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AttilaTheGeek
2014-07-14, 10:39 AM
I'm considering undertaking a great rite of passage: designing my own RPG. However, the vast majority of my experience has been in d20 systems, and I want to ask the playground about the strengths and weaknesses of various alternatives. To give some examples, why might I choose a dice pool over a single die roll? What is the effect on the game of having success be binary or having various degrees of success?

Yora
2014-07-14, 11:14 AM
I think much more important than what dice are rolled or how, is when and how often they are used. I think the most problematic aspect of the d20 system is that dice are rolled for almost everything, even considering the Take 10 option. In contrast, OSR style games mostly roll only for attack rolls, damage, and saving throws. A huge amount of situations is simply assumed to be something a player character can just do without any struggle.

Related to that is the question how many special abilities characters get, and how specific they are. Because if there is a special ability for something, lots of people will assume that implicitly you need to have the ability or have no chance to attempt the action. Which leads to situations where players have an idea for a character, but have to wait until 12th level until they can actually use the character iconic combat style. Intentionally leaving abilities vague and open ended makes it much easier to represent a specifc concept in the game mechanics.

And then there is also the question of using character classes and levels or not.

Some RPGs approach things drastically different than the d20 system. I recommend taking a look at the free Fate Accelerated (I believe a shorter version of Core). Mouse Guard is also amazing, but I don't know how easy to get.
For a class and level based game, I recommend looking at a really compact OSR game. Swords & Wizardry looks decent and is also free. There is also OSRIC, but that is much thicker and maybe not such a great pick just to see the concept.

Requiem_Jeer
2014-07-14, 11:36 AM
Well, d20's primary downside compared to a dice pool is that it doesn't adhere to a bell curve. The difference between 11 and 30 is massive, and it makes successful people screw up far more then the skill level involved would generally imply, purely due to the probability distribution. On the other hand, a die pool means the screwups happen at a more believable rare case. Yes, you can still botch or just fail at something moderately difficult, but you're looking at a 2-3% chance, not a 5-15%. You also have a similar low chance at amazing success compared to your skill level.

Bell curves provided by die pools overall make a character's accomplishments more consistent, which is more true to what a practiced professional actually does.

Segev
2014-07-14, 12:03 PM
There are 3 other dice systems (d10 based) in which you might be interested for research purposes.

White Wolf's has you assemble a die pool based (primarily) on a stat+skill (they call it Attribute+Ability). Roll a number of d10s equal to this. A 7+ is a "success" on a given die. A 10 is two successes. Many, many actions require no more than 1 success; you got a success so you succeeded. Opposed rolls and particularly difficult tasks might take more. The former because you have to roll more successes than the other guy; the latter because it's just that hard.

Legend of the Five Rings also has both stats and skills. However, you roll (stat+skill) dice and choose a number of dice equal to (stat) to keep. Any die that rolls a 10 "explodes," which means you roll it again and add 10 to it. Repeat until it doesn't roll a 10. (I've seen a 142 rolled on a die before.) You then sum up the number you kept to see if you can hit the target number you need to succeed.

A system I've never played and only read through once, "Godlike," was a pulp superheroes game. I forget how the die pools were assembled, but the goal in this one was to get matches on your dice. The more dice you had that matched, the faster your action went. The higher the number of your match, the better you performed. Failure occurred when you couldn't get any matches at all. Opposed rolls had rules, but I can't recall them. Likely, if speed was all that mattered, "wider" (that is, more numbers that matched) successes won; if any amount of quality was required, "higher" (that is, higher numbers) successes won.


In my own private homebrew efforts to model Wheel of Time's style of channeling magic, I adapt L5R's system in order to try to model the grasping at the power and the risks involved in overdoing it.

CarpeGuitarrem
2014-07-14, 02:49 PM
It's not just about the core mechanic, mind you. It's more about how the core mechanic feeds into the rest of the game. That's like asking "what brand of pen is the best one to use for making wonderful art?" It's a bit of cart-before-the-horse. Sure, all artists have their preferences, and there's some flat-out better art supplies, but what makes the most difference is the thing you make with it. Even MS Paint can make wonderful stuff.

