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[Cameo]

So I've cast a 20x20x20 obsidian tower/cube, and I'm currently designing it so the whole thing can be engraved for the glory of all dwarven might. One problem is I want to fill at least one (probably 2) layers of this beast with magma for use by forges and the like, but I can't think of any way to cast the last wall piece (have already engraved the entire outside).

What I wanted to do was dig a one square hole in the wall on each level that needs to be filled with magma, dig it all out, pump in magma, and then get water onto the tile that was dug out of the wall, hence preserving the cast-ness of the whole thing. I can't think of any way to do this so will probably just use a floodgate, but that seems like such a copout.

Thanks if anyone has any ideas

[Girlinhat]

I should think that you simply make it like a regular fort, and then fill the lava-pit with lava.  Have you tried going at it from above, like channeling the lava through the existing structure and letting it flow down into the reservoir?  This might mean flooding the entire structure in magma, until the thing fills to where you want, but if no one is living in it, then you can just re-smooth it later.

[Dorf3000]

20x20x20 solid obsidian cube?  and you want to put magma in it?  You do realize you could have done that while you were making it with almost no problems, right?

Probably the best way to do it would be to pump the magma in on the forge level and have it drop down into the magma chamber through the holes in the floor (you need holes in the floor for the forges to work anyway).  That lets you avoid the problem of the magma flowing back out while you try to create the obsidian wall again.  An obsidian wall can be created from 1/7 magma, if you have water flow onto it.

[Girlinhat]

If you're feeling particularly tired, DFHack.

[Tallefred]

20x20x20 solid obsidian cube?  and you want to put magma in it?  You do realize you could have done that while you were making it with almost no problems, right?

Probably the best way to do it would be to pump the magma in on the forge level and have it drop down into the magma chamber through the holes in the floor (you need holes in the floor for the forges to work anyway).  That lets you avoid the problem of the magma flowing back out while you try to create the obsidian wall again.  An obsidian wall can be created from 1/7 magma, if you have water flow onto it.

Casting obsidian without a solid floor underneath would be a pain in the ass. You'd have to cast one row at a time, to prevent cave-ins, and if somehow something did collapse you would be unable to fix it since it would be under two stories of magma. It could be done, but I could see how it would be simpler to just do it and figure out how to fix it later.

However, with delicate projects like this, working things out later often turns out to be very complicated. It's annoying working it all out to begin with, and obviously you can't see all the complications at the beginning of the project, but sealing a hole where magma is leaking can be a real pain in the ass, especially if it's in the side of a wall. I once lost an entire fort to a leaking magmaduct. Fucking thing wouldn't stop and I couldn't work out how to fix it, and eventually everyone dehydrated since the river wouldn't defrost.

If you do drill a hole, do it in the top. Much easier to seal, just construct a wall under it, cast a piece of obsidian to seal it, then deconstruct the wall. You could use a floor but then it will be there forever, and that sort of thing really annoys me even if I know it makes no difference and doesn't show. The problem is that you'll have to have a hole going from the top of your monument to the bottom, unless you have a staircase somewhere you can let it all flow down. Still have the problem of possibly overdoing it and having a draining problem, which as I mentioned before can be absolutely no fun at all.

You might be able to fill it from the bottom. I believe it is possible to pressurize magma using pumps? Test this, and if so, you can pump it in through a hole in the floor. Then you can either just leave the hole, or if you're a perfectionist, you can build a pond above your magma lake and drop the water into it. The wall-floor trick will come in handy here as well if you have room to work, if not, just use a disposable swimmer. Disposable as he may be sucked through your drain and obsidianized as well. The sacrifices we make, huh?

[Girlinhat]

wiki article Fluid Pressure, or something similar.  Magma will not pressurize naturally, but if pumped up to a location, then it will pressurize up to the location of the pump.  This sounds like one of the few non-!!FUN!! methods of pressurized magma in use.

[Tallefred]

wiki article Fluid Pressure, or something similar.  Magma will not pressurize naturally, but if pumped up to a location, then it will pressurize up to the location of the pump.  This sounds like one of the few non-!!FUN!! methods of pressurized magma in use.

Thank you for that. I've never been sure, and for some reason I've never tested it.

So yeah, my plan should hopefully work. If not, enjoy your box of magma.

[Girlinhat]

If not, enjoy your box of magma.

Step One: Cut a hole in the box.

[Tallefred]

If not, enjoy your box of magma.

Step One: Cut a hole in the box.

Step Two: Have fun sealing a hole you can't walk up to.

[Urist Imiknorris]

If you're feeling particularly tired sane, DFHack.

[Dorf3000]

Magma isn't that difficult to deal with as long as you've got a source of water above it; for 99% of situations this is usually true.  The real difficulty is getting rid of mined obsidian resting at the bottom of a tile filled with magma..

To cast obsidian over a magma pool without getting those random cave ins, you can use single-width bridges to drop water on it, or you can use spare dwarf labor combined with single-width pond zones - just have one active at a time until the dwarves fill in the whole length, then activate the next one, etc etc.  The bucket brigade version is quicker if you have a water source nearby and idle dwarves. The bridge method is quicker if you can get 2/7 or 3/7 water on the bridges, since you can just deconstruct the bridges in order rather than hooking them up to levers.

[Graebeard]

You can leave pockets of magma by laying down a layer of magma and then pouring water on it down from above while blocking the water from reaching the tiles you want to leave.  Let's say you're casting a 7x7 tower.

Z=0

Spoiler (click to show/hide)

Code: [Select]

OOOOOOOOO
O+++++++O
O+++++++O
O+++++++O
O+++++++O
O+++++++O
O+++++++O
O+++++++O
OOOOOOOOO
O = Constructed walls
+ = Constructed/natural floors.


