Heavily modified (logarithmic) damage system for GURPS: feedback wanted!

[Sam Baughn]

Inspired by Douglas Cole's Conditional Injury, but applying the logarithmic concept to every part of the GURPS damage process except recording injury, my system makes resolving damage quicker and easier.

Provisional name is 'Sort-Of Logarithmic Improved Damage System' or SOLIDS.

Features:

• Removes almost all division and multiplication calculations, replacing them with addition and subtraction.
• Reduces amount of dice rolled.
• Much faster resolution of multiple hits.
• Handles extreme values easily.
• Introduces mass-based collision and knockback rules for more accurate 'game physics'.
• Smaller numbers, less counting needed.
• Handles small / weak characters better than default system.
• Crippling and major wound thresholds do not need to be calculated for each character.
• Effects which should scale with HP but don't, like bleeding, handled better.
• Fully compatible with most popular optional rules, including Conditional Injury, Knowing Your Own Strength, and Survivable Guns. Actually makes them easier to implement in many cases.
• Potential for future optional rules to be added, taking advantage of features such as easily adding 'wounding modifier' between pi and pi-, 'armor divisor (1.5)', or more precise crippling thresholds (e.g. legs could easily be made slightly harder to cripple than arms, different injury needed to cripple with different damage types).

Drawbacks:

• Slightly less detail than existing rules, some ST scores no longer offer much difference (mostly fixed by combining with Knowing Your Own Strength).
• Some weapons no longer distinct from each other (notably, .45 ACP, .40S&W, and 10mm Auto usually deal the same damage).
• Adds several new numbers; mostly replacing existing ones, but overall count of things on character sheet goes up by at least one (Mass Class).
• Requires extensive conversion of existing items, replacing all HP, DR, and Damage (including armor divisor) values, and adding Mass Class (but conversion tables and formulas are provided).
• Requires some table look-ups (but progression is usually the same as the S&S/R Table, so it may be possible to make a cheat-sheet which covers all needed ones, and if you have the S&S/R Table memorized, you usually just need to 'shift' it a couple of steps).

At the moment, this is very much a 'first draft' which should be useable as-is, but could do with a lot of editing, proof-reading, and playtesting to bring it up to standard. I'd really appreciate any feedback people here can provide.
Anyway, here's the link (125 kB PDF):
https://drive.google.com/file/d/1rxt...ew?usp=sharing

[Varyon]

I like it, although something seems off. I decided to see what would happen if an unarmored, HP 10 character took a hit from a 2d+2 pi weapon (like a 9mm pistol). That would average around 7 HP Injury in the default rules, but I'm getting an average of 4.67 DP, which is off by around 1 SSR. You currently have a result of 1-2 on the damage roll be equal to 1, then 3 is 2, and it's +1 SSR beyond that; I think having 1 -> 1, 2->2, 3->3, 4->5, and so forth, following SSR, may work better (above, this gives us exactly 7 DP as an average).
(EDIT: Also, I'd suggest a damage result of exactly 0 DP to result in -1 Shock but no Injury, like a Severity -6 Scratch in Conditional Injury)
(EDIT2: Math error - 2d+2 pi should average 9 HP Injury, so the initial results were off by around 2 SSR. When I get some time later I'll run some tests vs an HP 10, unarmored character, to see how far off other damage results are)

Also, I notice it looks like you have opted to use SSR rounded down (so 4 becomes 3), rather than GURPS' normal trend of rounding SSR up (so 4 becomes 5). I think for consistency's sake, maintaining the "round up" trend for SSR would work better.

I'll also want to take a look at how this impacts muscle-powered weapons. The loss of resolution has the potential to have significant impacts there, where differences tend to be around +1 to damage. I do like that this allows Swing to simply be +1 DV compared to Thrust, however, and that things like Weapon Master (which seems like it's basically just +1 DV) no longer have large breakpoints when Striking ST is involved.

