D&D 5E Calculating fall damage in special situations

[mrpopstar]

Hey!

I was wandering how you all calculate fall damage in special situations. For example:

Last session my players ended surrounded by enemies on all sides while on a bridge (yes, a cliffhanger). Now thanks to their talk I know that they are planning to jump next session. When the barbarian jumps, he'll take 10d6 damage (100 foot drop) and he'll likely be raging so that's halved...that one is easy.
However, say that the druid turns into a cat or another small animal and falls while in the barbarian's arms. Would the druid take any damage?
What if they take bodies of fallen enemies to cushion the fall? How would that affect the damage?
Should a 100 foot drop have some other drawback? Like damage+lingering injury? Or system shock?

These guys are level 5 so surviving a fall like that with their hp is possible.

Thoughts?

In truth, there is nothing special about this situation.

At the end of their fall, each creature takes 10d6 bludgeoning damage and lands prone.
Being a cat offers no special advantage, and raging would not lessen the impact.

Reasoning: The druid can access beast shapes that would offer a special advantage in three more levels, and the barbarian has disengaged from the battle that fuels his rage.

I agree with [MENTION=60210]jaelis[/MENTION], I wouldn't consider a healing variant unless that's something expected by your group. The shock of an unmitigated fall alone will get everyone on the edge of their seat. Be sure to bring up the instant death rules while calculating damage after the fall. That'll shake everyone up.

 

[alienux]

Hey I seen a school teacher with a whip survive an atom bomb.

Now if they only had a refrigerator to go inside of before they fall.

 

[Edwin Suijkerbuijk]

However, say that the druid turns into a cat or another small animal and falls while in the barbarian's arms. Would the druid take any damage?
Thoughts?

Wel turning in a cat alone woulden't be enough to reduce the damage at this heigth.
The terminal velocity of a cat is half that of a suman so I would rule for a cat the max faling damage would be 10D6 instead of 20d6

 

[Blue]

We are toying with increasing the damage die for longer falls starting with a d4 for 10 feet. So, 10 is d4, 20 is a d4 and a d6, 30 adds a d8, 40 add d10, 50, add d12, d20 at 60 feet and then it's d20s for the rest of the damage. Falls from a serious height should make ANYONE think twice.

If I was trying to simulate reality, increasing the damage die is a good way to show the acceleration that you're moving more than twice as fast with twice the distance, but at the same time STOPPING adding dice after the d20 is a great way to show terminal velocity, where in reality it doesn't matter if you fall 500 feet or 10000 it's the same speed and damage when you hit the bottom.

On the other hand, I'm fine with the easy abstraction of d6 per 10', especially since I'm already working with an abstract system where HPs don't have to equate to physical damage but can be getting worn down, using up your luck, etc.

 

[Xeviat]

OK, research agrees with you: http://www.bbc.com/news/magazine-17492802
So I'm convinced. Probably I would just add a special ability to cats that they take half damage from falls.

Same article:

"A cat in the US city of Boston survived a fall from a 19-storey window and only bruised her chest. How do cats survive falls from such great heights?"

19 storeys. That's, like, what, 19x15=285 feet? That'd be 20d6 damage. At half, that's 10d6. The cat has 2 hp.

I'd have to talk to my physics friends (or say something grossly inaccurate on the internet and summon one), but force equals mass times acceleration, right? So it's directly proportional. You cut a creature's weight by x20 (200 > 10), they're going have 20 times less force imparted when they hit the floor. Instead of 20d6, that's 1d6. Then, cat's have an athletics check to negate falling damage further as a reaction. It's not quite like a bug that can fall endlessly and not take damage (rats can survive pretty decent falls too I've read).

As for the barbarian not continuing to rage as they fall because they disengaged from their enemy and they aren't taking damage, that's a situation where I'd adhoc rule the adrenaline from the fall is enough to keep the rage going. Or they bite their tongue for 1 damage.

And, similarly, I'd probably have giants have advantage on strength checks to resist being pushed prone, but have them take damage from falling. The bigger they are ...

 

[Xeviat]

If I was trying to simulate reality, increasing the damage die is a good way to show the acceleration that you're moving more than twice as fast with twice the distance, but at the same time STOPPING adding dice after the d20 is a great way to show terminal velocity, where in reality it doesn't matter if you fall 500 feet or 10000 it's the same speed and damage when you hit the bottom.

On the other hand, I'm fine with the easy abstraction of d6 per 10', especially since I'm already working with an abstract system where HPs don't have to equate to physical damage but can be getting worn down, using up your luck, etc.

I think it's unnecessary. You fall about 600 feet in the first six seconds. That's way beyond the max falling damage. A quick googling says a limp human would reach terminal velocity at 1880 feet, so well, well past the 200 feet required for 20d6. So ... falling damage maybe shouldn't have a ceiling?

Now I want to massage the equations to determine how much force is XdY damage.

 

[jaelis]

I'd have to talk to my physics friends (or say something grossly inaccurate on the internet and summon one), but force equals mass times acceleration, right? So it's directly proportional. You cut a creature's weight by x20 (200 > 10), they're going have 20 times less force imparted when they hit the floor. Instead of 20d6, that's 1d6. Then, cat's have an athletics check to negate falling damage further as a reaction. It's not quite like a bug that can fall endlessly and not take damage (rats can survive pretty decent falls too I've read).

