all feel of high adventure.
    I don't there is a one true system out there it is abut creating the mechanical feel that matches the story you are wanting to tell.


  • Coder

    @Bobotron

    On Aether, I coded a comparison system with output of the percentage better or worse one character was over another.

    Similar to the "60 - 20 = 40%" idea, but I think better framed letting the characters determine how a challenge with a 12% skill difference would go. (edit: in the above example, a 300% power difference, or 33% the power if you're the weaker.)


  • Coder

    @ThatGuyThere See this right here is a problem. If I am able to throw 100 tons around without a problem, there shouldn't be any /swinginess/ when I connect. It should do an immense amount of force on impact and there shouldn't be a feel of 'anything can happen' in super hero's in my opinion. If 'anything' can happen, then what is the point of having super powers if they end up being worthless due to a swingy dice system just screwing you over all the time?

    There is /nothing/ more frustrating than standing around and doing nothing because the dice have decided your highly skilled or highly powerful character simply cannot connect at all.

    We see this a lot in RIFT's and such systems as well, because your skills are all percentile based but they start off so low like a 30% chance of success or thereabouts that it is not remotely consistent at all.

    Sure you can miss a lot on a bell curve too if luck is against you, but overall it's a much smoother experience than with a d20 (as my poor half-orc cleric in 5E can tell you. +6 to hit at level 1 and she's missed 90% of the time due to d20 variance).


  • Pitcrew

    @Lithium said in RPG Percentile Mechanics:

    @ThatGuyThere See this right here is a problem. If I am able to throw 100 tons around without a problem, there shouldn't be any /swinginess/ when I connect. It should do an immense amount of force on impact and there shouldn't be a feel of 'anything can happen' in super hero's in my opinion. If 'anything' can happen, then what is the point of having super powers if they end up being worthless due to a swingy dice system just screwing you over all the time?

    But that fits the primary source of the genre at least in superheros. Despite Spiderman's being nearly impossible to hit sometimes the nameless gun man wings him.
    Thor is one of my favorite characters but he has a lot of bad loses over the years.

    I generally prefer the high luck systems to the bell curve ones, since the bell curve ones tend to be the more predictable and the whole point of the dice to me is to add unpredictability.
    While you don;t like the standing around because of bad luck there is nothing more boring to me then sitting around for hours to reach the result math said we would hit at the beginning of it.



  • @Lithium said in RPG Percentile Mechanics:

    This reminds me of a couple system ideas I've been working on instead of trying to convert a table top system to an unrelated environment.

    My first idea was to have dice cancel each other out, like if person 1 has 8 dice to attack and person 2 has 5 dice to defend then person 1 has only 3 dice to roll on attack against person 2 in normal situations.

    So essentially NWoD's combat method (Pool - Defense/Modifiers), just using 'their active dice pool' instead of a Defense attribute.

    My second idea was using d6's where your 'dodge' skill (or equivalent) would determine the target number to being hit. So if you had a 5 dodge skill then they'd need to roll 5's and 6's to hit on a d6. The only problem with this is having 1 in a skill was useless so I changed it so that you had to roll /higher/ than the skill. Still doesn't fix the problem of a 1 skill being pretty much crap. Still toying around with this idea as it's clearly not ready and needs modification.

    Yeah; the lower skills make it less ideal.

    The third idea I had was to go with a percentile based system where each point in stat + skill combinations equated to 10% chance to succeed, which was reduced by environmental factors, and your opponents defense stat + skill combinations. So if you had a 4 skill + a 3 attribute you'd have a base 70% chance for success. If the target had 3 skill + 3 attribute it'd be reduced to a base of 10%.

    This is what I'm fiddling with, using a number comparison to get the percentage. For example, attacker has a total of 10. Defender has a defense total of 10. Net 0, so you end up with 50%. Same scenario, but defender has a defense of 6. You have a total of 4, and the attacker then has a net bonus. So saying 5% increase per difference, you have 70%. Conversely, Attacker 10 and Defender 14, removes that down to 30%. 5% per differential is probably too high in most situations, and then you have to account for anything and everything you have that gives a bonus.

