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Author Topic: On the Construction of the First True Skyfort (Cave-ins ON)  (Read 21638 times)

itg

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On the Construction of the First True Skyfort (Cave-ins ON)
« on: December 05, 2013, 02:33:04 am »

For the 100th Anniversary of Heartmine (well, more like 96th, but who's counting), I have finished one of the all-time most sought-after megaprojects: a true skyfort, that is, a fully functional fort built with cave-ins ON and no connection to the ground. To my knowledge, this has never been done before, and in fact people have been saying it is impossible for years (see, for instance, posts from the Mythbusters 2010 thread. As per my usual format, here's a how-to with a bunch of pictures:

Spoiler: Bedrooms 1 (click to show/hide)
Spoiler: Bedrooms 2 (click to show/hide)
Spoiler: Statue Garden (click to show/hide)
Spoiler: Dining Hall (click to show/hide)
Spoiler: Stockpiles/Pastures (click to show/hide)
Spoiler: Workshops (click to show/hide)
Spoiler: Window plugs (click to show/hide)


Spoiler: Overview (click to show/hide)

Spoiler: Sky support (click to show/hide)
Spoiler: Why Sky Support Exists (click to show/hide)


Spoiler: Building and Casting (click to show/hide)

Spoiler: Beds (click to show/hide)
Spoiler: Magma Forges (click to show/hide)


Spoiler: Nail it to the Sky (click to show/hide)

Spoiler: Cutting the Tether (click to show/hide)

Spoiler: Overseer Screenshots (click to show/hide)

View the skyfort at DF Map Archive: http://mkv25.net/dfma/poi-31249-skyfort

Edit 3/25/14: Urist da Vinci disassembled the game to figure out why sky support exists. See "Why Sky Support Exists."

Ravendarksky

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Re: On the Construction of the First True Skyfort (Cave-ins ON)
« Reply #2 on: December 05, 2013, 03:05:50 am »

Wow this is cool :-) I will definitely have a play around with the physics behind this when I get a chance. I am in awe at your skills to handle such a delicate megaproject... Did a lot of savescumming occur? The lengths you've had to go to are extreme... I don't think I'd have figured out the magma forges.

Can I just check something.... Could a true freestanding fort be created over a frozen ocean? I was under the impression that when ice melts it doesn't perform a stability check so you can make floating structures that way.... I've never tried myself though. also i guess it might not survive a save/reload. I will have a look when I get home but I'm on my mobile just now.


Can I make a suggestion for your fortress? Have a mine cart launcher to allow migrants to fly up to your fort :-) or do you want to keep the ground pristine below?
« Last Edit: December 05, 2013, 03:12:08 am by Ravendarksky »
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Dwarf4Explosives

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Re: On the Construction of the First True Skyfort (Cave-ins ON)
« Reply #3 on: December 05, 2013, 07:31:21 am »

As always, your megaproject is one with only one practical usage that I can think of: easy disposing of nobles. Also, it's damn impressive.
« Last Edit: December 05, 2013, 11:47:43 am by Dwarf4Explosives »
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KingBacon

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Re: On the Construction of the First True Skyfort (Cave-ins ON)
« Reply #4 on: December 05, 2013, 10:22:43 am »

So how many corpses did this project generate?
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Ruhn

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Re: On the Construction of the First True Skyfort (Cave-ins ON)
« Reply #5 on: December 05, 2013, 12:42:46 pm »

This surely wins "megaproject of December 2013" in my books.

itg

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Re: On the Construction of the First True Skyfort (Cave-ins ON)
« Reply #6 on: December 05, 2013, 09:11:49 pm »

Wow this is cool :-) I will definitely have a play around with the physics behind this when I get a chance. I am in awe at your skills to handle such a delicate megaproject... Did a lot of savescumming occur? The lengths you've had to go to are extreme... I don't think I'd have figured out the magma forges.

Can I just check something.... Could a true freestanding fort be created over a frozen ocean? I was under the impression that when ice melts it doesn't perform a stability check so you can make floating structures that way.... I've never tried myself though. also i guess it might not survive a save/reload. I will have a look when I get home but I'm on my mobile just now.


Can I make a suggestion for your fortress? Have a mine cart launcher to allow migrants to fly up to your fort :-) or do you want to keep the ground pristine below?

Yeah, there was a bit of savescumming, mostly during the "why the hell am I getting random cave-ins" phase of the projects. Of course, that's how I discovered the "power mining" procedure. I also had a separate save file for testing with dfhack, so I could quickly do a lot of small-scale experiments.

I'm not sure whether the melting frozen ocean causes a stability check (although I think you're right that it does not). However, any structure built that way definitely wouldn't survive reloading.

The minecart idea is a good one. It's actually something I was thinking about doing, but I put it off because I wanted to figure out how far I can actually launch a minecart.


As always, your megaproject is one with only one practical usage that I can think of: easy disposing of nobles. Also, it's damn impressive.

