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[SixOfSpades]

We can only have 'cavern magic' in a world that has a high level of magic

Yes, unless Toady decides that cavern energy actually isn't magical in nature, that's just the way the DF world works. But either way, there needs to be a way for the player to control the amount of cavern life during worldgen, so that those who wish to make completely Earthlike (i.e., barren) caverns can do so.

and in that case we simply model the magical sources of stuff the same way we model stuff coming through cave entrances/rivers.

If it's magic, why does it have to be restricted to the same access paths as everything else? I see two more entertaining sources: Above and/or below.
Above: Suppose that there is a type of DF fungus/moss that grows on all rock ceilings that have nothing but Inside, Below ground, Dark tiles below them. This would eliminate everything but the caverns and tunnels--if you wish to rule out dwarf-mined tunnels, simply set the fungus's growth rate to 0 (it cannot spread from a cavern tile to one inside your fort). Now give the fungus bioluminescent spores that slowly fall straight down--and the brightness of the spores (& therefore energy released) is directly proportional to the number of z-levels that the spores have to fall. So the most open caverns would be relatively brightly lit, with plenty of biotic energy to support an ecosystem. (If you wish to make a token nod to realism and have the health of the ceiling fungus depend of groundwater seeping from above, that might work too.)
Below: Surface plants may get their life from the sun, but subterranean plants draw it right from the earth itself. The stones are naturally quite hospitable to plants, as long as there is adequate moisture there as well--splash some water on the bedrock and watch it bloom into life. All underground living stone floors are potential gardens and forests . . . until the very life is blasted right out of them by direct sunlight, that is. The size/health of underground plants are limited by the number of solid stone z-levels below them, and the vertical clearance of z-levels above them (so no trees can grow in a 1-tile tunnel and block the passage). The higher and healthier a bioluminescent tree grows, the more light/energy it puts out. Again, the bigger caverns are brighter (provided there's sufficient water, of course).

I do not think having a whole load of underground rivers to provide nutrients/oxygen to the caverns is in any way artificial, it is simply the realistic mechanism by which you would end up with lots of caverns that are more 'interesting' than real-life caverns. . . . we just have this go on on a larger scale than on earth in order to get more cavern life

I'm just afraid that it's really easy to take this too far. Having the habitat dictated by the creatures that (you want to) live there is literally preposterous, and can easily be seen as noticeably artificial. Think about it: Do all the underground rivers drain into an underground sea? Can the amphibious races in that sea therefore invade any cavern that drains into it? And how does that water reach the surface once again--is the water actually boiling, from being so close to the magma sea, and the world's volcanoes were actually formed by air pressure? The ramifications of this scenario demand that you tread lightly.

We do however actually want a lot of boring earth-like caverns and not too many interesting ones because it keep things balanced as the cave dwelling pops should be balanced against the surface ones.

Well, the surface races have huge swaths of (usually) fertile terrain to explore, roam, and colonize--the main thing keeping them in check is pressure from other surface beings. So if the cavern races have a similar setup, isn't that balanced?
But I agree on having at least a few barren caverns, if only for the sake of variety. Plus the aforementioned gas pockets and giant crystals. But I also mentioned archaeological ruins and fossils . . . which are problematic. I don't mind the DF universe not having oil, because as almost all worlds are generated with very short histories (even 1000 years is regarded as really pushing the envelope), there is no way oil would have had time to form. But then again, neither would fossils. Or, in fact, several things which are already IN the game, like petrified wood and limestone. This "age paradox" is something that should really be up for Toady alone to resolve, but I for one will try to avoid suggesting any new anachronisms until Toady says it's OK.

Temperature does not have to be modeled separately since realistically (not at the moment) the deeper into the earth you go the hotter it should get.

In general, yes, but some caverns will also be closer to magma tubes, or even have exposed pools right there IN the cave. I'm tired of video-game lava being completely safe as long as you don't actually touch it, the whole damn cave should be hot.

I think that oxygen should be superimposed onto the cavern biomes determined by the amount of water and nutrients

Wait--you just said that cavern plants shouldn't produce oxygen. Are you painting the underground rivers as the only source for everything? Water can only absorb so much oxygen, you know.

Populations, including civilized ones should reduce the available oxygen in a cavern but industry should have the greatest negative effect.  It should be possible to commit genocide effectively in a cavern if you decide to fire up your furnaces inside a cavern but the intelligent cavern creatures whoever they are should not simply die off passively. Hence metal should be scarce in caverns, with cavern dwellers preferring to mine ore and sell it to surface sites rather than trying to smelt it themselves.

