Should falling damage scale with size

DSMatticus · Post by **DSMatticus** » Thu Jan 09, 2014 7:25 pm

codeGlaze wrote:Mice should be kill-destroy-able by dropping them far enough.

The terminal velocity of an object falling in an atmosphere increases with mass and decreases with surface area (because drag). Mass is cubic, and surface area is quadratic. As size increases, mass goes up faster than surface area. All else being equal, terminal velocity increases with mass. If you dropped a mouse, a human, and an elephant out of an airplane and measured their velocity when they hit the ground, you would find that the mouse going ~5 mph, the human going about ~120mph, and the elephant going about ~300mph. In order to stop, the mouse will only have to decelerate from 5 to 0; the human, from 120 to 0; the elephant, from 300 to 0. Additionally, the mouse is very light, and the elephant very heavy. This means the force required to decelerate the mouse for each mph it is travelling is very low, while the force required to decelerate the elephant for each mph it is travelling is very high. (This is what makes even short falls dangerous to elephants, but not humans.)

A mouse does not care about short falls, because the force required to stop its body is very small. A mouse does not care about long falls, because its terminal velocity is very low and a long fall is about as easy to stop as a short fall.

A human does not care about short falls, because the force required to stop its body is small enough. A human does care about long falls, because its terminal velocity is fairly high and a long fall is much harder to stop than a short fall.

An elephant does care about short falls, because the force to required to stop its body is very high. An elephant does care about long falls, because its terminal velocity is very high and short falls already break bones.

You might think that being bigger comes with stronger bones, but bone strength is another thing that's quadratic while mass is still cubic, so the mouse's low mass is more important than its weaker bones and the elephant's high mass is more important than its stronger bones.

RadiantPhoenix · Post by **RadiantPhoenix** » Thu Jan 09, 2014 11:21 pm

ubernoob wrote:
RadiantPhoenix wrote:1m thick iron has almost 1200 HP. 1m thick magically treated adamantine has almost 3200 HP.

So, I'd expect that you'd need to lift a truly gigantic mecha around 90ft to reliably kill it. 110ft with the slight adjustment I added later. More if it's built more heavily than that.

You'd also get a tumble check to negate the first 10ft.
I don't think that's how the rules for constructs work. Frankly, no one cares how many unattended walls you can break. Constructs have hit dice and hit point pools that are unrelated to the amount of damage needed to destroy the metal they are made of.

Bigger creatures are more susceptible to falls of the same distance
Elephants that fall 20ft are in real trouble
Therefore, a creature with proportional hit points to an elephant that falls 20ft should also be in real trouble
The Tarrasque is twice as big as an elephant in all three dimensions
The Tarrasque has eight times as many hitpoints as an elephant
Therefore, the Tarrasque is a proportional elephant

Maybe elephants have too many hitpoints. If an elephant had half the hitpoints, I could reasonably drop the damage to doubling with each size increase, so a 30ft fall would be 48d6 (168) damage to a colossal creature, which isn't even enough to KO the 2e Tarrasque (300HP).

That said, tripping a colossus should be meaningful, so I'm not sure that colossal creatures being very vulnerable to bodyslams is a problem.

ubernoob · Post by **ubernoob** » Thu Jan 09, 2014 11:34 pm

RadiantPhoenix wrote:
ubernoob wrote:
RadiantPhoenix wrote:1m thick iron has almost 1200 HP. 1m thick magically treated adamantine has almost 3200 HP.

So, I'd expect that you'd need to lift a truly gigantic mecha around 90ft to reliably kill it. 110ft with the slight adjustment I added later. More if it's built more heavily than that.

You'd also get a tumble check to negate the first 10ft.
I don't think that's how the rules for constructs work. Frankly, no one cares how many unattended walls you can break. Constructs have hit dice and hit point pools that are unrelated to the amount of damage needed to destroy the metal they are made of.

Bigger creatures are more susceptible to falls of the same distance

Elephants that fall 20ft are in real trouble

Therefore, a creature with proportional hit points to an elephant that falls 20ft should also be in real trouble

The Tarrasque is twice as big as an elephant in all three dimensions

The Tarrasque has eight times as many hitpoints as an elephant

Therefore, the Tarrasque is a proportional elephant
Maybe elephants have too many hitpoints. If an elephant had half the hitpoints, I could reasonably drop the damage to doubling with each size increase, so a 30ft fall would be 48d6 (168) damage to a colossal creature, which isn't even enough to KO the 2e Tarrasque (300HP).

