Cubic ST and Double HP – combined

There’s an interesting thread with some strong opinions being given over on the SJG forums working out the details, pros, and cons of a house rule where you double HP (and DR). ST-based damage would be left alone, in order to restrict the muscle-powered weapon damage to penetration values more in line with firearms.

Given the wound probabilities (really, not necessarily that bad with modern medicine unless certain vital bits are hit – you’re going to be messed up but a fairly low probability of dying) the fix for firearms under this system would be to just give them all an armor divisor of (2).

So the general penetration formula remains the same. Wound modifiers would probably have to stack with hit location (so pi+ to the brain is x1.5 x4 = x6, while the vitals x3 and pi+ would be x4.5, rounded up to x5) in order to make up for the loss in low-grade lethality. Does that mean impaling goes from x2 to x4, and cut from x1.5 to x3? Probably not – those stay the way they are.

So, that’s the theory, and the pros and cons and dos and don’ts are pushing 90 posts, so it’s contentious in many ways.

Double HP and Cubic ST individual concepts

Still, I talked about this before. Rescaling GURPS HP had me musing about the pros and cons of using double the HP score, and its impact on resolution for things like body mass. My parting shot really only noted that the increased resolution that double ST/HP provided was pretty friendly.

However, even right before that, I’d noted that yet another concept, posited by forum user Wavefunction, which was figuring Basic Lift off of the cube of ST, rather than the “quadratic lift” basis of the current Fourth Edition rules (and compared again to the linear ST of the Third Edition and earlier rules).

The “good news” about that was that if you restricted ST to the current equivalent to a ST 20 (Basic Lift 80 lbs), that dropped the Cubic ST equivalent score to ST 16. At that point, you punched at 1d+1 (as much penetration as a .22 LR bullet), and swung for 2d+2 (as much penetration as a 9mm pistol).

Now, one should probably give significant armor multipliers to such blows – at least (0.5) if not (0.33) for fists and such – but at least the upper end didn’t have you swinging for enough penetration to make a 10mm bullet look like a poor trade.

Of course, that’s realism. As I was discussing this sort of thing tangentially with +Christopher R. Rice as I made a Captain America-type superhero at nearly 900 points – the issue with punching folks for a living isn’t that hitting them is more effective than guns. It’s that, in a world of guns, you usually can’t survive closing to fisticuff distance. From that perspective, both bows and fists/feet need the damage boost to make up for the fact that they just suck compared to ye olde .40 S&W. That’s an explicitly genre-balance argument, not a realism one, but nonetheless, the terrain is clear.

Let’s all eat Reese’s Peanut Butter Cups

What I did not do, and probably should have, is combine the two concepts. Ideally, this would give the increased resolution from doubling HP, the matching of ST and body mass for cubic ST and the cubic base of HP. We’ll need to tweak to get the damage scaling, but that’s tractable.

So, here we go. The Big Chart.

This one is scaled in HP, with the assumption that ST = HP, since my original thought was that you’re basically buying body mass, and then can tweak your ST by up to +4 on the upper end, Why that? We’ll get there.

So let’s look at the table for a bit. The green band is the starting HP for GURPS with no adjustment to how HP are calculated from body mass other than doubling. That is, take the cube root of weight (so 125 lbs –> 5) and multiply by 4. Unliving/Machine and Homogenous/Diffuse (p. B557) would thus be x8 and x16 times the cube root of object weight.

The shift to cubic ST means that (as you can see from the table) the 6xBL threshold and the actual object weight scale well, so a ST 50/HP 50 critter should move in the same manner as a ST 5/HP5 creature. That makes it easier to pick ST and HP values for oddball monsters, I think.

This probably means we can use the Size and Speed/Range Table for a comparison of muscle power to mass (ST to HP) and get pretty good “you can launch that object so far” values, which would make it relatively easy to accommodate ST in the jumping formula, as well as velocities and damages for thrown objects and weapons. Good stuff, and rationalizing all of that in one rule is worthwhile.

Anyway, the green band is the same default basis as the current rules, except HP are doubled. Basic Lift is left at 20 lbs.

Now, when looking at the upper end of the scale, what used to be ST 20 (and Basic Lift of 80 lbs), the scaling change means that that value falls to ST 32 on the new scale,with a Basic Lift of 82 lbs.