Yes--it's time to use the smoke/miasma code to simulate industrial pollution. Make players dig realistic ventilation systems, perhaps with Windmills used as fans (consuming power, rather than generating it) to pump the smoke out & fresh air in. Also, that's another advantage for the dwarves, as their "transitional" nature means they can dig up ores in the caverns, then take it topside for the smelting.

[EDIT: Added 2nd half of my reply.]

[SixOfSpades]

As for laying entities on the map, I say just record Z map data for every site. Just like how we allot X and Y tiles during embark, allow us to assign Z tiles as well, with the default being all 4 Z tiles (surface, first cav, 2nd, 3rd, magma sea).

Well, the actual elevations of the various cavern layers can't be assumed to fall neatly into 4 equal divisions, because for one thing you can control them in advanced worldgen: If you want to generate a world that has no less than 500 z-levels of uninterrupted stone before you reach the first cavern, and then only another 20 layers before you hit the magma sea, you can do that. Or were you referring to deliberately limiting embark size? For example, if your computer isn't that fast but you still want to build a 4x4 fortress, you could "stop" your map at the 2nd cavern level, thus giving your CPU less to think about?

A cool aspect about real caves? There's multiple kinds:
https://en.m.wikipedia.org/wiki/Cave
. . .
Map tiles would record 'Cave Mouth' in their tiles, like how they do with aquifiers and specific metals.
After forming the entrance, it can also vary the content according to real caves:
. . .
These structures would allow caverns to physically look distinct as well; whether they form large open Ramiform 'rooms', or thin, winding branchwork tunnels. Given our fantasy nature, I could also see fantasy tunnels being carved -- great open tunnels formed by gigantic worms, or patchwork mines dug out by dwarves, goblins, and other subterranean folk containing old equipment and rotted support pillars.

Strong yes to all of this.

[Qyubey]

As for laying entities on the map, I say just record Z map data for every site. Just like how we allot X and Y tiles during embark, allow us to assign Z tiles as well, with the default being all 4 Z tiles (surface, first cav, 2nd, 3rd, magma sea).

Well, the actual elevations of the various cavern layers can't be assumed to fall neatly into 4 equal divisions, because for one thing you can control them in advanced worldgen: If you want to generate a world that has no less than 500 z-levels of uninterrupted stone before you reach the first cavern, and then only another 20 layers before you hit the magma sea, you can do that. Or were you referring to deliberately limiting embark size? For example, if your computer isn't that fast but you still want to build a 4x4 fortress, you could "stop" your map at the 2nd cavern level, thus giving your CPU less to think about?

Strong yes to all of this.

I didn't think about it very hard, but probably that yeah. I've no idea how caverns generate in the game and I'm not going to even try to speculate.

And yeah, caves have a ton of variety in real life. Obviously that doesn't immediately translate into good code, but it's something for Toady to consider if he even goes back to redesign them.

[GoblinCookie]

http://www.bay12forums.com/smf/index.php?topic=76007.0  http://www.bay12forums.com/smf/index.php?topic=76578

  Giving that Toady is currently working on parts of the magic system and that ecology needs to be taken into consideration, these threads could be of great use in this discussion. You also need to keep in mind that there is going to be a special caste of Dwarves living in the caverns that need to be accounted for (sorry if they were mentioned already). It's also very important to keep in mind that creation  myths could end up influencing the structure of high magic worlds, so we'll actually need a number of these systems, not just one.

Given that both those threads are ancient dead threads from years ago the thread necromancy is *not* appreciated, even if linking to them is acceptable as long as we clarify that those are way out of date.  There are already a special 'caste' of dwarves living in the caverns but the game does not deal with their sites very well at all, aka mountain hall dwellers. 

Yes, unless Toady decides that cavern energy actually isn't magical in nature, that's just the way the DF world works. But either way, there needs to be a way for the player to control the amount of cavern life during worldgen, so that those who wish to make completely Earthlike (i.e., barren) caverns can do so.

Once building sites in the caverns freely becomes part of the game then we cannot simply state that caverns produce energy and nutrients automatically everywhere because otherwise dwarves and goblins (kobolds maybe as well?) will completely overrun the world because they can expand on 4 maps rather than 1 map.  The habitable cavern areas have to be a limited part of the whole in order for us to not only make caverns strategically important AND at the same time control the expansion of cavern dwelling civs.

