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[Loud Whispers]

Also, I wouldn't recommend supporting your entire fortress on Supports in case a FB or clown gets in there (they can breathe under water and destroy buildings).

1. Supports in most respects are invincible to building destroyers, as of yet.
2. Knowing that, the above are both excellent reasons to balance your fort on a single pillar of Dorfy symbolism.

[Sus]

Soo, why doesn't anyone just build a cave in generator above the sides of the waterlock?

Done right, you could drop an entire ring of obsidian and clear the whole perimeter.

This.

[ThatAussieGuy]

Soo, why doesn't anyone just build a cave in generator above the sides of the waterlock?

Done right, you could drop an entire ring of obsidian and clear the whole perimeter.

This.

How exactly is that related to a defensive mechanism designed to defend against tunnelling creatures?

edit: it's a moot point anyway - those are mined staircases.  The ring would stop on the top level and go no further

[Osmosis Jones]

Wait... staircases? What the hell do staircases have to do with anything?

Also, it was a response to dbay's post; rather than worry about traps on every level, you just have a generator. If somehow a aquatic/zombie miner gets through to the edge of the waterlock, you can drop a ring and the cave in will suck them into the shaft. If my memory of DF fall physics is correct, that means they will actually fall like there is nothing there, probably gibbing on the bottom.

[Mapleguy555]

Or one could just make the Lock double thick.

[micha]

What about multiple attacks on the same level but different approach (angle, side, w/e), if that level loses pressure?

for non-flying diggers keep 1 empty space around the inner box's stairs (so that there are 2 spaces between where someone digs in and any constructions you want safe from invading building destroyers.)

to protect against aquatic diggers you might want to add an inner box floating in magma

or just the whole thing from the top with a single space around and a single deep wall. not water or magma needed. ... ooops, never mind that, without magma or water it wouldn't be df <g>

cheers!

[Urist McSpike]

Couldn't you set it up with a double ring, with magma on the inner & 3/7 water in the outer?  Anything piercing the barrier would obsidian cast itself, wouldn't it?

[misko27]

Wow, I'm amazed. Wouldn'y of ever though of it. Will be the first thing I build when that dreaded day comes.

[hjd_uk]

Well I assume this would also exist in a theoretical build in that enemies can deconstuct walls, otherwise just brick-up your perimiter instead of leaving it as natural-stone.

[Xob Ludosmbax]

I'm attempting to build this in my current fortress.  It's not going so well.  I've had to restart a few times.  I haven't even gotten close before encountering lots of !!FUN!!.  But, I've got the perfect defense for almost everything.  Without further ado, I present:

The Cave-in Cannon
         and
The Cave-in Curtain

Steps:
* Embark on an aquifer.
* Dig a 3 tile wide channel from the ground to the semi-molten rock.  (Block off the aquifer so it doesn't leak in, of course)
* Build a tower to the top of the map.

* Build fortifications 1 tile out from the edge at the top of the map.
* Build a magma pump to pump large amounts of magma to the top floor.  (Use screw pumps as walls to prevent backflow, to get the building-destroyer requirement above.)
* Pump magma so that it creates a constant lava-fall curtain around the entire outside edge.
* Turn the pump stack off once you verify that it works, so that you can complete the rest of the construction.

* Build a 1 tile wide bridge all around the edge of the tower on the floor just below the top.
* Build a water pump stack to pump large amounts of water to the second from top floor, and create a water-fall curtain falling off of the bridge.

* Turn the magma pump stack back on.

At this point, assuming my theory holds water, the magma will fall off the top around the entire edge.  The water will flow off the edge all around the second from top floor.  As it reaches the edge, it will combine with the lava to form obsidian.  The obsidian won't stick to the bridge, so it will start to fall.  The three tile wide channel ensures that it doesn't catch the edge anywhere.  (The obsidian should be falling through the middle of it.)  And the SMR at the bottom eats the obsidian, so that more of it can fall. 

The only things I can think of that can kill you would be a flying magma-proof digger & building destroyer that flies over the top, and that can be mitigated by using bait (statues around the edge?) to get it to fly through the falling obsidian curtain.  And the other killer would be the massive FPS drop. 

Edit: And ghosts.

[Vehudur]

My idea?

Spoiler (click to show/hide)

Code: [Select]

W = wall
_ = floor
X = up/down stair (flooded with water)
M = up/down stair (flooded with magma)

One north-west corner and a section of wall are included.

WWWWWWWWWWWWWWWWWW
WWWWWWWWWWWWWWWWWW
WWWWWWWWWWWWWWWWWW
WWWW_W_W_W_W_W_W_W
WWW_WXWXWXWXWXWXWX
WWWWXXXXXXXXXXXXXX
WWW_WXXXXXXXXXXXXX
WWWWXXXWWWWWWWWWWW
WWW_WXXWMWMWMWMWMW
WWWWXXXWWWWWWWWWWW
WWW_WXXWMW  (fort)
WWWWXXXWWW  (fort)
WWW_WXXWMW  (fort)
WWWWXXXWWW  ☺ (Urist McStupid)
WWW_WXXWMW  (fort)
WWWWXXXWWW  (fort)
WWW_WXXWMW  (fort)

It is critically important that the wall of water filled up/down staircases be at least two wide, and preferably four or five wide or you risk sections being isolated, leaving a door into your fort.