[Sam Baughn]

Thanks, Varyon. I tweaked numbers repeatedly as I was writing it, so it's very possible that my assumptions about what damage value equated to what drifted by one or two points as I did. If the issue can be fixed simply by reducing all Toughness Ratings by one or two, that is easily done, at least.

Originally Posted by Varyon

You currently have a result of 1-2 on the damage roll be equal to 1, then 3 is 2, and it's +1 SSR beyond that; I think having 1 -> 1, 2->2, 3->3, 4->5, and so forth, following SSR, may work better...

Remember that the S&S/R Table actually goes 1, 1.5, 2, 3, 5... All I did was round down 1.5 HP loss to 1 (it could easily be rounded up to 2, giving 0, 1, 2, 2, 3, 5... but I prefer 0, 1, 1, 2, 3, 5... for purely aesthetic reasons, because it looks nicer on a graph and mimics the Fibonacci sequence). The rest of the sequence is intact, just shifted a few steps (I could have made it so it matches the S&S/R Table exactly, but I thought 0 equating to 'no damage at all' was more intuitive than setting that result to -3; not sure if being able to just use the S&S/R Table without modification would be useful enough to justify losing that).

Originally Posted by Varyon

Also, I notice it looks like you have opted to use SSR rounded down (so 4 becomes 3), rather than GURPS' normal trend of rounding SSR up (so 4 becomes 5). I think for consistency's sake, maintaining the "round up" trend for SSR would work better.

I used both approaches in different places, because I was concerned that I was creating some dubious break-points. For example, if damage went 3d+1 to 5d: DV 10, 5d+1 to 7d: DV 11, 7d+1 to 10d: DV 12, then rifles doing 5d+1 would be way better than ones doing 5d, and ones doing 7d+1 would be significantly better than those doing 7d, which is a big issue because a couple of really popular rifles sit at exactly those points. Making 7.62x39 about half again as good as 5.56 would lead players to strongly prefer Kalashnikovs to their NATO equivalents, while having .30-06 be 50% deadlier than .308 would be even more jarring.
However, it might be better to just stick to a consistent standard and tweak the results for balance on a case-by-case basis.

[Varyon]

Originally Posted by Sam Baughn

Thanks, Varyon. I tweaked numbers repeatedly as I was writing it, so it's very possible that my assumptions about what damage value equated to what drifted by one or two points as I did. If the issue can be fixed simply by reducing all Toughness Ratings by one or two, that is easily done, at least.

Yeah, it looks like shifting it one slot works - which conveniently works out to HP 10 having TR 10.

Originally Posted by Sam Baughn

Remember that the S&S/R Table actually goes 1, 1.5, 2, 3, 5... All I did was round down 1.5 HP loss to 1 (it could easily be rounded up to 2, giving 0, 1, 2, 2, 3, 5... but I prefer 0, 1, 1, 2, 3, 5... for purely aesthetic reasons, because it looks nicer on a graph and mimics the Fibonacci sequence).

Rounding down to 1 does indeed look better, and meshes with some precedents (Spaceships sets DR 15 as dDR 1, for example). Having run the numbers, rounding up is actually closer to the default injury, but it's not going to break anything for you to round down. Something interesting I found when throwing things into a spreadsheet - at least against a target with HP 10, this system consistently results in average injury that's a bit less than the default (although shifting by 1 step makes it instead markedly more than the default).
(EDIT: That last bit was poorly written. Shifting by 1 step - making characters with HP 10 have TR 10 - still has average wounding less than RAW. Shifting a further 1 step makes average wounding be more than RAW. For the curious, the currently-presented system puts average wounding around 50% of RAW, shifting 1 step - my suggestion of reducing TR by 1 - puts it at around 87% of RAW, and shifting 2 steps puts it at around 135%.)

And, yeah, one issue you can run into when making systems like this is at the breakpoints.

[Anthony]

It has the same problem most of my attempts at revising damage have run into: it's actually a lot of rules.