Games to Look At (suggested due to variety)

Sagas of the Icelanders: Simple core mechanic, leverages it in some unusual ways
Misspent Youth: Uses Craps as a core mechanic
Risus: Exceedingly simple core mechanic that gets a lot of mileage with smart design
Cortex Plus (Leverage, Firefly, Marvel Heroic, Smallville): A family of games that use a flexible, multipurpose dice pool system
World of Darkness: One of the foundational dice pool games, very streamlined in its approach
Burning Wheel: Great example of how to take a bunch of different mechanical systems and tie them together
A Dirty World: Radically unique implementation of the core mechanic also found in GODLIKE
Pendragon: Great classic example of how to use a d20 system (Runequest) for very unique gameplay

CombatOwl
2014-07-15, 10:51 AM
I'm considering undertaking a great rite of passage: designing my own RPG. However, the vast majority of my experience has been in d20 systems, and I want to ask the playground about the strengths and weaknesses of various alternatives. To give some examples, why might I choose a dice pool over a single die roll? What is the effect on the game of having success be binary or having various degrees of success?

Halt. Stop. First step in this journey is to get some experience outside of d20. Make your judgments about other systems yourself. I'd suggest trying first to modify or adjust a system that's already established. If you want something non-d20 that's easy to change without having massive consequences ripple throughout the game, Fate Core is a good choice. The core mechanic is rather "modular" with bits and pieces that can be added or removed or changed as required (admittedly it gets rather boring without aspects, though the system does work without them). That, and it also presents a fundamentally, philosophically different approach to an RPG than d20.


why might I choose a dice pool over a single die roll?

Statistics. The precise impact depends on how you use a dice pool. For example, fixed size additive dice pools (like, say, the 3d6 system used by GURPS) have a normal distribution of results, a bell curve. The statistical impact of increases in a dice pool vary depending on how the pool works. Moreover, if the pool is actually a pool of independent tests (such as how Storyteller works, where you count the number of dice that exceed a target value), that is statistically distinct from additive pools. Single die rolls have a flat, random distribution. You are just as likely to roll as high or low as possible as you are to roll any other result. This too can be manipulated with "exploding" dice rules.

Basically you pick a dice rolling mechanic that delivers results according to a distribution you feel best suits the tone of the game. Alternately, you just use one because it's well known and simple. Keep in mind that not every RPG uses dice exclusively to resolve conflicts. A deck of cards can be every bit as useful. It's also possible to make a system with no random conflict resolution at all, yet still be interesting (for example, each player gets a pool of tokens. Whomever is willing to pay the most out of their token pool for a given action "wins.")


What is the effect on the game of having success be binary or having various degrees of success?

Depends on what a binary result means in the system. The game effect of success (or degrees of success) is actually what you're determining when you build the system. There is no actual answer to your question.

awa
2014-07-16, 10:58 AM
a disadvantage to dice pool systems i don't think anyone has mentioned yet is that it takes more time. The more dice and modifiers on any given roll that need to be counted and added the longer any given actions going to take. This is particularly important if combat is indepth and common.

Arbane
2014-07-16, 01:21 PM
a disadvantage to dice pool systems i don't think anyone has mentioned yet is that it takes more time. The more dice and modifiers on any given roll that need to be counted and added the longer any given actions going to take. This is particularly important if combat is indepth and common.

Eh, it depends on how it works. If it's 'roll a d6, a d8 and a d10 and find the highest number'. that's reasonably quick. If it's 'roll 5d10, reroll and add on 10s, keep 3 dice and add 8 to the total', I could see that slowing things down a bit.

Speaking of systems where combat is indepth and common, I rather like Legends of the Wulin's dicepool system - you roll the same pool of d10s (usually 7d10) for everything, and look for sets of matching numbers. The number of dice is the 10s digit, the number rolled is the 1s digit. So if I roll and got 1, 1, 1, 5, 7, 7, 9, I could get a 31 (three ones) or 27 (two sevens). Then you add a modifier (always a multiple of 5) for things like skills, kung fu, and whatnot. The clever bit is that if you've got multiple sets, you can use them to do multiple things at once (like attack and insult someone so much that they start making dumb mistakes - and the system supports that mechanically, too).

Grod_The_Giant
2014-07-16, 01:37 PM
a disadvantage to dice pool systems i don't think anyone has mentioned yet is that it takes more time. The more dice and modifiers on any given roll that need to be counted and added the longer any given actions going to take. This is particularly important if combat is indepth and common.
It's also significantly harder to roll multiple times at once. In something like D&D, you can use different-colored dice and roll an entire attack routine at once. By contrast, in something like Exalted you'll be sitting there rolling attacks in your combo for ten minutes.

