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[Bikgn]

While pondering the various advantages/disadvantages of traps, I came up with the (probably incomplete) idea for the above design. I might also swap out the green glass for simple wood training spears. Before that, I'd like to ask a few questions so I can get a better understanding into the workings of the trap, as I made quite a few assumptions that may or may not necessarily be correct. Chances are that this trap will fail in more than a few ways, but I would like to know why so that I can make it better 

1. (I assumed that) goblin ambushes/sieges have a leader who they will follow, even if the leader drops down a z-level. When the leader walks to the animal on z-level -1, I'm hoping that the goblin ambush will try to path as close to the leader as it can and get impaled in the process, similar to how caravan guards try to follow their caravan into the fort. However, I am unsure as to whether this would work if, instead of an up/down stair, there was an impassable pit between the goblin leader and his entourage. Would the goblins still try to follow their leader even though he's on a whole other z-level?

2. Is there a tamable animal that can survive being submerged in water AND living on land? Failing that, is there a way that I could somehow save my lure animal on z-level -1 from drowning in the river's water while killing the goblins?

3. Can some monsters fly above my traps and evade them? Also, if monsters can fly, will the 100 z-level pit drop affect them at all? Or will they simply pass on as if nothing had happened? In my design, I obviously did not account for flying creatures...

Thanks in advance

[Girlinhat]

1) I'm not basing this on any evidence at all, but I assume that they path towards their leader.  If there is no path, then they do not path, and they sit still.  So, if you dropped the leader off Z levels, or otherwise relocated beyond reach, the followers would become idle until acted upon or they flee due to their time limit.  Again, no evidence.

2) All things are possible via the raws.  Adding [AMPHIBIOUS] to any animal will make it land and water, though you might end up with dogs fighting carp and mass dogo-cide from the vicious carp.  Outside of that, nothing comes to mind.  Clowns and Toads are the only thing that come to mind which are amphibious in vanilla.  Some mods may include various custom creatures, but that's custom.  You can use or not use this how you want.

Alternatively, if you push the bait's cage back a square, you can install a floodgate that activates along with the water release.

3) Anything on the same Z level will feel a trap, and most flying creatures stay on the same level.  As I understand it, flight means that the creature will path directly from A to B, taking the lowest altitude route.  This is why buzzards fly along the ground and get stuck in cage traps.  Also, with caged buzzards, I'd made a 15 Z tall execution tower, and was able to drop buzzards through it, even though it wasn't a solid tower.  It consisted of a stairway upwards, and a platform at the top with a hole in the center, allowing things to be dropped through he hole and down through open air to the ground below.  Buzzards appeared to splatter just as well as goblins.

4) You may have a problem.  Goblins seem to prefer line of sight when going after a target, so if there's walls in the way, they can't see something, and don't go towards it, same with all creatures really.  Goblins will, though, naturally path towards your fort via some unknown means, so if there's a way into your fort, or a way from the pit to the map's edge, the goblins will go that route.  You can use this to your advantage, or build the thing out of windows, because creatures can look through windows.

If you want to make a self-closing door, make a 1 tile wide hallway, place a door in it, and place a pressure plate in front of it.  When the enemy paths through the door, they walk over the plate, and the door locks, forcing them back.  No matter what, the enemy will remain locked in the crazy "soft wall" because as soon as they reach the edge, then the edge goes solid.

[Bikgn]

Thank you for your advice. After reading your tips, I thought some more and I believe that I've really simplified my original design, while still attaining the goal I wish to achieve. I do think that some major improvements could be made though...



A few notes: the pink border isn't anything; I drew it so I could keep my x and y-coordinates on top of each other. It also makes it easier to see where the 0 z-level begins and where the -1 z-level starts. The left picture is the 0 z-level, the right picture is the -1 z-level. Also, "adamantine weapon trap" should read "adamantine menacing spikes set on repeat".

First, I added a staircase to the map, so that when the leader falls down, his fellow goblins will (hopefully) attempt to reach him again by trying to get to the staircase - and to do that, they'll have to step on the spears themselves.

Second, I decided to scrap the whole "lure in water" idea. There is now only one lure, 99% safe from any real danger (unless goblins can shoot arrows through windows)

Third, any aerial creatures can make it through the first two hallways if they're lucky... but then they get mauled by cotton candy spike traps in the main lobby and in the pet area. To save cotton candy, I'll probably only put one or two spikes in each trap. If it's flying, I'm assuming it's not made out of anything tough or absolutely indestructible... right?

Fourth, I switched out A LOT of the walls for windows. There should be no problem with line of sight between the goblins and the bait now.

