The Piazza

For earlier iterations and inspiration, see here and here.

Base falling damage is 1d6 per 10 feet fallen, capped at 60d6 (usually at 600 feet fallen). For purposes of damage resistance, this is considered Bludgeoning damage.

• Falling onto a soft surface converts the first die of damage to a single hit point of damage. For example, falling onto mud from 20 feet up will do 1d6+1 hp damage.
• Any character who is conscious will reflexively try to protect their most breakable bits. A DC 10 Reflex save allows them to convert an additional die of damage to a single hit point of damage.
• If you intentionally jump down (rather than fall by accident), you can use your Jump or Tumble skill (choose your best one) to reduce damage. A DC 15 skill check lets you convert one die of damage to a single hit point of damage. This reflects rolling with the fall, and you will land prone (just like with a regular fall).
• Instead of rolling with the fall, you can intentionally try to land on your feet. This is a DC 0 (plus distance fallen) Jump check. If you succeed, you land on your feet, one die of damage is converted to a single hp (as for rolling with the fall), and you are considered to have rolled a natural 20 for both the save to avoid stun/daze condition, and for the save to reduce any Dexterity damage received. If you fail this skill check, you are considered to have rolled a natural 1 on each of the two saves listed above.
• If you are falling onto a body of water, you can attempt a dive instead. The water must be at least one-third as deep as the distance fallen to successfully attempt a dive. A dive requires either Swim or Tumble skill (choose your best one). The DC number is 15, +1 per 10 feet fallen. Success means you take no damage. If you fail, you take no damage for the first 20 feet, one die of damage for the next 20 feet, and one die of damage for each additional 10 feet, plus you must check for Dexterity damage and stun/daze effects as for a regular fall. Being stunned can be very bad for you if you can't breathe water. If the water is less than 10 feet deep, it is instead treated as a fall onto a soft surface.
• If you fall onto a spiked pit, this is treated as a regular fall. The spikes then perform an "attack", with 1d4 attacks, bab +10, and 1d4+4 damage per attack (these numbers are based on the Traps section of the SRD).

For each die of damage taken, you also take 1d6-3 (minimum 0) Dexterity damage. A DC 15 Fort save is rolled. Each point by which the DC number is beaten lets you reduce the Dexterity damage by one point. This damage recovers at the normal rate (one point per day), unless magical healing is available.

Roll a DC 15 (+1 per 10 feet fallen) Fort save. If you fail, you are stunned, and dazed for one round per 10 feet fallen. If you succeed, you are not stunned, and each point by which the save DC number is beaten lets you reduce the daze duration by one round.

So How Do Folk Survive Falling from Orbit or Aircraft?

If you have any action points to spare, you can spend one to cap hit point and Dexterity damage to "all but the last point".

Special Sci-Fi Environmental Considerations:

Air Pressure: The 60d6 damage cap is not affected for air pressures lower than Earth's. For higher air pressures, multiply the damage cap by (1 / cube root of air pressure). For example, Venus (95 atmospheres) would have falling damage capped at 13d6. Of course, you'll be simultaneously crushed, suffocated, dissolved, and roasted, once you land there...

Gravity: The effective distance fallen is multiplied by local gravity; a 60-foot fall on Earth's Moon (1/6 Earth-G) would be treated the same as a 10-foot fall on Earth. This can get dangerous fast on planets with high gravity. (Note that current theories of planet formation don't allow for rocky planets with surface gravities over 3 G; such bodies tend to sweep surrounding space of light elements, and become gas giants).

Spelljammer had some rules about this somewhere, but I can't recall where at the moment. I think the basic thing was that if you fell from orbit you would start to burn up from air friction before hitting the ground with maximum damage.

We will be needing to make some sort of rule for the 3e SJCS conversion. I'd be inclined to treat air friction as being a bit like the "landing on a soft surface" rule (so that a fall onto a world with air would have no limit maximum damage). SJ pretty much makes all planets have a 1G gravity, but if you want to make sci-fi rules (rather than D&D rules) I'd say you should bump up max damage for planets with high gravity and lower it for planets with low gravity.

