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Combat: PC rolling only


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#1 kreider204

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Posted 23 March 2014 - 08:14 PM

Okay, first of all, please don't interpret anything that follows as a criticism of BRP. I don't want to ruffle anyone's feathers ... Also, please stick to answering my question rather than telling me why I shouldn't ask it - that's one of my least favorite things on the Interwebz ... I'm just interested in trying something out, and would be interested in any suggestions, but I'm not really looking for approval or permission. ;)

More and more, I'm really like systems where PCs do all the rolling in combat. For example, in ICONS, attacking PCs make a roll vs. an NPC's defense rating, and defending PCs make a roll vs. an NPC's attacking rating. The Ubiquity system can essentially do the same thing, as long as you "take the average" for the NPCs' attack and defense rolls. I like this because it gives the PCs more to do and me, as GM, less to do. :)

I was wondering about something similar for BRP: I'd like my players to do all the rolling in combat. To that end, I was thinking of stat-ing NPCs in such a way that their defense skills are just negative modifiers to the PCs' attack rolls, and that their attack skills are just negative modifiers to the PC's defensive rolls. There's already some precedent to this in the BGB in the form of the defense skill, so it's not much of a stretch.

So, if I go this way, I need to think about what values to assign, perhaps in terms of how I would convert NPCs in published adventures. I was thinking 1/5. For example, if an NPC had a 50% Dodge skill, that would translate as a -10% penalty to the PC's attack roll; if the NPC had a 50% attack skill, that would translate to a -10% to the PC's defense roll.

Thoughts about that? Again, not if you agree or disagree philosophically; just whether the math seems reasonable, IF I decide to give this a try ...

Thanks in advance!

Edited by kreider204, 23 March 2014 - 11:08 PM.


#2 bturner

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Posted 23 March 2014 - 09:37 PM

Duplicating the actual odds of an attack-and-parry combo in BRP this way involves a bit of math, and isn't going to be a static effect. The actual chance of a strike occurring for some attack chance A% and parry chance P% is A% * ( 1 - P%). In the specific case of a PC with a 50% attack skill and an NPC with 50% parry, the effective penalty the PC suffers is -25%. If the PC's attack skill is higher (say, 70%) the effective penalty is higher at -42%.

So the first truth of this mod is that the results won't exactly match BRP results no matter what. However, the simplicity of having only PC's roll is still attractive. I think you will need to impose larger penalties if NPC's are going to represent a similar threat level to the PC's as they do under the unmodified rules. I recommend identifying a "baseline" PC skill level, a level that represents a reasonable skill level for a competent PC, and then using that and the equation above to determine the penalty levels for specific NPC skill levels.

Working from this plan, if the baseline PC skill level is 50% then the penalty value associated with an NPC is half of their skill.

Regards!

#3 kreider204

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Posted 23 March 2014 - 11:07 PM

That's great feedback, thank you! Ya, I'm okay with it not being an exact conversion, and just using some judgment and discretion. This gives me plenty to think about. Thanks again!

#4 bturner

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Posted 24 March 2014 - 01:16 AM

Hey, not a problem. Keep us all informed on what you decide, and how the conversion works out in actual play!

#5 Atgxtg

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Posted 24 March 2014 - 05:34 PM

I'm a fan of the old SAGA system that TSR used for Marvel and Dragonlance, and think it's a good way to go, but somewhat problematic to apply in BRP.

One approach you might want to try is to "zero out" the average opposition. In other words, when the PCs are fighting against typical foes, they don't have to subtract anything. That way, most of the time you can just go with straight rolls.

The subtract from method has some difficulties. For instance if the opponent skill rating is very high then the players skills are going to drop close to zero at some point. So you will need to figure out what you want to do in those cases. Plus the subtraction will reduce the PCs chances of critical, and special, while increasing their chances of fumbling- while the NPCs will be immune. So you might want to change the critical and special rules for your method, to make them independant of the opponent modifier.

What you might want to do is use the Resistance Table. It's actually a perfect way to do just what you want to do without over complicating things. What it does, is set it up so that if the skills are equal the PC has a 50% chance of success, and then adjusts from there based on relative skill scores. Which is pretty much what you are going to want for a method like your.
Smiley when you say that. :P

#6 kreider204

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Posted 24 March 2014 - 10:41 PM

Ah, the resistance table! Now that's very interesting. I'd have to figure out what counts as special and critical successes, but that wouldn't be too hard. Hmm, I might have to start working on that ... Thanks!

EDIT: Hmm, now I'm thinking about something like the Marvel FASERIP Universal Table. Columns for the difference between the active and passive skill, rounded off to 5%s - so the middle column would be 0% (for equal skills), then to the right +1-5%, +6-10%, etc., and to the left -1-5%, -6-10% etc., up to say +100% and -100% respectively. The Rows would be for the dice results. You'd roll, look up the result in the appropriate row, then read over to the appropriate column. The resulting cell would be color coded for fumble, failure, success, special success, and critical success. Now I just need to figure out the math ...

Edited by kreider204, 24 March 2014 - 11:06 PM.


#7 bturner

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Posted 25 March 2014 - 12:28 AM

IIRC, Pendragon moved from percentile skills to a 1-20 scale. The simplest way to apply the resistance table plan would be to divide all skills by 5 and use the result as if they were attributes. This will mean that a 10-point superiority will mean basically automatic success - but that's not going to work out too differently in the standard rules (e.g., 25% skill vs. 75% skill).

#8 Atgxtg

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Posted 25 March 2014 - 02:24 PM

Ah, the resistance table! Now that's very interesting. I'd have to figure out what counts as special and critical successes, but that wouldn't be too hard. Hmm, I might have to start working on that ... Thanks!