This new version works a lot like the old one, except after the leader gets beat down the pit, he finds that his only way to the glorious bait is through a gigantic winding maze which I have dubbed "The Intestines of Pain" (ironically, goblins do not feel any pain while they are there). While he walks through the maze, his friends (again, hopefully) stupidly follow him onto the spike traps, and they get tossed off as well. Hopefully, by the time the leader reaches the staircase at the end, his fellow goblins are already at least halfway through the maze. After the goblin goes upstairs to claim the poor animal's life, he finds that he must traverse the cotton candy traps, which are surely more than enough to tear him apart or drop him down to the semi-molten rock. Whichever happens first. After this, his friends will be 100% lost and will simply stand there stupidly, in the maze. It is at this point that I sound the bugle and open the floodgate, drowning all of the goblins in the maze or pushing them back to the deep pit next to the adamantine traps, where they fall to their doom. Instead of connecting the pit to the semi-molten rock layer, I might consider making the pit lead into a cistern over 70 z-levels into the ground instead so that I can gather the goblinite safely after it lands in the pit. In addition, the deep pit will be an automatic evaporating chamber; any excess water will fall down the pit along with the  goblins, and eventually all the remaining water in the intestines will evaporate on their own. The only flaws I can see here are:

- goblin safely makes it up the staircase, sees leader die, stands on staircase while the flood rages below, and remains there for all eternity (unless I can somehow get him to move)

- building destroyer comes by the traps, gets knocked down, and proceeds to destroy my floodgate. Since my main base is in a temperate environment, I can simply wait until winter to pick up the pieces and start anew, but this is still an unresolved issue...

If the enemy is trapavoid, it will die when it reaches the adamantine spikes. Nothing really much has changed except for the addition of the stairs on the side; the enemy might dodge onto the stairs, go down, destroy the floodgate, and run back up, but it'll still have to deal with adamantine spikes and giant pits of death.

Again, thank you for your help, it's helped me a lot in my planning 

[Girlinhat]

You may be interested in water pressure effects, actually.  Water will naturally rise up to the point that it sources from, allowing a U bend pipe to overflow if fed by a higher water source.  You can pressurize water using a pump, best if attached to a windmill so it can be deactivated, and you can null pressure by sending it through diagonal walls (wiki it if confused).  You could use this to push water up from the floor (perhaps a locked hatch?) that would then overflow into the entire chamber, making a drowning pit that fills from the bottom.  Your bait animal could be rendered safe by putting it one Z above the source pump, so that the water will not pressurize up to the creature itself.  Magma, actually can also be pressurized via a pump, but will not naturally.

Secondly, to deal with building destroyers, you could build two drawbridges that connect to the spike dodge thingy.  These bridges should be set up so that when raised, it leaves the spikes on a sort of floating island, where the beast cannot path off it, nor can it attack the bridges.  Then, just repeat the spikes until it's skewered.  This can easily be done by adding a few tiles between the spike row and the rest of the trap, to allot for bridges.

[Bikgn]

After thinking about it some more, I decided that I had completely forgotten about a cheap way to protect my buildings: fortifications. Putting one next to my floodgate shields it from any possible harm. Using screw pumps might be a pain until I can figure out an easy way to prevent water from freezing outside. If not, I'll have to resort to digging a magma bath underneath the new reservoir of water. The pressurized water will now reach the goblins upstairs, pushing them onto the traps and into the pit. Same for the goblins on the other end of the stream; they get shoved into hell as well.



After looking at this design, everything seems perfect. However, I noticed that windows are actually buildings and not constructions. Can building destroyers still knock them down?

Again, thank you so much. I have a feeling that this trap might just be the thing my fortress has been lacking this whole time.

[Girlinhat]

This is correct, building destroyers will destroy windows, but in my experience, building destroyers will not destroy something as long as they have a living target in sight.  So, if there's a proper bait animal, then your windows should be safe, however ultimately this will come down to trail and error to make a system where the destroyer sees the bait before destroying anything.  If the destroyer is in the act of smashing a building, and sees an animal, it will divert, so it's very easy to place your bait somewhere very visible from the entrance and have it attract aggro.

Also of note: Fortifications allow sight and cannot be destroyed, but they allow fluid passage and sometimes projectile.  Your bait would not be 100% safe behind a fort, and any dragon or similar creature that can breathe fire, would completely ignore the fort and shoot firebreath straight through it.  However, dragons can be captured by a single cage, so I'd suggest building a moated, magma-safe drawbridge that allows you to hide, and then you can build a cage trap at your entrance and let the dragon in to get caught.  Dragons make fantastic war animals, seeing as a single breath of fire can wash out half a battlefield - including your own men.  Hopefully, placed atop a battlement, it can fire-breathe down on goblins, but I dunno if it can fire across Z's, never captured one myself.

