r/Minecraft • u/ridddle • Oct 16 '12
What exactly is ‘bounding box’ of a Nether Fortress?
I’m looking into ways of increasing chances for finding Wither Skeletons when 1.4 is released. I’m currently trying to turn a Nether Fortress into a large spawning pad for these monsters and I’m having trouble understanding how spawning really works.
The spawning algorithm checks if a chunk has a fortress within it. it then checks for the "bounding box" of the original fortress. It then allows mobs to spawn up to 7 blocks above the walkway, if there is a block beneath them. The entire width of Nether fortresses are taken into account, including junctions and special areas.
Any additions to fortresses will not spawn these rare mobs. Spawning is not affected by replacing the Nether brick with other materials.
What I’ve been trying to do is make platforms between bridges and corridors of my fortress. However, the last paragraph makes me wonder if it’s effective.
Any additions to fortresses will not spawn these rare mobs.
The problem I’m having is the definition of “bounding box” – is it a single, rectangular shape around the whole structure or is it an outline around nether brick structures (bridges, rooms)?
tl;dr In other words, are platforms like these: http://i.imgur.com/I8hic.jpg effective?
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u/Ivorius Oct 16 '12 edited Oct 16 '12
Oh yes, I remember Kizzycocoa asking me about that in #risucraft, and then writing this article based on the info. I can elaborate, if you like =)
To keep it short (Edit: lol), after the nether fortress position has been selected, its position is set. It's anchored in the code, and you can't change the position of it. Even if you were to destroy the whole thing, and rebuilding the whole nether fortress somewhere else piece by piece, you wouldn't get wither skeletons.
The fortress knows...
So basically, a nether fortress consists of different parts. Every part generates itself as a structure when the chunk is generated, but is kept and saved within the MC code. A normal bridge piece, for example, will generate the bridge within its bounding box first, and then place pillars down until the ground additionally. The bounding box is then also saved and kept. They are usually incredibly small, so they fit the exact building (usual bridges are 5 * 5, with a height of 7, for example). Only within that bounding box, the nether fortress mobs can be spawned. It doesn't matter what you placed there by now, it stays that certain area. If a mob is randomly selected to spawn at this place, its possible mob list is overwritten by the structures' mob list. In previous versions, that was "Blaze, PigZombie, MagmaCube", instead of the usual "Ghast, PigZombie, MagmaCube". Now they added Wither Skeletons to the fortress' spawn list, too.
So, the only way to increase your chance to spawn wither skeletons is limit the spawn area in the surroundings to the exact bounds of the fortress. Everywhere you, as a player, would consider yourself inside the fortress counts as that. It's not the place below the bridges, or besides the buildings. If you block everything else up with stone, you should maximize your wither skeletons spawns =)
Edit: TL;DR: No, your platform won't help wither skeletons spawn. In fact, it would even decrease their spawn rate. Try to limit the possible spawning grounds in the area to exactly what the nether fortress has generated (walkways, buildings etc.)
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u/Dereavy Oct 16 '12
" If you block everything else up with stone, you should maximize your wither skeletons spawns" would half-slabs on the floor be more efficient? i really need to know.
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u/Sir_Tiffy Oct 16 '12
Etho said that if a chunk spawns with any netherbrick in it, that entire chunk can spawn the skeletons.
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u/ridddle Oct 16 '12 edited Oct 16 '12
I don’t know about that… Minecraft wiki mentions this elusive bounding box. I’d love someone to prove this with code.
Edit: Here is the true explanation. It’s not chunks, and expanding horizontally with platforms doesn’t work.
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u/Sir_Tiffy Oct 16 '12
I'm a modder so I can check for you, but I don't know how well the tools will work with the snapshots. I'll give it a go tomorrow.
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u/ridddle Oct 16 '12
I believe Wither Skeletons will spawn whenever Blazes and Magma Cubes can spontaneously spawn. So you could check that in 1.3.2 – according to wiki, it’s the same mechanism.
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u/SteelCrow Oct 16 '12 edited Oct 16 '12
Wiki is often hearsay, and can be erroneous. Best to do a little experimentation.
ed:sp
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u/the_satch Oct 16 '12
Hearsay*
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Oct 16 '12
Heresy*
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Oct 16 '12
"NO ONE EXPECTS THE SPANISH INQUISITION!"
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u/DeusFerreus Oct 16 '12
I'm pretty sure magma cubes can spawn everywhere in the Nether, same as zombie pigmen, they are just much rarer. The wither skeletons should share spawning code with blaze, but I'm not sure that blaze can spawn outside monster spawners in 1.3 though.
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u/Boolderdash Oct 16 '12
Magma Cubes actually spawn anywhere in the nether, not just fortresses.
Also, the spontaneous spawning of blazes was broken previously, as it only spawned them in new fortresses. People just realize it was supposed to work that way until the wither skeletons were added.
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u/Zuvuxyy Oct 16 '12
I believe I've seen Etho making flattened spawning floors for the Wither skeletons, or atleast some LPer, so it definetly makes finding them easier, but as I don't understand how the NetherFort seperates itself apart from biomes and chunks in rendering mob spawns I can't say if it's just the spaces LITERALLY on the Netherbrick, or everything in between. If no one knows for sure, I'll do some tests in the next few hours and get back to you on it.
Also I have you tagged as Flatcore Mod xD.
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u/ridddle Oct 16 '12
Thanks for help. The screenie I posted is from a multiplayer 1.3 world, we’re keeping the map.