That said, tripping a colossus should be meaningful, so I'm not sure that colossal creatures being very vulnerable to bodyslams is a problem.

The Tarrassque is two size categories larger than an elephant. Each size category is a doubling of dimensions and *8 weight. A Tarrasque just by virgue of its size category is ~64 elephants. It weighs as much as 37 elephants.

Hit points are an abstraction. Seriously. I cannot believe you are making the argument Bigger size = more hit points. Classed creatures exist in D&D. 20th level barbarians exist in D&D.

Seriously, hit points are an abstraction.

RadiantPhoenix · Post by **RadiantPhoenix** » Thu Jan 09, 2014 11:39 pm

Elephants aren't classed creatures.

Also, Elephants are 15ft to a side, and the Tarrasque is 30ft to a side.

ubernoob · Post by **ubernoob** » Thu Jan 09, 2014 11:43 pm

RadiantPhoenix wrote:Elephants aren't classed creatures.

Also, Elephants are 15ft to a side, and the Tarrasque is 30ft to a side.

No, no, no, no. A size increase is a doubling in horizontal and vertical dimensions. Seriously, that's how size categories work. An Elephant is Huge size. The Tarrasque is Colossal sized. In between those size categories is Gargantuan. Two whole size categories in between.

Space on the battle mat != width. You are not 5' wide. If you were, you would not be in combat.

RadiantPhoenix · Post by **RadiantPhoenix** » Thu Jan 09, 2014 11:52 pm

Huh. You appear to be correct.

That would actually go even further in the direction I was arguing.

ubernoob · Post by **ubernoob** » Thu Jan 09, 2014 11:59 pm

RadiantPhoenix wrote:Huh. You appear to be correct.

That would actually go even further in the direction I was arguing.

The direction you are arguing is nonsense. A colossal creature is 64' tall or more. Picking up its foot and taking a step is a large enough vertical displacement for falling rules to come into play. Every step.

Arguing about square cube laws on a fantasy roleplaying game is bullshit. There are people that fly by sheer willpower. Physics need not apply.

Now, if you wanted to say, institute that tripping someone (no matter what the size) caused them to fall on their ass and deal level appropriate damage for falling on their ass, you would be speaking from somewhere sane. That helps tell better stories.

Basing your game engine physics off the square cube laws is bullshit though. Large creatures don't get double hit points for being large. They get +2 con. That's 1 hit point/hit die.

So yeah, if you were going to do anything at least base it off of what a creature gets by virtue of gaining a size category (+2 con/increase) and just say something like +1 damage/die to scale up with larger creatures a bit.

Doublings are bullshit and we both know that. Having Titans explode when you push them off a trip is stupid. It's a fucking Titan. Third level wizards survive falling off cliffs. A CR 20 creature should not be susceptible to instant death that a third level wizard can avoid.

RadiantPhoenix · Post by **RadiantPhoenix** » Fri Jan 10, 2014 12:04 am

Then nonmagical animals should have less HP, and cats should be able to survive stuff they can survive in real life. Like being dropped off of a 26 story building.

Also, the damage for tripping a creature of height Xft should be less than the damage for making it fall Xft, and tripping colossi should be meaningful and seriously injure them, because it's genre appropriate.

ubernoob · Post by **ubernoob** » Fri Jan 10, 2014 12:11 am

RadiantPhoenix wrote:Then nonmagical animals should have less HP, and cats should be able to survive stuff they can survive in real life. Like being dropped off of a 26 story building.

Also, the damage for tripping a creature of height Xft should be less than the damage for making it fall Xft, and tripping colossi should be meaningful and seriously injure them, because it's genre appropriate.

Tripping anyone should deal damage because it's genre appropriate. You fell on your ass. The falling rules are fine. If you have that much HP that you can fall 20 stories, you're already a supernatural creature as is. Having Titans crash into the earth and stand back up is pretty genre appropriate.

codeGlaze · Post by **codeGlaze** » Fri Jan 10, 2014 1:51 am

ubernoob wrote:
RadiantPhoenix wrote:Then nonmagical animals should have less HP, and cats should be able to survive stuff they can survive in real life. Like being dropped off of a 26 story building.

