Recently while writing up some situational modifiers for combat and difficulty levels for skills I came up with a bit of a conundrum. Is it better for a modifier to be applied to the skill or to the dice roll?

Here is an example of what I'm talking about.

A character has a skill of 65 with a longsword and receives a +10 modifier for attacking an opponents flank for a total score of 75. The player rolls the dice and gets a 68, so the character scores a hit.

or

A character has a skill of 65 with a longsword and receives a -10 modifier to for attacking an opponents flank. The player rolls the dice and gets a result of 73. We subtract 10 for the modifier for a final result of 63, so the character scores a hit.

I want all modifiers and difficulties to remain consistent throughout the game (i.e. I don't want to mix the two).

Although each method appears to have pros and cons, I'm worried there is something I'm over looking. Any thoughts?

As a matter of cognitive psychology, addition is marginally faster for a lot of folks and feels more faster (if I may use the technical term :) ) than it is. While I don't know of any comparable hard info about the effects of applying modifiers at which step, I strongly suspect that applying modifiers before the roll, so that you end up with total X and roll to see if you get that or not without doing anything further to the roll measuring success or failure, will feel better to players. I personally sometimes feel had with a mechanic where I achieved what would normally be success but which turns into failure after post-roll modifiers get applied, for what it's worth.

Which is better depends upon a lot of things, including the system you are using.

With the one you mentioned in your example, I'd go for modification of the skill - for the reasons Bruce mentioned (though I'd point out that it isn't always addition). In that case, though, they are mathematically equivalent, so that's not an issue.

If you are rolling a die pool vs. a target number, you can get mathy issues. Changing the target number has a different effect than changing the die pool.

Stuart

Keep in mind that perhaps the most attractive change that was made in ADD3E was to change all the modifiers so that + means good, and - means bad. If your system can stand it, always go that way. Again, as Bruce puts it, it seems that for a majority of players that this seems to feel correct, and as such is easier to remember and deal with.

In fact, this was first corrected in D&D design by Rolemaster which also, coincidentally is a "percentile" sort of system. That game solves the problem by having a constant target number. So, you add the +10 to skill to get 75, and then add your roll to get over 100 (actually there are graded results depending on how high you roll, but you get the idea). So not only are high modifiers good and high skills good, but high rolls are good as well. All keeps with that intuitive feel.

Mike

Thanx for the input guys. I thought adding to the skill was a bit more intuitive as well. Something came up that made the other method seem like a viable solution to a problem, but I think in the long run it would cause more problems than it would solve so I'll stick with modifiers affecting the skill rather than the dice roll.

Though it was mentioned that people are generally intuitively faster at addition than subtraction, what about simple multiplication?

The reason I ask is that the combat system includes a damage bonus that depends on the result of the dice roll. Originally I had come up with a chart that could be used to compare a characters skill with what they rolled to determine the damage bonus, but I hated the chart as it is cumbersome and I wanted to eliminate looking things up on charts as much as possible. So I came up with (what I feel is) a simple formula that is applied to the skill (after modifiers if any) to determine what the damage bonus is.

So, the dice roll determines not only "if" you hit, but also "how well" you hit. The damage bonuses are simply multipliers applied to whatever damage is rolled and they range from a 1x multiplier for an average hit, to as much as a 3x multiplier for a solid, well placed hit. A low result on the to hit roll is better and scores more damage. The ranges for damage multipliers increases as a character's skill increases. So a highly skilled swordsman is more likely to hit where it hurts and hit more often than a less skilled person.

The formula works like this...

Skill (or less) = 1x damage multiplier (normal damage)
Skill x 0.4 (or less) = 2x damage multiplier
Skill x 0.1 (or less) = 3x damage multiplier
Always round down.

The 2x damage multiplier range may be difficult for some people to do, so as an alternate formula there is "Skill x 0.1 x 4 (or less) = 2x damage multiplier".

Now maybe you can see why I was considering making modifiers affect the dice roll rather than the skill. By doing so I eliminate the need to apply the formula each time a modifier increases or decreases a skill.

What do you think? Is the formula simple enough, or would it bog things down because its too much math?