If it's magic, why does it have to be restricted to the same access paths as everything else? I see two more entertaining sources: Above and/or below.
Above: Suppose that there is a type of DF fungus/moss that grows on all rock ceilings that have nothing but Inside, Below ground, Dark tiles below them. This would eliminate everything but the caverns and tunnels--if you wish to rule out dwarf-mined tunnels, simply set the fungus's growth rate to 0 (it cannot spread from a cavern tile to one inside your fort). Now give the fungus bioluminescent spores that slowly fall straight down--and the brightness of the spores (& therefore energy released) is directly proportional to the number of z-levels that the spores have to fall. So the most open caverns would be relatively brightly lit, with plenty of biotic energy to support an ecosystem. (If you wish to make a token nod to realism and have the health of the ceiling fungus depend of groundwater seeping from above, that might work too.)
Below: Surface plants may get their life from the sun, but subterranean plants draw it right from the earth itself. The stones are naturally quite hospitable to plants, as long as there is adequate moisture there as well--splash some water on the bedrock and watch it bloom into life. All underground living stone floors are potential gardens and forests . . . until the very life is blasted right out of them by direct sunlight, that is. The size/health of underground plants are limited by the number of solid stone z-levels below them, and the vertical clearance of z-levels above them (so no trees can grow in a 1-tile tunnel and block the passage). The higher and healthier a bioluminescent tree grows, the more light/energy it puts out. Again, the bigger caverns are brighter (provided there's sufficient water, of course).

Cavern plants do not presently grow on rock, they only grow on soil.  There is also no way to draw 'life' from the rock itself, that whole concept is completely unrealistic in the extreme.  Also this is insanely unbalancing in favour of dwarves, since if all I have to do is carve up solid rock and I get plants I now have effectively limitless carrying capacity for my enviroment, but not for anybody else.

On a positive note, if there are sufficient nutrients in a cavern we could have bioluminescent trees along the lines you mentioned and then we could have cavern plants (not fungus) that photosynthesis using the light from said trees, if they are in sufficient quantities; providing an alternative source of oxygen to the surface in biomes lucky enough to have such unique cavern plants. 

I'm just afraid that it's really easy to take this too far. Having the habitat dictated by the creatures that (you want to) live there is literally preposterous, and can easily be seen as noticeably artificial. Think about it: Do all the underground rivers drain into an underground sea? Can the amphibious races in that sea therefore invade any cavern that drains into it? And how does that water reach the surface once again--is the water actually boiling, from being so close to the magma sea, and the world's volcanoes were actually formed by air pressure? The ramifications of this scenario demand that you tread lightly.

Of course the rivers can drain into an underground sea, because the actual ocean *is* underground.  It is not too much of a stretch to have underground rivers drain into the actual sea itself, as happens in real life.  The model I am using can also be used to represent undersea civilizations as well, should the devs or modders deign to add them in, since the ocean floor will always be at one of the levels. 

Well, the surface races have huge swaths of (usually) fertile terrain to explore, roam, and colonize--the main thing keeping them in check is pressure from other surface beings. So if the cavern races have a similar setup, isn't that balanced?
But I agree on having at least a few barren caverns, if only for the sake of variety. Plus the aforementioned gas pockets and giant crystals. But I also mentioned archaeological ruins and fossils . . . which are problematic. I don't mind the DF universe not having oil, because as almost all worlds are generated with very short histories (even 1000 years is regarded as really pushing the envelope), there is no way oil would have had time to form. But then again, neither would fossils. Or, in fact, several things which are already IN the game, like petrified wood and limestone. This "age paradox" is something that should really be up for Toady alone to resolve, but I for one will try to avoid suggesting any new anachronisms until Toady says it's OK.

No, the surface races have only one map to colonise between themselves, the cavern dwelling races have all 4 maps.  Thus it has to be the case that the cavern maps are less habitable than the surface world or else those civilizations will dominate the surface world because they also dominate the underground world.  In this case as already mentioned realism goes hand in hand with game balance needs. 

In general, yes, but some caverns will also be closer to magma tubes, or even have exposed pools right there IN the cave. I'm tired of video-game lava being completely safe as long as you don't actually touch it, the whole damn cave should be hot.