[RyanW]

Looks a lot like my perpetually WIP system. I'll have to tear into it later.

[ericthered]

Why do you add four to the modified damage value if the armor value is 0? What if the damage value is 2?

[Sam Baughn]

Originally Posted by ericthered

Why do you add four to the modified damage value if the armor value is 0? What if the damage value is 2?

Damage values are four lower than they would be if armour didn't exist.
If DV = AV, then the DR is roughly sufficient to stop an average damage roll in the standard system, but high damage rolls might still get through. I treat this as about 20% of damage getting through.
If DV=AV+1 then in the standard system, DR would stop roughly 2/3 of average damage. I treat this as about 33% of damage getting through.
If DV=AV+2 then in the standard system, DR would stop roughly 1/2 of average damage. I treat this as about 50% of damage getting through.
If DV=AV+3 then in the standard system, DR would stop roughly 1/3 of average damage. I treat this as about 67% of damage getting through.
If DV=AV+4 or better, then less than a quarter of the damage would be stopped by DR. Since that wouldn't be enough to drop most damage into the next step of DV down, I treat this as 100% of damage getting through.

Think of it as actually being -4, -3, -2, -1, or -0 instead of +0, +1, +2, +3, or +4. Because those values are the same, only shifted up by four steps, I can treat them as equivalent by just adjusting some other value by four steps.

Because AV 0 is no armour at all (as opposed to what it 'should' be in a true logarithmic scale, which is about equivalent to one-third of a point of DR) it offers no protection, so the maximum bonus (equivalent to no penalty) always applies.

[Varyon]

Originally Posted by ericthered

Why do you add four to the modified damage value if the armor value is 0? What if the damage value is 2?

Looks like part of an interesting mathematical trick to make armor work easily in a logarithmic system - basically, DV is 4 lower than it should be, but when you add the difference (to a maximum of that 4, which means if average damage is 5xDR or more, the armor doesn't really accomplish anything) between DV and AV back to DV, it gets where it should be, given the effect of the armor. DR 0 should actually be something like AV -∞, given 0 is off the SSR scale, so it automatically results in that +4 maximum.

Arguably, human skin (+ normal clothing) should have somewhere around DR 0.3 or 0.5. for AV 0 (rather than AV -∞) or AV 1. However, handling it that way would result in 1d-5 being unable to harm a typical character - DV 1 vs AV 0 means effective DV 2, TR 10 reduces this to DV -8, and even a maximum damage roll does nothing. 1d-4 is in better shape, but still a bit low - DV 3 vs AV 0 means effective DV 6, TR 10 reduces this to DV 4, so a roll of 5 or 6 results in damage 1 or 2, each of which are -1 to DP (instead of those two being 1 and 2 HP damage, RAW).

[ericthered]

Originally Posted by Varyon

DR 0 should actually be something like AV -∞, given 0 is off the SSR scale, so it automatically results in that +4 maximum.

Ahah! that's it! I wonder if using AV -Infinity wouldn't make more sense.

Arguably, human skin (+ normal clothing) should have somewhere around DR 0.3 or 0.5. for AV 0 (rather than AV -∞) or AV 1. However, handling it that way would result in 1d-5 being unable to harm a typical character - DV 1 vs AV 0 means effective DV 2, TR 10 reduces this to DV -8, and even a maximum damage roll does nothing. 1d-4 is in better shape, but still a bit low - DV 3 vs AV 0 means effective DV 6, TR 10 reduces this to DV 4, so a roll of 5 or 6 results in damage 1 or 2, each of which are -1 to DP (instead of those two being 1 and 2 HP damage, RAW).

I mean, 1d-5 is pretty pointless already. Having human skin at AV 0 isn't terrible. Setting it to -1 might work well.



Since we're already using tables and bumping things numbers up from the Size and Range table, I'm curious if a different bump number isn't desirable.