Post/Author/DateTime	Post
Count Arioch the 28th 01-25-08, 12:41 PM	As part of a brainstorming activity, I'm trying to design two other inhabitable planets in the fictional solar system of my campaign world. Because I'm not that creative, they will be based off of Mars and Venus in real life. The planet farther out will still be habitable by humanoids, but will be colder, have "low gravity" trait, have more severe wind, and have thinner air than the world humans, elves, and whatnot come from. (I will use the rules for high altitude for beings not native to the planet. Since the tsochar are the dominant sentient race on that planet, I'm putting the weirder, more alien creatures on that planet, such as Wystes and such.) The inner planet will be humid, hot, have normal gravity, and have insectoids as the dominant sentient races (Abeils, Formians, Thri-kreen, Dromites, etc. It will also be the neogi homeworld, but they've been driven off the planet.) I have decided that the planet will have a heavier atmosphere, possibly with a slightly higher oxygen content than the main world. How would you stat that in D&D terms? I want them to be noticeable, but nothing that a moderate to high level group of PCs can't overcome.
Man in the Funny Hat 01-25-08, 07:11 PM	The planet farther out will still be habitable by humanoids, but will be colder, have "low gravity" trait, have more severe wind, and have thinner air than the world humans, elves, and whatnot come from. (I will use the rules for high altitude for beings not native to the planet. Since the tsochar are the dominant sentient race on that planet, I'm putting the weirder, more alien creatures on that planet, such as Wystes and such.)Lower gravity means taller, larger, and at the same time more FRAGILE creatures (which is to say they will be weaker and more fragile when in a "normal gravity" environment.) What do you mean by "thinner"? If it means just lower oxygen content then okay, but if it means significantly lower density then you might want to rethink a bit. High altitude air is indeed lower density and the biggest problem from this is that it means a much lower amount of oxygen with each breath - in turn meaning more/faster breathing to get the oxygen you need. If this is the case then life will adapt to suit with larger lung capacities or lowered levels of activity to use LESS oxygen. Lower density air means a much lower height at which creatures can fly, not just because of the reduced oxygen but because you need disproportionately larger wings/higher speed to keep aloft. I have decided that the planet will have a heavier atmosphere, possibly with a slightly higher oxygen content than the main world. How would you stat that in D&D terms? I want them to be noticeable, but nothing that a moderate to high level group of PCs can't overcome.In denser air, smaller wings/lower speeds are needed to get the same amount of lift. I believe sound travels better/further in denser air and I think for an otherwise equivalent explosion you get greater concussive force over a larger area. More oxygen means smaller chest cavities needed to get sufficient oxygen (and more still if the air is also denser), or else that greater speed and endurance are possible and/or with smaller physical size. Creatures from a low density, low oxygen environment who suddenly find themselves in a high density, high oxygen environment may be drunk with O2 but otherwise find themselves able to perform excessively well if they don't pass out from hyperventilation. Unless the difference is REALLY significant in which case look at oxygen toxicity: http://en.wikipedia.org/wiki/Oxygen_toxicity For the opposite - creatures from a high density, high oxygen enviroment that find themselves in a low density, low oxygen environment will be weakened and pass out with low amounts of effort as you would with a very rapid climb to high altitudes without proper conditioning. If extreme enough you might be looking at hypoxia: http://en.wikipedia.org/wiki/Hypoxia_(medical) I'm sure I'm wrong a few finer points but this is where my thinking takes me.
Count Arioch the 28th 01-26-08, 01:19 AM	That's informative, but it doesn't quite answer my question. The PCs get dropped on a planet with an atmospheric pressure that's slightly higher than what is typical at sea level, but is not immediately fatal, what are the effects in game mechanics?
Krusk 01-26-08, 01:43 AM	I would use any rules you can find for going deep underwater. If there are none in stormwrack they might be in the DMG. You could also houserule something small like an over time pressure. that deals 1 damage a round. So you slowly pop, instead of immediatly.
Count Arioch the 28th 01-26-08, 03:11 AM	Actually, you won't explode due to decompression. Your capillaries might rupture underneath your skin, but your skin and frame will do a pretty good job of holding you together. Some ideas for the heavier atmospehre world: Positive effects for people of normal atmospheres: Can eliminate fatigue, or reduce exhaustion to fatigue with a full round action. (Result of the higher content of oxygen in the air, which is high enough to be noticably higher, but not high enough to cause oxygen toxicity) Flyers (creatures with a fly speed as an exceptional ability, not fly through a spell or supernatural ability) get their aerial mobility upgraded by one, due to the fact that it's easier to fly in thicker air (max of perfect, of course.) Air elementals get 1 hit point per hit die when summoned in a heavy atmosphere area. (Perhaps. I'm not in love with that idea, it's something I was thinking so I wrote it down.) The natives of this planet will of course not have these effects, being adapted to a thicker atmosphere and a higher oxygen content. (Most of the native creatures will be insectile in nature, which to me makes sense because in our world, the amout of oxygen in the air limits the size of insects, arachnids, and so forth.) When a PC is at an altitude of :Low peak of high pass", the air will be about equal to sea level on the main world. At "high peak", they will suffer the effects of altitude sickness (Fortitude save each hour (DC 15, +1 per previous check) or be fatigued. , note that at this altitude, the PC will not be able to take a full round action to remove the fatigue, as he would elsewhere on the planet.) Weather patterns will be milder, but the temperature will be much, much higher. (Upped by one temperature band, as presented in It's Hot Outside) The planet with a thinner atmosphere will be treated as one altitude band higher for all intents and purposes. (Altitude sickness at sea level, sever altitude sickness at low peak/high pass, and near vaccuum at high peak, which I may have to stat myself.) Air will be thinner, making flying harder, but gravity will be lower, for all intents and purposes flying will remain unchanged mechanically. Temperature shifted down one band, as presented in It's Cold Outside. Weather, especially winds, will be severe, and most of the planet will be desert, and filled with grit and dust. I've decided that I will fill the planet with alien, worm-like beings. Tsochar will be a dominant race on the planet, but so will beings such as Psurlons and Wystes.