As I understand it, most people can deal with multiplication, but it's slower than addition. Way faster than division, tho -- and note that when I say "division" I include multiplying with a decimal. In my experience, dealing with fractions other than 1/2 tend to be considered "more complicated" by most people...

It would seem that your logic is that damage increases proportional to skill? Well, by that logic, wouldn't a bonus to skill make damage increase proportionally as well? To do other than add these together would mean a linear addition to damage.

Ex: If my skill is 50, then I normally have a 20 for x2, and a 5 for x3. If I subtract ten from the roll (as opposed to adding to skill), this essentially changes to 60. 30, 15. As opposed to adding to skill, and recalculating which results in 60, 24, 6. This disparity gets more extreme as the bonus increases. At, say, +30, you are at 80, 50, 35 vs. 80, 32, 8.

BTW, this is the system used in Call of Cthulhu where either five or ten percent of skill rolled under (can't recall exctly) produces an "impale" result for double damage.

The other option is to do the linear thing completely. Thus, you'd do like RM, add the roll, and then caculate damage from the result. Thus, 100 could be a hit for normal damage, a 140 for double, a 180 for triple. This, of course causes problems with limted ranges unless you use an open-ended system.

Another linear option is the Unknowm Armies method where a hit is anything less than your skill, but the higher the roll, the better. Thus, you could have a *3 damage within 5 of stat, a *2 within 20 of stat, and anything lower is x1 (in UA the damage is equal to the actual roll).

I take it that you need a "percentile" sort of system?

Mike

Mike Holmes wrote: It would seem that your logic is that damage increases proportional to skill?

Well, by that logic, wouldn't a bonus to skill make damage increase proportionally as well? To do other than add these together would mean a linear addition to damage.

Ex: If my skill is 50, then I normally have a 20 for x2, and a 5 for x3. If I subtract ten from the roll (as opposed to adding to skill), this essentially changes to 60. 30, 15. As opposed to adding to skill, and recalculating which results in 60, 24, 6. This disparity gets more extreme as the bonus increases. At, say, +30, you are at 80, 50, 35 vs. 80, 32, 8.

BTW, this is the system used in Call of Cthulhu where either five or ten percent of skill rolled under (can't recall exctly) produces an "impale" result for double damage.

The other option is to do the linear thing completely. Thus, you'd do like RM, add the roll, and then caculate damage from the result. Thus, 100 could be a hit for normal damage, a 140 for double, a 180 for triple. This, of course causes problems with limted ranges unless you use an open-ended system.

Another linear option is the Unknowm Armies method where a hit is anything less than your skill, but the higher the roll, the better. Thus, you could have a *3 damage within 5 of stat, a *2 within 20 of stat, and anything lower is x1 (in UA the damage is equal to the actual roll).

I take it that you need a "percentile" sort of system?

Mike

xiombarg wrote: As I understand it, most people can deal with multiplication, but it's slower than addition. Way faster than division, tho -- and note that when I say "division" I include multiplying with a decimal. In my experience, dealing with fractions other than 1/2 tend to be considered "more complicated" by most people...

redcrow wrote:

Mike Holmes wrote: It would seem that your logic is that damage increases proportional to skill?

Yes and no. The potential damage range is independant of skill and always remains static. Skill just determines whether you will hit in the upper portion of that range more often or less often.

I think I understand where you are coming from. However, the damage multipliers are based on the skill not on the dice roll.

The impetus for my game design comes from the fact that I have played dozens of RPG's over the years. Each one had an element or two that I really liked and thought worked well, but each also had many aspects that I thought could be done better. I'm simply trying to combine all the things that I thought were good and worked well into a single system.

What does happen if I have a 25 skill, and 30 points in penalties? Automatic failiure?

My poorly made point was you might want to look at CoC to see how they do it, as it might be informative.

redcrow wrote: Regardless of bonuses or penalties a natural die result of 01 is always a hit and result of 00 is always a miss. So if a penalty reduces your skill to -50, you could still hit by rolling a 01, or conversely if a bonus increased your skill to 150, you could still miss by rolling a 00. In the case of the former, the GM is of course capable of determining that something is simply impossible. In this situation the GM simply needs to inform the player that the attempt is doomed to failure.