    The problem with this is that it'd drag out combats to an insane degree for equally skilled combatants so this too needs further tweaking.

    I ran about 20 test rolls using that earlier, it was 12 pass/8 fail; but the dice are going to skew how they fall no matter what. Any dice system is going to veer your outcomes. I ran a bunch of d10 WoD style stuff and lo and behold, I had a 20 dice test where I got 2 successes.

    The other way to use percentile is to just have a chart. A few games back in the day were percentile based and used a chart to determine whether or not you hit or missed based on the weapon, range, and skill of the shooter. This can work, but if you start using a chart, and then start getting into the minutiae of it based on range, environment, cover, etc it's a lot of charts and math which some people do not enjoy.

    Doable. I have very little experience with the 'roll on a chart' systems, though. But yes, you get into crazy minutiae and it becomes bogged down. But it's probably a good option if people are willing for it.

    Which is why I am leaning on a static TN 5 on a d6 for my new system with counteracting dice pools reducing to a minimum of 1. This works for both hit and damage so there is a variety of ways to defend, dodge, or armor, and both are equally effective over all.

    Let me know how that works for you. I'd run some tests on something similar but it wasn't as ideal as I would have liked.


  • Pitcrew

    @ThatGuyThere Oh yes, you absolutely have to tailor your system to your theme. That's actually why D20 works so well for D&D: it's heroic fantasy and characters start out really quite bad at what they do, so wild swings of luck are appropriate (obviously, some D&D campaigns aren't this way, I'm generalizing). Something based on a radio serial series (or, in the same vein, Indiana Jones), would also do well with a single-die system.

    Non-action-movie modern systems, gritty investigation, or systems where you come out of chargen quite capable... I'm much more in favor of a bell curve for.



  • @Lithium said in RPG Percentile Mechanics:

    See this right here is a problem. If I am able to throw 100 tons around without a problem, there shouldn't be any /swinginess/ when I connect. It should do an immense amount of force on impact and there shouldn't be a feel of 'anything can happen' in super hero's in my opinion. If 'anything' can happen, then what is the point of having super powers if they end up being worthless due to a swingy dice system just screwing you over all the time?

    Because there's never been a comic book ark where the characters punch at each other and miss repeatedly, but nevertheless end up hitting walls, cars, lamp posts, etc...

    Just because you don't connect with the target doesn't mean you don't connect with -something-. Dice are against you and you're having bad luck? Talk about some of the collateral damage that happens in the wake of that. Superhero fights are almost never neat and tidy. Look at Hancock for an example of how batshit that can get. Not connecting doesn't mean both characters are bad, either. It can just as easily signify that both characters are highly competent combatants and are totally on their freaking game today, dodging deftly and returning masterful counterstrokes that are dodged equally deftly.

    Dice don't have to come up with big numbers and huge wins to make cool story.


  • Politics

    relevant


  • Coder

    @Derp Let's see how you feel when that happens for 5 scenes straight, which equates to over a month and a half RL time. Kind of hard to feel 'highly skilled' at anything.

    Especially when you're still getting hit right and left.


  • Pitcrew

    I played a game once (I can't think of the name, sorry) where the "to succeed" roll was based on a percentile of 50 + (Player A's Attribute/Skill - Player B's Attribute Skill). So if Player A had a Fighting of 60 and Player B had a Fighting of 45 their To Hit roll would be 65 (50 + 15). In the reverse Player B's To Hit would be 35 (50 - 15).

    Maybe this came from the old Call of Cthulhu/Basic RP system? I don't remember. I did not care for it, however, because even relatively small disparities in skill led to entirely one sided altercations.


  • Pitcrew

    @Derp
    Exactly I think on of my all- time favorite comic fights involved most attacks missing.
    It one of the early fights between Snake Eyes and Storm Shadow and they clash for a bit with neither being able to really get a shot in on the other, granted the job of that scene was to build the rivalry and reader anticipation for the bigger fight later instead of providing a conclusive winner but it did that job brilliantly.


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