Aha, I forgot about those things.  The underground temperature should be determined generally by how deep you are, this is a detail presently missing from the game.  Actually it should generally be too hot to access the magma in most places, a volcano or magma tube should be the only place that something like a magma smelter should be possible.  On most maps your dwarves should burn to death a few levels above the actual magma sea.   

Wait--you just said that cavern plants shouldn't produce oxygen. Are you painting the underground rivers as the only source for everything? Water can only absorb so much oxygen, you know.

What I mean is that biomes should be generated first and then the oxygen level calculated, so that we have zones on top of the biome.  I am talking about the mechanics of how the oxygen levels would be dealt with, that is separately from the biomes but superimposed onto them. 

Yes--it's time to use the smoke/miasma code to simulate industrial pollution. Make players dig realistic ventilation systems, perhaps with Windmills used as fans (consuming power, rather than generating it) to pump the smoke out & fresh air in. Also, that's another advantage for the dwarves, as their "transitional" nature means they can dig up ores in the caverns, then take it topside for the smelting.

[EDIT: Added 2nd half of my reply.]

The need for the player to take into account ventilation should be a major part of fortress mode.  It also adds a whole set of defensive issues, since enemies might be able to use the ventilation shafts to attack, truly putting an end to the sealed can defense we presently use.  If you try and brick off your dwarves then you would simply dig yourself into your own tomb to survive you would need access to the outside either caverns or surface but enemies could use those to attack. 

[Bumber]

You also need to keep in mind that there is going to be a special caste of Dwarves living in the caverns that need to be accounted for (sorry if they were mentioned already).

There are already a special 'caste' of dwarves living in the caverns but the game does not deal with their sites very well at all, aka mountain hall dwellers.

I think he's talking about deeper dwarves:

Capntastic:   So the deep down dwarves, when they come up, maybe they should just be very very allergic to the sun?
Toady:   Well they will be cave adapted.
Rainseeker:   Exactly.
Capntastic:   But extremely cave adapted, have another tier.
Toady:   Maybe blind, they'll just lose their eyes.
Capntastic:   They'll be blind and they'll be completely white, you know, like those cave fish.
Toady:   Beardless, beardless, no, they'll have flesh that replaces the beard or something like these tendrils that come out..
Capntastic:   Fleshy beards?
Toady:   Translucent fleshy beards that generate light, but they don't have eyes, so it doesn't mean anything. And yeah, they have alcohol detectors in their stomachs and so on, they waddle around and roll in the mud. And yeah, so that's about like a dwarf. That's what we expect from a dwarf.
Rainseeker:   Ya, that's pretty good.
Toady:   A Cthulu-esque mob that comes out of the deep.
Capntastic:   But they're friendly and they talk with a Scottish accent.

[SixOfSpades]

http://www.bay12forums.com/smf/index.php?topic=76007.0  http://www.bay12forums.com/smf/index.php?topic=76578
Giving that Toady is currently working on parts of the magic system and that ecology needs to be taken into consideration, these threads could be of great use in this discussion.

Given that both those threads are ancient dead threads from years ago the thread necromancy is *not* appreciated, even if linking to them is acceptable as long as we clarify that those are way out of date.

Actually, I've never heard that old-thread-linking was frowned upon, nor do I think it should be. If I was going to chastise Gargomaxthalus for anything, it would be for bringing up two very tl;dr threads for us to pore through, rather than going through the threads personally and plucking out a couple of choice quotes, or even paraphrases, to pique our interest on how those threads could constructively relate to ours.

But while we're on the subject . . .

AFAIK, caverns are going to be affected by sphere (nature, wealth, fire, etc.) biomes, once implemented. Supposedly even the HFS will be replaced.

This confuses me somewhat. Okay, so a cavern will have to be in a "jewels"-affiliated biome in order to have gems in it? At least, in a world with Magic turned all the way up? In other words, if I want lots of priests, dragons, and magical artifacts, I have to settle for a world in which only certain biomes (those with ties to the spheres of nature, trees, water, agriculture, etc.) can have living caverns, and the caves everywhere else in the world must be barren?

Yes, unless Toady decides that cavern energy actually isn't magical in nature, that's just the way the DF world works. But either way, there needs to be a way for the player to control the amount of cavern life during worldgen, so that those who wish to make completely Earthlike (i.e., barren) caverns can do so.

. . . we cannot simply state that caverns produce energy and nutrients automatically everywhere because otherwise dwarves and goblins (kobolds maybe as well?) will completely overrun the world because they can expand on 4 maps rather than 1 map.