This means that unlike the range of 10-16 we got with just Cubic ST with no change in HP, players can easily make finer resolution distinctions in ST scores within the normal range. Given that 6-8xBL is probably a good proxy for world-record bench presses, anywhere from ST 34 to ST 36 represents a human maximum. I’ve previously pegged squats as around 1.5x that value, so 9-10xBL works there, and again, dead-lift and squat of around 800-1,000 lbs tags well there. On the “low” end, it’s not crazy-town to have a 160-lb person pressing 240-lbs, so having HP 22 (166 lbs) be as strong as ST 26 (6xBL of 265 lbs) doesn’t strain credibility.
What about bows? Using the Deadly Spring’s pegging of maximum bow draw as about 2.5xBL, and allowing an extra +4 to ST with leveled Strongbow perks and perhaps another +4 for Arm ST with Special Exercises, our HP 22/ST 22 person could wind up with ST 30 for the purposes of drawing a bow – that would be a 68-lb. basic lift, or a draw weight of 170 lbs. That’s a proper adventuring-strength bow! It’s also on the upper end of the Mary Rose reconstructions, which hit as much as about 185#. Mark Stretton, one of the more famous heavyweight longbow guys (but not the only one) masses a lot more than 165 lbs., and he pulls a 200# bow (he may pull more; I’ve seen the video of the 200# one). I’ve seen a much more svelte guy draw back a 170# bow and make it look easy, so I’m not scared of the results here.

Whither Damage?

The big question here is what happens to damage? Well, with the forces in pounds, energy for penetration should probably go as the square root of basic lift. That will scale it on the same trajectory as firearms, with is one of the goals of such projects.

Where do we put 1d, though? I don’t have much of a problem with old ST 14 (with 39 lbs basic lift) having a 1d thrust score. If we assume that stays constant with a BL of 39, that means 1d thrust happens for us at ST 25. If swing gives about double the force of thrust, that’s about 40% more damage.

That’s about +3 per 2d (which is messy), but a +1 or +2 per die is less so. Let’s give it +2 per die, which is still about a 40% reduction in both the absolute value of damage as well as cutting down the scaling quite a bit. So: ST 25 is 1d thrust and 1d+2 swing. Note that if you give thrusts with an appropriately-constructed weapon an AD of (2), this results in the thrust being better able to penetrate armor than the swing.

What about default and maximum ST?

ST 20, our new default, clocks in at 2.5 points of damage, which is exactly 1d-1. That’s actually a one-point boost over ST 10 using the table on p. B16. For swing, it should be about 3.9 points, which is between 1d and 1d+1, so the “2 per die” thing is a bit generous, but not horrible, giving 1d-1 for thrust and 1d+1 for swing.

At the upper end with ST 32, scaling as the square root of Basic Lift, we get 5 points of thrust penetration and about 7.9 points for swing. That’s between 1d+2 and 2d-2 for thrust, and about 2d+1 for swing, which means the 1d+1 would be a better fit for thrust.

That very much reduces the range of damage between average and what’s considered the normal human maximum. That’s going to make things cheaper, since the highest proportion of the cost of ST is Striking ST.

Cost Breakdown

ST is one of the only attributes to break neatly and easily into its component costs. GURPS values striking at 5 pts per level, lifting at 3 points per level, and HP at 2 points each. That means you pay about 10 points per point of thrust damage.
Applying similar scaling to this new scheme, we get:
  • HP are straight-forwardly 1 point per HP. Going from ST 20 to ST 32 should be 12 points.
  • Striking ST thrust damage goes from 2.5 points to 5 points in the new scaling. That should be 25 points if the cost per point of damage stays the same. We’ll assume that it does, since one of the purposes of the re-scale is to lower the ability to deal penetration.
  • Finally, the move from Basic Lift 20 lbs to Basic Lift 80 lbs costs 30 points in the current rules. We can make that same move in Basic Lift cost the same amount. So Lifting ST 20 to Lifting ST 32 costs 30 points.
Total it up, and going from ST/HP 20 to ST/HP 32 should be 12+25+30 = 67 points for 12 ST/HP. We’ll call it 5 points per level, which pleases pentaphilia as well as acknowledging that damage especially isn’t worth what it used to be.

The breakdown is 1 point per HP, 2 points per point of Striking ST, and 2 points per point of Lifting ST. That again works: Lifting goes up faster than it used to so it’s worth more; damage is less valuable because it scales slower and flatter, so it’s worth less.

What about new ST/HP 100? That’s going from ST 20 to ST 100, or +80ST, which will cost 400 points. You’re lifting more than a ton with Basic Lift alone, but your damage is only about 8d thrust, and 8d+16–> 12d+2 swing.

Parting Shot

A lot of the games in which I play lower the cost of ST anyway. 5 points/level or even 7 points/level seems like a common value. The trade-up with the higher resolution but increased scaling for lift provides a bunch of small steps with which to differentiate between characters by virtue of physical power.

The real benefit here, to my mind, is the unification of ST and HP values so that they’re explicitly tied to mass and movement capability. When you can say “if your ST and HP match, you’ll move like a human in terms of acceleration, jumping, climbing, etc.”

There will be things that go wrong, of course. The wound thresholds for when one makes death checks might need adjustment – perhaps halving them on the negative end, or just using the usual breakpoints from the Size and Speed/Range Table.