Also, the damage for tripping a creature of height Xft should be less than the damage for making it fall Xft, and tripping colossi should be meaningful and seriously injure them, because it's genre appropriate.
Tripping anyone should deal damage because it's genre appropriate. You fell on your ass. The falling rules are fine. If you have that much HP that you can fall 20 stories, you're already a supernatural creature as is. Having Titans crash into the earth and stand back up is pretty genre appropriate.

Yea the infinite loop involving giant things dropping from the sky to wreak havoc crossed my mind earlier, too.

@walking = damage
Walking wouldn't constitute fall damage because it's a natural muscle-controlled action. Their feet/legs aren't free-falling each time they take a step.

RadiantPhoenix · Post by **RadiantPhoenix** » Fri Jan 10, 2014 2:01 am

ubernoob wrote:Having Titans crash into the earth and stand back up is pretty genre appropriate.

I see what you're saying, and I think that the solution is to have low level gigantic giants, dragons, and golems that just die from falling short distances, and then have high level ones that don't.

(Titans would still need to fall about 120ft to die under my x3 system, because they're huge creatures with 370HP)

deaddmwalking · Post by **deaddmwalking** » Fri Jan 10, 2014 2:05 am

Tripping a giant and having it do damage is cool.

Tripping a giant and it dying is fucking lame.

ubernoob · Post by **ubernoob** » Fri Jan 10, 2014 2:31 am

RadiantPhoenix wrote:
ubernoob wrote:Having Titans crash into the earth and stand back up is pretty genre appropriate.
I see what you're saying, and I think that the solution is to have low level gigantic giants, dragons, and golems that just die from falling short distances, and then have high level ones that don't.

(Titans would still need to fall about 120ft to die under my x3 system, because they're huge creatures with 370HP)

The moment your system makes baleful transposition + flight more of a save or die than it already is, your system has failed.

RadiantPhoenix · Post by **RadiantPhoenix** » Fri Jan 10, 2014 2:45 am

Titans are 25ft tall, so if we take my x3 system and round to the nearest...

Oh wait, I don't have a tripping rule. New one: tripping counts as falling half your height, rounded to the nearest.

So, 9d6 damage. About 31.5 damage, when they have 370-ish HP.

Cloud giants are huge and about 20ft tall, with 170HP. Same damage, bigger chunk of HP, but still not lethal.

An Elder Titan is colossal, and I'm going to assume 100ft tall. 1000-ish HP vs 1400-ish damage: Splat. But... they're from the complete joke book.

I mean, I think this is probably "realistic", but I can kind of see your point. Maybe we want a linear damage growth after huge?

Fine and diminutive take no damage
Tiny caps at 1d6
Small takes half damage
Medium takes normal damage
Large takes x5 (x{1 + grapple size modifier})
Huge takes x9
Gargantuan takes x13
Colossal takes x17

So, our sample is:

Horse (large, 19HP, ~8ft)
Ogre (large, 29HP, 10ft)
Elephant (huge, 100HP, ~10ft)
Cloud Giant (huge, 170HP, 20ft)
Titan (huge, 300HP, 25ft)
Tarrasque (colossal, 860HP, 50ft)
Elder Titan (colossal, 1000HP, 100ft)


Creature	Trip damage	Trip/HP	Terminal Velocity damage	TV/HP
Horse	0	0	100d6	1840%
Ogre	0	0	100d6	1200%
Elephant	0	0	180d6	630%
Cloud Giant	9d6	18.5%	180d6	370%
Titan	9d6	10.5%	180d6	210%
Tarrasque	34d6	13.8%	340d6	138%
Elder Titan	85d6	29.8%	340d6	119%

Fuck it, elephants just have too many hit points to make the system work right. Let's fix that first.

Until then:

Diminutive and fine creatures never take falling damage.
Tiny creatures are capped at one die of damage.

ubernoob · Post by **ubernoob** » Fri Jan 10, 2014 2:57 am

Radiant, what the fuck. 9d6/10 feet of falling damage for a huge creature.

What part of "It is genre appropriate for titans to crash into the earth and get back up" is hard?

http://www.d20srd.org/srd/monsters/athach.htm
That thing is a CR 8. A blasting spell deals 8d6 damage when you fight it.