Admittedly, the primarily-surface races like elves & humans need more above-ground relative advantages if they are going to stay be competitive on their home turf. But that doesn't mean that each of the cavern maps should be considered to be even close to equivalent to the surface map. In a cavern, you can easily hunt the local wildlife to extinction, which in the real world would spell starvation--but on the surface, there's always another herd of something wandering by. Besides, I specifically said "there needs to be a way for the player to control the amount of cavern life during worldgen". Maybe this means a decreased chance of caverns being fertile, maybe it's a modifier on how potent cavern energy is (relative to sunlight). I'd be fine with either, or both.

Cavern plants do not presently grow on rock, they only grow on soil.  There is also no way to draw 'life' from the rock itself, that whole concept is completely unrealistic in the extreme.

Yeah--and, currently, if you sprinkle a few drops of water onto bare stone, you somehow get soil. I have always hated this mechanic, which is why I'm using this discussion as another reason to draw attention to it. I am not, however, opposed to (underground) plants magically drawing energy from rock--at least, as long as it's "living" stone that has never been mined and is therefore still directly connected to Armok. After all, this is a universe where certain creatures can be composed of bronze, ruby, gabbro, magma, steam, and vomit, and still be considered to be "alive", so extending the concept to the earth itself isn't that much of a stretch. So I will continue to insist on all plants & most fungi needing at least some actual soil to grow, but I'll also support cavern "trees" having short roots that just reach the stone & then stop--because that's as far as they need to go.

Of course the rivers can drain into an underground sea, because the actual ocean *is* underground. It is not too much of a stretch to have underground rivers drain into the actual sea itself, as happens in real life.

Sorry, I forgot to mention sea level as a consideration. Underground "rivers" below sea level (or the level of whatever they're draining into) do not flow, so whatever water keeps getting added from above will quickly flood the whole cavern. This won't be an issue for forts located in mountain biomes, but sites close to the shore can have no cavern rivers at all. Lakes, yes, but not rivers.

Wait--you just said that cavern plants shouldn't produce oxygen. Are you painting the underground rivers as the only source for everything? Water can only absorb so much oxygen, you know.

What I mean is that biomes should be generated first and then the oxygen level calculated, so that we have zones on top of the biome.  I am talking about the mechanics of how the oxygen levels would be dealt with, that is separately from the biomes but superimposed onto them.

I don't see the need for these oxygen "zones", particularly as that's such a general word that already has a perfectly good DF definition, it doesn't need another one. I think it'd make more sense to just generate the caverns at worldgen, see which ones are damp, populate those with appropriate flora, calculate the oxygen generated by those flora, and then have the gods magically generate the appropriate amount of animal life to equalize that oxygen surplus. Oxygen percentage inside the fortress would be calculated (probably monthly) as an average of the outside (unless you're walled in), any breached caverns, and any farm plots / orchards sharing fortress airspace, all divided among your dwarf / guest / livestock / pet population. As for more localized air quality such as that created by a particularly lush tree, the noisome fumes of a geothermal vent, or the smoke of a smelter, those can be handled similarly to a happy thought generated by expensive furniture.

[Bumber]

AFAIK, caverns are going to be affected by sphere (nature, wealth, fire, etc.) biomes, once implemented. Supposedly even the HFS will be replaced.

This confuses me somewhat. Okay, so a cavern will have to be in a "jewels"-affiliated biome in order to have gems in it? At least, in a world with Magic turned all the way up? In other words, if I want lots of priests, dragons, and magical artifacts, I have to settle for a world in which only certain biomes (those with ties to the spheres of nature, trees, water, agriculture, etc.) can have living caverns, and the caves everywhere else in the world must be barren?

I would think it's more like a jewels biome having huge gems jutting out of the walls, etc.

A tree or ocean sphere might exclude gems due to lacking rock walls, instead having (petrified) wood or salt pillars.

[Qyubey]

...This discussion about environmental magic is really reminding me of something else I used to play a lot; the Thaumcraft mod for Minecraft. Specifically thaumcraft 2, since they basically redid the entire mod for v3 onwards and I didn't really like the changes.
Anyway, Thaumcraft 2 was essentially a mod that added the concept of Environmental Magic to minecraft, and it was pretty interesting. Magic existed in two forms; Vis, which was the magical energy contained within physical objects and beings, and Aura, which was the latent, environmental version of this energy. All of the world had magic, specifically an equal baseline level that would cause supernatural things to occur (or maybe they were drawn by it, who knows). This balance was maintained because any magic that went over a certain threshold would either crystallize into solid reservoirs (Vis crystals), or seep into adjacent areas of a lower Vis.

