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[Trails]

Hallo all!

I'm on a map with a sizeable volcano, and I had an amusing little idea for my fort's main fortress. The plan:

1) Drain the volcano.

2) Construct a winding walkway (with roof and walls to make it more of a tunnel) spiraling up through the empty shaft. The tunnel will for the most part have no floor, just drawbridges. Hatches will be set at intervals along the ceiling.

3) Allow the volcano to refill around the tunnel.

If things work the way I hope, I'll end up with a winding road through the volcano that any visitors to my fortress will have to walk. Any unwanted guests will not be able to destroy the ceiling hatches from below, allowing me to flood sections of the walkway at any time and then use the drawbridges to atomsmash for drainage. As an added bonus, since the drawbridges form the only floor in most sections, I can pull them out from under light-weight invaders to send them straight to the abyss; if I understand correctly, since magma is not pressurized, it will not bubble up to fill the tunnel even when the bridges are raised.

Potential problems: Draining the volcano is taking forever (see my post in this thread), but more distressing is that I'm not exactly sure how volcanoes refill. Presumably all the spaces within the volcano have a special designation that cause them to spawn magma, similar to river tiles that spawn ice. But will building my tunnel remove this designation on affected tiles? If not, will magma endlessly spawn inside my tunnel? Because that would be sad.

Or, if the magma is somehow pushed up from the sea below, will pressure get weird and force me to put floors underneath my drawbridges?

In short: what flaws do you find with this idea?

[Crashmaster]

A volcano refills by 'spawning' up to two squares of 7/7 magma on a random bottom level 'lava flow' tile. This pushes that square's whole stack of magma blocks up as much as two squares above the top magma level (or lowest empty space above it). Then the pushed up magma spreads out to some of the eight sides and is absorbed into the top level of the magma or spreads out if it is already 7/7 on top. I don't think constructions will stop magma flow tiles from working because a plugged magma pipe will re-fill as much as it can.

I do know that magma can rise up and flood into a level through a hole in it's floor that's channeled into the magma sea - whether this is from the re-filling action or some pressure mechanic because the game treats the re-filling spawning as a kind of pumping I do not know.

If I was implementing your plan I would make the tunnels 2-3 z high inside with the retracting bridges only 1 z from the ceiling. The extra walls acting like a kind of caisson against the possibility of some sort of pressure. I think I would also suspend another floor a z level or two underneath the extended walls to prevent the magma flow tile spawned magma from being pushed up into the tunnels. You would lose having invaders fall all the way to the SMR but they should mostly still die just fine.

[Dariush]

Nobody (except those immune to magma, but they don't walk anyway) will path on a submerged path.

[Trails]

Really? Even if the tile to be pathed on is perfectly dry? That seems...odd. It suggests that the pathfinding algorithm checks the passibility of a space by looking at the spaces above it rather than just checking the contents of the space itself for magma/water.

Or maybe it notices the "lava flow" tag Crashmaster mentioned (or something similar) and stops there without checking to see if there's actually any magma on the space. That might make sense...but blast, there goes my really !!fun!! idea.

@Crashmaster: That is consistent with something I noticed when draining--the lava seemed to bubble, with little blips of higher levels popping up periodically and then dissipating. I figured that was the refill mechanic (++awesome for looking like a bubbling lake of fire), but the details still seem fuzzy. Doesn't teleportation usually spawn fluids in the destination spaces rather than in the source space, as in magma-piston and water-under-pressure-in-u-bends dynamics? If the lava is indeed spawned at the bottom of the volcano...what does "pushing" look like? If the lava being pushed up encounters an obstacle and cannot go straight up, does it get pushed out into neighboring columns instead? On the meta level that sounds extremely computationally expensive to me, compared to just adding 7/7 magma to the two spaces at the top of the column.

However, it's complicated if the magma just gets added to the top of the column too...behavior will depend on how precisely Toady implemented it. How does the game track where the top of the magma column is? If the magma starts to rise into the tunnel and I atomsmash it, does the game continue trying to spawn magma at that location? And then, once the rest of the caldera has filled and magma has spilled over the top of the tunnel, will the game still think that the top of the magma column is inside the tunnel, even though there's x 7/7 levels of magma above it?

But if Dariush is correct, none of this will matter anyway. Sigh. And I was thinking about building my baron a glass house out underneath the whole structure, too.

[ShinWalks]

No, they'll walk through a dry tile that's inside a tunnel. They won't path through a submerged tile, but while the tube in closed and empty it won't be submerged.

Do you have a plan in place for re-draining the path after you flood it to kill unwanted visitors?

[Trails]

Hope is renewed!

Yep--the plan is to raise and lower the drawbridges that will form much of the tunnel's floor (and repeat as necessary). Will that work?

[utuki]

Probably no. There isnt anywhere to drain below the bridge, magma in volcano is refilling and wont absorb magma from tunnel.
As crushmaster said you can crush some magma below tunnel with raising drawbridges but then you cant drop enemies into hell.

[aepurniet]

This will totally work.  Hatches should provide a quick way to fill the walkway with magma.  You will have to block the lower doors (its gonna be either the entrance or exit.)  I don't think you need draw bridges at all. Drainage of the walkway can be done by opening a drain at the bottom near the entrance / exit.

Drainage can be lightning quick if the magma is pressurized.  If magma is not pressurized, you can prepressurize it by creating a cistern above the walkway. If you go that route, then filling can be done with just one hatch at the top.