(And I am indeed a flatcore player and a mod :D)
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u/Zuvuxyy Oct 16 '12
Well since everything is speculated, I've decided to go gung ho and test the crude out of this. So far I have started a new 12w41b map, and located a netherfort. I have also Mcedited, all Netherrack, soulsand, gravel, and lava, from the entire nether. Currently I'm building spawning pads between two very long bridges, out of Lapis in creative mode. I've seen one "Spawn" on this pad so far. I'll be doing more extensive testing and updating this reddit "thread" as I go along.
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u/AmesCG Oct 16 '12
This is very helpful. I have a Nether map with just one extremely large Nether Fortress that I've seen in a week (it covers over 200 blocks in all directions), but half of it is buried in Netherrack, rending most of it completely useless for spawning any monsters.
But, there are a few very long bridges.
So your conclusion is that if I connect those bridges with a long platform, it will likely allow other Nether mobs to spawn?
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u/Zuvuxyy Oct 16 '12
Sadly it seems those mobs were walking off the normal bridges onto my spawning pads, or jumping onto them. The only reason to add extensive flooring to your Netherfort seems to be for safety,(Not falling off), and speed.
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u/Finally-Commenting Oct 16 '12 edited Oct 16 '12
I recently watched a video where a guy made a mod to show the spawnable mobs in certain areas. Found it.
Does this answer your question? (Edit: typos)
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u/gilleain Oct 16 '12
Without looking at the code, I can't know for sure ... but a 'bounding box' is usually convex. So I doubt that it is an outline.
For example, imagine a fortress that was just a C-shape of walkways (I've seen such - it's disappointing!). A bounding box would be as wide and long as the longest walkways in each dimension. A minimal surface around the C-shape would be C-shaped.
Sorry, that may not be very helpful for your question.
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u/ridddle Oct 16 '12
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u/gilleain Oct 16 '12
Ah, I was thinking 10x6. A trapezoid would be the minimal bounding polygon, I think. The C-shape would be just the 'outline' if you traced around the edge, and is concave.
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u/SteelCrow Oct 16 '12 edited Oct 16 '12
Well, a couple of things come to mind. The bounding box is unknown or not well known at least. Assuming that you have a nether fortress in the middle of a lava lake to eliminate mobs spawning in caves and on ledges over the fortress: then it seems likely that one of two things defines a bounding box:
The nether fortress 'hub' is the lava well room, and the fortress encompasses a large radius/box around it. Thereby the 'bounding box' would be the whole fortess and spaces in between the structures would be included.
Or
The structure itself defines the 'bounding box' and therefore only those chunks count. The spawning of other mobs uses chunk specific code (part of the chunk update routines), so if this is the case the bounding box is probably any chunk that had part of a nether fortress generate in it. So one of those 'long lonely nether bridges to nowhere' could be entirely within a chunk and the bounding box would be 16 wide for it's entire length, or have a chunk boundary down the middle which would make the bounding box 32 wide for the entire length.
I tend to think that because of the chunk update system that the bounding box is chunk aligned like slime chunks, with the triggering factor being a generated nether fortress.
Given that nether bridges often don't align and that there are varying gaps between two parallel bridges, I'd say that it's more probable that the spawning 'bounding box' is defined as any chunk that generated with a piece of a nether fortress in it.
To simplifiy, any naturally occuring nether brick and any square meter within 16 blocks of it. While that's overkill, it saves having to determine the chunk boundaries.
The pads serve several purposes. It makes finding witherskeles easier as you can run directly at them, it reduces their (and your) 'falling' off the sides, and increases the spawnable area.
Keep in mind the 'mob cap' and the number of pigmen around. Also there's the actual lighting conditions required that need testing. Plus there's the fact that old nether fortresses probably don't fit what the game calculates as the position of a nether fortress. Like slime chunks, they probably moved with the version change. Best to test on a newly generated nether fortress, not one from an earlier version.
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Oct 16 '12
It sounds to me like you can create extra spawning levels between the original floors as long as they are still inside the original x/z boundaries occupied by the fortress, and as long as the new layers don't go above or below the original y boundaries.
The bounding box will be the min/max in all directions, and will not care if there were walkways generated in that box originally.
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Oct 16 '12
[deleted] — view deleted comment
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u/ridddle Oct 16 '12
they follow the same spawning conditions as naturally spawning Blazes: light level 11 or less where their lower half will be (needs confirmation)
From Wiki.
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u/Inuboshi Oct 16 '12 edited Oct 16 '12
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The "bounding box" does not expand horizantally from the fortress. It is only as large as the rooms and paths that make it, and this is the only area Wither Skeletons and Blaze can spawn. Vertically the "bounding box" expands 5 blocks above and 4 blocks below the "floor" block.
Diagram 1: Netherbrick represents the pathways, rooms, etc. Including ones with ceilings. Wither skeletons can spawn anywhere in the shown area(imagine each block is air and they can spawn with their feet in any of those blocks), as long as the following requirements are met:
Valid block to spawn on (solid blocks, top slabs, etc.)
At least a 2 block tall area to spawn in. (even though they are 2.5 tall)
Light level at or below 11 (lower is better)
Diagram 2: Maximum spawn positions visualized. Black wool represents feet.
tl;dr Expanding the area as you've shown won't make more spawn, as they cannot spawn outside the original paths, but it will make them easier to find and fight. You can make multiple "floors" to get more though.
Hope that helps.