IT:DR (Armored Flesh)

[lexington]

Ah, just skipped the later parts to be honest. Sorry.

I still think "round down" is insufficient to represent the way a mass of hard material behaves. I can't do any damage to a block of steel with my fists, okay that's solved by rounding down fair enough, but a one meter cube would probably ignore a rifle bullet too. That requires IT:DR 18 in order to work.

If we're trying to get behavior kind of like GURPS RAW then a one meter steel cube can withstand an APFSDSDU round without taking any damage. IT:DR 1387 (round down) strikes me as a strange way to represent that resilience. A weapon twice as powerful (four times the energy) would then do one or two points of damage. Little Boy (the bomb that destroyed Hiroshima) wouldn't even reduce it to 0HP, barely a noticeable amount of damage. Remember, objects in 4e get to survive down to -HP just like characters.

(Yes I have a bad habit of editing after I post, so, uh, yeah.)

[Varyon]

Originally Posted by lexington

Ah, just skipped the later parts to be honest. Sorry.

No problem.

Originally Posted by lexington

I still think "round down" is insufficient to represent the way a mass of hard material behaves. I can't do any damage to a block of steel with my fists, okay that's solved by rounding down fair enough, but a one meter cube would probably ignore a rifle bullet too. That requires IT:DR 18 in order to work.

Fortunately, we have IT:DR 54, meaning we'll ignore (on average) up to 15 dice of damage. The problem with round down is on the other end - an arbitrarily thin metal plate ignores up to 15 dice of damage, and we know this isn't true (otherwise armor would be far more effective). We can get away from this if we start by getting rid of "round down," then use the previously-linked houserules, which prevents any damage from occurring with very large chunks of steel being struck by weak attacks, while still allowing for those same attacks to break through very small bits of steel.

Originally Posted by lexington

If we're trying to get behavior kind of like GURPS RAW then a one meter steel cube can withstand an APFSDSDU round without taking any damage. IT:DR 1387 (round down) strikes me as a strange way to represent that resilience.

RHA steel should only always have IT:DR 54 or so. A 1 meter cube of steel would give 2756 DR. How much damage is that APFSDSDU round doing? Even if doesn't punch all the way through, I'd imagine something like that to at least cause some damage to the cube.

[Otaku]

Varyon, I am not seeing the problem with the normal rules. As I read your responses, it seems like you can't get the rules to model what you are looking for... because you're expressly avoiding the rules that you need to be using.

HP and DR are abstractions and you need to to model what is happening as closely as possible the RAW before turning to something homebrewed; you're getting "weird" results because you aren't modeling what is; a block of steel is not "steel HP" wrapped in "steel armor"; the DR of a block of steel represents the difficulty of damaging the steel itself. If you put more than a superficial scratch, dent, or ding into the steel you should be dropping its HP. If we had a block of fleshlike material, there is no DR. If a being is composed of fleshlike material (but not that of a standard biology) so that a pin still pricks him but an arrow doesn't appear to penetrate too far or cause him serious injury, it means he's got an incredible amount of HP.

At least, I thought it did. >.>

[naloth]

Originally Posted by Otaku

<snip>
If you put more than a superficial scratch, dent, or ding into the steel you should be dropping its HP. If we had a block of fleshlike material, there is no DR. If a being is composed of fleshlike material (but not that of a standard biology) so that a pin still pricks him but an arrow doesn't appear to penetrate too far or cause him serious injury, it means he's got an incredible amount of HP.

That's fine, but HP and DR also represent other things. HP usually assumes a certain amount of mass (and is therefore used in slams and collisions) and determines how fast you're killed/broken in any meaningful way.

DR gives you a shell of protection - often an eggshell syndrome at high TLs where you have lots of DR and any attack that can reasonably penetrate hundreds/thousands of DR by a few percentage points will completely wipe away a dozen or two HP in a single hit.

Last, if you're using point values IT:DR scales (much like SuperST was introduced to scale ST) where DR doesn't. Using straight DR just gives you absurdly high point values that doesn't accurately represent it's usefulness.

[Varyon]

Originally Posted by Otaku

Varyon, I am not seeing the problem with the normal rules. As I read your responses, it seems like you can't get the rules to model what you are looking for... because you're expressly avoiding the rules that you need to be using.

HP and DR are abstractions and you need to to model what is happening as closely as possible the RAW before turning to something homebrewed; you're getting "weird" results because you aren't modeling what is; a block of steel is not "steel HP" wrapped in "steel armor"; the DR of a block of steel represents the difficulty of damaging the steel itself. If you put more than a superficial scratch, dent, or ding into the steel you should be dropping its HP.

The problem I'm seeing is that, particularly for large chunks of steel, you have a large range of damage where you are doing nothing more than superficial scratches, followed by a very narrow range of damage where you are actually causing physical damage to the steel. That looks and feels like "'steel HP' wrapped in 'steel armor,'" which I don't think should be the case.

