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Old 07-10-2013, 11:08 PM   #1
hal
 
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Default 4E's hit point philosophy

Hello Folks,
As I drove into work recently, my mind wandered on the topic of why 4E hit point rules leave me so dis-satisfied.

My mind went on the road or train of thought that started with "Why is it that hit points scale with the cube of the weight" but then doesn't follow known physics when it comes to reality?

For instance? Suppose I had a given amount or mass of water. Suppose I had to use X energy to instantly vaporize that water from room temperature into vapor. With the laws of physics, we know to the Joule, how much energy is required to vaporize water based upon mass and room temperature (ie, how much energy is required at a given starting temperature of a given amount of water).

So, the question becomes one of:

If you quadruple the mass of water, would you expect that the energy required to vaporize that larger mass of water to be a function of the cube root of the mass of that water times 8, or would you expect the energy to vaporize four times the water by mass, to be approximately equal to 4 times the energy required to vaporize the smaller mass of water?

My instinctive response would be 4x the energy.

Now why did I take the example of water instead of say, wood, flesh, or something else?

GURPS has the rationale that X points of damage will render an object non-functional, and that 10x that level of damage will obliterate it with total destruction (more or less). Killing a character in GURPS works because you only need to cause vital organs to cease function, and the entire organism ceases to live. Damaging a car engine needs only for some vital "thing" to be damaged to where the engine ceases to function. But in each case, there is an upper limit to how much damage any given thing can take.

So, the water illustration was meant to be a VERY simplified demonstration of what I'm having problems with. Dumping energy into water in the form of a plasma bolt for instance, can be a function of a weapon attack on a non-living thing.

So, in the end, I ponder "Why did SJGames go with the idea that hit points do not scale directly with mass, but scales as the cube root? Energy affecting a given volume isn't a function of the cube root of the volume, nor the cube root of the volume's mass, but a direct function of the mass itself. At least, that is what I seem to recall from the pre-historic era of my education in physics back in the late 70's and early 80's (and yes, I'm OLD - but still breathing at least!)

Comments?

By the by? What started this whole train of thought, is the issue that stems from why Age of Sail ships in history could take the pounding that they did historically, but can't take with the current rules in GURPS 4e. If we know the kinetic energy contained within a cannonball travelling at 1,200 feet per second - and we know that historically, ships could not only take 200 such hits and remain in existence - but be repairable and ready for battle within 14 days - well, you know why I'm really having second thoughts about the cube root function as currently written. :(
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Old 07-10-2013, 11:39 PM   #2
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Default Re: 4E's hit point philosophy

The 4e hit point philosophy is that 'damage' should scale with penetration, and the amount of penetration required to reach a specific depth on a target does basically vary as the 1/3 power of mass. In addition, there is plenty of evidence that, once you have adequate penetration to reach important targets, increasing projectile power does not provide a linear increase in lethality.

GURPS hit points work out okay if you give everything some DR with 6x hardened, at about 10% of hit points. Or just give all large objects 10 hit points and IT(DR) with Cosmic, so all the trivial hits just round down to zero.
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Old 07-11-2013, 01:20 AM   #3
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Default Re: 4E's hit point philosophy

Quote:
Originally Posted by hal View Post
My mind went on the road or train of thought that started with "Why is it that hit points scale with the cube of the weight" but then doesn't follow known physics when it comes to reality?
Because it's a game, not a master's thesis.
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Old 07-11-2013, 01:20 AM   #4
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Default Re: 4E's hit point philosophy

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Originally Posted by Anthony View Post
GURPS hit points work out okay if you give everything some DR with 6x hardened, at about 10% of hit points. Or just give all large objects 10 hit points and IT(DR) with Cosmic, so all the trivial hits just round down to zero.
The problem is - I shouldn't have to use "meta-roleplaying" mechanics to model something that the current rules seem to not handle very well. I say Seem, because while some people are saying it "is realistic", I'm saying that we can already see instances where it isn't.

Chopping through a sword blade is not the same as chopping through a perfectly made sphere of the same material, despite the fact that both the blade and the sphere are of the same overall mass. Likewise, when one can find a reference to real life damage control for age of sail, only to discover that the rules as written make ships of the line sinkable by musket fire - something or someone is off target here.

Likewise, dumping energy into a substance requires a linear application of energy, not something that is based upon the cube of the mass, which when you stop to think about it, is more a matter of density per cubic unit of volume than it is about "weight" per se.

Now, I'll grant you, firing upon moving parts in an engine that requires all of the parts to be functioning without damage - would require far less "damage" or applied kinetic energy than a solid mass of metal. But solid materials shouldn't be as easily destroyed as complex moving parts kind of things, or even those objects whose density approaches that of water (aka - flesh and blood living creatures).

So, from where I sit, any time we have to utilize "Cosmic" in describing ordinary "physical world stuff", we're already in trouble.

In the beginning, it was the goal of GURPS to try for reasonable "realism" or a facsimile there of. Now, I'm not so certain. To this day, I can still recall one of the selling points of THE PHOENIX COMMAND game system where the advertisement said "are you tired of games where a person puts a handgun (I forget the caliber now) to their head, and the character will routinely survive the shot?"

