What are your thoughts on roll-under/roll-high mechanics?

[Thomas Shey]

I understand the elegance/simplicity of roll-under or roll-low...but I just don't like it.

Thought experiment: imagine a roll-above game where lower ability scores are better. Same math as some roll-under games, but....low ability scores? It's just wrong.

Not quite the same dynamic though; roll low generally is just directly asking the question "Is this task within your capability?" instead of of doing so indirectly the way roll high does.

 

[Theory of Games]

That's a bit of a drastic example. If the gap between your fastest character and the second fastest is the difference between the Flash and the Joker, then yeah, I don't see why we're rolling.

That's essentially what I meant despite my phrasing being off.

However, in most games (including D&D) the gap is much more narrower. The odds are absolutely in the favor of whoever has the best bonus, but the dice represents the alea of life (context, luck, surprise, or anything) else that can happen. The "best" team sometimes loses in sports.

I'm fine with a narrow gap as long as the opposition is close in capability. I'd also argue that when the best team loses, it's usually due to poor tactics + bad luck - not just bad luck.

I always had the opposite perspective and saw this exact critic of D20. It's very swingy and the majority of the odds lie in the dice and not in your bonus. Where systems like 2D6 for example, have a different curve that makes the dice much more predictable, and so the bonus much more reliable too.

The "swing" of d20 is very well documented and debated. I used to hate it but later realized 1d20 produces randomness better than most dice solutions. And the roll results are managed by character bonuses. Of course I champion GURPS a lot on this site because its '3d6 roll under' is my favorite process: fast and easy task resolution.

I’m not sure I entirely agree with your last point, especially in a system with a bell curve.

I'm not seeing how the bell-curve (like with GURPS) figures when the player has to roll low AND close to the TN. Rolling high or low should be enough. It's hard enough for a GM to maintain pacing and consistency running a campaign, goofy dice rules just make task resolution more complicated and slows everything down IME.

 

[Bill Zebub]

Not quite the same dynamic though; roll low generally is just directly asking the question "Is this task within your capability?" instead of of doing so indirectly the way roll high does.

Not sure I agree with that interpretation. "Is the task within your capability?" is a question about the situation, something that exists before dice are rolled. The die roll determines how well you perform on this particular attempt.

If you have to roll below a 16, the task is within your capability with a 75% chance of success. If you have to roll above a 5, the task is also within your capability with a 75% chance of success.

What I will agree with is that roll low (or "roll under your ability score") does more directly map the die roll to the ability score, instead of requiring the indirect step of first converting the ability score to a modifier. Which is exactly the same thing as "low ability scores are better; roll above them".

 

[Staffan]

It sounds like a solution in search of a problem. It is more complicated than many other mechanics, but I don't see what payoff we are supposed to get for that added complication.

You don't say what genre you think will be well-served by such a mechanic, of what issue(s) you perceive with other mechanics that this is supposed to fix.

Specifically - the interesting point of blackjack is that it is a "push your luck" game. The player has decision points of whether to take another card or not. What decisions do players have in this rolling mechanism?

It's not a decision-making mechanic. It's a simple way of dealing with opposed rolls and quality-of-success.

If you start with a linear roll-under system, it's easy to at first assume that the lower your roll, the better you did. Succeeding by 10 is better than succeeding by 2. If we're fighting and I succeed by 8 and you by 3, I did better than you and therefore win that round of fighting and I get to deal damage to you.

But that requires that we, for each roll where it matters, calculate a margin of success by taking our skill value and subtracting the actual roll. That's not rocket surgery, but it's still a step of arithmetic. If we instead just compare the rolls themselves (with any roll above your skill being a failure and thus not counting), the probabilities are identical but we don't have to do math. Win!

You could also use it to determine quality for other rolls, but I've rarely seen that in the wild. For example, maybe a successful Survival check provides food for yourself + roll/4 others. Maybe picking a complicated lock requires that you accumulate total rolls of 50 to unlock with one roll made per round

 

[Umbran]

It's not a decision-making mechanic. It's a simple way of dealing with opposed rolls and quality-of-success.

I think you misunderstood.

In engaging with any mechanic, players make decisions to influence the outcome. In blackjack, for example, after every card is dealt, if the total is not yet over 21, the player gets to choose - hit or stay?

I am looking for where the player engages with this mechanic.

 

[Thomas Shey]

Not sure I agree with that interpretation. "Is the task within your capability?" is a question about the situation, something that exists before dice are rolled. The die roll determines how well you perform on this particular attempt.

I wasn't clear in my expression. "Is the task within your capability" is something that looking at your skill tells you in general. Its saying "I have a 75% skill so in the kind of tasks foreseen as being typical to roll for in the game, I'll pull it off three quarters of the time."

As you note, and I've referenced in another thread, the roll-high approach can have the same probabilities (say, a +16 skill when you expect default target numbers to be 20), but there's an extra step in there in understanding what that means. With the roll low approach, its self evident just from looking at it.

If you have to roll below a 16, the task is within your capability with a 75% chance of success. If you have to roll above a 5, the task is also within your capability with a 75% chance of success.

What I will agree with is that roll low (or "roll under your ability score") does more directly map the die roll to the ability score, instead of requiring the indirect step of first converting the ability score to a modifier. Which is exactly the same thing as "low ability scores are better; roll above them".

As you can see, that's what I was talking about. But I don't agree it has the same intuitive impact as your last sentence. "Roll within your skill" seems much more true of that than "low ability scores are good".

 

[Thomas Shey]

Honestly, the big benefit of "roll within but high" compared to the traditional BRP style "roll within but low" is it doesn't require subtraction. There are other benefits in that you can bake in some thresholds without doing much in the calculation (EP2e does this with 33 and 66) but that's probably the biggest reason systems do it.

 

[Bill Zebub]

I wasn't clear in my expression. "Is the task within your capability" is something that looking at your skill tells you in general. Its saying "I have a 75% skill so in the kind of tasks foreseen as being typical to roll for in the game, I'll pull it off three quarters of the time."

As you note, and I've referenced in another thread, the roll-high approach can have the same probabilities (say, a +16 skill when you expect default target numbers to be 20), but there's an extra step in there in understanding what that means. With the roll low approach, its self evident just from looking at it.



As you can see, that's what I was talking about. But I don't agree it has the same intuitive impact as your last sentence. "Roll within your skill" seems much more true of that than "low ability scores are good".

But maybe only because we're used to "high ability scores are good"? There are lots of places where the lower number is better ("1st Place") and we do just fine with it.

 

[Staffan]

I think you misunderstood.

In engaging with any mechanic, players make decisions to influence the outcome. In blackjack, for example, after every card is dealt, if the total is not yet over 21, the player gets to choose - hit or stay?

I am looking for where the player engages with this mechanic.

You engage with it the same way you do with a check in D&D, which is to say generally not unless there's some external mechanic that lets you do it (e.g. in D&D you have things like Bardic Inspiration that lets you retroactively mess with a roll). Some games that use Blackjack rolls do have ways of interacting with it – for example, the Troubleshooters (which uses a d100 version) lets you spend 2 Story Points to flip the d100 (read tens as ones and vice versa), but that's not inherent to the Blackjack roll mechanic itself.

 

[Thomas Shey]

But maybe only because we're used to "high ability scores are good"? There are lots of places where the lower number is better ("1st Place") and we do just fine with it.

Sure. But the reaction is the reaction, at least initially. Which you can argue is the case with the roll low thing too, of course, but in my experience the intuitive quality overcomes that faster if someone hasn't been in the roll-high sphere for too long.