Applying the modifiers to the skill rather than the dice roll does seem intuitively better, but what are your thoughts on the formula for determining damage multipliers. Is it simple enough that most people could do it without the need of a calculator?

Mike Holmes wrote: For the 01 auto success, I assume x1 damage? I assume that modifiers would never raise effective skill over 250? Because at that point all rolls would do double damage, except for the failure condition on 00.

redcrow wrote:
I would be interested if you could recommend an RPG that does a good job at simulating a sort of Three Musketeers/Swashbuckler themed combat system. Something that implements feints, parries, ripostes, etc., well?

My setting is sort of a Three Musketeers meet Cthulhu theme, so the swashbuckling style combat is what I'm looking for.

Check out The Riddle of Steel for a combat system that does a great job with cut, thrust, parry, riposte, feint, and more.

And you know, I haven't heard many things about it here, but GURPS combat always at least made sense to me, unlike the combat in many other games (Storyteller, Shadowrun, D&D, etcetera, etcetera, etcetera).

Completely off topic: If the definition of indie around here is "Creator Owned", does GURPS qualify as an indie RPG?

As often happens to me, this thread has appeared and exploded during the day, and I'm thinking I should add to it but am having trouble sorting out my input.

The original question concerned whether to add a bonus to the chance of success or subtract a bonus from a die roll; yes, people would prefer to add than to subtract; I'm not convinced it's that big a deal. Yes, addition feels more like a bonus, but it can work the other way around (particularly if you invert the system, such that high rolls succeed and low rolls fail).

We use percentiles with many different kinds of modifiers in Multiverser; sometimes you subtract from your die roll, and sometimes you add to your chance of success. But because of the fact that the die roll means more than pass/fail, these have different outcomes. If that's not relevant in your case, that wouldn't matter.

Of greater concern, you might consider whether normal play is going to place targets closer to the top or the bottom of the scale. If play is going to involve a lot of probabilities of success that are close to 100%, increasing the probability of success to greater than 100% (theoretically, as a target number) means that the player will feel he has lost the benefit of his advantages, because he can't roll that high; reducing his roll will work better in that regard. At the other extreme, if very low probabilities are the norm, increasing his chance of success will "feel" like it's upped his odds more than decreasing his roll. It's a psychological thing, but very much part of player reactions.

On your damage multipliers, I'm not sure I'm getting it; however, I think the formula works out (allowing for the imperfections of odd outcomes in division) such that all the variance between skilled and unskilled characters is in whether or not they hit at all; damage multipliers are based entirely on their chance of success, and thus scale with that chance of success. That is, ten percent of all hits will do triple damage, regardless of whether they are dealt by experts or novices. The expert does triple damage more often only because he hits more often; the ratio of hits which do this extra damage against those which do normal damage is the same as the novice--always one out of ten hits.

This would seem to go against

what you wrote: So a highly skilled swordsman is more likely to hit where it hurts....

Jason Kottler wrote: And you know, I haven't heard many things about it here, but GURPS combat always at least made sense to me, unlike the combat in many other games (Storyteller, Shadowrun, D&D, etcetera, etcetera, etcetera).

First, let me say thanx to everyone for your input, ideas, and suggestions.

M. J. Young wrote: This would seem to go against

what you wrote: So a highly skilled swordsman is more likely to hit where it hurts....

He is more likely to hit more often, but any given hit has the same average damage characteristics as the completely unskilled character.

Unless I misunderstood?

Multiverser ties damage to the roll directly; it also ties it to the character's skill independent of the roll. The latter aspect is that a character with skill of a professional level automatically doubles damage (actually gets a damage category bonus, which varies in value depending on the base damage category, but is close to doubling in most instances). The former aspect uses the attack roll to determine damage. Because greater chance to hit means you can roll higher and still hit, the character with the greater chance of success not only hits more but averages more damage on a hit.

You could achieve a similar effect with thresholds. For example, set your thresholds at 50 and 80 (Multiverser uses these as thresholds for certain kinds of skills that are not damage-related). If the character rolls a successful roll greater than 50, double his damage; if he rolls a successful roll greater than 80, triple his damage.