I just stepped out of my opaque fortress (with opaque doors), and there was a creeper right there. POOF. Blew up before I made 1 square.
Has anyone noticed this? I have a creep farm that has a level where they land and have 1 heart left. From time to time, there will be a creeper that drops, and just blows up immediately.
For this to be the cause of the mob farm exploisions, the player station would need to have been built so as to allow the game to occassionally think the falling creeper hit box ovelapped that of the player. [Assuming I'm understanding the mechanic properly, creepers don't simply explode on impact.]
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"Why does everything have to be so stoopid?" Harvey Pekar (from American Splendor)
WARNING: I have an extemely "grindy" playstyle; YMMV — if this doesn't seem fun to you, mine what you can from it & bin the rest.
For this to be the cause of the mob farm exploisions, the player station would need to have been built so as to allow the game to occassionally think the falling creeper hit box ovelapped that of the player. [Assuming I'm understanding the mechanic properly, creepers don't simply explode on impact.]
Creepers don't actually explode due to impacting the player; they still need a direct line of sight to trigger their aggro state, so they can be several blocks away and still explode (aggro distance is 3 blocks, after which you have to move more than 7 away to stop the countdown). The reduction in the explosion delay is due to fall damage (only triggered by impacting blocks, not entities) reducing the fuse time by 1.5 ticks per block fallen down to a minimum of 5 ticks or a quarter second (which is more or less instant due to reaction times); this means that a fall distance of 17 blocks (rounded down to 25 ticks) is required to achieve the minimum delay (note that they will normally never drop down this far, usually it is because they were pushed off a ledge by another mob, and mobs can only detect players from +/-4 blocks vertically):
Otherwise, lag can cause such behavior due the way the server tries to catch up after falling behind (normally each tick runs every 50 ms but if it falls behind it will process ticks as quickly as it can with no delay between ticks with up to 2 seconds of real time being simulated in a much shorter period of time, enough to cause a creeper to appear to explode instantly since their countdown is 1.5 seconds). As for why it happened right after you opened the door, it is possible that MC-17630 is still present to some degree (zombies, and possibly other mobs, tracking you will cause a lot of lag due to multiple failed pathfinding attempts covering a large area until you clear a path, then the lag disappears and the server catches up. Anything else that causes the server to temporarily fall behind while it is otherwise capable of running normally will cause the same behavior).
If you are playing on a version of 1.13 that doesn't have the cod AI fix, this could cause lag enough to produce instant creeper explosions. This method was used by Gnembon to kill TangoTek in his "How do you kill a Tango?" challenge (the challenge had a constraint that Tango would be approximating AFK state by not doing anything after the initial button press/lever pull/etc to trigger the sequence).
This is definitely not true, I have seen mobs observe me from much larger elevation differences than just 4 blocks. Whether they decide to jump down or not is dependent on whether you are above or below and by how much, how far apart you are on the XY plane (creepers in particular will risk falling to come close enough to you if you are within ~5 blocks displacement), the presence of other mobs, particularly those who have not noticed the player, and of course on whether they have a ranged weapon to close the gap.
This is definitely not true, I have seen mobs observe me from much larger elevation differences than just 4 blocks.
Did the mobs actually try to get to you? Try spawning mobs in a glass cage (they cannot see through glass, this just makes it easy to observe them) and you'll see that they will turn around to look at you from time to time (at least, this happens in 1.6, since their "gaze" AI doesn't take obstructions into account); the bug report mentioned is referring to part of their AI that targets players (which is also different from what Endermen and Ghasts, or "old AI" mobs prior to 1.8, use to target players).
Also, the exact vertical difference required depends on the sizes of the bounding boxes of the mob and player, which are 1.7 blocks and 1.8 blocks for creepers and players respectively (if you look at the code given it calls boundingBox.expand(), which increases the size of the mob's bounding box by the specified amount in each direction, 4 for the y-dimension). It also appears that once they are locked onto a target this doesn't matter (likewise, while most mobs will stop moving past 32 blocks from a player they can still actively pathfind from further away, up to 100 blocks for zombies in 1.6).