The player, as a component, could melt down items and crystals to extract literal liquid magic (although it seeped into the environment if you exposed it to the air) or build a condenser machine that converted aura into vis. With Vis you could do all the magical building and research and junk, but the tradeoff was that melting down objects was very inefficient and tended to convert most of it into Taint. That was the 'evil' side of magic that had a habit of exploding containment tanks, seeping into the atmospheric aura, and making the entire biome evil and spawn monsters. The entire system was this interesting ecological and environmental experiment, with a weird analog about pollution. You needed Vis to do magic, but the cleanest ways of producing it were slow, so you went for cheap and fast ways that produced a lot of pollution that would take a lot of effort to purify down the line.

Not saying we should exactly have this system, but having tiles record a value for environmental magic that is absorbed by creatures, and then gets released when they die, is interesting. I suppose I should also rundown Thaumcraft v3+ since it changed up the system (although it kind of lost that pollution analog).
V3+ had the same concept of magic being inside everything, but instead each item had it in the form of certain 'aspects'. So like a tree has 'Arbor' aspects while 'Ignis' is for fire-related things. Magic itself is collectively called the 'aura' and is seen to permeate the entire world, but it can be expressed in two raw forms; Vis and Essentia. Vis is basically just mana for casting, but Essentia is either the liquid or crystalline concentration of a certain aspect. Magic also tends to congregate at certain points in the world as 'nodes' - which you can do a lot with; break them and get a big harvest of magical items, drain them and let them slowly replenish (with more complex aspects taking longer), or contain and relocate them [the environment determines their aspect generation].

The other aspect of the mod is Flux; since magic in the environment is technically in equilibrium (anything that uses it tends to just release it back into the ecosystem to be reabsorbed), taking magic from one place and introducing it into another can disturb the balance. I don't think having low magic produces any effects, but high magic is called Flux. It causes the generation of a lot more magical things, like floating wisps, magical creatures, and crystals - but also tends to push the biome towards being more corrupted.

I think the new system they use is a little too insular for my tastes. I love the concept of Nodes since they're not really physical things, and they can exist potentially anywhere - in midair, under the sea, in lava or pure rock - and generate aspects based on the tiles around them. Finally getting up to the point where you can 'bottle' one is a good achievement. However the removal of keeping a balance between Vis/Taint whenever you convert energy is really sad to me, since it was so interesting.

Anyway, mostly just dumping for idea fuel's sake.

[GoblinCookie]

Admittedly, the primarily-surface races like elves & humans need more above-ground relative advantages if they are going to stay be competitive on their home turf. But that doesn't mean that each of the cavern maps should be considered to be even close to equivalent to the surface map. In a cavern, you can easily hunt the local wildlife to extinction, which in the real world would spell starvation--but on the surface, there's always another herd of something wandering by. Besides, I specifically said "there needs to be a way for the player to control the amount of cavern life during worldgen". Maybe this means a decreased chance of caverns being fertile, maybe it's a modifier on how potent cavern energy is (relative to sunlight). I'd be fine with either, or both.

Remember that this is not a cavern vs the surface world.  It is the surface world+3 caverns, since everybody other than kobolds is going to have the ability to live on the surface as well.  Unless all caverns are lifeless any caverns at all gives those races an advantage, since it caverns+surface, only with kobolds are the 3 caverns actually competing with the surface world.  This means that 'mysterious cavern energy' is not needed as an explanation as it creates fertile caverns everywhere, but we do not actually want to see this situation as it is unbalancing.  Modelling how actual caverns get nutrients from the surface or higher caverns is not only more realistic but actually better mechanically a better fit than using magic. 

The transfer of nutrients would just be another value, the higher the value the more efficiently the process works and hence the more life will tend to be found in the caverns.  Another value would control how large the caverns generated from the initial caves would be, the initial caves are already a value but you might have another value to determine the likelihood of downward passages existing within any given cavern.  'Obviously' if you have large caverns without a high rate of nutrient transfer then most of the area of those caverns will be bare stone with nothing much growing, while if you have small caverns you will not end up with any barren stone.  A large number of initial caves+a large cavern size value results in large caverns, the number of initial caves will determine the evenness of cavern spread regardless of cavern size. 

