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Old 09-24-2021, 11:01 AM   #11
malloyd
 
Join Date: Jun 2006
Default Re: Damage to Force (in Newtons or any other unit)

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Originally Posted by Varyon View Post
Damage is a bit... abstract.
Damage is [ridiculously] abstract.

It takes dozens of bad things that can happen to people (and other targets) lumps them on one scale and calls it close enough. To think about the weeds you'd have to get into in GURPS terms, look at the diversity of rules for disease, starvation and radiation, all of which could have been, arguably should have been, and in various others systems are modelled with the same damage mechanic as (the several kinds of not necessarily any more equivalent types of) wounds, and realize that if you are going to justify "damage" you need multiple other systems at least as involved as any of those for every one of the other dozens of bad things, and then somehow equate the results.
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Old 09-24-2021, 12:32 PM   #12
DouglasCole
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Default Re: Damage to Force (in Newtons or any other unit)

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Originally Posted by Polydamas View Post
What you want can't be done. Bullet penetration is based on a simple physics model by Douglas Cole of Gaming Ballistic. It still needs to take three variables as input and there is a physics professor in the United States who does not like his model. (But Cole is an engineer with postgraduate degrees too, and I can't track down the works the physicist cites or judge what is a reasonable simplifying assumption).
Luke (the author of the above model) is very sharp. The model I created is entirely empirical, however. I took variables such as mass, velocity, sectional density, caliber, and real-world penetration of RHA steel in tests, plus a few others and put them into a polynomial model including interaction parameters, then "improved" the model by throwing out terms until something that was "good enough" was derived. The process I used is familiar to anyone who has done this sort of thing looking to build a phenomenological model from data.

While Luke is doubtless correct about the specific physical regimes involved, having pulled from quality literature for them, for a game-relevant model, needing only KE and caliber is a fine abstraction, and with that simplification it also happens to get you within spitting distance of published values for both GURPS existing damage as well as matching real-world results.

Much like Luke's model, mine also diverges for cannon, though the penetration of armor steel by the 406mm "AP" shells of the Iowa-class battleships are used as a fitting input to mine, the regime-dependent effects are enough that letting THAT go out of the model is the better choice.

In short: he ends up with his model pretty much where I end up with mine for most game-weapons (from a points of damage perspective), and "all models are wrong, some are useful." So pick one, go with it, and that is likely to suffice for your game as long as the results are believable (both are) and consistent (both are).

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Trying to model bullet damage is something which gets hunters and ballisticians and engineers and pathologists screaming at each other. And as for hand-held weapons ... those are even harder to model! If teams of PhDs throw up their hands, gamers are not going to come up with a good-enough solution.
This is what I also found when digging into the Deadly Spring article. Turns out that while bows have existed for zillions of years, a closed-form solution (rather than a modeled one using heavy-duty computation) was - at the time I wrote my article - not available, thought to not be possible. Even the "brute force mechanical models" that just threw huge computational cycles at the problem had their own issues. By comparison, firearms were quite simple!
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Old 09-24-2021, 02:10 PM   #13
Anthony
 
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Default Re: Damage to Force (in Newtons or any other unit)

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Originally Posted by DouglasCole View Post
This is what I also found when digging into the Deadly Spring article. Turns out that while bows have existed for zillions of years, a closed-form solution (rather than a modeled one using heavy-duty computation) was - at the time I wrote my article - not available, thought to not be possible.
While complete modeling is usually a giant mess, there do tend to be simple and mostly accurate transforms, where if you have a solution at one set of values you can change multiple variables at once and wind up with a solution.

The big one, with applicability over a very wide range of weapons, is that if you multiply all linear dimensions by N (resulting in multiplying weight and energy by N^3), you can apply the same multiplier to the hole it makes (N times deeper, N times wider, etc). It tends to break down at extreme scales but it's probably going to work okay over a couple orders of magnitude. There are also cases where you can say "I don't know what the optimal solution is, but there are certain things you can say about what that solution will be". For example, the mass of elastic material in a well-designed bow will be linear in draw energy.
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Old 09-24-2021, 07:11 PM   #14
Polydamas
 
Join Date: Jan 2006
Location: Central Europe
Default Re: Damage to Force (in Newtons or any other unit)

Some versions of D&D embrace "hit points as abstraction" by having nasty effects work on a certain number of Hit Dice or Hit Points of victim. Its a little hard to explain why the death spell can kill 20 veterans or 100 raw recruits, but its hard to explain everything about death spells.

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Originally Posted by DouglasCole View Post
Luke (the author of the above model) is very sharp. The model I created is entirely empirical, however. I took variables such as mass, velocity, sectional density, caliber, and real-world penetration of RHA steel in tests, plus a few others and put them into a polynomial model including interaction parameters, then "improved" the model by throwing out terms until something that was "good enough" was derived. The process I used is familiar to anyone who has done this sort of thing looking to build a phenomenological model from data.
Yes, one issue is that I am an empiricist not a rationalist, so I'm more comfortable with things derived from experiments than things purely derived from principles. But I can't obtain Luke's sources and my calculus is rusty and most importantly I don't have experience making first-principle physics models and judging what simplifying assumptions are reasonable.
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