The SF considerations are specifically written to deal with RL physics, not SJ physics

If you fall from orbit, you're pretty much going to hit the maximum damage for that planet anyway. The maximum damage is a function of terminal velocity, which is a function of atmospheric resistance, rather than gravity. The actual effects of air pressure are almost irrelevant to falling damage, truth be told. You'll hit that terminal velocity sooner with a high gravity planet, but the terminal velocity will be lower with a planet that has a high density atmosphere.

Incidentally, the highest density atmosphere that is normally considered breathable in SF settings is about 1.5 atmospheres. Under the formula in my OP, that would cause damage to be capped at 52d6. It still takes less dice to roll up a new character

I purposely ignored the thermal effects of orbital re-entry for this rule. When written, I expect it will be on the lines of "lots" of fire damage (probably 3d6 fire damage per round for n rounds; most re-entry vehicles will have fire resistance 20). The falling damage would only then be relevant if you survive the fire damage.

For SJ...

Since gravity is always either 0G or 1G, the gravity rule is irrelevant. The air pressure rule can also be ignored (treat everything as capped at 60 dice), since SJ doesn't deal with air pressure except in a binary, vacuum/Earth-normal sense. Whether orbital re-entry has thermal effects is probably something that depends on the physics of the sphere in question.

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The main issue I am unhappy with for now is that this system requires no less than three saving throws, plus damage rolls. It's a bit too much like a dice-rolling festival for my tastes.

Slightly OT, but I love the falling rule from 7th Sea. You take no damage at all if you fall on something soft:

* Water
* A pile of Hay
* Onto the saddle of a horse



Havard

Collisions

Danger: thinking out loud and extreme maths ahead.

ref pages:
http://www.safespeed.org.uk/killspeed.html

Related to falling is the impact from a vehicle.

Your final velocity from a fall is 9.80665 m/s multiplied by the time spent falling. The actual distance fallen is your average velocity over that period (ie. half your final velocity) multiplied by the time spent falling. Suitable use of conversion factors can then produce conversions for final velocities at various speeds and various distances. In short, it should be possible to equate every possible vehicle speed to an equivalent "falling distance" for damage purposes. As raw, non-massaged figures, this yields the following figures:

* Speed 0-25 mph (0-40 kmph): no meaningful damage
* Speed 25-43 mph (40-70 kmph): 1d6 damage
* Speed 43-56 mph (70-90 kmph): 2d6 damage
* Speed 56-66 mph (90-107 kmph): 3d6 damage
* Speed 66-75 mph (107-121 kmph): 4d6 damage
* Speed 75-83 mph (121-134 kmph): 5d6 damage
* Speed 83-90 mph (134-145 kmph): 6d6 damage

and so on.

This suggests that any impact of 25+ mph is liable to kill a commoner more than half the time. That seems to tie in with the government statistics quoted on the web page. The web page, however, notes that the government statistics appear to have been made with the assumption of crash test dummies and psychotic drivers. That is certainly not the case in the real world. Thankfully for our purposes however, it is alarmingly often the case in an RPG, which makes their numbers useful for us.

Unfortunately, these numbers blatantly do not scale up appropriate for vehicles and typical vehicle hit point totals. This can of course be fixed by multiplying appropriately for the vehicle size (larger vehicles have less structural integrity, and are less able to withstand impacts).

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Aside 1: How d20 Modern handles collisions
http://www.12tomidnight.com/d20modernsr ... hicles.php

The size of the damage die depends on the speed, and the number of damage dice depends on the size of the smallest object involved. A literal reading of these rules says that a naked human can run into a commoner, inflict 4d2 damage, and guarantee a kill
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Aside 2: How GURPS handles collisions

damage inflicted by an object is based on (velocity x hit points), with velocity measured in yards/second, and hit points being typically 10 for a standard human. Falling has a special rule, in that damage is doubled if you fall onto a hard surface (such as most floors).

