Creative Corner > Game Design
d20 vs 2d10 and it's effect on defense
Mooncrow:
In order to not clutter up a thread with off topic chatter, I'm moving this here.
--- Quote from: Mooncrow on December 08, 2011, 01:06:59 PM ---
--- Quote from: Basket Burner on December 08, 2011, 11:13:06 AM ---Bell curves wouldn't really work. It got lost in the flamefest, but at one point someone suggested 2d10 instead of 1d20 for the RNG. The result of that would be that enemy actions succeed more often, and player actions would either succeed more or less often depending on the encounter.
Low level is completely unplayable because the entire game is a simple D20 check. If the Orc rolls at least a 10, you die, and there is nothing you can do about it. Beyond that though it tends to only become a luck fest with weak characters. The strong ones avoid that. They also go off the RNG, but then if they weren't, there'd be no way to survive campaigns. Even with those other things, there'd be too many failed saves. It isn't just save or loses. Simple attacks 1-2 round people just the same.
--- End quote ---
It's slightly more complex than that though - what it does, is even out the the cost per effect curve a bit. With the d20 - costs to increase a defense scale upward, at least when talking about items rather than spells, while the benefit remains the same: 5% per point, basically. (at least when talking about a single effect; calculating multiple effects has it's own probability curve, but it's still more linear than not) With 2d10 (or 3d6 or whatever other variant you want to name) however, the benefit curves upward, making the marginal cost of the next point of a given defense less. So it ends up rewarding (or punishing less, depending on how you want to look at it) those that put in the effort and cost to optimize their defense.
--- End quote ---
--- Quote from: Basket Burner on December 08, 2011, 03:02:07 PM ---No, it doesn't. It means you get more benefit as you approach the mid point, and then less as you move past it. It does not make it so that each point is better than the one before it.
Slight problem though. Physical defense is always going to be well to the left side of that line. You just can't get enough AC to make a difference past the low levels, especially if you want to be able to hurt things as well unless you're a CoDzilla or something. Magical defense is always going to be well to the right side of that line, if you know what you're doing that is.
So all you've really done is make physical attacks hit you 99% of the time instead of 95%, save or loses not land quite as often on the enemy and slightly less often on you, and that's it. All of that amounts to enemies destroy you more and not less, as defenses mean less against them.
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I'm actually glad to pick this topic up with a more civil tone. I realize that when you're eyeballing it, it does look that way, but if you look at the probability curve, that's not how it works. It's probably easiest to think of it like this: you're not looking at the overall percentage, you're looking at the marginal benefit of adding +1 to the defense, and the benefit is calculated as the area under the curve that you're getting rid of, the percent of the percent, as it were. So, when you go from hitting on a 16 (15% chance) to hitting on a 17 (10% chance), you're increasing the value of your defense by 33% percent. Or from hitting on an 18 (6% chance) to hitting on a 19 (3% chance) - well, you see how it works. And no, probability isn't intuitive.
Granted, there are several other assumptions I make in my games, which is why I brought it up originally as something that works for me - I assume T1 - T3 in my games and that the players are all working to optimize their defenses. "Melee" without several levels of cleric or something similar are pretty non-existent, or in the one case of the one pure mundane that I do have, he has Leadership for an Archivist cohort :p
Basket Burner:
Except that going from a 94% chance to dodge to a 97% chance to dodge is a 3% difference, less than the 5% you get from a linear system. And that's the problem with it. The greater benefits per point are towards the middle of the range. But physical defense will be far to the left no matter what, and special defense will be far to the right if you know what you're doing, so the default assumptions of the meta do not change. What does change is the results - you get hit even more often by physical attacks, and a significant number of enemies are less prone to being taken out, giving them more chances to take you out. Saying you get hit half as often going from 18 to 19 on 2d10 is the same as saying you get hit half as often going from 19 to 20 on 1d20. Technically true, but what matters is how many attacks are successful. The benefit on a point by point basis is secondary.
I tried to leave my games out of it as much as possible and instead focused on the game. If I were to apply those same principles to my game, then what'd happen is that Koth would have been 99% invulnerable instead of 95%. So instead of the party of optimized, mostly 1-2 classes finishing the fight with most of the party in single digits or worse and very few spells left, he would have used his fourth Wings of Flurry, then just attacked whoever was left for the sweep. Looking at things from the PC side those that cared about AC had 28 points of it at level 6, with conditional bonuses on top of that. Mooks hit on a 12-14 or so, so it wouldn't make any real difference. The main threats hit on a 2 or 3. That would help them.
Said party has since leveled up, and gotten a fair bit of loot for their efforts. These numbers have improved and are liable to improve more. 30s are starting to show themselves. And that's without conditional bonuses. Enemies still have little difficulty hitting, of course. The point of all of that being that in optimized games, offensive abilities improve substantially. Defensive abilities, not as much on the physical side but much better on the special side. Everyone has at least a 75% chance of passing almost any save thrown at them.
JohnnyMayHymn:
When you switch to a bell curve rolling system (3d6 is most likely to result in 10 or 11) it raises the minimum roll and skews the result toward the center (2d6 is more likely to result in a 7 than any other sum of the two results).
One pro is that in low levels, mooks are far less likely to one hit crit a party member.
Also crit range increases become much better.
One adjustment I would make is to change the base AC to match the most likely roll, (14 for a 4d6 system).
Mooncrow:
I don't bring my games up very often either - for the same reason, but in this case I did originally, so I'm explaining why it works under a slightly different set of assumptions. My list of house rules is extensive though, so we'll leave them out, unless you're actually interested.
But you're still not looking at the math quite right - it's a lot easier to see on a probability graph, but I'm not sure how to insert one, so words will have to do =/
It's easier to see the farther to the edge you go, so let's try this: the difference between 95% and 99% doesn't sound like a lot, but in practice, it means that a given effect will land once every 20 times vs an effect landing once every 100 times. So, effectively, the 2d10 method makes that last point of defense 5x more valuable than it would be under the d20 system. Does that help the visualization?
Basket Burner:
This thread really should not have been put here. I keep forgetting about it as I normally don't check this subforum.
--- Quote from: JohnnyMayHymn on December 08, 2011, 05:54:28 PM ---When you switch to a bell curve rolling system (3d6 is most likely to result in 10 or 11) it raises the minimum roll and skews the result toward the center (2d6 is more likely to result in a 7 than any other sum of the two results).
One pro is that in low levels, mooks are far less likely to one hit crit a party member.
Also crit range increases become much better.
One adjustment I would make is to change the base AC to match the most likely roll, (14 for a 4d6 system).
--- End quote ---
At low levels they might be less likely to one hit crit but they are more likely to hit in the first place. Orc goes from threatening a crit 15% of the time to 10% of the time... but as a 10 or better most likely hits, and that went from being 55% likely to 64% likely, and the normal hits still OHKO or 2HKO people...
Moon: I've already seen what happens when you use a set of houserules to attempt to fix the system and then throw powerful characters at it. It works better than the default, and you can potentially get enough AC to make a difference, but a 2d10 RNG still reduces the value of defenses. I also understand the distribution just fine, that is why I say that their values are reduced. The main point though is that your physical defense is already going to be too low because you can't help it and your special defense is already going to be too high because you'd be stupid not to help it. So basically, everyone is Blissey. Watch those Close Combats, now.
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