Let's scale down my old example to a one-inch cube, which gives cover DR of 70. What would the stats of this cube be by GURPS RAW? HP is easy enough - it's eight times the cube root of the cube's weight in lb (a 1 inch cube weighs 0.28 lb, for HP=5). As a homogenous object, we know only 1/4 of this value is used for cover, so it's just 1. This means the additional DR 69 must be possessed by the cube itself. I don't think GURPS ever outright states if natural DR is assessed twice or only once for determining how much cover something gives, so we'll calculate doing both. Let's shoot this chunk of metal with a pi bullet.

We'll start assuming DR 34.5, assessed twice. Up to 10d, our bullet simply bounces off, causing nothing more than a cosmetic scratch. At 11d, the bullet punches into the cube (3.5 damage, for 1 injury) but can't get through. At 12d it gets a little further (5 damage - the blowthrough limit), but doesn't really cause any more damage (still 1 injury). At 13d-19d, it doesn't get any further whatsoever. Finally, at 20d, it just barely punches through (without enough energy remaining to cause damage), and after this it punches through reliably.
If we ignore the blowthrough cap, then starting at 11d the cube continuously takes damage. At 20d, it takes 35 damage, for 11 injury (pi is 1/3 for homogenous, right?), meaning it risks destruction at this point.

Next we'll look at DR 69, assessed once. Up to 19d, nothing happens. At 20d, the bullet just barely punches through (1 damage, for 1 injury). After this, it punches through reliably.

Now, let's give IT:DR 54 a shot, using lwcamp's injury houserules (and allowing for fractional damage, which is unfortunately necessary here on account of such a small chunk of matter). Up through 4d, we again see no damage (less than 1/16 HP). At 5d, we have .32 damage - a Scratch (bullet managed to make a dent). This is still the case from 6d to 9d, but at 10d we upgrade to a Minor Wound (got a bit further). We hit the blowthrough limit (1.25) at 20d, just as we blow through (for what is still a Minor Wound). So, we end up with a bit more natural of a stepwise progression.
I should note here that the injury houserules are pretty much mandatory, as otherwise this chunk of steel is either extremely vulnerable (taking 1 point per hit without Round Down) or extremely resilient (requiring 16d to actually take any damage with Round Down).


EDIT: We can get an even smoother progression if we extend out lwcamp's injury rule to allow for single hits to give multiple "wounds." That is, you could have a single hit function as multiple Scratches if it's closer to the middle of the Scratch range. So, injury up to 1/8 (=10/80) HP is normally a Scratch - now we'll say this is 5 Scratches. Injury up to 9/80 HP is 4 Scratches, 8/80 is 3 Scratches, 7/80 is 2 Scratches, and 6/80 (but more than 5/80=1/16) is 1 Scratch.
Obviously, using such rules in play requires having a chart for the character to determine each "injury threshold," but that's a good idea in general with lwcamp's house rule.

[lexington]

Originally Posted by Varyon

Next we'll look at DR 69, assessed once. Up to 19d, nothing happens. At 20d, the bullet just barely punches through (1 damage, for 1 injury). After this, it punches through reliably.

So? I don't see what the problem is with this. That kind of transition happens with all kinds of things.

A weak person cannot lift 100 pounds.
A moderately strong person struggles to lift 100 pounds.
A very strong person can easily lift 100 pounds.

A weak bullet cannot do any damage.
A more powerful bullet struggles to do damage.
A very powerful bullet easily does damage.

Originally Posted by Varyon

Now, let's give IT:DR 54 a shot, using lwcamp's injury houserules (and allowing for fractional damage, which is unfortunately necessary here on account of such a small chunk of matter). Up through 4d, we again see no damage (less than 1/16 HP). At 5d, we have .32 damage - a Scratch (bullet managed to make a dent). This is still the case from 6d to 9d, but at 10d we upgrade to a Minor Wound (got a bit further). We hit the blowthrough limit (1.25) at 20d, just as we blow through (for what is still a Minor Wound). So, we end up with a bit more natural of a stepwise progression.
I should note here that the injury houserules are pretty much mandatory, as otherwise this chunk of steel is either extremely vulnerable (taking 1 point per hit without Round Down) or extremely resilient (requiring 16d to actually take any damage with Round Down).

I'm not sure I see how this addresses the problem of crazy results, a one inch steel cube is a relatively poor test case for this. For a 1 inch thick steel wall a scratch requires (60/16)*54=202 basic damage (67d) under your system. I suspect Luke's rules are meant for people and things with generally less than 20HP.

