The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

Tuesday, October 31, 2023

The difference in penalties in AD&D1 and D&D5

Sunday was our gaming group “Hallowe'en One Shot” (which is now at least a “duo shot” as we didn't finish) and for some reason, I got to thinking about the penalty differences between AD&D and D&D5.

Everyone in our group started out playing AD&D (or the original Dungeons and Dragons) and in that system, if you are trying to hit something you can't see, you subtract 4 from your (20-sided) die roll (d20) when trying to hit it. But in D&D5, you roll two 20-sided dice (2d20) and take the lower value (called “disadvantage”). I was curious as to the actual difference between the two. I did a bit of programming and I got the following graph:

[A graph of AC (x-axis) and chance of hitting (y-axis) with various penalties, bonuses, and just plain hits]

Along the X-axis is AC. In AD&D goes from 10 (basically, nothing) to -10 (nigh impossible to hit) while in D&D5, it goes from 10 (basicaly nothing) to 30 (nigh impossible to hit), so the range is the same. So the X-axis is AC, going from 2 to 20. In both systems, rolling a 1 is an automatic miss, so I'm not bothering with even listing an AC of 1. The Y-axis is the probability of hitting said AC, from 1 (always a hit) to 0 (always amiss).

The red line (the one cutting diagonally across the middle) is just the result of rolling a d20 and is prety much what one would expect, a straight line. The light-green line (the lower diagonal line) is the AD&D penalty of subtracting four from a d20 (d20-4). Again, it's a straight line but giving a lower chance of hitting.

What I find fascinating is the blue line (the lower curved line). This is the D&D5 “disadvantage” roll. What's interesting about this is that at lower and higher ACs, it's better than a -4 penalty, but between ACs of 7 to 15, it's worse!

When I saw that, I just had to do the plot with a bonus. The purple line (the upper diagonal line) represents a d20+4, and the curved dark green line (the upper curved line) is the D&D5 “advantage” roll—where you roll 2d20 and take the higher. It's the opposite of “disadvantage”—you do worse at lower and higher ACs, but better between ACs of 7 and 15.

Wierd!


Discussions about this entry

Obligatory Picture

An abstract representation of where you're coming from]

Obligatory Contact Info

Obligatory Feeds

Obligatory Links

Obligatory Miscellaneous

Obligatory AI Disclaimer

No AI was used in the making of this site, unless otherwise noted.

You have my permission to link freely to any entry here. Go ahead, I won't bite. I promise.

The dates are the permanent links to that day's entries (or entry, if there is only one entry). The titles are the permanent links to that entry only. The format for the links are simple: Start with the base link for this site: https://boston.conman.org/, then add the date you are interested in, say 2000/08/01, so that would make the final URL:

https://boston.conman.org/2000/08/01

You can also specify the entire month by leaving off the day portion. You can even select an arbitrary portion of time.

You may also note subtle shading of the links and that's intentional: the “closer” the link is (relative to the page) the “brighter” it appears. It's an experiment in using color shading to denote the distance a link is from here. If you don't notice it, don't worry; it's not all that important.

It is assumed that every brand name, slogan, corporate name, symbol, design element, et cetera mentioned in these pages is a protected and/or trademarked entity, the sole property of its owner(s), and acknowledgement of this status is implied.

Copyright © 1999-2024 by Sean Conner. All Rights Reserved.