D&D General Replacing 1d20 with 3d6 is nearly pointless

[Horwath]

I find that 3d6 is very reliable, especially in skill checks and saving throws.

In attacks it can be little predictable and it requires finding advantages and other bonuses if targets AC is too high. Some other house rules might be included.

For crits, if you want similar chance then treat 16-18 on 3d6 as 20 on d20, 15-18 as 19-20 and 14-18 as 18-20.

 

[NotAYakk]

@NotAYakk, do you know any systems that actually use runs, doubles etc like you're suggesting?

For RPGs, ORE extracts 2 values out of each roll (width and height).

In other non-RPGs, lots of stuff.

In D&D, rolling 2d10 and saying doubles crit gives you a crit rate of 10% times hit chance (so the same as nat 20 in d20 if a 50-50 chance to hit).

Many dice pool RPGs have 1s or 10s doing something special.

 

[pemerton]

Many dice pool RPGs have 1s or 10s doing something special.

Sure - eg in Burning Wheel a 6 can be exploding under some circumstances.

It's the runs and doubles/triples I found interesting.

 

[BrokenTwin]

I've debated moving the next d20 game I run over to 2d10 numerous times. The idea of doing something interesting with doubles is a lot of fun, too. I'd probably do something simple like doubles being added to damage, although I don't know if I'd add the combined or the singular (double sixes adding 6 or 12 damage, for example). I'd probably have it still damage on a miss, just so the roller always gets SOMETHING out of it. It would theoretically speed combat up enough to offset the added time caused by rolling another number.

Oh, if I went with both dice being added, then Advantage/Disadvantage (r3k2d10) could be x3 and x1 number on dice in extra damage, respectively.

Would this system be worth the extra headache it produces? Probably not. But it's fun to imagine.

 

[Michael Silverbane]

I much prefer 3d8-3 (or 3d8 and add +3 to all DCs), if moving to a 'bell curve'. If you do criticals only on a 3 or a 24, it results in only one critical (success or failure) out of every ~250 rolls. Even if you do crititicals on 3 and 4 and 23 and 24, it is still only a critical (success or failure) out of every ~50 rolls. Also, 3d8 has a smaller effect on bonuses than the 3d6 roll.

On the down side, 3d8 is definitely more difficult to add up than 3d6 (which is harder still than 1d20). I play with some people who are very nearly completely innumerate, so even very small increases in maths complexity can make a big difference. That said, I do almost all of the maths (and by maths, I mean adding and subtracting) at the table in both of the gaming groups that I currently frequent.

 

[dave2008]

I no you want out, so sorry to quote you back in - but I just wanted to say a bit more to explain NotAYakk's point (and if you already fully got it and I'm just telling you how to suck eggs, apologies again).

NotAYakk is saying that (with crits to one side) the reduction in randomness that comes from replacing d20 with 3d6 (which I have certainly seen advocated on these boards from time to time) can be achieved to the same extent by sticking to a d20 but doubling all bonuses (or, in the case of AC, doubling the different between the AC and 10). And he is suggesting that the second option is preferable to the first because the maths all happens in prep rather than having to add numbers at the point of resolution.

And his speculation about runs, doubles etc is that that would be a good reason to go to 3d6 rather than d20 because it uses features of a 3d6 roll that can't easily be emulated on a d20 roll.

@NotAYakk, do you know any systems that actually use runs, doubles etc like you're suggesting?

No worries, and yes I understood him/her. Though, to be honest I don't understand why simply shifting the range further from 10, but I don't need to either (though as a side note I have thought about remove ability modifiers and just using ability scores in the past and this would have a similiar effect i would think). In D&D I am not really interested in dice pools, except for a way to reduce crits, but I have a better method to achieve that as well.

 

[Ovinomancer]

Example:
A strong is any hit where you have at least 1 double (about 50:50). Or maybe that gives you a 2nd attack with 1 less die.
A crit is any with a triple (1/36 hits)
A fumble is a triple that misses.
A run on attack dice (456 etc) that hits makes your damage explode, or gives you a bonus attack, or whatever.

This needs playtesting, as evaluation time goes up.


So 2d10 has a standard deviation (average distance from the average roll) of about 2/3 1d20. As anydice likes integers, I took 3x 2d10 snd comapred it to 2x 1d20; the result has the same standard deviation. Then I subtracted each of their average so they are centered on 0.

This corresponds to scaling bonuses by 50% more (and DC distances from 10.5) on d20 and comparing that to standard DC/Bonuses on 2d10.

The point is that the math on each roll (adding, slowing play) is really doing the same job as throwing larger DCs and higher bonuses at PCs (which is one-time math, not per-roll).

In other words, if you think skills are too swingy in 5e, double proficiency bonus on attribute checks and add (stat-10) instead of (stat-10)/2. Then scale DCs so a 12 becomes 14, 15 becomes 20, 18 becomes 26, 20 becomes 30 etc.

You'll get the same results as rolling 3d6+standard mods.

That... no, that's not how that works. Tgat you can inflate a distribution to get a similar stdev doesn't maje the distributions similar ar all. You still have a flat distribution and a normal(ish) one. This is mathturbation.

 

[DND_Reborn]

I did an extensive analysis of 3d6 vs d20 a while ago when we considered going to 3d6. Like a lot of people, it works best for skill checks and even saving throws because they are simple "all-or-nothing" rolls. Using 3d6 increases the likelihood of "typical results" which is what I'd expect from a single-roll test.

Combat, as a series of tests, becomes bell-curved because you are making multiple "trials". If combat was a single roll, I would want it to be 3d6 as well.

Ultimately, the probability differences between 3d6 and d20 aren't enough except at the extremes to make it worthwhile IMO.

 

[NotAYakk]

That... no, that's not how that works. Tgat you can inflate a distribution to get a similar stdev doesn't maje the distributions similar ar all. You still have a flat distribution and a normal(ish) one. This is mathturbation.

Have you looked at the graphs I've been linking to, or not?

How math works is you do steps and results come out.

Do I have to take a screen shot? I have to take a screen shot. naughty word.

So here we have the CDF (cumulative distribution) of 1d20 and the CDF (cumulative distribution) of 3d6 with different averages and standard deviations normalized.

The 1d20 curve is a line. The 3d6 curve is the set of black points. Notice how the 3d6 curve is close to, but not exactly on, the 1d20 line. It only differs significantly at the 5% "critical hit/miss" cases that correspond to 1 and 20 on the d20 roll.

I horizontally scaled 3d6 by a factor of 2, which corresponds to "bonuses and penalties are twice as large, conceptually, in a 3d6 based situation".

So yes, that is how that works. The distributions are similar in CDF, because you can see it. Yes, one is a flat distribution and the other is a normal(ish) one, but we aren't playing "can you roll a 7", we are playing "can you roll a 7+" when we play D&D. And "can you roll a 7+" corresponds to the CDF (the integral) of the distribution.

And when you integrate things, the differences between a flat distribution and a curved one fade away pretty fast.

This isn't "mathturbation", because I actually checked my results. I even shared links to those results being checked. I am not sure why I expected people to actually click on those results before saying "this is naughty word".

Anyhow, here is the results inline.

Quite possibly a slightly different value than "2" would be more correct once we neglect tails -- a different value than "2" would correspond to a change in the slope of the 3d6 part of the graph, and making it slightly less steep might improve the match (except for the tails). But 2 is so close I really don't care.

 

[Smarmot]

Replacing d20s with 3d6s is infringing on the rights of kobolds.