CarpeGuitarrem
2014-07-16, 02:43 PM
It's also significantly harder to roll multiple times at once. In something like D&D, you can use different-colored dice and roll an entire attack routine at once. By contrast, in something like Exalted you'll be sitting there rolling attacks in your combo for ten minutes.
Mythender defies your weak dice-rolling-fu! :smalltongue:

Just try rolling thirty d6es at once! MWAHAHAHAHAHA!

Requiem_Jeer
2014-07-16, 10:01 PM
Mythender defies your weak dice-rolling-fu! :smalltongue:

Just try rolling thirty d6es at once! MWAHAHAHAHAHA!

I've had times where that many d10's get tossed on the table at once in Exalted before.

Vitruviansquid
2014-07-16, 10:43 PM
One point I haven't seen brought up is that your core mechanic could not involve dice.

Savage Worlds uses a deck of poker cards for combat initiative. You (or NPC's) get a special "super" turn if you (or they) draw a joker, and the deck is not shuffled until a joker is drawn. This creates tension in moments when the deck is getting thin, but no joker has turned up yet. There's also that famous RPG (was it called "Dread?") using Jenga as a core mechanic, one using runestones, and so on.

Stellar_Magic
2014-07-16, 11:30 PM
Well, d20's primary downside compared to a dice pool is that it doesn't adhere to a bell curve. The difference between 11 and 30 is massive, and it makes successful people screw up far more then the skill level involved would generally imply, purely due to the probability distribution. On the other hand, a die pool means the screwups happen at a more believable rare case. Yes, you can still botch or just fail at something moderately difficult, but you're looking at a 2-3% chance, not a 5-15%. You also have a similar low chance at amazing success compared to your skill level.

Bell curves provided by die pools overall make a character's accomplishments more consistent, which is more true to what a practiced professional actually does.

This is a very good point that I think a lot of people miss. A lot of systems outside the standard d20 use multiple dice as a sort of normalizing factor, every-time you increase the number of die that are thrown the likelihood of extreme results (like rolling 10d10 and getting 100 or 10) is reduced. As a result, most D6 systems tend to have much more normalized outcomes to roles.

However... highly normalized results and values make more sense the less random things become, so it actually doesn't work as well for combat actions as the sheer randomness of the d20 in my opinion. While rolling 4d6-4 may give you a 0-20 range, you're not going to land a 'natural 20' 5% of the time... It'll be a lot less common.

Percentile systems take this randomness to an extreme, and are used quite a bit in table top wargaming. I can possibly see the use there to account for the one in a million rifle shot taking out a tank commander, but usually... I think they tend to be a bit over-complex for everyday role-playing, though they are great if you're a realism or immersion junky.

Also, keep in mind it's not just the core mechanic that varies wildly between RPGs... sometimes RPGs that share the d20 core mechanic can have wildly different results. Mutants and Masterminds is D20, 3ed DnD is D20, 4ed DnD is D20, 5e Dnd is D20, Saga Edition is D20, Pathfinder is D20. All of them are very different in some fashion. Saga Edition and 4e use passive defenses instead of saves (which I personally like) while Mutants and Masterminds goes so far as to make every damage roll a save.

It all comes down to how you want the game to play, how predictable or random you want it to be, and so forth.

Requiem_Jeer
2014-07-17, 12:25 AM
Exactly. The core mechanic is just a means of choosing your probability distribution. Each method has it's upsides and downsides, but the game itself is much more important then the exact means of resolving your probabilities.

Arbane
2014-07-17, 01:37 AM
There's also that famous RPG (was it called "Dread?") using Jenga as a core mechanic, one using runestones, and so on.

Yep. Dread's the one that uses Jenga for resolution. It's a horror game, and the player who collapses the tower will be the next one to have their character die. Which works well with the whole 'try to forestall our inevitable doom as long as possible' theme.

Firest Kathon
2014-07-17, 02:43 AM
I personally like the dice mechanics of The Dark Eye (Das Schwarze Auge), which uses a three-d20-roll-under mechanic.