Hehe, I consider myself a leading authority on uselessness.

So how many corpses did this project generate?

About 10-15, mainly deconstruction accidents while taking down the pump stacks.

This surely wins "megaproject of December 2013" in my books.

Thanks!

wierd

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Re: On the Construction of the First True Skyfort (Cave-ins ON)
« Reply #7 on: December 05, 2013, 09:15:26 pm »

What I am curious about, is if you can nail to the map edge instead of the sky, using obsidian casting on top of say, a bridge.

That would give horizontal support without the caveats of sky support.
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misko27

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Re: On the Construction of the First True Skyfort (Cave-ins ON)
« Reply #8 on: December 05, 2013, 10:00:55 pm »

Well well. Wow. And I bet they called you mad to even try. Dwarf Physics has gained a great piece of knowledge from your endeavor; and Dwarven architecture has gained a new powerful new tool, one that has granted a a record setting fort. Urist McScience thanks you, and the Dwarves thank you.


So wait, if you had support on the bottom of one of the held-up pillars, and that support carried a number of walls and/or natural rock beneath it, and you connected that support to a lever, you could drop cave-ins from the sky? From now on, no enemy is safe from our wrath; for we have combined the height of the sky and the might of the mountains.
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wierd

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Re: On the Construction of the First True Skyfort (Cave-ins ON)
« Reply #9 on: December 05, 2013, 10:44:09 pm »

Nono-- more horrible than that.

1) sky support overrides ground support, with some caveats.
2) sky support is only vertically transferred. It does not provide horizontal support.

This means:

If you build a "tube" of supports up to the sky, and tack it on, any ground that *was* receiving horizontal support will become unsupported(1), and cave in.

The lack of horizontal support transfer is why his floating fortress requires buildings and floors to be constructed in place, and then cast inside the obsidian during construction, because there won't be support for them otherwise.(2)

That means that if you create such a tube reaching up to the sky, and descending all the way to the SMR, leaving JUST ONE horizontal support providing wall to hold it up-- the very second that wall is carved into a support, the entire tube and all of its contents will "collapse" into the SMR and be destroyed. Using some additional trickery, this can also destroy the otherwise unminable tiles on the edges of the map. You can cause almost complete annihilation of the entire embark, by ordering the final support be carved.


Last dwarf standing can have his vengence, and literally take them all with him straight to hell.
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King Mir

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Re: On the Construction of the First True Skyfort (Cave-ins ON)
« Reply #10 on: December 06, 2013, 12:39:54 am »

Very cool.


Why does sky support even exist?

cue

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Re: On the Construction of the First True Skyfort (Cave-ins ON)
« Reply #11 on: December 06, 2013, 01:15:25 am »

I've always thought of sky support as a weapon, this takes it to new heights(mind the pun). How long in hours did this take you to do?
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Ruhn

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Re: On the Construction of the First True Skyfort (Cave-ins ON)
« Reply #12 on: December 06, 2013, 12:20:14 pm »

Should something be added to the wiki for this discovery?

I'm thinking a new section in Physics (http://dwarffortresswiki.org/index.php/Physics) that talks about supports, or maybe gravity.
If itg agrees, we can also add an entry in the list of mega project ideas (http://dwarffortresswiki.org/index.php/DF2012:Megaprojects).

itg

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Re: On the Construction of the First True Skyfort (Cave-ins ON)
« Reply #13 on: December 06, 2013, 12:32:56 pm »

What I am curious about, is if you can nail to the map edge instead of the sky, using obsidian casting on top of say, a bridge.

That would give horizontal support without the caveats of sky support.

Unfortunately, the map's edge doesn't provide any support at all.

Very cool.


Why does sky support even exist?

Very good question. I can't imagine why it would be intentional behavior, but if sky support was not intended (I wouldn't call it a bug, per se), it's hard to see how that behavior could be produced accidentally. Pure speculation: maybe the game checks for support in the z direction first (logical enough, since most tiles will have support directly below), but when it hits the sky, it doesn't know what to do, so it just aborts the check. Those tiles which were part of the aborted check now don't get flagged as "supported," but neither do they trigger a cave-in.

Should something be added to the wiki for this discovery?

I'm thinking a new section in Physics (http://dwarffortresswiki.org/index.php/Physics) that talks about supports, or maybe gravity.
If itg agrees, we can also add an entry in the list of mega project ideas (http://dwarffortresswiki.org/index.php/DF2012:Megaprojects).

I'd love to see it on both wiki pages. I can add it myself eventually, but if you or anyone else want to beat me to it, go for it.

gchristopher

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Re: On the Construction of the First True Skyfort (Cave-ins ON)
« Reply #14 on: December 06, 2013, 12:59:10 pm »

Wow, I love it! Not just the ingenuity to figure out all the physics, but the dedication to really bash your face into them so thoroughly! Very nice work!
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