To make this a little more automatic, use a double helix strucutre where people exit and enter at the top. Prepressurized magma won't over flow that way. The only manual thing will be draining.

[aepurniet]

Forgot if glass is magma safe or not, but build the whole thing out of glass blocks for extra bonus points.

[Crashmaster]

I don't know if the magma spawns from the bottom but my observations were that when it appears on the top of say a 5/7 layer, the square of the 5/7 layer will change to 7/7 and the 'new' magma above the top level will be 5/7. This happens in one frame I think so either it spawns from below and pushes up or spawns above and splits the 7/7 of new magma at the same time.

I have never seen any magma spawn in the open space more then two levels above the current top level.

I think you would be able to clear even a full 7/7 of magma from inside the tunnel with the raising drawbridge floor. Of course when you want to dump enemies in the magma some will be crushed instead.  So it shouldn't even matter if the magma can bubble up into the tunnel because you could atom smash it faster. If your entire floor is not raising draw bridges there would be quite some down-time while waiting for left-over 1/7's of magma to dry up so units can path that way again. I like aepurniet's double helix idea so you can have one tunnel to use while the other is drying out.

[Trails]

Probably no. There isnt anywhere to drain below the bridge, magma in volcano is refilling and wont absorb magma from tunnel.
As crushmaster said you can crush some magma below tunnel with raising drawbridges but then you cant drop enemies into hell.

Mm? But won't the floor drawbridges do the crushing for me?

Side-view schematic:

Enemies in tunnel
~~~~~~~~~~~~~~~~~
###-###-###-#####
_____g____g_g___^
~~~~~~~~~~~~~~~~~

Raise floor-bridge
~~~~~~~~~~~~~~~~~
###-###-###-#####
|               ^
~~~~~g~~~~g~g~~~~ <-- gobbos drop to hell

More enemies in tunnel
~~~~~~~~~~~~~~~~~
###-###-###-#####
_____T____T_T___^
~~~~~~~~~~~~~~~~~

Open hatches, flood walkway
~~~~~~~~~~~~~~~~~
###~###~###~#####
_~~~~~~~~~~~~~~~^
~~~~~~~~~~~~~~~~~

Raise floor-bridge...
~~~~~~~~~~~~~~~~~
###~###~###~#####
|~~~~~~~~~~~~~~~^
~~~~~~~~~~~~~~~~~

...and atomsmash. Walkway is reset.
~~~~~~~~~~~~~~~~~
###~###~###~#####
________________^
~~~~~~~~~~~~~~~~~


So the tunnel is still drainable, while enemies can still be flushed for superfluous !!fun!!

In theory, at least...will atomsmashing this way not work, you think?

This will totally work.  Hatches should provide a quick way to fill the walkway with magma.  You will have to block the lower doors (its gonna be either the entrance or exit.)  I don't think you need draw bridges at all. Drainage of the walkway can be done by opening a drain at the bottom near the entrance / exit.

Drainage can be lightning quick if the magma is pressurized.  If magma is not pressurized, you can prepressurize it by creating a cistern above the walkway. If you go that route, then filling can be done with just one hatch at the top.

To make this a little more automatic, use a double helix strucutre where people exit and enter at the top. Prepressurized magma won't over flow that way. The only manual thing will be draining.

I'd rather not pressurize the magma; I think the drawbridges are worth it because they double as trapdoors for dropping enemies to their fiery doom while also providing instant drainage.

Forgot if glass is magma safe or not, but build the whole thing out of glass blocks for extra bonus points.

This was my original plan (glass is magma safe). However, I had forgotten that sandy loam isn't actual sand, so I don't have the infinite glass source I expected to have. I'm trying to import enough sand for the project while the volcano drains.

I don't know if the magma spawns from the bottom but my observations were that when it appears on the top of say a 5/7 layer, the square of the 5/7 layer will change to 7/7 and the 'new' magma above the top level will be 5/7. This happens in one frame I think so either it spawns from below and pushes up or spawns above and splits the 7/7 of new magma at the same time.

I have never seen any magma spawn in the open space more then two levels above the current top level.

I think you would be able to clear even a full 7/7 of magma from inside the tunnel with the raising drawbridge floor. Of course when you want to dump enemies in the magma some will be crushed instead.  So it shouldn't even matter if the magma can bubble up into the tunnel because you could atom smash it faster. If your entire floor is not raising draw bridges there would be quite some down-time while waiting for left-over 1/7's of magma to dry up so units can path that way again. I like aepurniet's double helix idea so you can have one tunnel to use while the other is drying out.

Okay! It seems feasible enough to merit the investment in man hours to try it out...FOR !!SCIENCE!!

Oooh, good point with the blocked-while-evaporating hallway. I hadn't thought of that. I'll need more glass for a double helix, but two is always better than one in DF

[Crashmaster]

In theory, at least...will atomsmashing this way not work, you think?

You should run a small scale test while draining to see if a bridge can atom-smash without a floor - the wiki says it needs a floor I see...

http://df.magmawiki.com/index.php/DF2010:Dwarven_atom_smasher

Might be that with no floor the magma would end up back on top of the bridge?

New thought; make a floor for the bridges out of suspended floodgates; build walls, then build floodgates on top of the walls hooking them all to a lever, then de-construct the walls and the floodgates will remain suspended in midair with no floors underneath them. You can build a bridge that goes over floodgates as long as it's anchored to solid rock or constructions. Then you can retract the floodgates and raise the bridges to drop invaders or use the floodgates as a floor to atom-smash the magma against.

complicated project is complicated

post project updates please