Effects of Body Mass

[Varyon]

As a working document/set of justifications, the above post - particularly with needing to back-reference other posts - is nasty to read through. Here's something (a bit) cleaner and more complete.

In addition to normal traits, characters also have a Mass and Volume, both expressed in pounds. Mass is actually "Pounds the character would weigh at 1G," Volume is actually "The space an average human of the given weight would take up." These assume a default of 160 lb; in a campaign with a different default, feel free to adjust the below values (if the default is 320 lb, every +40 lb is equivalent to the +20 lb values below, for example). Most characters have each of Mass and Volume equal to 8/5*(HP^2) lb. For Mass and Volume based on ST, substitute ST for HP. For Mass and Volume based on SM, multiply 160 lb by the cube of the linear ratio (SM 0 is 2 yards; SM +1 is 3 yards, or 1.5 times this, so multiply 160 lb by 1.5^3; SM -1 is 1.5 yards, or around 0.7 times this, so multiply 160 lb by 0.7^3).

Mass affects Grappling (see Weight and Grappling, TG8), Knockback, Slams, and Falls. For the latter three, use (Mass/1.6)^(1/2) to determine your effective HP for these effects. Point cost is equal to this effective HP, minus 10.

Volume affects the weight and cost of armor and clothing. Simply multiply the weight and cost of any armor or clothing item made for the character by (Volume/160)^(2/3). Point cost is [-5*((M*100)^(1/2)-10)]; follow normal GURPS rounding conventions. Volume is constrained by SM - a character's Volume must fall between the averages of 1 SM smaller and 1 SM larger.

Characters with a Mass and/or Volume that doesn't correspond to the average for their SM, ST, and/or HP can purchase certain Advantages and Disadvantages to represent this. See the list below for examples.

Athletics/Movement/Carrying Capacity: You're carrying around more or less weight than you "should" be, so you can move more or less easily. Characters with a higher Mass than their ST indicates start out somewhat encumbered - every +(1/10)*BL lb is worth [-1] up to +2*BL lb, after which point every +(3/10)*BL lb is worth [-1]. Characters with lower Mass start out somewhat unencumbered - every -(1/10)*BL lb is worth [1] down to -2*BL lb, after which point every -(3/10)*BL lb is worth [-1]. These values are added directly to any encumbrance the character has, and can result in negative encumbrance, with effects as outlined in the following table (weight is the multiple of BL the character is carrying, Mass would be the total weight of an ST 10 character+gear to reach that level):

Weight	Mod	Move	Mass
-5	+4	x1.8	60 lb
-2	+3	x1.6	120 lb
-1	+2	x1.4	140 lb
0	+1	x1.2	160 lb
1	0	x1	180 lb
2	-1	x0.8	200 lb
3	-2	x0.6	220 lb
5	-3	x0.4	280 lb
10	-4	x0.2	360 lb

Blowthrough: Bullets and the like rip through more or less of your flesh before shooting out the other side, causing more or less injury than anticipated. A character with higher Volume than his HP indicate has a higher blowthrough cap - +20% justifies Vulnerability x1.5 (Piercing/Impaling, only for calculating Blowthrough cap) [-10], +40% justifies Vulnerability x2 [-20], and so forth. A character with lower Volume than his HP indicate has a lower blowthrough cap - -20% justifies IT:DR x0.7 [10], -30% justifies IT:DR x0.5 [20], and so forth. You can determine the multiplier/divisor by squaring the character's Volume/(HP Volume).

Toxins: You've got more or less tissue to disrupt, granting you more or less resistance to poisons and the like. A character with higher Mass than his SM indicates can have IT:DR (Poisons, Occasional) [10/level], and higher Mass than default (160 lb) justifies Resistance to Poisons [3/+2 HT]. One with lower Mass than his SM indicates can have Vulnerability (Poisons, Occasional) [-10/level], and lower Mass than default justifies Susceptibility to Poisons [-3/-2 HT]. You can determine the multiplier/divisor as the character's (SM Mass)/Mass. For Resistance/Susceptibility, every +1 SSR from default (160 lb) to Mass justifies +1 to HT.

Consumption: You've got more or less mass to support, so you need to consume more or less food and water. As variable levels of consumption at any size are justifiable, this is the least necessary modification. That said, characters of higher Mass than default (160 lb) can justify Increased Consumption, while those with lower Mass than default can justify Reduced Consumption. Amount of food/water consumption scales as (Mass/160)^(2/3).


For characters of SM greater or less than 0, simply use the above guidelines. In addition to the above traits, every +1 to SM gives IT:DR (Everything but Explosions/Area Effects) [25/level], at x0.7, x0.5, x0.3, x0.2, etc. Every -1 to SM gives Vulnerability (Everything but Explosions/Area Effects) [-25/level], at x1.5, x2, x3, x5, etc. These assume you scale wounding modifiers by SM; if you don't disregard these. There are other SM-related effects, such as Reach, ability to be seen/attacked, etc, but these work out to an overall Feature.

[Varyon]

Originally Posted by Andreas

Wheter this is appropriate depends a lot on what the extra resilience from more hp represents. If it is just being better able to deal with an equally sized injury, then this is approprite. However if it represents the body being harder to injure in the first place (for example someone with low HP for his mass might have bones that break easily, skin and muscles that tear easily etc.), then blowthrough should scale with HP rather than mass.