sblaxman 01-26-08, 04:04 PM	If it is *significantly* thicker, then you could argue for a reduction in movement, ala "slow" spell for non-natives, or some variation of underwater combat, due to the increase in drag. Anything for a 10% movement reduction to a full out 'slow' spell effect
Loren Pechtel 01-26-08, 06:12 PM	At low levels it would increase endurance. As the pressure rises you'll see more effects: Missile ranges will drop due to increased drag. The atmosphere will become lethal to anything used to our atmosphere. There are two problems here: 1) Nitrogen narcosis. (While the name refers to nitrogen it really applies to all gases other than oxygen. It's just different gases have different degrees of effect.) Long before you reach anything remotely resembling Venus this will be lethal. 2) Oxygen toxicity. Again, long before you reach Venus this will become lethal. To some extent you can overcome these with something like an oxy-helium atmosphere with a low oxygen percentage. (You'll need a big planet to hold onto the helium, though.) As you push this to the limit you'll find an important effect: Fire will become impossible Flight will become possible with smaller wings. Note that flight does not become *EASIER*--you have to work just as hard to fly. The result will be bigger flying creatures as they don't need big wings--the limit on flying critters is not how heavy they can be to fly, it's wing loading. With sufficient density you'll see the emergence of balloon creatures. They will chemically split water to make hydrogen gas and use that to float. Such creatures will probably rely on photosynthesis.
Count Arioch the 28th 01-26-08, 06:34 PM	That's one idea, maybe add -2 to all ranged attacks due to increased drag. Like I said before, there are organisms on this planet, and I don't want it to be instantly fatal to a PC group. (There will in fact be inhabited planets that will mostly be fatal to PCs without severe precautions, but the three main planets I want to be viable for adventure locations from mid-levels on. Now, a Thri-kreen wouldn't be able to survive on the outer of the three, and a tsochar would find the inner of the three equally hostile unless inside of a suitable host, but that's different.) But I don't want real-world venus, I want something that looks somewhat like this: http://i35.photobucket.com/albums/d160/ZantiRocks/VENUSMAP.gif (Credit goes to Chris Wayan for the pic)
Voran 02-01-08, 07:06 PM	Hm, I'm not sure if this would help, but there may be online resources for the old Spelljammer stuff that had 'worldbuilding within a crystal sphere' kinda information.
BruteSquad01 02-02-08, 11:21 AM	...I believe sound travels better/further in denser air and I think for an otherwise equivalent explosion you get greater concussive force over a larger area.... Actually, the opposite is true. "Sound" is our perception of waves of moving air. Less air = less resistance = sound waves moving farther. More air = more resistance = sound dies out in a shorter distance. To put it another way, a sound is a wave of energy that will move an amount of air based on its amplitude and frequency. If we make a sound on earth, it will move x amount of air. If we make the same sound on the other planets, it will move the same amount of air, as it has the same energy level. In a denser atmosphere, there is more air in any area than on earth, so x amount of air will be moved in a shorter distance than on earth. In a lighter atmosphere, there is less air than in any area on earth, so x amount of air will be moved over a longer distance.
Arcane-surge 02-06-08, 12:37 PM	There are some simple traits in Unearthed Arcane that might help. There's one that halves movement, while increasing hp, and one that decreases hp slightly while increasing movement (But not doubling it). Seems ideal for illustrating the subtleties of pressure/gravitational difference. Then again, I'm a philosopher, not a physicist.
sblaxman 02-07-08, 01:17 PM	There are some simple traits in Unearthed Arcane that might help. There's one that halves movement, while increasing hp, and one that decreases hp slightly while increasing movement (But not doubling it). Seems ideal for illustrating the subtleties of pressure/gravitational difference. Then again, I'm a philosopher, not a physicist. And I'm the opposite (engineer)... A lot of good ideas from everyone I've read... You could try to go an uber-realistic way, or go for a more "game flavor" way, which actually would probably more fun. The hardest part, IMO, will be to make sure you are consistent... I can imagine mid-session totally forgetting the atmosphere effect for a while, but if you make good solid notes it should work. Have fun with it!