If you fill this with magma and then pour water over it you'll have a 7x7 cast obsidian square.  Repeat this above as many times as you want to build the tower up.

Now let's say you want to leave some magma in the tower.  All you need to do is block the water you're pouring down from touching the tiles you want to leave.  You can do this a few ways, but one of my favorites is by building artificial floors to block the water that will be transformed into natural obsidian floors.  Let's say you're 3 levels up now.  You still have the artificial walls, but now the floors are natural obsidian.  You want to leave one tile of magma in each corner.  You start with just the artificial molding walls.

Z=3 step 1

Spoiler (click to show/hide)

Code: [Select]

OOOOOOOOO
O+++++++O
O+++++++O
O+++++++O
O+++++++O
O+++++++O
O+++++++O
O+++++++O
OOOOOOOOO
O = Constructed walls
+ = Natural obsidian floors.


Go ahead and cast the whole thing with obsidian.

Z=3 step 2

Spoiler (click to show/hide)

Code: [Select]

OOOOOOOOO
OoooooooO
OoooooooO
OoooooooO
OoooooooO
OoooooooO
OoooooooO
OoooooooO
OOOOOOOOO
O = Constructed walls
o = Natural obsidian walls


Dig out most of the level, leaving enough obsidian walls in each corner to support the artificial floor tile we'll build above.

Spoiler (click to show/hide)

Code: [Select]

OOOOOOOOO
Ooo...ooO
Oo.....oO
O.......O
O.......O
O.......O
Oo.....oO
Ooo...ooO
OOOOOOOOO


Go up to the next level and it looks like this:

Z=4 step 1

Spoiler (click to show/hide)

Code: [Select]

OOOOOOOOO
O++...++O
O+.....+O
O.......O
O.......O
O.......O
O+.....+O
O++...++O
OOOOOOOOO

O = Artificial walls
+ = Natural obsidian floors


Now you can cover the tiles you want to keep with artificial floors.

Z=4 Step 2

Spoiler (click to show/hide)

Code: [Select]

OOOOOOOOO
O++...++O
O+*...*+O
O.......O
O.......O
O.......O
O+*...*+O
O++...++O
OOOOOOOOO

O = Artificial walls
+ = Natural obsidian floors
* = Artificial floors


Fill Z=3 with magma again, and then pour water down from above.  You'll end up with this:

Z=3 final:

Spoiler (click to show/hide)

Code: [Select]

OOOOOOOOO
OoooooooO
Oo7ooo7oO
OoooooooO
OoooooooO
OoooooooO
Oo7ooo7oO
OoooooooO
OOOOOOOOO


This is great, you say, except that there are constructed floors on the level above that you can't engrave.  Well, that's true for now.  If you want to leave the magma below exposed you could just deconstruct the floor.  If you do that be sure to construct it out of a non-magma-safe stone that will just melt when it falls into the magma.

If you don't want to leave it exposed and want to replace it with a natural obsidian floor the solution is easy.  Just cast Z=4 with obsidian, and the artificial floor will be replaced with a natural obsidian floor that can be engraved.  Now you have a pocket of magma, and every tile in your tower can be engraved!  Note that this same procedure will work for larger pockets of magma in any shape you want to make

[Cameo]

If I'd've been thinking when I cast it I could've dug out 2 layers that'd been cast and then completely filled the bottom layer so they water couldn't reach it, but it's a bit late for that now..

Might just dig out a one-square channel all the way up on the side and recast it all. Probably go through a few masterpiece engravings but my engravers both have so many they won't care. Other problem with that is I've already collapsed all the wall used to contain the casting, and both pump stacks, and the stacks at least'll needa be completely remade, although this time I might just use one and bucket brigade water, probably be a bit easier. Why must I be so pedantic about having the whole thing engraved I suppose is the big question, but why bother with making an obsidian tower if you don't?

Speaking of engraving, I read somewhere that only the room on the side the engraver stands on gets the increase in quality. Can anyone confirm this?

[Hans Lemurson]

I think that it is unlikely that engravings would be directionally specific.

I'm assuming you've already carved-out most of the cube, yes?

The plan I would advise to get magma into one of the levels is to just carve a single hole in the side and pump the magma in through that.  The trick though I suppose is sealing it back up again afterwards without leaving a hole or being forced to...construct *shudder* an obsidian wall.

Despite having only minimal experience working with obsidian-casting, I'd advise building a magma-safe pump right into the wall of your cube such that its impassible tile is where obsidian once was. Use that to pump the magma in from a reservoir created by your pump-stack, and then once the magma-level is full to your satisfaction, build a cistern around that pump and pour water into it.  Just 3/7 water, since dwarves will need to wade through it.  Once the magma-safe pump it partially submerged, deconstruct it.  When it deconstructs, magma and water will flow into the once-impassible tile and combine to form an obsidian wall seamless with the rest of your fortress.  Either that or the water will flow into the hole faster than the magma, and solidify the magma INSIDE your walls resulting in an artistic-looking alcove where you can house a statue for siegers to admire.

[Dorf3000]

Speaking of engraving, I read somewhere that only the room on the side the engraver stands on gets the increase in quality. Can anyone confirm this?

I believe it was confirmed in 40d (no idea about the new version) that if there was already a room defined that included the wall, the value of the room would only increase if the engraver was standing on that side.  If you engraved the wall and then defined a room on it, it didn't matter which side the engraver stood on when doing it, and you could even define rooms on both sides and both rooms would have the extra value.