I see it as being able to be either, or even both. An HP 16, 160 lb character might simply be 300%* more badass than your average guy (justifying IT:DR against blowthrough), he might have flesh and bone that is 300% more resilient than your average guy's (so full HP blowthrough cap), or he might only be 100% more badass and 100% more resilient.

*As damage scales as the cube root of energy, I'm using here the ability to shrug off said energy. 1.6^3 is around 4, so x4 (+300%). For the two 100%'s, that's because those effects would be multiplicative - 2x2=4.

[Flyndaran]

We humans vary little in ability to resist injury, but our ability to survive and recover from types and severities of injury vary significantly.
I call that tightly grouped HPs for given masses, but large differences in HTs.

[Varyon]

Originally Posted by Flyndaran

We humans vary little in ability to resist injury, but our ability to survive and recover from types and severities of injury vary significantly.
I call that tightly grouped HPs for given masses, but large differences in HTs.

I rather agree with you, but that's a realistic interpretation. GURPS doesn't deal exclusively with realism. If you wanted to use this system and maintain this, it's fairly simple - require characters to have HP that varies by no more than 1 from that predicted by their Mass. So, a 160 lb character must have HP between 9 and 11, while a 200 lb character must have HP between 10 and 12.

[Flyndaran]

Originally Posted by Varyon

I rather agree with you, but that's a realistic interpretation. GURPS doesn't deal exclusively with realism. If you wanted to use this system and maintain this, it's fairly simple - require characters to have HP that varies by no more than 1 from that predicted by their Mass. So, a 160 lb character must have HP between 9 and 11, while a 200 lb character must have HP between 10 and 12.

If you throw realism out the window, then extra HPs may come from literally anything the GM allows.
I do believe that stats can always be worse than the normal range.

[Andreas]

Originally Posted by Flyndaran

If you throw realism out the window, then extra HPs may come from literally anything the GM allows.
I do believe that stats can always be worse than the normal range.

You don't need to throw realism out the window for there to be a need for basing many things on mass rather than HP. It is not just humans that are given stats. Things like animals, vehicles and robots are sometimes given stats as well. Many such things could have very different ability to resist injury compared to what is the case for humans.

[Varyon]

Originally Posted by Flyndaran

If you throw realism out the window, then extra HPs may come from literally anything the GM allows.

Of course! It's just that, if I decide to build my Zombie Cloak-wearing necromancer as weighing a mere 80 lb (because I want the cloak to be able to support her weight), should simply writing down "Weight: 80 lb" on my character sheet be sufficient for this? Should there be any other benefits or drawbacks, and what would be a fair point cost? This exact question is what caused me to design this system in the first place. Now, by this system, 80 lb implies the necromancer should only have ST/HP of 7 or so but her clothing and armor should weigh 63% of what an average person's would. Of course, in this case the necromancer actually has comparable Volume, strength, and resilience to an average human - her incredibly low weight is because she's in the process of becoming a wraith - so only the Mass based effects would apply.

[Flyndaran]

Originally Posted by Andreas

You don't need to throw realism out the window for there to be a need for basing many things on mass rather than HP. It is not just humans that are given stats. Things like animals, vehicles and robots are sometimes given stats as well. Many such things could have very different ability to resist injury compared to what is the case for humans.

Earth animals will have very similar flesh stats pound per pound. Vehicles and robots are purposely made machines, and therefore depend entirely on the setting's technological parameters.

[Flyndaran]

Originally Posted by Varyon

Of course! It's just that, if I decide to build my Zombie Cloak-wearing necromancer as weighing a mere 80 lb (because I want the cloak to be able to support her weight), should simply writing down "Weight: 80 lb" on my character sheet be sufficient for this? Should there be any other benefits or drawbacks, and what would be a fair point cost? This exact question is what caused me to design this system in the first place. Now, by this system, 80 lb implies the necromancer should only have ST/HP of 7 or so but her clothing and armor should weigh 63% of what an average person's would. Of course, in this case the necromancer actually has comparable Volume, strength, and resilience to an average human - her incredibly low weight is because she's in the process of becoming a wraith - so only the Mass based effects would apply.

Magic works how the GM dictates it to, and rarely can anyone argue it isn't "right".
I'm now sure what would even be realistic let alone best for gaming with regards to mass and correlated traits.
Some people are quite heavy/light for their strength even after taking fat percentage into account.
The grappling supplement covers the combat benefits of heaviness, and I think the non-combat benefits of being light should be relatively easy to imagine.
Being low mass but otherwise the same stat-wise should give something like slow fall aka uncontrolled gliding, gliding, or DR for falls only. "The bigger you are, the harder you fall" in reverse.

[Varyon]

I'm... not entirely certain what you're arguing here, Flyndaran. It looks like you're agreeing with me, but the manner of writing implies you're disagreeing, so I'm not certain how to respond to most of your post. That said:

Originally Posted by Flyndaran

Being low mass but otherwise the same stat-wise should give something like slow fall aka uncontrolled gliding, gliding, or DR for falls only. "The bigger you are, the harder you fall" in reverse.

Well, you only use your Mass-based HP for falls under my system, so for example the 80-lb necromancer (Mass-based HP of 7) is only taking 70% as much damage from falls as her HP 10 indicates. This handles part of what you're suggesting. For the rest, you'd need something like IT:DR (Falling Crushing Damage Only, -80% at a guess), either with an Enhancement or Special Effect that this is actually just a slow fall. If you fall slowly enough for Uncontrolled Gliding to be available, you'd need to buy that trait while you're at it.