Yeah--and, currently, if you sprinkle a few drops of water onto bare stone, you somehow get soil. I have always hated this mechanic, which is why I'm using this discussion as another reason to draw attention to it. I am not, however, opposed to (underground) plants magically drawing energy from rock--at least, as long as it's "living" stone that has never been mined and is therefore still directly connected to Armok. After all, this is a universe where certain creatures can be composed of bronze, ruby, gabbro, magma, steam, and vomit, and still be considered to be "alive", so extending the concept to the earth itself isn't that much of a stretch. So I will continue to insist on all plants & most fungi needing at least some actual soil to grow, but I'll also support cavern "trees" having short roots that just reach the stone & then stop--because that's as far as they need to go.

As I understand it most water in the game has mud in it, are you sure that the cavern plants are not growing in the mud left behind by the water not on the rock itself?  As for magical sources of energy/nutrients, we should handle them seperately; the amount of nutrients transferred from the magical sources of energy would be controlled by the same values as nutrient transfer in general, with the likelihood of such sources existing being random with odds determined by how magical your world is. 

Sorry, I forgot to mention sea level as a consideration. Underground "rivers" below sea level (or the level of whatever they're draining into) do not flow, so whatever water keeps getting added from above will quickly flood the whole cavern. This won't be an issue for forts located in mountain biomes, but sites close to the shore can have no cavern rivers at all. Lakes, yes, but not rivers.

Nope, water flows downhill, this only means towards sea level on the surface. I surmise that underground rivers (and water flow in general) tends to flow along the surface of the less porous rocks eroding their way through the more porous rocks but always going downwards if possible.  This means they will ultimately end up back on the surface or they will end up in the ocean, since the ocean depths are very deep. 

I don't see the need for these oxygen "zones", particularly as that's such a general word that already has a perfectly good DF definition, it doesn't need another one. I think it'd make more sense to just generate the caverns at worldgen, see which ones are damp, populate those with appropriate flora, calculate the oxygen generated by those flora, and then have the gods magically generate the appropriate amount of animal life to equalize that oxygen surplus. Oxygen percentage inside the fortress would be calculated (probably monthly) as an average of the outside (unless you're walled in), any breached caverns, and any farm plots / orchards sharing fortress airspace, all divided among your dwarf / guest / livestock / pet population. As for more localized air quality such as that created by a particularly lush tree, the noisome fumes of a geothermal vent, or the smoke of a smelter, those can be handled similarly to a happy thought generated by expensive furniture.

Because if we recall not all worlds are going to be highly magical.  Oxygen has to arrive from the surface just like everything else, adding it in separately allows us to affect the oxygen levels in the general world through our actions in fortress mode.  Having the biomes layered underneath the oxygen level allows us to accidentally create new habitable caverns in the wider area because our fortress acts as a cave letting the oxygen into an otherwise airless cavern. 

[SixOfSpades]

Okay, so a cavern will have to be in a "jewels"-affiliated biome in order to have gems in it? At least, in a world with Magic turned all the way up?

I would think it's more like a jewels biome having huge gems jutting out of the walls, etc.
A tree or ocean sphere might exclude gems due to lacking rock walls, instead having (petrified) wood or salt pillars.

Huge gems like the Empress of Uruguay? That could be cool. If the sphere's effect is more inclusive than exclusive, I'm good with it. But I'm less good with the idea of caverns made of very water-soluble stone right next to, presumably, an ocean.

Magic existed in two forms; Vis, which was the magical energy contained within physical objects and beings, and Aura, which was the latent, environmental version of this energy.
 . . .
Anyway, mostly just dumping for idea fuel's sake.

If the rest of the game is any indication, I'm sure DF will have its own dizzyingly complex magic system . . . but personally, I'd rather see the Religion arc get nailed down before we throw Magic into the mix as well. I'll start a new post on that, right after I finish this one.

As I understand it most water in the game has mud in it, are you sure that the cavern plants are not growing in the mud left behind by the water not on the rock itself?

"Water contains mud" is bullshit, because almost all of the game's hydrology is bullshit. When a literally infinite amount of rain can fall on a large patch of bare dirt, and still generate LESS mud than a bucket of crystal-clear well water dumped onto a floor made of glass, that's bullshit. I welcome any & all comments that refute my arguments based on the game's (current) mechanics.