Now it is getting to where someone can point to GURPS and GIGGLE at some of the rules and lack of realism. Hell, wasn't MURPHY'S RULES intended to poke fun at the really whacked out unrealistic rules? Having a cartoon where the Ship's captain is yelling "They have muskets, we have to take this 100 gun ship of the line out of their range or we'll be sunk!" strikes me as about right for someone to lampoon GURPS 4e vehicle rules.

So, my point still stands as best as I can see. Needing to utilize some form of "cosmic" is little more than an acknowledgement that the rules are NOT as they should be, and they need to be revisited or redone.
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Old 07-11-2013, 01:27 AM   #5
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Default Re: 4E's hit point philosophy

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Originally Posted by Andrew Hackard View Post
Because it's a game, not a master's thesis.
Andrew - it may be a game, but we have an example of GURPS VEHICLES for GURPS 3e to compare/contrast expected reality, and see that GURPS 4e went the other (or wrong) direction as far as realism goes.

If all we're supposed to view GURPS as, is a game that has no real need to stick to any level of realism, then why are we bothering to create formulas for gun damage based upon actual scientific principles? Filling in bullet weight/mass, along with bullet velocity, expansion of gases, etc - all just to get some level of precision relative to all other weapons firing bullets seems to imply one mindset, and then a slightly bewildering opposing tack when dealing with vehicles, hit points, masses of living creatures, etc.

If you don't mind MURPHY's RULES lampooning GURPS 4e, that's fine. It is, after all, just a game, not a master's thesis. <shrug>
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Old 07-11-2013, 01:33 AM   #6
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Default Re: 4E's hit point philosophy

As if to underscore my point about "realism" and using real numbers in GURPS 4e, take a look at this thread, where people are discussing realistic damage levels of sling bullets.

This is why I'm thinking there is a disconnect in the game overall. We can pin it down for the smaller arms stuff, but we can't pin it down for large vehicles? Something smacks of a major disconnect to my view.
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Old 07-11-2013, 02:13 AM   #7
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Default Re: 4E's hit point philosophy

Quote:
Originally Posted by hal View Post
My mind went on the road or train of thought that started with "Why is it that hit points scale with the cube of the weight" but then doesn't follow known physics when it comes to reality?
[...]
If you quadruple the mass of water, would you expect that the energy required to vaporize that larger mass of water to be a function of the cube root of the mass of that water times 8, or would you expect the energy to vaporize four times the water by mass, to be approximately equal to 4 times the energy required to vaporize the smaller mass of water?

My instinctive response would be 4x the energy.
Two things being discounted or abstracted here are organization and distribution. The water can be organized into a vessel that allows the heat to be evenly distributed to the water touching its inner surface by conductivity, and the heat is then distributed within the volume of water by conduction and convection currents. If living flesh was similarly homogeneous and organized in such a way where heat could be efficiently distributed to it, then you could also expect so-much heat energy to fatally cook so-much flesh, and 4x the amount of heat energy to do the same for 4x the amount of flesh. But outside of gelatinous cubes and slime molds, that's not how it works out.

Living things have workarounds for damaged parts (organization), they have delicate parts protected behind more robust parts (organization, distribution), and they tend to bleed somewhat randomly. The same sized hole might bleed a little or a whole lot depending heavily on where in the organism it is poked . The water can do this trick as well, if it is in fact not water, but snow, 100 lbs of snow packed into a snowman can last days longer than the many tons of it remaining on the ground in the same yard in the same weather, because it is grouped to expose as little surface area to the sun as possible unlike that still on the ground.

These are all processes subject to the same laws of physics, but they are not so easy to break down into intuitively solvable expressions like F=ma . If you've heard of differential equations or "diffy Q", that's the area of math devoted to describing the way quantities with such indirect relationships change at different rates, and it's notoriously difficult.
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Old 07-11-2013, 02:51 AM   #8
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Default Re: 4E's hit point philosophy

Quote:
Originally Posted by hal View Post
Andrew - it may be a game, but we have an example of GURPS VEHICLES for GURPS 3e to compare/contrast expected reality, and see that GURPS 4e went the other (or wrong) direction as far as realism goes.
Whereas I would argue that VEHICLES was the wrong direction, which is why 4e moved away from it. You seem to be a hardcore simulationist; just thinking about that kind of game makes me break out in hives. There comes a point where the system HAS to have some sort of contrafactual abstraction or it's unplayable.
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Old 07-11-2013, 03:12 AM   #9
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Default Re: 4E's hit point philosophy

It is possible to avoid mocking realism without going hardcore simulationist as you put it. Happy mediums coupled with house rules detailing areas individuals want detailed.
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Old 07-11-2013, 03:23 AM   #10
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Default Re: 4E's hit point philosophy

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It is possible to avoid mocking realism without going hardcore simulationist as you put it.
My point is that it's not a flaw in the system when the system doesn't do something that it was never designed or intended to do. You might as well complain that a hammer makes a poor butter knife.
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