Did the mobs actually try to get to you? Try spawning mobs in a glass cage (they cannot see through glass, this just makes it easy to observe them) and you'll see that they will turn around to look at you from time to time (at least, this happens in 1.6, since their "gaze" AI doesn't take obstructions into account); the bug report mentioned is referring to part of their AI that targets players (which is also different from what Endermen and Ghasts, or "old AI" mobs prior to 1.8, use to target players).
Also, the exact vertical difference required depends on the sizes of the bounding boxes of the mob and player, which are 1.7 blocks and 1.8 blocks for creepers and players respectively (if you look at the code given it calls boundingBox.expand(), which increases the size of the mob's bounding box by the specified amount in each direction, 4 for the y-dimension). It also appears that once they are locked onto a target this doesn't matter (likewise, while most mobs will stop moving past 32 blocks from a player they can still actively pathfind from further away, up to 100 blocks for zombies in 1.6).
The mobs did try to get to me, that''s the weird thing. I know what you mean, at least informally, by the gaze AI being disjoint from the target-finding AI, but I have indeed had creepers, zombies, spiders, and even skeletons try to jump down to me, or even lean so far on a ledge below me that they fell down, no other mobs nearby. The absolute value of the height difference was around 10 blocks.The distance horizontally was small, less or equal to 5 blocks in most cases when they fell. Mobs noticed me though, from heights of around 10 and distances of up to 8. That's around the time when I started thinking the game had a mind of its own. There was even a case where a skeleton saw me from such a distance through a lava flow blocking my view of it, and I got startled by an arrow on fire coming straight out of lava!
This is dating back to when I started playing in 1.5.1 and has not changed as far as I have observed, not that I'm trying to find it. It is possible, actually very likely, that mobs have reduced 'height vision' in recent versions.
However, as you play 1.5 and 1.6 and regularly mod and analyze those versions, I expect at least for those versions that you know better what you're talking about than I do.
I've seen this, but it's roughly 1 in 200 Creepers. It's more likely in my exp. that it's due to Skeletons shooting something in-the way of the Player - Mob Infighting - and then Creepers get into it (they tend to "'end' [such] conflicts").
Since I've never-really used an artificial Mob Spawner enough to see what you're seeing, though, I can attest to the Original Post(er). And it's why I'd increasingly-turned to Glass-containing entrances /exits (lately even the whole Ground Floor, of Main Base, with all moved-upwards, beyond Any Hostile's reach [Phantoms as - New - exception]), when on anything-like Ground-level Bases (there's also the "MC 'Noob Test'," which generally shows that at-least 3 far-enough apart entrances and /or exits are necessary to - Mainly, for - avoid[ing] Creepers: Many of us end-up with *counts* 6-9++ ; ways of especially-exiting Bases, to Despawn them by moving-away, as by going-off a roof).
That way I see them coming. When I'm - in any case - going.
I just stepped out of my opaque fortress (with opaque doors), and there was a creeper right there. POOF. Blew up before I made 1 square.
Has anyone noticed this? I have a creep farm that has a level where they land and have 1 heart left. From time to time, there will be a creeper that drops, and just blows up immediately.
Depending on the local "geography" this may be the cause:
New creeper fall mechanics; creepers will now explode, if they fall on the player from a certain height....added in 1.4.2
(from https://minecraft.gamepedia.com/Creeper )
For this to be the cause of the mob farm exploisions, the player station would need to have been built so as to allow the game to occassionally think the falling creeper hit box ovelapped that of the player. [Assuming I'm understanding the mechanic properly, creepers don't simply explode on impact.]
Creepers don't actually explode due to impacting the player; they still need a direct line of sight to trigger their aggro state, so they can be several blocks away and still explode (aggro distance is 3 blocks, after which you have to move more than 7 away to stop the countdown). The reduction in the explosion delay is due to fall damage (only triggered by impacting blocks, not entities) reducing the fuse time by 1.5 ticks per block fallen down to a minimum of 5 ticks or a quarter second (which is more or less instant due to reaction times); this means that a fall distance of 17 blocks (rounded down to 25 ticks) is required to achieve the minimum delay (note that they will normally never drop down this far, usually it is because they were pushed off a ledge by another mob, and mobs can only detect players from +/-4 blocks vertically):
Otherwise, lag can cause such behavior due the way the server tries to catch up after falling behind (normally each tick runs every 50 ms but if it falls behind it will process ticks as quickly as it can with no delay between ticks with up to 2 seconds of real time being simulated in a much shorter period of time, enough to cause a creeper to appear to explode instantly since their countdown is 1.5 seconds). As for why it happened right after you opened the door, it is possible that MC-17630 is still present to some degree (zombies, and possibly other mobs, tracking you will cause a lot of lag due to multiple failed pathfinding attempts covering a large area until you clear a path, then the lag disappears and the server catches up. Anything else that causes the server to temporarily fall behind while it is otherwise capable of running normally will cause the same behavior).
