Witches stop respawning at witch huts

This may be do to the fact that water surrounding a witch hut, can drastically reduce witch spawns. If you have solid blocks and normal terrain around the hut, you will see many more witches.

I had my witch farm recently stop working in the release before 1.16.220. It had the AFK spot 128 blocks above the witch spawn point and there were no other spannable areas in that radius. Constant witch spawns turned into not a single spawn between sessions. I knew I was not at the mob cap (I'd broken it with too many sheep before) because hostile mobs spawned all over the surface when I moved down so it was in range. I'd tried flying hundreds of blocks away and back to make sure, and no difference.

In a creative copy of the world, I discovered I had 9 persistent cave mobs within the 9x9 chunk population area around the witch hut spawn point. 2 zombies holding items and 7 drowned (see below for ways of persisting). These 9 persistent mobs filling the 8 mob hostile mop cave population cap and the +1 structure cap were all in caves I had never been in before so not persisted by any of my actions.

As soon as I killed the two zombies, witches started spawning again.

I am sure these mobs are persistent because the commands I used to find them were executed when I was over 128 blocks above any spannable point. FYI - those commands were of the form /execute @e[type=zombie] ~~~ fill ~ ~+2 ~ ~ ~+100 ~ concrete 11

I've attached an image showing the results:

There were a lot more persistent hostile cave mobs in the wider simulation area as you can see in the image. Close to 80 in total! There were also about 10 zombies I'd killed previous to this when I just checked for them in an earlier copy. If this trend continued at the same rate for about the same amount of time, it would reach the overall mob cap and break a lot more stuff!

As for the reasons the mobs were persisted:

• The zombies and zombie villagers I checked were all holding items (confirmed it persists them in creative) that can naturally drop in caves like mob-drops (arrows, slime balls, rotten flesh) I assume from natural deaths (e.g. lava, drowning, falling) since I had never been in any of those caves. Or gravel. I'm assuming it generated unsupported and then received an update somehow.

• The drowned I checked were mostly holding nothing or default items. They were mostly in water filled holes though, so were probably zombies that fell in and drowned while holding an item they picked up on the surface. The drowned will stay persisted even if they drop the item on conversion (tested in creative). 

• Some drowned were holding items like rotten flesh, so these may have been normally spawned (or non-persisted converted) drowned that just picked up an item.

• The skeletons were all wearing armor at or near the surface in areas near where I'd been. I assume they were persisted by picking up armor I'd left on the ground after killing other mobs near by (tested in creative for skeletons and zombies).

Note: All the testing I did in creative was with naturally spawned mobs and I would always test alongside another mob without the change to ensure it would despawn while the other didn't.

A further note on the last point in the description about the 8 + 1 density cap for structures being easily defeated by the 8 density cap filling up then an additional mob wandering in: It seems like it would be much easier to fill than that since it checks around where each mob spawn. The 8 + 1 limit for the witch hut is around that specific chunk and that area cap is only checked for a spawn at that point. Any other mobs in that area will have checked their own 9x9 chunk which will overlap, but may not be the same. This would allow 8 mobs to spawn to the North-West with the witch spawn in the corner of their 9x9 chunk area. Another 8 could spawn to the North-East still overlapping the witch spawn but not the other 8 mobs, and the same for the two South corners. That's 32 mobs that could be contributing to the a population density check at the witch hut location without any mobs moving after spawning or violating their own density cap checks.

If the mechanics from the wiki this is based on are correct, it means a +1 structure cap is not effective at ensuring that structure can spawn a mob. It only ensures a spawn in the structure chunk will not prevent the structure from spawning an additional mob, not spawns in other chunks in it's 9x9 chunk density area.

This illustrates the point:

The grid in the middle is the witch hut 9x9 chunk density area. The "8"'s in the corners represent groups of 8 mobs with the density areas they check on spawn in the corresponding color. They are all in the witch hut density area, but they do not overlap any mobs from another density area.

ticket should be re-opened? several ways to reproduce this it seems.

(not sure if it was mentioned, theres a lot to read) having water surrounding the hut significantly reduces witch spawning , and in certain cases can prevent spawning altogether, if you try to spawn proof the area by slabbing the witch hut itself.

I confirmed the water slow-down issue.

• With flat grass at sea level (63) for the 9x9 chunk around a witch hut, I got 202 witch spawns in half an hour.