Well I can happily fill in the role of a physics friend But to start, it's clear that the dnd falling rules are based on game play and simplicity, not any attempt to model reality. I think that is a good thing.

But just to think about reality a bit: Probably the most accurate simple way to think about falling damage is in terms of stress, which is basically like pressure, equal to force per area. A given material can typically withstand a certain maximum stress before breaking.

The force need to bring a body to rest is indeed the mass M times the acceleration. The acceleration however is a little complicated, and depends on how much the material compresses as it strikes the ground. If the body compresses by an amount D, then the acceleration will be about V^2/(2*D) where V is the velocity just before hitting the ground. That velocity is given by the height H of the fall as V^2 = 2*g*H where g is the gravitational acceleration. So that says the acceleration experienced as you hit the ground is g*H/D. The the force is M*g*H/D.

Anyway, the stress is the force per area. Since the bodies of different creatures have about the same density, the area hitting the ground is proportional to the mass to the 2/3 power. So the stress should scale like M^(1/3)*H/D.

Finally, if you assume the bodies act sort of like springs, then the amount they compress D will be be proportional to the speed they hit the ground at, V. Since V goes like the square root of H, that leaves the stress S proportional to the cube root of M and the square root of H.

So up to the validity of those sketchy assumptions, this says a creature that weighs 8 times less could fall four times as far and take the same amount of damage. A creature that weighs 27 times less could fall 9 times as far.

Whee!

 

[phantomK9]

Well I can happily fill in the role of a physics friend But to start, it's clear that the dnd falling rules are based on game play and simplicity, not any attempt to model reality. I think that is a good thing.

But just to think about reality a bit: Probably the most accurate simple way to think about falling damage is in terms of stress, which is basically like pressure, equal to force per area. A given material can typically withstand a certain maximum stress before breaking.

The force need to bring a body to rest is indeed the mass M times the acceleration. The acceleration however is a little complicated, and depends on how much the material compresses as it strikes the ground. If the body compresses by an amount D, then the acceleration will be about V^2/(2*D) where V is the velocity just before hitting the ground. That velocity is given by the height H of the fall as V^2 = 2*g*H where g is the gravitational acceleration. So that says the acceleration experienced as you hit the ground is g*H/D. The the force is M*g*H/D.

Anyway, the stress is the force per area. Since the bodies of different creatures have about the same density, the area hitting the ground is proportional to the mass to the 2/3 power. So the stress should scale like M^(1/3)*H/D.

Finally, if you assume the bodies act sort of like springs, then the amount they compress D will be be proportional to the speed they hit the ground at, V. Since V goes like the square root of H, that leaves the stress S proportional to the cube root of M and the square root of H.

So up to the validity of those sketchy assumptions, this says a creature that weighs 8 times less could fall four times as far and take the same amount of damage. A creature that weighs 27 times less could fall 9 times as far.

Whee!

So then it would seem that a simple calculation could be derived based on the factors of Height and Mass yes?
Considering that the gravitation pull wouldn't change.

Height of course is easy to derive: How far is the fall.

Mass is a bit more tricky, but I think D&D does give us some easy guide there, with Size Categories.
We could even further derive the mass by looking at the Strength score, or maybe just the Modifier, thinking that a smaller, weaker creature with less muscle mass would have a lower Strength.

Off the top of my head maybe reduce the damage dice by X per reduction in size category, or increase by X per increase in size category. Or maybe just half or double....*shrug*

Then modify again based on Strength, so -1 die per -1 Modifier, +1 die per +1 Modifier??


Taking the real world example from above, of a cat falling 200+ feet.
That would be 20d6 damage base.
Divided by 1/4 for two size category reductions to 5 dice of damage.
Now reduce by 4 dice for the cat's -4 Strength Modifier, down to 1 die of damage.

Generous GMs might add in an Athletics/Acrobatics roll to reduce the damage taken??

Does that track?

This means of course that the Barbarian might be a little extra screwed and elephants would be completely boned, but they have lots of hit points, so maybe not that big of a deal.

 

[jaelis]

Well, thinking about it some more probably what I did there was really only valid when the fall is a pretty short distance. Once the forces get large enough to start breaking things, the damage probably doesn't scale with the stress any more, and your tissue doesn't act much like a spring.

Probably it gets complicated in reality, but I would guess that once damage is being done, that the "amount" of damage would scale like the total energy being dissipated in your body, divided by the total volume of your body. If that's right, then the damage would scale directly with the fall distance (until you approach terminal velocity), and it would be independent of your mass (except that terminal velocity depends on mass). That basically conforms to the dnd rules.

So my calculation might be reasonable for determining how far you can fall without taking any damage, but maybe once you are taking damage the dnd rule is a good way to handle it. At least it scales in a sensible way.

If you wanted to make things more realistic then, maybe you have a "safe fall" distance that depends on creature weight (and composition), and you take 1d6 damage for every 10 ft you fall past that distance.

 

[Euberon]

Just to clarify, we don't have a d20 ceiling on our draft rule. It's a d20 for every 10 feet after 50. Should be some sort of max, I suppose. Something to consider.