Causing it to fall 10' deals more damage than failing a save vs a level appropriate blasting spell. Causing it to fall 40' (baleful transposition is a second level spell) is literally its entire hit point pool on average.

What part of "Insane scalings that make falling off a 30' ledge for creatures 60' high is stupid" did you not understand.

Here, let me show you some maths.

A colossal animated object is a CR 10. It has 256 hit points.
A 40' fall would basically kill it. A 50' fall always would.

I mean, if you want to play Defend Your Castle instead of rocket launcher tag, that's fine. Just don't pretend that you've added any depth to the game.

Just fucking write a "trip damage" table and be done with it. Absolutely no need to reference the falling rules.

DSMatticus · Post by **DSMatticus** » Fri Jan 10, 2014 3:26 am

ubernoob wrote:
RadiantPhoenix wrote:
ubernoob wrote:Having Titans crash into the earth and stand back up is pretty genre appropriate.
I see what you're saying, and I think that the solution is to have low level gigantic giants, dragons, and golems that just die from falling short distances, and then have high level ones that don't.

(Titans would still need to fall about 120ft to die under my x3 system, because they're huge creatures with 370HP)
The moment your system makes baleful transposition + flight more of a save or die than it already is, your system has failed.

Baleful transposition requires that the subjects are connected by some solid(s). It also has a range of close.

The goal here (whether laudable or lamentable) is to make knocking over big ass things a big deal relative to knocking over not so big ass things.

The problem with adding level appropriate damage to trip attacks and patting yourself on the back is that big ass things will care less about level appropriate damage than equivalently CR'd things that are not big ass.

The problem with adding level appropriate damage to trip attacks and modifying by size of target is that big ass things should not really care what knocked them over in determining how much it hurts them to fall over.

The problem with juryrigging the fall damage physics to doing damage for combat actions is that fall damage is level-independent. There will be big ass things of a lower level that asplode and big ass things of a higher level that don't give a fuck, and your system will only work for the single point inbetween. Also, D&D hitpoints are broke as fuck to begin with.

I don't see any immediate problems with adding a monster ability "The Harder They Fall" that triggers whenever the monster is tripped and deals damage to them. If you are inside the monster entry, then you necessarily know what sort of damage quantity would be meaningful but not overwhelming. It's the fire vulnerability of falling on your ass.

Seerow · Post by **Seerow** » Fri Jan 10, 2014 3:28 am

By comparison, the suggestion I made back on page 1 would have making the Athach fall 10ft makes it take 3d6+6 falling damage. The 40ft fall is 6d6+12 damage. So the first is low, but noticeable damage, the second is about on par with (slightly above) a level 8 blasting spell. Simply tripping it gets you 2d6+4, which is nice bonus damage when you consider tripping a creature generally comes with a free attack.

ubernoob · Post by **ubernoob** » Fri Jan 10, 2014 3:38 am

DSMatticus wrote:The goal here (whether laudable or lamentable) is to make knocking over big ass things a big deal relative to knocking over not so big ass things.

The problem with adding level appropriate damage to trip attacks and patting yourself on the back is that big ass things will care less about level appropriate damage than equivalently CR'd things that are not big ass.

The problem with adding level appropriate damage to trip attacks and modifying by size of target is that big ass things should not really care what knocked them over in determining how much it hurts them to fall over.

The problem with juryrigging the fall damage physics to doing damage for combat actions is that fall damage is level-independent. There will be big ass things of a lower level that asplode and big ass things of a higher level that don't give a fuck, and your system will only work for the single point inbetween. Also, D&D hitpoints are broke as fuck to begin with.

Agreed on all of the above.

I don't see any immediate problems with adding a monster ability "The Harder They Fall" that triggers whenever the monster is tripped and deals damage to them. If you are inside the monster entry, then you necessarily know what sort of damage quantity would be meaningful but not overwhelming. It's the fire vulnerability of falling on your ass.

Super agreed on this.

radthemad4 · Post by **radthemad4** » Sat Jan 11, 2014 5:18 pm

Yeah, that makes sense.

