Converting D&D DC to GURPS Skill penalties - Page 2

kmunoz · 02-08-2008, 09:48 AM

My gaming group, which can't meet as regularly as we'd like, has decided to do a series of one-shots from different systems. But then they decided that they'd rather stay with GURPS rules. So I'm picking up some published adventures from various systems and converting them over to GURPS.

Our first foray will be a D&D 3.5 dungeon crawl. (Dungeon Fantasy 1 & 2 came out just in the nick of time.) I'm not having trouble with the monsters, or any of the seriously crunchy conversion stuff. But I'm completely stumped on how to convert DC (difficulty class) to GURPS skill penalties. I want to do it with some semblance of mathematical accuracy rather than an arbitrary "DC 15 = easy and Skill-0 = easy." Unless that's truly accurate, of course.

It's one thing to talk about probabilities and die rolls... but DCs are open-ended. The die roll is added to skill ranks and attribute bonuses. Which presents a problem: in D&D the die roll is vastly more determinative than it is in GURPS. Say you have skill rank 1 in Open Locks. Before I started working this out I imagined this to be equal to, say, Lockpicking-DX in GURPS. But the average schmoe with Lockpicking willl have Lockpicking-10, the average schmoe with Open Locks will have Open Locks 1.

So I roll 3d6 vs. Lockpicking, and just under 50% of the time I will succeed against a crappy lock (no skill penalty). Same situation in D&D terms: crappy lock, say DC 15. 35% of the time I will succeed (because I only need a 14 or better, so 13 times out of 20 I will fail.)

But a simple DC 15 / GURPS no penalty lock is pretty much the only one that makes sense to me. Let's take it up to DC 25... that's a nice, moderately tough lock. Say skill penalty -6 in GURPS. Same skill rank/level. In GURPS I'd be rolling against Skill-DX-6, which for the average person would be 4. Possible... insanely hard, but possible.

Completely impossible for a D&D character with 1 skill rank. Can't "roll" higher than a 21. Needs at least 4 more skill ranks to make it at all doable. But DC 25 is a *common* difficulty for things like locks... it *assumes* characters will have skill ranks and modifiers totaling above 1.

So here's the question: what does that mean for GURPS? If a DC 25 lock *requires* at least a +5 modifier via ranks & attribute modifiers, what's the best way to translate that requirement over to GURPS skill level penalties? In GURPS terms you'd (grossly generalizing here) want to have enough skill to offset the penalty enough to make it a 50-50 shot (say, Lockpicking-16 or 17, to offset a -6). Should I therefore be looking at matching required skill ranks to required CP cost (to boost the skill to 50-50)?

Am I overthinking this? I'll bet I'm overthinking this.

02-08-2008, 09:48 AM	#1
kmunoz Join Date: May 2006 Location: Seattle, Washington	Converting D&D DC to GURPS Skill penalties My gaming group, which can't meet as regularly as we'd like, has decided to do a series of one-shots from different systems. But then they decided that they'd rather stay with GURPS rules. So I'm picking up some published adventures from various systems and converting them over to GURPS. Our first foray will be a D&D 3.5 dungeon crawl. (Dungeon Fantasy 1 & 2 came out just in the nick of time.) I'm not having trouble with the monsters, or any of the seriously crunchy conversion stuff. But I'm completely stumped on how to convert DC (difficulty class) to GURPS skill penalties. I want to do it with some semblance of mathematical accuracy rather than an arbitrary "DC 15 = easy and Skill-0 = easy." Unless that's truly accurate, of course. It's one thing to talk about probabilities and die rolls... but DCs are open-ended. The die roll is added to skill ranks and attribute bonuses. Which presents a problem: in D&D the die roll is vastly more determinative than it is in GURPS. Say you have skill rank 1 in Open Locks. Before I started working this out I imagined this to be equal to, say, Lockpicking-DX in GURPS. But the average schmoe with Lockpicking willl have Lockpicking-10, the average schmoe with Open Locks will have Open Locks 1. So I roll 3d6 vs. Lockpicking, and just under 50% of the time I will succeed against a crappy lock (no skill penalty). Same situation in D&D terms: crappy lock, say DC 15. 35% of the time I will succeed (because I only need a 14 or better, so 13 times out of 20 I will fail.) But a simple DC 15 / GURPS no penalty lock is pretty much the only one that makes sense to me. Let's take it up to DC 25... that's a nice, moderately tough lock. Say skill penalty -6 in GURPS. Same skill rank/level. In GURPS I'd be rolling against Skill-DX-6, which for the average person would be 4. Possible... insanely hard, but possible. Completely impossible for a D&D character with 1 skill rank. Can't "roll" higher than a 21. Needs at least 4 more skill ranks to make it at all doable. But DC 25 is a common difficulty for things like locks... it assumes characters will have skill ranks and modifiers totaling above 1. So here's the question: what does that mean for GURPS? If a DC 25 lock requires at least a +5 modifier via ranks & attribute modifiers, what's the best way to translate that requirement over to GURPS skill level penalties? In GURPS terms you'd (grossly generalizing here) want to have enough skill to offset the penalty enough to make it a 50-50 shot (say, Lockpicking-16 or 17, to offset a -6). Should I therefore be looking at matching required skill ranks to required CP cost (to boost the skill to 50-50)? Am I overthinking this? I'll bet I'm overthinking this. __________________ Natural Encyclopedia: 660 GURPS bestiary entries It Came from the Forums: A Community Bestiary with 160 entries (last updated 2009...someday I will revisit.)