This makes a 10-yard fall "typically lethal", with a 50:50 chance of killing. Acrobatics skill can be used to reduce the effective distance fallen (similar to d20's Tumble/Jump skill usage).
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Curiously, I seem to have adopted the same "physics" approach that GURPS uses, except that I use size class as a multiplier on damage inflicted, rather than using hp to measure mass, as GURPS does. Each size class larger adds the base damage once more (x2 for Large, x3 for Huge, etc.), and each size class smaller divides the base damage (/2 for Small, /3 for next size class down, etc.).

In order to account for the GURPS assumption that a collision is equivalent to falling on a soft surface, vehicle damage should be halved.

This is all getting rather complicated. Making I should rethink this.

Worked example: Human (medium size) gets hit by a car (huge size) moving at 50 mph. That's a base 2d6 damage. The human inflicts that much damage on the car, because he is medium size. the car inflicts 6d6 damage (x3) on the human, because it is two size classes larger than the base value. That's 6d6 damage. No commoner is going to survive that, and even heroes are in for ouch time.

I will have to admit I was always partial to the rule update in some very early Dragon magazine: 1d6 per 10' for every 10' fallen, which was supposedly the original AD&D rule (before an editor deemed it redundant and simplified it). This means 1d6 at 10', 3d6 at 20' (1d6 + 2d6), 6d6 at 30' (1d6 + 2d6 + 3d6), etc.

I think I liked it because it kept higher-level characters from jumping off cliffs to escape stuff

Gives the sense of acceleration too! I like it.

More on Falling:

The GURPS formula makes falling damage proportional to the square root of the distance.

http://www.avsec.com/interviews/vesna-vulovic.htm

In game terms, she spent an action point to survive that fall. Judging from the number in the final paragraphs, despite gravity being 9.8 m/s2, a human body doesn't accelerate that fast.

Actual experimental data about fall survivability is, perhaps not surprisingly, hard to find.

http://www.cdc.gov/niosh/topics/falls/

I don't think that realism is the way to go with this. Trying to decide exactly how likely you are to die from falls of different distances and adjusting the falling damage accordingly is like trying to find out how likely you are to die from a getting sword through the head versus an axe in the head in order to work out weapon damage.

Basically, when it comes to falling in the real world, what you land on and how you land is much more important than how far you fell. You can fall 10' from a ladder and land on your head on jagged rocks and die, or you can fall 10,000' from an aeroplane without a parachute and survive because you landed on a snowy slope covered trees.

So I think that falling damage should be covered by the Rule of Cool and the Rule of Drama.

Do you want concealed pit traps to be a danger rather than an inconvenience? Then make falling damage big.

Do you want characters to be able to heroically jump out of high windows and land in conveniently placed haystacks? Then make falling damage small.

But I don't think any attempt to realistically model falling damage using hit points is going to work alongside D&D's fairly arbitrary hit-point system where damage that is guaranteed to kill a peasant can be shrugged off by someone with fighting experience even though the damage is unrelated to fighting expertise.

I'm with Blacky on this one. In the end, the fun of the game is paramount, seconded only by the drama of the story.

Roger

My primary concern with the overall project is to be able to play a game that looks and feels realistic. Creating cinematic is easy - just pull some numbers out of a hat. The only question is how cinematic is that. 1d6 per 10 feet is plainly cinematic once you hit 40 foot falls, even for a 3rd level hero. 1d6 per 5 feet? per 20 feet? Hard to say. There's no objective scale to judge how much a cinematic fall hurts.

There is, however, an objective scale (albeit untested by extensive experimental data) on how much a realistic fall hurts. And it happens to be quite easy to modify a realistic set of rules to deal cinematic damage. It is a lot harder to modify a cinematic rule to realistic levels. That's why the base rules assumptions I am writing are for realistic injuries.