• With water 13 blocks deep (50 to 63) in that same area, I  got 26 witch spawns in half an hour.

• Interestingly, with a single layer of water, the spawn rate did not change, getting 208 witches in half an hour. Two layers seems to where it kicks in all at once.

I have attached two worlds indicating this. One for the grass case (

), the other for the 13 blocks of water case (

). If you stand on the spawn block and flick the switch, it will kill all entities, then give you an item for each witch spawned after that.

Note: The 9x9 chunk area is not significant. I just chose it because that is the density cap area. I'm pretty sure only the witch hut chunk matters. If a 16x16 roof of spawnable blocks is placed above the witch hut chunk (e.g. at level 80) and lit up in the water world, the spawn rates are fully restored to normal.

It does seem to come down to spawnable columns within the chunk. With grass, the full 256 are spawnable, With water, there are only 38 (the flat part of the roof and the porch). This 256:38 spawnable block ratio matches up with the 202:26 spawns per half hour ratio pretty well.

Edit: Updated to remove stairs as unspawnable. They are transparent to spawn attempts if there is at least one block gap below them.

This means there are three separate issues that can affect witch hut spawning:

• Water causing a major reduction in spawn rates. Described in this comment. This can be resolved via adding a solid spawnable-block roof over the chunk.

• Normal cave mobs spawning in the 9x9 chunk density area around the hut chunk and exceeding the 8+1 structure spawn limit, temporarily preventing any witches spawning. See my second comment above. This can be resolved by moving far enough away that the mobs despawn. If you are not above the hut such that it is the only spawnable area, the mobs could very quickly build up and exceed the density limit again once you return to the area.

• Persistent cave spawns, not caused by any player interaction, building up in the 9x9 chunk density area around the hut chunk and exceeding the 8+1 structure spawn limit, permanently preventing any witches spawning. See my first comment above. This can only be resolved by somehow finding and killing the persistent mobs which can be very difficult without using commands.

Ideally you would not need to be aware of all these mechanics and their workarounds for the witch hut to spawn witches reliably.

Reopening and updating to "community consensus" based on recent comments.

Please note, however, that the issue reported here is reasonably consistent respawning at witch huts, not perfectly consistent or maximum respawn rates at every hut in every world. I resolved this report after 1.16.0 because I thought the despawning changes provided for reasonably consistent respawning. Prior to 1.16.0 it was often necessary to spend hours lighting up caves to get a single witch to respawn. The situation now is not like that.

That said, the following behaviors described by Steve Mellross above may be considered unintended bugs:

• Persistent monsters can still build up over time in areas the player has never visited, especially hidden caves, and fill the population cap for witch respawns. (MCPE-125111)

• The cave monster population cap for the witch hut chunk can be filled by mobs in chunks that do not affect each others' caps, with the result that the cap limiting witch spawns can be exceed by up to 4x over time.

I think the first of these deserves its own report, and when I have time I will follow up link it back here.

There are other bugs that make the situation worse, too. Consider the following infinite loop, which involves both of the above issues and more:

1. zombie spawns with armor on the surface

2. zombie wanders into a pool and drowns, dropping its armor

3. converted drowned now occupies the cave cap (MCPE-61721)

4. converted drowned immediately picks up the armor, becoming persistent

5. repeat step 1

Prior to 1.16.0 the loop above was triggered by zombies targeting players or other mobs, rather than by picking up items. That was the underlying cause of MCPE-34032. So we have the same issue now, it's just much slower, because most zombies do not wear armor and cannot pick up items.

Also consider Steve Mellross' mention of zombies/skeletons picking up equipment that was dropped by others and not picked up by the player. This is a much bigger problem than it should be because of MCPE-80504.

All that being said, I expect the issues with surface water and random spawning and despawning in the area affecting with respawn rates, as mentioned in comments above, might be considered as a reasonable variations in behavior between different huts in different worlds. Mojang may well consider them intended behavior or not worth trying to fix.

Bottom slabs on the surface of the chunk, though, limit respawns for the same reason as 2-deep water: they cancel spawn attempts without giving them a chance to fail. Failed spawn attempts trigger structure spawn attempts in the same chunk, but cancelled spawn attempts do not. That is arguably an unreasonably obscure mechanic, because most players would not expect slabbing/flooding vs. lighting the surface of a chunk to make a difference.

