Tuesday, March 31, 2009

Converting 3.0/3.5 DC checks to 1E/0E Xin6 rolls

I'm in the middle of converting a Goodman Games Dungeon Crawl Classic for a game as yet to be played, and I ran into this nice set of conversions of some DCCs to 1E.

One of the aspects of 3E that always proves challenging to convert (for me) is the Difficulty Class. I've been learning to wing it with Xin6 chances, per Rient's Rule #1. However, in looking at 3.0/3.5 resources, it seems like almost everything has a DC. Deciding how to adjudicate these can be frustrating because I can occasionally see the utility of making a check, but not the clarity of how to go from DC to something useful in 0E/1E. One of the conversion documents discusses this and included a nice d8 chart:

SRD Difficulty Class Examples Corresponding 1E, Basic D&D, D8 Values, roll within the range to succeed. A natural roll of 1 is always a failure. A natural roll of 8 is always a success.
Very easy 0-4 no die roll.
Easy (5-9) 2-8
Average (10-14) - 3-8
Tough (15-19) 4-8
Challenging (20-24). 5-8
Formidable (25-29), 6-8
Heroic (30-39) 7-8
Nearly impossible (40), 8

Well, this is nice and all, but I roll with the d6, so I had to modify it for d6 usage. There is absolutely no real math in this aside from an eyeballing of the differences between a d6 and d8. I didn't want to put that much time into doing an exact statistical analysis, so if you want to and you have a good correction for me, I'll edit the post and make the change.

SRD Difficulty Class Examples D6 – 1 always fails, 6 always succeeds.
Very easy 0-4 No roll.
Easy (5-9) 2-6 (5 in 6)
Average (10-14) 3-6 (4 in 6)
Tough (15-19) or Challenging (20-24) 4-6 (3 in 6)
Formidable (25-29) or Heroic (30-39) 5-6 (2 in 6)
Nearly impossible (40) 6 (1 in 6)

Apply +1 for favorable conditions/modifiers, -1 for unfavorable conditions/modifiers

Now admittedly, I'm liable to use this only if there's a question in my head. Nine times out of ten, if it's easy or average, I'm going to just say "Yes" and move on. I usually apply DCs only when things are tough, when there's a good chance of failure and an interesting result that could happen on failure. Having this chart in my back pocket, though, allows me to get through some of the conversions quicker and use the DC/dice to retain the feel when it makes sense. Perhaps you could find it useful as well.

Credit must go to the authors of the conversion document: H.J. Martin, Barrataria, G. B. MacKenzie and Rich Franks.

(And BTW, copying/pasting tables out of Word into Blogger and then trying to edit the table is a nightmare. Blogger needs a better table editing mechanism.)


P_Armstrong said...

I don't know why but for some reason when I play OD&D or B/X I just about always default to the x-in-6 mechanic but for AD&D I instead default to a % roll.

Joshua Macy said...

A statistical analysis would be silly; it's not like the original authors set the DCs by any kind of exacting standard and thorough play-testing. In fact, I think a rule that it's automatic unless the chance of success is less than 1/3 is probably better than the original, as well as being more 0e.

Michael S/Chgowiz said...

I think I was just raised on the d6, it feels natural to think about it.

jamused - You're probably right, but I know some people love the statistics of dice and there's probably a good chance I'm mis-representing the odds of DC's. Personally, I'm more apt to really care when there's a consequence to failure. Just to see something or find something, I go back to a negotiation to "Yes." or just tell them if they are doing something appropriate.

John Matthew Stater said...

I don't know how well it jibes with old D&D rules, though. You have a 1 in 6 chance to listen at a door, which in this system translates into hearing anything from the other side of a door being "nearly impossible". The problem may stem from the DC system scaling with character level, and the x in 6 system being static (hence the thief's special skills).

Alex Schroeder said...

I would try without a chart. Skip tests altogether unless both results are interesting in which case you wing it. Otherwise you'll be shuffling through your notes mumbling "just a second I have the number right here somewhere instead if jumping up, raising your hands to the heavens and roaring "You succeed!!!! Aaarrr!!!"

Michael S/Chgowiz said...

Matt - that's very true. I think in this case, I'm choosing to ignore that correlation. I know, that sound funny - but for things that need converted over, this makes an easy "off the cuff" system - and IIRC, listening at doors has a DC in 3E as well, so I guess you could extend across the whole line. I don't know, I was just coming up with something off the cuff... my mental thought process was about 30 seconds from "Huh" to "Hey, this'll work!"

@Alex - this is mainly for the rare occasion I'm going to need a DC check. I'm not really fond of them. This was just for something that someone doing 3E to 0E/1E might find useful, or not. I agree, I'd rather wing it than read charts.