So instead of every -1xHP something bad happens for your life, it might happen at -HP, -1.5HP, -2xHP, -3xHP, -5xHP. Auto-death would thus be at -3xHP, and unrecoverable mess at -5xHP. Note due to doubling that’s about where they used to be.

Characters will be able to take a lot more gunshots to the torso before expiring. One shot to the generic torso with a 5d rifle will leave you reeling but not in danger of KO or death if you have more than 18 HP. One shot with a generic 7d rifle will threaten an average person, but 25 HP and higher (more than about 240 lbs body weight) and you can take one shot.

To the vitals, those hits turn into 51 HP and 75 HP (more or less) respectively, putting Joe Average to -30 (-1.5xHP) and -55 (more than -2xHP but not -3xHP) respectively. So you’re looking at death checks there.

For pistols, the usual 10 HP  per shot (2d–>7 pts x 1.5 for pi+, or 9pts for 2d+2 pi) means that to the torso, you can soak up two shots and still be reeling but in no danger of immediate loss of consciousness. To the vitals, again, we wind up with about 30 HP per hit, so a shot to the Vitals puts you at one death check. So shot placement matters more in this system, which is to the good.

It’s cheaper to get to maximum Basic Lift for regular humans of 80 lbs. That’s 12 points of additional ST, for 60 points, instead of the 100 pts it costs under RAW. Again, that’s not tragic.

Tying HP and ST more closely together is a thing for me, so that doesn’t bother me. Lacking GM permission or superheroic genre, the “you may increase ST to as much as 4 points higher than your mass-based HP” means you need to be about 350-lbs to hit 80-lbs basic lift, which means you’re probably capable of pressing nearly 500lbs with arms alone, and dead-lifting or moving with your back something like 800-900 lbs. Having the mass of a heavy athlete in order to do feats of strength that heavy athletes do? Win – for me.

An equivalence of HP and weight would make a lot of in-game calculations easier, since you could look at strength-to-weight ratios easily by looking at shifts on the size and speed/range table – it’s logarithmic in nature, so looking at differences in the modifiers on the table means you’re doing ratios. Again, this unifies and simplifies the normally complex.

The down side here is that the ability to do penetration-based damage, with thrust or swing, has been utterly and totally nerfed. If a plate harness has just gone to DR 12 where it used to be DR 6, you’re totally immune to blows of less than 2d. For some, this is the reason for doing all this. For others, such as anyone playing Dungeon Fantasy, it may well be a “and that’s why I’m not ever going to do this. Nope.” death-knell.

Oh, and a word about bows and arrows. The switch to damage as sqrt(lifting) probably means that calculations using The Deadly Spring can be based right off of ST. The ST 16 yew longbow (128 lbs draw) does 1d+1 “realistic” damage. That requires a Basic Lift of 51 lbs, which is ST 28 on the new, revised scale. Thrust damage there is 4.1 points, or between 1d and 1d+1. Cinematic damage for this bow was 1d+3. So if a longbow did thr+1 in a realistic campaign or thr+3 in a cinematic one, that would probably simplify things quite a bit.

Crossbows? Heh. The medieval crossbow from The Deadly Spring requires a Basic Lift of 90-95 lbs to span by hand. That’s ST 33 in the new system, for thrust of 1d+2. However, the actual damage of this crossbow is 1d-1, because even though it’s got a draw strength of 740 pounds, the efficiency with which it launches the bolt is low. So crossbows do thr-3 (2) imp damage on the realistic scale, and thr-1 (2) imp for a cinematic one. That two-point differential seems to hold for both types of launcher.

So for bows, you no longer need math – just the table and a ST lookup – to get either realistic or cinematic bow penetration. Injury – which can be quite severe – will be taken care of with the stacking of x2 for imp with x3 for vitals – an arrow to the heart for 1d+1 is no joke, turning into 6d+6 injury, for 27 HP on the average, enough to force KO checks immediately and depending on how harsh one is for bleeding, death by blood loss soon after.

Again – I’m sure there are issue here, but by math alone, it’s not fatally flawed. I’d definitely be interested in seeing this in play for a few sessions.

5 thoughts on “Cubic ST and Double HP – combined

  1. Interesting analysis!

    I'd go for it … cubic ST, double HP – but would skip doubling DR, mostly because that turns armored combat into "lets dance about aiming for the joints/eye slits and missing until someone gets lucky."

    If you're going to do that, might as well play D&D (armor makes you harder to hit). Same result at the human level, but faster play…

    1. The double HP, double DR – often adding your (2) AD to guns instead of increasing their inherent lethality – came about to keep the relationship between penetration the same for firearms, which are the most tractable in GURPS. It also, obviously, has the side-effect of having 1mm of RHA armor be about DR 5.5 instead of 2.75, which increases the resolution of such things, if that's desirable. The real axe that people want to grind here is the scaling of ST-based damage with respect to guns, since swing damage gets very, very high at the upper end of human-normal ST.