Sorry, I forgot to mention sea level as a consideration. Underground "rivers" below sea level (or the level of whatever they're draining into) do not flow, so whatever water keeps getting added from above will quickly flood the whole cavern. This won't be an issue for forts located in mountain biomes, but sites close to the shore can have no cavern rivers at all. Lakes, yes, but not rivers.

Nope, water flows downhill, this only means towards sea level on the surface. I surmise that underground rivers (and water flow in general) tends to flow along the surface of the less porous rocks eroding their way through the more porous rocks but always going downwards if possible.  This means they will ultimately end up back on the surface or they will end up in the ocean, since the ocean depths are very deep.

Sorry, but that's dead wrong. If a river that is below sea level connects to the sea in any way, the salt water will immediately flow up the river until it rises up to sea level again, flooding any caverns along the way. Now, there may still be trapped air pockets (potentially even quite large air pockets) left, but the atmospheric pressure there would be equal to the hydraulic pressure of the water. (This would vary with depth--just below sea level, it would be quite manageable, but at the average depths for the bottom of Earth's oceans, it's a pulverizing 10,000psi.) This would likely be quite prohibitive for land life, because even if an organism's tissues could withstand being crushed, the plant or animal would probably be unable to respire: The external pressure would be so much greater than the internal that gas exchanges could only flow in one direction. Why yes, I'm great at parties.

Now, you could still have an undersea river, IF it evaporated without reaching the ocean. For example, it drains into a lake that is constantly boiling due to its proximity to magma. That would result in a cave mouth with cool water constantly draining in, and warm air perpetually coming out. Now, I can see a DF world with a few of these self-draining rivers sparsely scattered around the map, but if they're so common that just about every 4x4 fort has one, that would feel preeeetty darn artificial. Besides, can you imagine what a river flowing into an ever-boiling lake would do to your FPS?

Oxygen has to arrive from the surface just like everything else, adding it in separately allows us to affect the oxygen levels in the general world through our actions in fortress mode.  Having the biomes layered underneath the oxygen level allows us to accidentally create new habitable caverns in the wider area because our fortress acts as a cave letting the oxygen into an otherwise airless cavern.

I keep forgetting that you don't believe caverns should have trees. But in a cavern with both plants and animals--even a cavern that is completely sealed off from the surface, mind you--the O₂ and CO₂ would endlessly cycle, finding and maintaining a balance of gas exchange, for as long as there's an energy source (call it photosynthesis, call it what you will) to keep the plants alive.

[Sethatos]

I know this topic is old, but I recently had the same idea. During WorldGen have a map you can Tab between surface and underground layers with civs and sites in all three caverns to explore. Having an underground map would enable fast travel in adventurer mode. And finally, an HFS with sites to explore would be amazing.

[SixOfSpades]

I know this topic is old, but I recently had the same idea. During WorldGen have a map you can Tab between surface and underground layers with civs and sites in all three caverns to explore. Having an underground map would enable fast travel in adventurer mode. And finally, an HFS with sites to explore would be amazing.

I know that Embark Scenarios are coming, but I also think that a more broad-scale "Improved Embark" is in the works, albeit more vaguely. (If it isn't, it certainly should be.) Although I doubt you should be able to embark directly into a cavern, unless that cavern is directly contiguous with one controlled by one of your civ's existing (and still occupied) settlements.

It still never fails to irk me that I can embark only with above-ground animals, but only below-ground seeds.

[Shonai_Dweller]

I know this topic is old, but I recently had the same idea. During WorldGen have a map you can Tab between surface and underground layers with civs and sites in all three caverns to explore. Having an underground map would enable fast travel in adventurer mode. And finally, an HFS with sites to explore would be amazing.

I know that Embark Scenarios are coming, but I also think that a more broad-scale "Improved Embark" is in the works, albeit more vaguely. (If it isn't, it certainly should be.) Although I doubt you should be able to embark directly into a cavern, unless that cavern is directly contiguous with one controlled by one of your civ's existing (and still occupied) settlements.

It still never fails to irk me that I can embark only with above-ground animals, but only below-ground seeds.

Embarking underground is one of the few confirmed (well, slightly more likely to happen than not) additions for Starting Scenarios.

Probably depending on how successful fixing/rewriting the underground goes during mythgen development I guess.

[GoblinCookie]

I know this topic is old, but I recently had the same idea. During WorldGen have a map you can Tab between surface and underground layers with civs and sites in all three caverns to explore. Having an underground map would enable fast travel in adventurer mode. And finally, an HFS with sites to explore would be amazing.

Have the map be exportable as well.