[NightS]

what about a sammich? Like this: FWF F is fortification W is window. They can see the bait anc it is waterproof and indestructble

[Girlinhat]

Also viable, though it uses more room.  For that matter, FWCF would would, with fort, window, creature, fort.  The middle fort isn't needed, since no one is attacking the window from the inside.

[Xenos]

Put fortifications in front of windows.  this will protect windows and still allow for sight but not projectile pathing.

[Bikgn]

Thanks for the help guys! I tried to draw up a new model, but I realized that I really don't know anything about how line-of-sight works (other than requiring one thing to see another). The wiki did not seem to have any information about this, so I would like to ask some questions about the line-of-sight system, if I may:

1. Does line-of-right require a clear, unblocked straight line between the attacker and the victim at all times? Or will the attacker continue the whole way through and try to kill the victim as soon as a connection is established?

2. Can line of sight continue past z-levels? If a goblin sees a restrained animal in a small tower covered in fortifications, will there be line-of-sight between the goblin and the animal? Or does the goblin have to be on the same z-level as the animal?

Thanks in advance 

[Minnakht]

As far as I know, z-levels are deceptively lacking in barriers. Bolts and arrows travel z-levels when needed. Miasma and smoke spread vertically. It takes a dwarf the same amount of time to go up or down stairs as it takes him to move one square on the same z-level.

Therefore, line of sight also travels up and down easily, most possibly.

I've had hunters shoot at sturgeons down in the river, 2-3 z-levels down. That requires seeing them, right?

[Shootandrun]

If you are searching a really good trap, I have one that could help.

I once made really simple (the design is simple, but the actual building can be quite long) trap that could kill every thing, quite easily. It needs a volcano or a magma pipe if you don't want to pump, and water. Here is a really simple design.

z+1
**************
============

z0
:============:

z-1
~~~~~~~~~~~

Key:
* is magma
= is a bridge
~ is water
: is a floodgate.


Make really big rooms. Link the two bridges and the floodgates to the same lever (the bridges must be open while the floodgates are close, and vice versa). Make enemies path in z0. Pull the lever. That's all. The enemy will fall into the water and become obsidian. I think a flying magma immune "thing" could possibly survive, but nothing else. This single trap design killed at least two hundred goblins, one dragon, two bronze colossus, a lot of titans. There are some problems (you need to clean up the obsidian after each try, so its not a repeating trap, for example) but I find it really great in general. And it's really dwarfy to obsidianize your enemies and then mine them.

[Bikgn]

If you are searching a really good trap, I have one that could help.

I once made really simple (the design is simple, but the actual building can be quite long) trap that could kill every thing, quite easily. It needs a volcano or a magma pipe if you don't want to pump, and water. Here is a really simple design.

z+1
**************
============

z0
:============:

z-1
~~~~~~~~~~~

Key:
* is magma
= is a bridge
~ is water
: is a floodgate.


Make really big rooms. Link the two bridges and the floodgates to the same lever (the bridges must be open while the floodgates are close, and vice versa). Make enemies path in z0. Pull the lever. That's all. The enemy will fall into the water and become obsidian. I think a flying magma immune "thing" could possibly survive, but nothing else. This single trap design killed at least two hundred goblins, one dragon, two bronze colossus, a lot of titans. There are some problems (you need to clean up the obsidian after each try, so its not a repeating trap, for example) but I find it really great in general. And it's really dwarfy to obsidianize your enemies and then mine them.

Hmm, I'm not sure if this trap is exactly what I'm looking for.

First of all, how does the bridge work if a titan steps on it? I thought that megabeasts and tons of goblins prevented bridges from retracting.

Second, ambushes are invisible to begin with, so in order to detect them, I'll have to use a cage trap or leashed animal or something. The problem is, those require constant maintenance on my part; when the animal dies or the cage goes off, I'm going to have to put in a new one, which can be risky for my dwarves. And if I forget to reload it, I would be none the wiser until the ambush finally comes a-knocking at my front door. If I used something automated, such as a weapon trap or pressure plate, I could destroy the ambush without even knowing it's there.

Third, if I used a pressure plate to automate the retracting bridge, I would have to make sure that the delay is long enough that it catches the entire ambush all at once. For some reason, after the leader dies, the entire ambush group just camps at the front of my fort, preventing me from killing them.

Don't get me wrong; it's a really good trap design and definitely far simpler to use than mine. But my playstyle (lazy and laid back, try to play it absolutely safe, don't really do anything until the very last moment) will probably make me foul this trap up at least a couple of times in the near future 

Also, that tip about z-levels is very helpful. Does that mean that if an archer cannot shoot at a target, then there is no line of sight?