What you could do is to separate rolling low from the critical and special and instead use the ones die. Any successful result that ends in a 0 or 5 is a special success. Any successful result that ends in odd doubles ("11", "33", "55", "77") is a crtical. This will give you percentages close to the core rules, and is easy to figure out during play.


EDIT: Hmm, now I'm thinking about something like the Marvel FASERIP Universal Table. Columns for the difference between the active and passive skill, rounded off to 5%s - so the middle column would be 0% (for equal skills), then to the right +1-5%, +6-10%, etc., and to the left -1-5%, -6-10% etc., up to say +100% and -100% respectively. The Rows would be for the dice results. You'd roll, look up the result in the appropriate row, then read over to the appropriate column. The resulting cell would be color coded for fumble, failure, success, special success, and critical success. Now I just need to figure out the math ...


I think it is easier just to take the special success chance for the skill (i.e. skill divided by 5) and cross reference that up on the standard resistance table. No need to get too fancy.

Or, if you don't mind dropping percentile dice, you could go with btuner's idea of D20+rating (on a 1-20 scale).
If you did do that, you could drop specials and critical and instead tie the results directly to the difference between the target number and the roll. So if the player wins by 5 he does 5 damage, and so on.
Smiley when you say that. :P

#9 fmitchell

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Posted 26 March 2014 - 12:07 AM

Most of the "PC rolls only" systems I know of use roll-over dice conventions: players roll dice, add modifiers based on their own abilities and assets, and try to match or exceed a Difficulty Number set by the GM. If you're willing to re-work all skills as bonuses on a percentile (or d20?) roll, that may be the way to go. You'd have to distinguish +0% from "no skill", re-think difficulty numbers for normally un-opposed rolls, and re-define experience rolls (e.g. skill + die < 100%).

The most BRP-ish system I can think of would use an extremely coarse-grained system: to hit or parry "average" foes require only a normal success, while more challenging foes may require a "special" or even "critical" success just to hit. One could also use the Easy - Average - Hard modifiers from BRP (double or half skill), or the bonus/penalty die from COC7 (roll two "tens" dice, and pick the higher or lower depending on whether the player has a penalty or bonus to his action).

None of this will yield the same probabilities as the old two-dice system, and I doubt they'd even be close. But I think these options play faster at the table and/or follow the "BRP Way".
Frank
"A hidden corridor! Fortunately it was labeled!" -- Sadie Doyle, "Beyond Belief: Sarcophagus Now", The Thrilling Adventure Hour

#10 Atgxtg

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Posted 26 March 2014 - 12:25 PM

That's pretty much what RoleMaster did. Skill rating were added to the roll and the result compared to a target number. 100 was the default target number, since that way a characters skill rating was their normal chance of success. RM also used "open-ended" rolls, where resultsd of 96+ got to roll again and add to the total, thus allow characters a chance to pull off very difficult things.

To adopt that in BPR the GM would simply need to add 100% to the opponent's skill to get the Target Number. The drawback is that the math is a bit slower.
Smiley when you say that. :P

#11 fmitchell

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Posted 26 March 2014 - 09:42 PM

To adopt that in BPR the GM would simply need to add 100% to the opponent's skill to get the Target Number. The drawback is that the math is a bit slower.


Not so much if target numbers are multiples of 10.

d20 can manage a Players Roll All The Dice variant because only the "active" party rolls a single d20 in every situation. BRP isn't that simple: not only bigger numbers but opposed die rolls that make odds calculations nonlinear.

If you really want PCs to roll all dice without having to rewrite and rescale large parts of the system, the only reasonable way I see is to modify PC skills either as straight percentiles or as multiples of the PCs skill.

My preferred way to handle things, which is mathematically equivalent to Rolemaster and several other methods above, is that NPC stats list a penalty (or bonus) that adjusts the player's effective skill (including critical successes, etc.). E.g. If Skarl meets an NPC shopkeeper with Fast Talk -20%, his Fast Talk 48% becomes 28%. The same shopkeeper might have Intimidation +30%, so Intimidation 24% turns into Intimidation 54%. If the GM wants to keep these factors secret, players call out their skill and their roll and the GM applies modifiers. As I said above, it's easiest to work with difficulties that are multiples of 10, and +/-0% would be the most common value. Penalties/bonuses should stay above -50% except in extraordinary circumstances, e.g. dragons or demigods. Anything above +50% might as well be an automatic success unless the player is really incompetent. (I still prefer a difficulty ladder using skill multipliers, but without a lookup table the extra calculations consume more brainpower than single-digit addition and subtraction.)

Ultimately what we all like about BRP is its simple and fast resolution mechanics, so more complicated procedures will make many players long for another system.

Edited by fmitchell, 26 March 2014 - 10:14 PM.
reorganized

Frank
"A hidden corridor! Fortunately it was labeled!" -- Sadie Doyle, "Beyond Belief: Sarcophagus Now", The Thrilling Adventure Hour

#12 kreider204

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Posted 26 March 2014 - 10:54 PM

Wow, this is a really great discussion, and it's giving me a lot of insight to the way the rules work. Lots to think about here, thanks!

#13 Atgxtg

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Posted 27 March 2014 - 01:44 PM

Wow, this is a really great discussion, and it's giving me a lot of insight to the way the rules work. Lots to think about here, thanks!



With something like this is boils down to two things. The first is what your objectives are, and the second is what the existing game mechanics are suited towards. Each game system has things it's good at and things that it is poor at. Unfortunately, BRP is poor and lacks the "beat the difficulty" game mechanic that your idea sorta needs to work. With most other RPGs it's much easier- you just assume that the opposition rolled the average result and use the opposed roll rules. But that doesn't work in BRP since everyone is rolling under their skill, and they don;t generate a total.
Smiley when you say that. :P




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