10-23-2017, 02:21 PM | #1 |
Join Date: Apr 2005
Location: San Rafael, CA
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Converting DND 3.5 DC to DFRPG
There is a particular DND 3.5 adventure (Necropolis) I want to run using DFRPG. I would like to avoid having to convert everything ahead of time. I will be winging it on the monsters or using the closest DFRPG analog I can find. However, for traps, locked doors, etc., I wanted to see if there was a way I could convert the DND 3.5 Difficulty Classes ("DC") for these tasks to a (range of) DFRPG difficulty modifiers for the analogous exploit.
The problem is the DC scale is linear, while the DFRPG has a bell curve. Has anyone done such an analysis and arrived at a conversion of DND 3.5 DC to DFRPG difficulty modifiers? Thanks. |
10-23-2017, 03:03 PM | #2 |
Wielder of Smart Pants
Join Date: Aug 2004
Location: Ventura CA
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Re: Converting DND 3.5 DC to DFRPG
The easiest way is probably just compare the Task Difficultly Modifiers to the generic DC table and match similar descriptors. So:
DC 0=Very Easy=+6 or +7 DC 5=Easy=+4 or +5 DC 10=Average=+0 DC 15=Tough=Unfavorable=-1 DC 20= Challenging= Hard=-4 or - 5 DC 25 =Formidable= Very Hard =-6 or - 7 DC 30= Heroic= Dangerous = -8 or -9 DC 40 = Nearly Impossible = Impossible = -10 The difficulty with a more rigorous approach might be to say that to have a 50 % of DC 10 you need skill 0 which would therefore be statistically equivalent to Skill-10, but that means that untrained skills in D&D are better than GURPS defaults by about 40-48%. If instead you assume that default use is equivalent, "Average" difficulty in D&D is actually equivalent to Very Easy to Easy in GURPS, which makes it non-trivial to assess what the equivalent of Skill-10 is. At any rate once you have decided on what Skill-10 is equivalent to you can use that baseline and the fact that each +1 to DC is - 5% chance of success and compare that the Probability of Success table and then subtract 10 to get a modifier. Assuming +0=Skill-10 then: DC 5=75%=~Skill-12=+2 DC 10=50%=Skill-10=+10 DC 15=25%=~Skill-8 = -2 DC 20=5%=~Skill-5 = -5 And then you run into the problem that nothing higher is even possible to roll on 1d20 whereas 3d6 goes down to half a percent. Last edited by sir_pudding; 10-23-2017 at 03:16 PM. |
10-23-2017, 09:13 PM | #3 |
Join Date: Apr 2005
Location: San Rafael, CA
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Re: Converting DND 3.5 DC to DFRPG
Thanks, sir pudding. I like the simplicity of your first suggestion and will give it a try.
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10-23-2017, 10:52 PM | #4 |
Join Date: Mar 2008
Location: Northern Virginia, USA
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Re: Converting DND 3.5 DC to DFRPG
Maybe this is overly simplistic, but I treat a DC 15 task as skill +0, and add +2/-2 to skill for each 5 points above or below that. Easy enough to remember:
DC 5: +4 DC 10: +2 DC 15: 0 DC 20: -2 DC 25: -4 DC 30: -6 DC 35: -8 DC 40: -10 Then I'll add or subtract another +1 for the numbers which are more than 1 DC off from a multiple of 5. So DC 19 and 21 are -2 just like DC 20, but DC 17 and 18 are just -1, and DC 22 and 23 are -3. Note: I haven't played much D&D 3.5, so I can't say if these are exactly right, but the module I converted seems to have a lot of DCs in the 15 to 25 range, and this yields modifiers in the 0 to -4 range, which seems like a reasonable challenge for Dungeon Fantasy characters, who tend to have pretty good ability and skill levels. And it has occasional DCs in the 40 range for tasks that are supposed to be very hard, and a -10 does reflect very hard (but not impossible with high skill) pretty well. So I've been pretty happy with this simple system. |
10-24-2017, 02:08 AM | #5 |
Join Date: Aug 2004
Location: Wellington, NZ
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Re: Converting DND 3.5 DC to DFRPG
Note that a 1st level D&D 3.5 character with a Stat of 10-11 and max ranks (4) in a skill for a total of +4 has a 50% chance of making a DC15 check, and DC15 is what d20 systems tend to think of as a average check. Thus +0 for DC15 is about right - someone with some training an no great talent will have about skill-10 in GURPS.
D&D 3.5 tends to consider an situation that would give a modifier worth a +-2, so where something would give that, give a +-1 in GURPS (masterwork non-combat gear does this,m for example, while 'good' equipment gives a +1 in GURPS). Jumps in DC in D&D usually come in 5-point chunks unless part of some formula, while B343-344 uses 2-point increments for difficulty, so each +5DC would give a -2 penalty (as other posts also suggest). If this doesn't seem to make life hard enough, just go to -3 per step.
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10-24-2017, 11:17 AM | #6 | |
Wielder of Smart Pants
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Location: Ventura CA
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Re: Converting DND 3.5 DC to DFRPG
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10-24-2017, 12:14 PM | #7 | |
Join Date: Apr 2005
Location: San Rafael, CA
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Re: Converting DND 3.5 DC to DFRPG
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10-24-2017, 01:44 PM | #8 | ||
Join Date: Jan 2005
Location: Minneapolis, MN, USA
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Re: Converting DND 3.5 DC to DFRPG
And in GURPS, a difficulty +/-0 task is a typical task for adventurers.
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10-24-2017, 03:32 PM | #9 |
Wielder of Smart Pants
Join Date: Aug 2004
Location: Ventura CA
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Re: Converting DND 3.5 DC to DFRPG
If you are converting adventures meant for low level characters for 250 point delvers having tasks be -1 instead of +0 is probably a feature.
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10-24-2017, 07:19 PM | #10 |
Join Date: Apr 2005
Location: San Rafael, CA
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Re: Converting DND 3.5 DC to DFRPG
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