      DR in GURPS doesn't serve the design goal for some, which is "complete protection." It's wound mitigation, a la D&D in a way, where armor is supposed to (and does) provide some life insurance, but isn't designed to turn PCs into invulnerable tanks.

      Some thing armor doesn't protect enough (that's where the Edge Protection rule crept into Low-Tech) against cutting weapons especially.

      In any case, you may be right, that since I've nerfed damage pretty hard in order to bring it on the same scaling (sqrt KE) as bullets, you no longer need the doubling of HP or DR, or maybe double HP but not DR, etc. Might need more substantial wound effects for being smacked with a sword, though.

      That's the other way to go for some of this stuff – lower penetration numbers, but higher injury multipliers. Getting thwacked with a big-ass sword is going to hurt.

    2. I'm wondering how games will actually play when party members are invulnerable to a majority of edged weapons (as well as bites, claws, etc.) and are fighting normal opponents (not ST 18 dungeon fantasy supermen or whatever) with ST 11-13.

      Can the fight be resolved in a reasonable amount of time on a 1-second GURPS scale without excessive complexity? Do the GURPS hit location penalties to bypass armor (which are pretty severe, often -7 to -10) work? Does the melee risk degenerating into alternative series of All Out Attacks for the eye slits, in which you either hit and kill with single shots, or miss?

      Does grappling become the major weapon? Does increasing armor protection plus the GURPS rules end up successfully enforcing combat behavior on the part of PCs and NPCs that reflects the way that soldiers in heavy armor (e.g., men at arms on the line in, say, the Wars of the Roses) actually fought one another?

      To determine this, can you recommend any good accounts (contemporary or based on recreations by modern fighters) of what fights are like between warriors who are fully-armored (in medieval plate and mail) in terms of actual casualty production and how the fight was terminated? There are certainly a lot of videos showing armored combat from various modern fighting associations, but given the assumption that a "hit" will not, in nearly all cases, penetrate the armor, how valid are these going to be? The basic question is "how did they achieve an incapacitate or kill result? and what tactics were used to do that?" I'm sure the data is out there; I'm just not familiar with it.

      But before making a judgement I'd like to see a bit of reality checking and comparing how the rules match with simulating that reality in a fashion that makes for an interesting combat sequence.

    3. Well, thrust damage for ST 11-13 (now ST 20-24 in my rescale above) is 1d-1 to 1d. Thrust damage for ST 20-14 is 1d-1 to 1d (just shy of 1d). So from that perspective, a +2 per die increase for swing and a (2) for impaling/thrust weapons, you get basically 1d-1 (2) imp to 1d(2) for thrusting weapons (punching through DR 5-7, which used to be 2.5-3.5, or about 1mm of RHA steel) and 1d+1 or 1d+2 for swung weapons for DR 3.5-5.5 (formerly 1.75 to 2.75, or 2/3 – 1mm RHA).

      So you'll be better protected if you assume that mail is DR 6-8 – average people can't punch through armor to take advantage of wound channel modifiers (which probably need to go up).

      So that will mean grappling, takedowns, and finishing with a knife or a braced AoA type blow. Seems legit from what I know.

      Swung impaling weapons like picks, though, will likely do 1d+2 (2) in that range, which will threaten DR 11 (old DR 5.5). So 2mm of steel is the threshold for protection here, more or less. Maybe more if it's lower grade metal at DR 2/mm instead of 2.75.

      The hit location question is a good one. The requirement to pile on many bonuses to offset location penalties is realistic but an impediment to fun in many cases.

      I think a good place to start for me for "how did they really fight" are places like Talhoffer, Silver, Fiore, and the manuals they published. You see an awful lot of "hit him with the handle of the sword," "grapple the arm while you stab the neck," and "secure a hold, and take him down" in there, plus the usual "strike him in the vulnerable spots" illustrations.

    4. Thanks for the analysis. My impression is that men at arms on foot in the 15th century battlefield fought with heavy weapons (halberd, pole axe, pick, etc.) plus the sword as needed, so I suppose the pick effect is workable.

      I've never been entirely convinced about the size of the penalties for GURPS to hit the face or head. It doesn't seem to fit the logic of the Speed/Range + Size modifier table as far as I can see, and it certainly looks (from watching boxing and martial arts) that fighters often take more head shots than they do shots for the center torso… But it's not my area of expertise.

      A few years ago I dig give the medieval manuals a go. I think most of them were more concerned with duels and street fights in less than full armor, from what I recall, but with some armor-busting techniques like half-swording for extra power.

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