You may have multiple rows of columns full of magma.  Here they are columns and not solid walls of up/down stairs to conserve magma, but this is up to you.

Optional:  Replace the floor tiles with lowered floodgates.

The magma and water are both pressurized.  You can use a hanging pump stack inside a cistern full of magma near the top of your fort that is filled with magma by another pump stack that is only on when filling or build your fort around a volcano to prevent pump-FPS death.  The outer water tiles will not be pressurized, but the inner columns of steps are.  Your water and magma sources should be within the perimeter of the fortress to prevent them being cut off by enemies.
SuperDwarf bonus: Build several layers of this.

I know it seems crazy, but this IS the result of reasoned thought and engineering.

So what's the idea?

Step 1: Invaders arrive and are defeated by conventional defenses (optional).
Step 2: Invader begins to dig tunnel.
Step 3: Invader reaches outer floor tiles and connects with them.  Water begins to flood the tunnels, slowing them down by pushing them back with water flow.  This may flood the tunnel enough to stop them on its own, but no guarantees.  Due to the fact that this water is not pressurized, the majority of the water above this point is not drained.
Step 4: Lets assume zombies.  The zombies won't drown, and thus will continue to dig as soon as the tunnel is flooded.  The zombies reach the pressurized section shortly, but with the majority of their tunnels flooded there is little water lost.
Step 5: They breach the wall behind that, possibly in a different location entirely, and breach the magma.
Step 6: The pressurized water and magma meet, obsidianizing the gap and possibly the creature that dug it.  It's possible the magma tube will be plugged from this, which is why I advise multiple, redundant layers.
Step 7: If they begin to break through you have plenty of time to be warned about it and prepare accordingly.

[Circusdawg]

ust use floors they cannot dig those

[Mistercheif]

I wonder if instead of having columns of only magma, have alternating columns in such a way that if they don't directly breach only a single column (in that case, they'll be pushed back by the water or magma) then they will diagonally breach both, in which case they both flow into the gap, sealing it in obsidian.  Hmm.  I wonder how we can deal with a direct breach of a single column, and if there is a way to make it auto-sealing like the enemy trying to dig between the columns would cause...

[Vehudur]

I wonder if instead of having columns of only magma, have alternating columns in such a way that if they don't directly breach only a single column (in that case, they'll be pushed back by the water or magma) then they will diagonally breach both, in which case they both flow into the gap, sealing it in obsidian.  Hmm.  I wonder how we can deal with a direct breach of a single column, and if there is a way to make it auto-sealing like the enemy trying to dig between the columns would cause...

This gave me another idea.

Another possibility is a grid:

Spoiler (click to show/hide)

Code: [Select]

W = vertical shafts full of water
M = vertical shafts full of magma
X = wall

(fort goes here)
XXXXXXXXX
XWXMXWXMX
XXXXXXXXX
XMXWXMXWX
XXXXXXXXX
XWXMXWXMX
XXXXXXXXX
XXXXXXXXX
XXXXXXXXX

(invaders go here)


Those shafts are channeled shafts, and not columns of up/down stairs.  This is to prevent things from crossing right through a vertical shaft without breaching the opposite liquid shaft on the other side.  It is unlikely diggers will be able to do so while flying or swimming, or across a full 1z gap.

The supply for it at the top is rather complex, but nothing any player advanced enough to be doing something like this can't handle.  I created a diagram to explain a rather simple method of filling these shafts from the top (so that they're pressurized).

In this diagram, the water is supplied to the large blue square from one z-level above it.  The magma is supplied from that level.  The right side is the fort side.   The top one is one z-level above the bottom one.  This area is, by nature, constructed above the surface within your walls.  The big arrows show possible supply points for pressurized water / magma.

My advise would be to build this in sections, each one hydraulically isolated from the other in case one section is breached and thus depressurized.  This would ensure the integrity of other sections in case of an attack there.  A drain should be included in the bottom of each section to allow for the draining and repair of damaged parts.  I advise drop hatches into a large cistern under each shaft to allow for quick drainage and repair, even for the magma columns.  Drainage of the cistern is optional - you could always just obsidianize whatever lands down there and dig it out again.

Spoiler (click to show/hide)

A corner:

Spoiler (click to show/hide)

This is also the part where I put in a needless disclaimer that you should never use just one line of defense - if that line fails for any reason, you're screwed.  Defense in depth is key, the goal of this is not to stop an enemy forever but to slow an enemy this cannot destroy long enough for active defenses to respond..  I will note it will stop most things forever by the nature of magma.

[ThatAussieGuy]

That's quite the clever design, Vehudur.  If I can suggest a modification though?

The magma should be filled from within, not from above.  Take the Z+1 level and remove the inner row past each magma column, making that the inlet channel for the red fun stuff.  You can then let Z+2 and the lowest level of the barrier be part of my basic all-enclosing waterlock design as a floor and ceiling  (with some sort of tunnel variation to encircle the magma pumpstack leading into the 'locked' area)