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?
If you are playing on a version of 1.13 that doesn't have the cod AI fix, this could cause lag enough to produce instant creeper explosions. This method was used by Gnembon to kill TangoTek in his "How do you kill a Tango?" challenge (the challenge had a constraint that Tango would be approximating AFK state by not doing anything after the initial button press/lever pull/etc to trigger the sequence).
This is definitely not true, I have seen mobs observe me from much larger elevation differences than just 4 blocks. Whether they decide to jump down or not is dependent on whether you are above or below and by how much, how far apart you are on the XY plane (creepers in particular will risk falling to come close enough to you if you are within ~5 blocks displacement), the presence of other mobs, particularly those who have not noticed the player, and of course on whether they have a ranged weapon to close the gap.
Did the mobs actually try to get to you? Try spawning mobs in a glass cage (they cannot see through glass, this just makes it easy to observe them) and you'll see that they will turn around to look at you from time to time (at least, this happens in 1.6, since their "gaze" AI doesn't take obstructions into account); the bug report mentioned is referring to part of their AI that targets players (which is also different from what Endermen and Ghasts, or "old AI" mobs prior to 1.8, use to target players).
Also, the exact vertical difference required depends on the sizes of the bounding boxes of the mob and player, which are 1.7 blocks and 1.8 blocks for creepers and players respectively (if you look at the code given it calls boundingBox.expand(), which increases the size of the mob's bounding box by the specified amount in each direction, 4 for the y-dimension). It also appears that once they are locked onto a target this doesn't matter (likewise, while most mobs will stop moving past 32 blocks from a player they can still actively pathfind from further away, up to 100 blocks for zombies in 1.6).
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?
Wow.
I really have never heard of this. It could be lag or maybe it's just on your version.
It must be hard to survive those creepers!
The mobs did try to get to me, that''s the weird thing. I know what you mean, at least informally, by the gaze AI being disjoint from the target-finding AI, but I have indeed had creepers, zombies, spiders, and even skeletons try to jump down to me, or even lean so far on a ledge below me that they fell down, no other mobs nearby. The absolute value of the height difference was around 10 blocks.The distance horizontally was small, less or equal to 5 blocks in most cases when they fell. Mobs noticed me though, from heights of around 10 and distances of up to 8. That's around the time when I started thinking the game had a mind of its own. There was even a case where a skeleton saw me from such a distance through a lava flow blocking my view of it, and I got startled by an arrow on fire coming straight out of lava!
This is dating back to when I started playing in 1.5.1 and has not changed as far as I have observed, not that I'm trying to find it. It is possible, actually very likely, that mobs have reduced 'height vision' in recent versions.
However, as you play 1.5 and 1.6 and regularly mod and analyze those versions, I expect at least for those versions that you know better what you're talking about than I do.
I've seen this, but it's roughly 1 in 200 Creepers. It's more likely in my exp. that it's due to Skeletons shooting something in-the way of the Player - Mob Infighting - and then Creepers get into it (they tend to "'end' [such] conflicts").
Since I've never-really used an artificial Mob Spawner enough to see what you're seeing, though, I can attest to the Original Post(er). And it's why I'd increasingly-turned to Glass-containing entrances /exits (lately even the whole Ground Floor, of Main Base, with all moved-upwards, beyond Any Hostile's reach [Phantoms as - New - exception]), when on anything-like Ground-level Bases (there's also the "MC 'Noob Test'," which generally shows that at-least 3 far-enough apart entrances and /or exits are necessary to - Mainly, for - avoid[ing] Creepers: Many of us end-up with *counts* 6-9++ ; ways of especially-exiting Bases, to Despawn them by moving-away, as by going-off a roof).
That way I see them coming. When I'm - in any case - going.