Each skill is mapped to three attributes (e.g. Climbing uses Bravery, Strength and Agility), and you roll a d20 trying to stay under your attribute (two 1s is always a masterful success, two 20s is always a failure). If you go over, you can compensate with your skill ranks. If you have at least one point over, you succeed. For longer tasks (e.g. climbing a wall) you have to collect (leftover) points. For some skills, an attribute may be replaced based on the specific task (e.g. Tracking uses Intelligence to find tracks, but Constitution to follow them). It takes a lot of rolling dice, but I find it more "realistic" as it does not only depend on one single attribute for each skill.

Combat, just to be complete, is just a single d20-roll-under-attack-value, though you can voluntarily make the roll harder to use special combat maneuvers (such as feint or power attack).

Example: My character Kosimo has Bravery 12, Strength 11 and Agility 15, and a climbing skill of 14. I roll 7, 14, 17 on my d20s, so I match the first attribute, miss the second by 3 and the third by 2. I have now 9 points left (14-3-2). However, I have a talent specialization in climbing, which allows me to compensate for an additional 2 points, giving me 11.

Airk
2014-07-18, 12:28 PM
Echoing the general consensus that the "Core mechanic" of the game isn't really THAT important, and is just a matter of choosing what kind of probability distribution you like. (I have come to intensely dislike large flat probability maps like the d20 for exactly the reasons stated in this thread.) I disagree that dice pool mechanics are any slower than the d20 style in most cases either (Rolling 12d6 and counting how many come up 4/5/6 is comparably fast to rolling d20 and adding +2, -3, +4 and +1.) except in cases where you are basically repeating the exact same action several times in rapid succession (basically: multi-attacks.). This is enough of a fringe case for me to disregard the time allotment - especially as the dice pool method is often actually quicker in many situations.

The really important thing is not what dice you roll, but why, and what the results mean.

Do not even ATTEMPT this project if all you know is D20. Indeed, do not even attempt this project if all you know is D20 and GURPS and Storyteller. DO, however, just ramble on over to the latest Bundle of Holding (http://bundleofholding.com/index/current) and give them $25 for 12 games that will expand what you know about RPGs by a factor of...well, probably about 12. :P

oxybe
2014-07-19, 01:52 AM
I would say first and foremost, before deciding on what dice or bell curve to use, to decide on the scope of your game.

Basically, run a "diceless" scenario with a party of theoretical characters.

It can be something as simple as a 3 part adventure: information gathering, exploration, combat, done.

During this step, you'll get a good idea of how things are being resolved in the game and what expected success rates are. Take notes on where you want the players to feel tension, where you want them to feel powerful, where you want them to feel weak, etc...

This will help you decide on the kind of core mechanics you're looking for: single dice for variance, dice pools for more consistency.

Afterwards it's all about adjusting your bell curve. knowing that on a d20 and 3d6, you both have 10.5 as your average, you can start sliding the bell curve of target numbers up or down if you want players to succeed more or less often. Same with dice pools, if you know that 3 rolls of 4+ on you Xd6 pool is your average success you can slide it so more or less rolls are required, or that the target number on the dice goes up or down.

Basically: find out how the game plays, then figure out the best dice system to emulate the play.

Cronocke
2014-07-19, 03:33 AM
Speaking of systems where combat is indepth and common, I rather like Legends of the Wulin's dicepool system - you roll the same pool of d10s (usually 7d10) for everything, and look for sets of matching numbers. The number of dice is the 10s digit, the number rolled is the 1s digit. So if I roll and got 1, 1, 1, 5, 7, 7, 9, I could get a 31 (three ones) or 27 (two sevens). Then you add a modifier (always a multiple of 5) for things like skills, kung fu, and whatnot. The clever bit is that if you've got multiple sets, you can use them to do multiple things at once (like attack and insult someone so much that they start making dumb mistakes - and the system supports that mechanically, too).

Something I positively love about Wulin that I wish more games did was that you roll your dice pool before you decide what actions you're going to perform with it. This, in my experience, leads to players being far more creative with how their actions are described, since they know how they rolled. A 73 will likely get a player to talk about hopping into a volley of arrows, leaping from one to another, to close the gap so they can strike, while with a measly 21 they'll often feed you ideas about what their character is doing wrong.

This doesn't really affect the chances of them failing, as NPCs can pull the exact same trick, it just means there's more incentive to be daring and superhuman.

I also love how debates and medicine use the same basic rules as combat, and... really I could go for pages about the things I both love and hate about that game. Lots to love, some big things to hate. But nothing's perfect, no?