The bug
I spawned a couple of hundred hostile mobs into a reasonably sized bedrock enclosure, it was unnoticeable with a few mobs but as soon as their number became greater than approximately 100 they all seems to start moving into the corners of the enclosure and merging together.
As the mob count increased to around about 200, the mobs were clearly sucked into each corner and compiling there, furthermore mobs would be flung at incredible speeds between the corner groups.
Around 250 mobs (creepers in this case) they were just zooming all over the pen from one corner to another.
Graphical glitches are also frequent (mob model moving outside the enclosed space then zooming back to correct position) when spawned numbers are high.
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Confirmed. When they move they sound very weird.
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I noticed that behavior before with a 3x3x2 pit with many cows in them, that one was back in 1.3 .
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Actually very likely in survival with mob pits. I had an inven full of seeds and bred chickens in a 20x10 room until I had a nice fluffy carpet, but then they all grouped and stuck in a corner next to a crafting table.
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Is this still a concern in the current Minecraft version 1.7.2 / Launcher version 1.3.4 ? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
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Updated for 1.7.2, the bug is still present.
galaxy_2alex
Is this still a concern in the current Minecraft version 1.7.4 / Launcher version 1.3.8 or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
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Is this still a concern in the current Minecraft version *14w11b / Launcher version 1.3.11 or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
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Is this still a concern in the current Minecraft version 14w21b / Launcher version 1.4.4 or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
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Still present in current 1.7.10
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500-600 entities clearly shows the corner attraction behaviour. Hopefully 1.8's AI overhaul will resolve this.
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it's modded minecraft
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Oh good input @Mega linial X! Very well done! Yes the first two pictures show 'Rei's minimap' BACK IN v1.5, since then all the screenshots are vanilla minecraft!
What about the screenshots I uploaded for 1.7.10? It's very easy to build a bedrock holding cell then spawn hundreds of mobs and see what they do, so why don't you try it yourself on vanilla minecraft, and see if you can reproduce it too before posting such unhelpful and factually incorrect comments.
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This might take a little explaining but I think I understand most of this behavior. You can repeat the merging behavior by placing a single block far above the ground and spawning multiple mobs on the block. If the position of any mob on that block is updated, they will all fly off at high speeds. This behavior might be caused by a similar stacking glitch/bug like tnt minecart explosions; the push back effect when two mobs collide will get multiplied, forcing the mobs away from each other at high speeds. As for the tendency of gravitating toward the edges, I will have to figure out how I will explain that.
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I believe it relates to hitboxes glitching around, similar to the graphical glitches of mobs being seemingly pushed through the walls. They gravitate to corners because the game is still assuming that the holding cell is filled with the hitboxes of the mobs, meaning once they find themselves in those corners, it's impossible for them to move. This behavior is progressive, as you can see it happening with fewer mobs but becomes so extreme with higher quantities that you can no longer see the visual representations of the hitboxes that are causing the effect.
I just can't imagine how this glitch could be fixed, aside from forcing mobs to not stack on top of each other.
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This can not be properly fixed if the number of mobs is large enough. Lets say you have about 100 mobs within a 1 block wide by 2 block long pen. Using normal blocks to build the pen, the mobs hitboxes seem to only go to the middle of a block. So the 100 mob hitboxes would have to fit into the 1 block long space. This combined with the push back effect of mob collisions would easily cause the hitboxes to overlap, and even share positions along the edges. It also doesn't help that the push back effect is multiplied when mobs stack. They get stuck on the edges because nothing is pushing them back towards the center to counteract the mobs pushing them outwards.
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you are in creative mode so the creepers are not trying to chase you. so tey walk just randomly. if there is a wall the are trying to move forward but they cant bekause there is a wall if they are in a corner they will as long as they dont change the direcktion stay at the same place
kumasasa
Is this still an issue in the current Minecraft Snapshot 15w45b or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.
tryashtar
Uploaded a new screenshot from 18w07c. Looks good to me. Please respond if you can still reproduce.
MalbaCato
Can we change the name to exclude the unhelpful 1.5 in there? Thanks!
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Confirmed for 1.13.1.
muzikbike
Looks like this affects 19w14b
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Confirmed for 1.16.5 and this was reported years ago it seems like. I am really confused what is taking so long. Just curious is all.
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Any updates on this?