What monsters would you attach the ability to? Perhaps 'The Harder They Fall' could have varying damage rates with some rough guidelines as to what creatures they might apply to (e.g. I'd expect a flesh colossus to take less trip/fall damage than a stone colossus)

fectin wrote:How do baby colossi survive learning to walk?

Colossi are built, not born according to the srd at least.

RadiantPhoenix · Post by **RadiantPhoenix** » Sat Jan 11, 2014 5:40 pm

I considered the idea of making falling damage scale with weight, but the first few creatures I looked up didn't have that listed.

radthemad4 · Post by **radthemad4** » Sat Jan 11, 2014 5:49 pm

ubernoob wrote:Hit points are an abstraction. Seriously. I cannot believe you are making the argument Bigger size = more hit points. Classed creatures exist in D&D. 20th level barbarians exist in D&D.

Seriously, hit points are an abstraction.

For the most part yes. It shouldn't apply to class levels, but there are creatures that grow in size category by advancing HD. Whether or not fall damage being linked to this is mechanically desirable, I don't know, but for those creatures at least bigger size does equal more hitpoints.

Vebyast · Post by **Vebyast** » Sat Jan 11, 2014 9:14 pm

Part of the issue is that all these examples are already violating expectations; anything you do can only expose new manifestations of those violated expectations. For example, an "Architecture Colossus" made out of skyscrapers and with a house as a foot makes perfect sense, but if you took the same house and just lifted it off its foundation and dropped it three stories you'd expect it to turn to rubble. Making it so the Architecture Colossus takes damage when it falls on its hands instead of its feet breaks its exemption from reality and conflicts with its "that makes perfect sense".

So reasonable general solutions are out. Which is fine, because giving every monster a specially-tailored "The Harder They Fall" ability is something you'd have to do anyway - when you get right down to it, Mechagodzilla takes significantly less fall damage than a Jaeger, and a Gunmen takes no fall damage at all.

RadiantPhoenix · Post by **RadiantPhoenix** » Sat Jan 11, 2014 9:24 pm

Something I just realized: Titans have Levitate at will. Thus, they only even take falling damage if they fall less 150ft or less, because otherwise they get an action while falling.

Cloud Giants have Levitate 3/day, and Storm Giants have it 2/day.

deaddmwalking · Post by **deaddmwalking** » Sat Jan 11, 2014 10:35 pm

RadiantPhoenix wrote: Cloud Giants have Levitate 3/day, and Storm Giants have it 2/day.

Because fuck Jack and his beanstalk, that's why.

tussock · Post by **tussock** » Fri Jan 24, 2014 12:48 pm

1: Yes, falling damage should scale with size. Halflings should be safer climbers than Ogres, because they have to climb a lot more things on account of being so small.

1a: Climbing and shit should be vastly easier by size too. At least not a Str skill.

2: Oh god, the math. Big things accelerate longer and decelerate harder. By a lot.

http://irl.cs.ucla.edu/papers/right-size.html

Read that, it's fun, and shows that the silly surface-tension pool monsters from early D&D are simply a side-effect of us being shrunk to the size of mushrooms when travelling in parts of the underdark. Oh yes, it's not that the spiders grow large down there ....

Anyway, medium animals have about 2HD, 12 Con, and +10 negatives for 20 hit points, or a 30-40' fall to kill them. That says D&D is close enough.

Huge animals have about 8HD, 18 Con, and +10 negatives, for 80 hit points, and they should die at 20'? Whut? No. That's ($TEXAS)d6.

So you do ... this.

Fine: -4 per die. Max 10'.
Dimi: -3 per die. Max 20'.
Tiny: -2 per die. Max 50'.
Small: -1 per die. Max 100'.
Medi: 1d6/10'. Max 200'.
Large: +2 per die. Max 400'.
Huge: +5 per die. Max 600'.
Grg: +10 per die. Max 800'.
Col: +20 per die. Max 1000'.

Or something similar. Swarms of smaller things take no damage from a fall. Collisions for charging and trample damage and slams or whatever should work similarly. As should dropped rocks. Speed after falling 10' is ~25' per second, or a Move of ~40' when running or ~80' hustling.

Ideally it ramps up a bit quicker and dragons explode like a bomb for massive area damage when falling from on high, like http://what-if.xkcd.com/12/

A high level Halfling Monk walks into a bar. Takes 1d6-1 damage. Bu-dum-tish.