In sum, there are a lot of underlying issues here, and while Mojang could choose to do something with the structure spawning mechanics (like change the +1 effective cap) or witch spawn rules (like separating them from the monster cap, as was done with pillagers), I am not sure they will agree that a witch hut-specific bug needs to be fixed. But I will leave it for them to address.

@Steve Mellross: Would you be able to estimate how much total time you had spent around your witch farm before it stopped working?

It's hard to say. I spent a heap of time AFKing - but that was ~128 blocks up, intentionally chosen to be out of range of any non-witch hut spawns, so would not contribute to mobs building up. At a very rough guess, it would probably be around the 24 hour mark of time spent on or near the surface because I'd built three other farms and the witch hut farm collection system in the area. I probably also left my character unattended at the witch farm collection area under the witch hut for a few hours here and there as well. I'm generally pretty careful about that though since I'm not overly confident in the spawn proofing there.

I was probably getting waves of spawns whenever I came near the surface bringing previously out-of-spawn-range areas into range, so it might have been just as dependent on how many times I'd been in and out of the area. Although, mobs would need time to die to drop items to be picked up as well... So, a quick fly into range then up to the spawn point might not contribute at all.

It is worth noting that I had two Zombie drowning holes pretty close to the 9x9 chunk boundary. One with 8 persistent mobs about 16 blocks out, the other with 7 (one an Illager?) about 20 blocks out.

If they had been in range, it would have broken faster. Luckily those holes are relatively easy to fill in. I'd already filled in quite a few early on. I'd previously (mostly) spawn proofed the 12 chunk simulation area around my iron and slime farms. All mob spawning had stopped in the area, mostly due to large holes that had ~50 drowned in them each (resulting in multiple double chests of gold armor gear as I was collecting it all at the time to smelt it). I did AFK near the surface there though. Because of this, that was one of the first things I checked for in the witch farm area.

It's also worth noting that I could not get the slime farm spawning any slimes (surface or cave) even after filling in all these holes and lighting up all the caves I could find in survival. Which was no small task! It took weeks. I had to create a creative copy after that and use the commands above to find the remaining caves and holes (some had what I assume were persistent surface spawn zombies trapped in them) before even a single slime would spawn. I had AFK'd at the iron farm on the surface for quite a while before this point though. I have no idea how long for. Still, it's pretty game breaking if there is no reasonable way to resolve it in survival only.

@GoldenHelmet, do you want me to create a separate issue for persistent spawns building up without player interaction? I was going to add it to Minecraft Feedback since it seems to be a side-effect of intended mechanics but happy to treat it as a bug instead since it seems to break lots of farms and general mob spawning over time.

@Steve Mellross: I've made the general report on persistent monsters building up at MCPE-125111. Could you leave a comment there with the first screenshot you posted here and your seed and coordinates?

I could not reproduce this on the worlds that you provided in the bug, nor on my worlds (new or old). Could any of you that still experience the issue in your worlds, export and attach them here, or upload elsewhere and link here if Jira can't handle the attachment?

To be clear, I need the specific, original worlds that experienced the issue first.

I have attached a test world,

The local player is about 30 blocks east of a witch hut that generated surrounded by water. Command blocks are set to automatically kill any witches that spawn in the hut and update a scoreboard system. The scores are kept by the three named pigs under the player:

• "Time (s)" tracks elapsed time in seconds.

• "Last Witch" saves the elapsed time at which the last witch was detected in the witch hut.

• "Witches" tracks how many witches have been killed.

You can verify how the system works by going inside the hut and using a witch spawn egg.

In addition to the tracking system, there is a command block named "Beam Me Up" on top of the glass that can be used to teleport the player to Y = 250 where there are 2 more commands blocks: "Beam Me Down" sends the player back down again, and "Greet" has all non-item entities say "hi". The "Greet" command block is useful for checking how many persistent mobs have accumulated, because teleporting the player to Y = 250 despawns all non-persistent mobs.

When you open the world, only one score is displayed: the count for "Time (s)", which shows that over 2 hours have elapsed since I got the system set up. In that time, no witches have spawned at the hut! If you use the "Greet" command block you will find that 4 persistent monsters have accumuluated: 2 Drowned, 1 Zombie, and 1 Zombie villager.