Expanding the Underground

Has anyone of you ever read the Metro series by Dmitry Glukhovsky? I am pretty fascinated by that.

When you go into e.g the subway tunnels all you are going to see is mostly spiders and some eldritch horrors. Maybe a lab but those are boring and way too common for my taste.

What I’d like to see is something other than just rock. When the portal storms hit, I assume the entire planet was affected. The biggest part of Earth is not the surface, but what is below. I could imagine there being a variety of stuff. We already have lava in the mines, which are known to be infested by otherworldly stuff. There could be lava vents and caves down below, maybe even strange ores and minerals. This would also make wilderness runs a bit “easier” since getting metals is possible this way. But this is not my main point.

I want to concentrate on the subway tunnels first, which is also why I mentioned Metro in the beginning. First of all, it is just boring tunnels currently. But we have some implicit lore:

This just screams Metro to me. The gray goo, the fungi (which appear to be different from the mycus), the twisted rails.

In real life, it is not just tunnels. There are also rooms beside the tunnels for technical equipment. There are cables, vents and ducts, too.

I could imagine people seeking shelter in the tunnels (since not all of them are lab tunnels and therefore dangerous) and therefore little settlements existing underground, maybe full of trogdolyte mutants (which already randomly roam the tunnels but are always hostile).

Since there is not much light, people would gather and farm fungi (just like in the books). There are currently more reasons to stay out of the tunnels than to enter them but for mutants with fitting traits it would have advantages. Reasons why folks would flee the surface is weather, especially portal storms and maybe acid rain and radiation, zombies, war (ever noticed all the craters, which also contain active alien bombs?) and the temperatures. It should be constantly relatively cold down there but there are no extremes. Folks could still go out to scavenge and maybe even set up little stations for solar power (since the non-vehicle powergrid is a thing finally!).

In terms of dangers, spiders seem inappropriate here. Worms or molerats look better to me. Spiders could be appropriate near vents and stuff.

The implicit lore also states these weird almost paranormal things. Tunnels being windy, especially when the roots or explosions have broken up the ceiling could definitely be a thing. There being shadow entities or something would also work.

Strong portalstorms could still affect the underground but are significantly weaker down there, but the constant exposure warped it. When exploring the tunnels, you should be mindful of more than what is in front and behind you. There being random rooms potentially containing monsters jumping at you will make it a bit more dynamic and less boring.
Worms and molerats making their den would expand the network of tunnels. Humans/mutants will also continue to dig. Collapsed, flooded or infested tunnels will also make your life harder.

The Black Gulch from Dark Souls 2 could also be a good source of inspiration for underground biomes:

It seems nightmare-ish enough for the Cataclysm.


We have a pretty big hurdle in the way of larger subway locations, and those are (surprise surprise) old labs and their hardcoded tunnel gen. I’ll try to keep it brief, but it’s got to do with how our worldgen works:

Generating an overmap begins on z0, rivers, biomes and cities are placed first, with roads getting placed between cities and towards the overmap borders to establish connections with the neighboring maps. After that, the overmap is cut up into 15x15 sectors, with an overmap special being placed in each, including all their above/belowground tiles based on those tiles’ location restriction. After that, if the special has a “connection” array it will get hooked up to a suitable connection - roads, in effect, for reasons we get to later. This is pretty amazing, since you can also define if a location gets to generate their own road, or if it only gets placed if its location roll landed on a pre-existing road.

Now, here’s the catch: at the point of time when specials (and connections) get placed, no subway tunnels, stations or labs exist outside of their single-tile z0 start location. They use hardcoded placement rules to allow for old lab’s procgen, and they get generated layer-by-layer in overmap::generate_sub() or similar, which also handles hooking up the actual subway connections to predesignated overmap terrains. This system doesn’t care about or paths to preexisting conditions, so if you’d go to the trouble of adding a bunch of normal locations using the connections system generate_sub will just make a whole parallell system, leading to very jumbled maps. It also means that you couldn’t place locations that need preexisting tunnels as normal specials (mole rat nests connecting to a cave or fun like that), and you can’t trust an old lab not to get procedurally placed around a lower special.

It’s not all doom and gloom, of course : one can do good work with map extras, and EOCs allow for dynamic gamaplay. As the snippets show I do have some fun ideas for the tunnels, but I stuck in Limb Stuff for the forseeable future - but I’d like to scatter some mob feeding/breeding grounds on the upper, and some mutant camps in the lower tunnells time permitting.

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Wow, thanks for the amazing insight! That is a great explanation.

I am aware of how tricky subway-stuff can be as I am still occupied with single-track tunnels in a PR and my post was mainly “Hey what if we have”, mostly just planning for stuff. The most I’d anticipate right now is a few small utility rooms here and there.

The sewers are also pretty hacky right now since I tried to make them have proper walls but because everything is map extras down there these tunnels need to be accessible from all 4 sides, so proper walls are pretty much impossible right now.

Note that the cataclysm just happened, so I’d be surprised if anyone had taken up fungal farming: 10 years down the line, assuming things don’t deteriorate (which they do), I could imaging small groups of survivors doing that, though. It does make sense to use subway stations for shelter from which scavenging raids could be carried out, but that approach gets killed by the undead infestating every subway station I’ve seen (with those who tried likely having become part of the infestation).

I wouldn’t be surprised of there are occasional rooms along the tracks for servicing vents and the like, but anything major would likely be placed together with the stations.