Recently I have considered replacing the d20 roll with the 3d6 roll, at least for a few sessions to see how it feels. This will be for a 4E game and will come with a few house rules necessary for this, like increasing threat ranges to similar percentiles, and making abilities that grant rerolls give additional dice to the pull (so oath of enmity means you roll 4d6 and ignore the lowest die, and if you get a second reroll you roll 5d6 and ignore the two lowest dices etc.). I understand the basic arguments about it, that it decreases randomness, may decrease combat speed because it is a more complicated process, and heck requires a lot of d6 around and I want to give it a try. Does anyone have any experience using 3d6 in place of the d20? How much does it truly affect gameplay? Any feedback is welcome.
Killing the d20-The Bell Curve roll
tuxgeo
Adventurer
Hm: 3d6 eliminates all possibility of rolling 1 or 2; and you need to fudge it with rerolls to get up to a 19 or 20. Have you considered rolling 2d10 instead? That way, you get a triangle instead of Bell curve, but wider range (and curse ENworld's parser for forcing me to format this vertically, by automatically cancelling multiple consecutive blank spaces! Any ASCII art is right out, isn't it?):
| _2
| _3 _3
| _4 _4 _4
| _5 _5 _5 _5
| _6 _6 _6 _6 _6
| _7 _7 _7 _7 _7 _7
| _8 _8 _8 _8 _8 _8 _8
| _9 _9 _9 _9 _9 _9 _9 _9
| 10 10 10 10 10 10 10 10 10
| 11 11 11 11 11 11 11 11 11 11
| 12 12 12 12 12 12 12 12 12
| 13 13 13 13 13 13 13 13
| 14 14 14 14 14 14 14
| 15 15 15 15 15 15
| 16 16 16 16 16
| 17 17 17 17
| 18 18 18
| 19 19
| 20
That way, only the 1 in unrollable; and there are exactly 100 possible outcomes, so figuring the percentages is a piece of cake. (Achieving them is another story: if you use 18-19-20 for Crits, that's 6% instead of 5%.)
(Caveat: I haven't actually tried this. I'm way behind the curve, such as it is.)
Well my intention would be that you have automatic success at a roll of 18 and an automatic failure at a roll of 3, so I don't see what I lose by losing 1.2.19.20 from the rolls. Plus the objective is to normalize rolls and 3d6 sticks to the bell curve.
As for the oath of enmity, rolling d20 twice and keeping the best and rolling 4d6 and keeping the three best are not that unlike as possibilities go, in fact 4d6 method has a slightly higher average I think. Keep in mind that critical ranges would of course be changed. Chance to crit on a 20 becomes chance to crit on 16-18 (19-20 becomes 15-18, 17 or 18-20 becomes 14-18 and 15 or 16-20 become 13-18 or at least that's the best approximations I can get).
Keep in mind that this will mean that bonuses and penalties to die rolls when you're near the middle of the curve or triangle will be significantly greater than out near the ends.
Marking a creature that has a 50% chance of hitting your allies with a d20 means it goes down to a 40% chance of hitting them. That same mark is far more powerful on 3d6, as it now only has an approximately 26% chance of hitting them.
Also, as chance to hit drops off at a far faster rate, the range of monsters that can be safely used in combat gets reduced. An AC that your best attacker is hitting 30% of the time with d20 rolls, they're hitting less than 5% of the time with 3d6.
Basically, all of the math in the system is based on the idea that a d20 roll is the core mechanic, and the game's assumptions about appropriate DCs, defenses, bonuses and penalties are going to be wrong with 3d6.
Marking a creature that has a 50% chance of hitting your allies with a d20 means it goes down to a 40% chance of hitting them. That same mark is far more powerful on 3d6, as it now only has an approximately 26% chance of hitting them.
Also, as chance to hit drops off at a far faster rate, the range of monsters that can be safely used in combat gets reduced. An AC that your best attacker is hitting 30% of the time with d20 rolls, they're hitting less than 5% of the time with 3d6.
Basically, all of the math in the system is based on the idea that a d20 roll is the core mechanic, and the game's assumptions about appropriate DCs, defenses, bonuses and penalties are going to be wrong with 3d6.
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There's always the option of making critical successes and failures harder to achieve, such as rolling a 3 for a failure and rolling an 18 for a critical success.
The harder part is figuring out what the AC's of the monsters should be, as well as things like saving throws. How exactly would monster ACs change with hit dice (in older editions) or level (in 4E).
The harder part is figuring out what the AC's of the monsters should be, as well as things like saving throws. How exactly would monster ACs change with hit dice (in older editions) or level (in 4E).
3d6 and 1d20 have different standard deviations, and very different probability distributions.
Adding modifiers (bonuses/penalties) to a 3d6 roll changes the probabilities in a nonlinear manner, while modifiers added to a 1d20 roll changes the probabilities linearly.
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