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[Melting Sky]

I haven't played many forts. My first fort went about a year and a half without any serious problems before I realized the design was terrible and started over. Thus I didn't have time to see the underworld. I never made it more than a few layers deep.

My second fort is 13 years old and going strong. It's located on the slopes of a tall volcano next to a river. Anyway, I had to dig DEEP to find my caverns. I think the first cavern was maybe 30 levels of rock down from where my fort's main body is located. Each cavern layer beyond that goes down much deeper than that. The underground includes a 50Z level candy spire, a couple of chasms, magma pipes etc. All in all the embark is close to 200Z levels deep. It's vast to say the least. I thought this was pretty much normal until I made my next embark.

My next embark was completely different. It's like the underground was pancaked. The caverns are like half a dozen levels below the soil and the magma sea is maybe 20 beyond that.

My question is what effects the depth of the underground in advanced world generation? I think I made the caverns more open in my second world and left them untouched in the original one. Is this the reason for the difference between the two embarks or is this normal natural variation? Is the volcano the reason the second embark is so much deeper than the third?

[greycat]

My next embark was completely different. It's like the underground was pancaked. The caverns are like half a dozen levels below the soil and the magma sea is maybe 20 beyond that.

I love those.  I wish I knew how to get that every time (though yours sounds even shallower than any I've ever seen).  There's no need to move magma, or set up convoluted transport systems, when it's so close you can just stroll down to it.

[sal880612m]

Some science on the effects of cavern openness and density can be found here. It is an old thread though so results may have changed.

While this is only my theory, thus probably not true, I think that how many Z-levels between surface and cavern and so on is based on elevation of your embark area. The higher the elevation of the area is the greater your embark depth is. Again just a theory I don't feel like proving/disproving at the moment.

[Melting Sky]

My next embark was completely different. It's like the underground was pancaked. The caverns are like half a dozen levels below the soil and the magma sea is maybe 20 beyond that.

I love those.  I wish I knew how to get that every time (though yours sounds even shallower than any I've ever seen).  There's no need to move magma, or set up convoluted transport systems, when it's so close you can just stroll down to it.

Its so pancaked that there really isn't even room for a decent sized fort. Just the entrance hallway to my old fort would literally carve through half the Z levels present in this new embark site and pierce deeply into the caverns.

[arbarbonif]

In advanced world options there are options for minimum levels between each the magma sea, each cavern and the surface (by default it is like 1 layer between each cavern and 5 to the surface I believe).  I think that that is for the lowest elevation on the big map square, so if there is a mountain and a river valley in the same square the valley will be compressed and the mountain will be super deep.  Volcanos tend to jut above the surroundings so they tend to be deeper than the surrounding sites.

[Melting Sky]

In advanced world options there are options for minimum levels between each the magma sea, each cavern and the surface (by default it is like 1 layer between each cavern and 5 to the surface I believe).  I think that that is for the lowest elevation on the big map square, so if there is a mountain and a river valley in the same square the valley will be compressed and the mountain will be super deep.  Volcanos tend to jut above the surroundings so they tend to be deeper than the surrounding sites.

Yeah I always make my worlds using the advanced settings. I never messed with the minimum layer options but I might actually consider doing that next time. I like a good bit of natural variance to keep things fresh but at the same time the pancake embarks are really going to limit the sort of fortress I can build. I guess I should be happy that magma is so close.   

[ancistrus]

or just play with 1 layer

[Melting Sky]

Some science on the effects of cavern openness and density can be found here. It is an old thread though so results may have changed.

While this is only my theory, thus probably not true, I think that how many Z-levels between surface and cavern and so on is based on elevation of your embark area. The higher the elevation of the area is the greater your embark depth is. Again just a theory I don't feel like proving/disproving at the moment.

Thanks for the heads up. That link is great and I think you are right about the link to elevation. I did a couple of random embarks to areas with varying elevation and the high elevation embarks were all deep sites. I have yet to find an extremely deep site under a low elevation embark area although I only did a handful of embarks to test this.

[GavJ]

Basically the caverns have, like, a fixed amount of space that they take up, I have found. So if you increase their "openness" they end up being shallower, because more of their quota is filled on each level. Density doesn't seem to matter. The "quota" appears to be only the amount of empty space that WOULD be, if density were zero.

Then also the variance of elevation on the surface affects map depth. It doesn't start counting anything as underground layer depth until the whole screen is underground, so mountains make for much much deeper maps overall.

Finally, the remaining variables are the "depth above layer 2" etc. etc. in the world gen parameters, which are the layers in between each cavern and the next cavern or the surface or whatever.


So for shallowest maps, set all those to 0 or 1, cavern openness to maximum, cavern layers to only 1 layer (this will usually prevent you getting nethercaps and stuff, though), and embark on a flat area. I don't know if it matter if it is near sea level. Guy above me suspects that it is. I have doubts, but it would be easy to test for the non lazy person. Just find two different elevation FLAT maps on the same map.

[Lav]

DFHack "prospect" command reports the number of layers in embark area when used on embark screen. This number includes all the SMR and HFS layers, but otherwise gives a pretty good estimate.

[greycat]

I think that how many Z-levels between surface and cavern and so on is based on elevation of your embark area.

That seems like a good theory, but... how do you know the elevation of your embark area?  Is this visible before embark, or after embark, and if so, how do you learn it?  Some DFhack command?

[Lav]

You can estimate elevation very roughly by one of embark window modes.

You can get exact number of layers with DFHack command.

Assuming that elevation == layers, these two should match.

[greycat]

You can get exact number of layers with DFHack command.

Assuming that elevation == layers, these two should match.

Which command?  I don't see any obvious ones.  Of course there's "prospect all" but that gives WAY more information than desired, and would probably miss any layers that have no minerals.

The only other one I could find that was even close was "probe", but that doesn't give a tile's elevation.

[Dirst]

You can get exact number of layers with DFHack command.

Assuming that elevation == layers, these two should match.

Which command?  I don't see any obvious ones.  Of course there's "prospect all" but that gives WAY more information than desired, and would probably miss any layers that have no minerals.

The only other one I could find that was even close was "probe", but that doesn't give a tile's elevation.

I think they're referring to the range of z-levels shown at the end of a "prospect all".  If it says something like "-4 to +3" then the ground is probably warm from the nearby magma.

[sal880612m]

Vanilla embark has two elevation views, one for relative that has numbers and another for general elevations that uses colors only. If your embark is all zeros on the relative scale that means that it will be a single color on the general elevations.

Which command?  I don't see any obvious ones.  Of course there's "prospect all" but that gives WAY more information than desired, and would probably miss any layers that have no minerals.

The only other one I could find that was even close was "probe", but that doesn't give a tile's elevation.

I think they're referring to the range of z-levels shown at the end of a "prospect all".  If it says something like "-4 to +3" then the ground is probably warm from the nearby magma.

I think DFHack calls it embark depth or something like that.

I had trouble with Lav's use of layers as my first thought was not Z-levels which does appear to be the intended use. Largely because I associated layers with caverns, magma sea, stone types, and soil types which all are likely to be spread across multiple Z-levels.