[gjc8]

You appear to be DRAMATICALLY misunderstanding the way GURPS DR is assigned to objects. The one-inch steel cube does not have DR 69. The one-meter block does not get the benefit of DR 2520 for itself. Not even close. You can't back-calculate from the simple, approximate cover DR equation. The primary source of resilience for large homogeneous chunks of stuff is their HP. They have some DR, but drastically less you seem to be assuming.

You're operating from a drastically incorrect baseline, and it seems to me that the results your getting are making objects absurdly resilient. 6dx3 is a pound and half of TNT; 6dx100 is 2500 pounds of TNT, more than a ton.

[Otaku]

Originally Posted by naloth

That's fine, but HP and DR also represent other things. HP usually assumes a certain amount of mass (and is therefore used in slams and collisions) and determines how fast you're killed/broken in any meaningful way.

Yes... but you said it yourself: usually. GURPS injury/damage rules are built first and foremost for people. Sometimes armored people, but people. Not vehicles, not golems/supers made of a homogenous substance and thus lacking blood, vital organs, etc. They try to be as generic and universal as possible... but there is only so much you can do and as good as they are those writing the books aren't perfect.

The important thing to remember is that these are ultimately abstracts because legitimately calculating how much energy is being exerted by a guy swinging a sword at you, exactly where he should hit, and exactly how the energy will transfer from the blade to your armor (if being worn) and flesh (or whatever constitutes you) is complicated... even before we consider that your body isn't homogenous.

It also sounds like the relationship here is being inverted; a certain mass usually indicates a certain amount of HP; as a complete abstraction, HP scores are assigned based on reality checking (when applicable) or creator intent (with regards to function in the setting) when that isn't an option.

Originally Posted by naloth

DR gives you a shell of protection - often an eggshell syndrome at high TLs where you have lots of DR and any attack that can reasonably penetrate hundreds/thousands of DR by a few percentage points will completely wipe away a dozen or two HP in a single hit.

Damage Resistance reduces the damage done to a target... that is all that is safe to assume. Generic and Universal, remember? Sometimes it is a literal shell, other times a force field around the subject... but it could also be something unidirectional. Its questionable usage at higher TLs is irrelevant to the discussion... and I am longwinded enough as is without giving me extra material. ;-)

Originally Posted by naloth

Last, if you're using point values IT:DR scales (much like SuperST was introduced to scale ST) where DR doesn't. Using straight DR just gives you absurdly high point values that doesn't accurately represent it's usefulness.

I am not familiar with the "Super ST" rules... but if we are trying to accurately reflect reality, that doesn't matter, does it? Reality isn't always point optimized, and if something realistic isn't cost effective, it means the cost assessed is wrong and not the mechanics to which that point cost is assessed.

For example, Extra Hit Points cost 5 points per level under the 3e rules. They didn't prove worth that, so in 4e they now only cost 2 points per level (I think-no book handy). It made a lot more sense to do that than to come up with some new mechanic that was priced more fairly.

[lexington]

Originally Posted by gjc8

You appear to be DRAMATICALLY misunderstanding the way GURPS DR is assigned to objects. The one-inch steel cube does not have DR 69. The one-meter block does not get the benefit of DR 2520 for itself. Not even close. You can't back-calculate from the simple, approximate cover DR equation. The primary source of resilience for large homogeneous chunks of stuff is their HP. They have some DR, but drastically less you seem to be assuming.

No, he's right about the DR of metal objects. A one inch steel cube is probably sufficiently outside the intent of the rules that absurd results will come out but calculating the DR and HP of a large block of steel is easy.

We know that a 1 inch plate of steel covering ten square feet (that's one meter on each side) gets DR56 and HP60. When you double the thickness DR doubles. When you halve the thickness DR goes down by half (this is true down to 1/8" so it seems to be the canonical progression). HP has a canonical progression based on mass which is easy to get.

A one meter cube would then get DR2205 and HP202. The vast majority of its durability is represented by DR.

I think the issue is that "fails to penetrate DR" does not mean "bounces off" it just means "does not threaten the structural integrity of the object".

[gjc8]

Originally Posted by lexington

I think the issue is that "fails to penetrate DR" does not mean "bounces off" it just means "does not threaten the structural integrity of the object".

But what does "not threaten the structural integrity of the object" mean in the context of, eg, explosions? Or, really, anything but piercing/impaling. I agree that you could fire bullets into a block of iron all day without have a serious impact, but the issues GURPS has with piercing attacks versus objects are long-standing; we just recently had a thread on the "volley of muskets destroys a frigate" issue. I'm less convinced you can set off large bombs, or hack half-way through the cover DR with cutting damage, without any problem.

Originally Posted by lexington

A one inch steel cube is probably sufficiently outside the intent of the rules that absurd results will come out but calculating the DR and HP of a large block of steel is easy.

Actually, I'm pretty sure that attacking anything but a lump of flesh (and probably a more-or-less human-dimensioned lump of flesh) is outside the design case. The frigate and the muskets come to mind.