mojira.dev
MC-460

Experience orb position client-server desync

Experience orbs sometimes keep swirling around you, without ever being absorbed no matter how long you wait. This is because the client and server disagree on where they are.

In a recent Minecraft version, more sync event have been added, so now the orbs are jumping back to where the server think the orbs are about once every second or so. But it is still obvious that they are buggy. One specific issue is half-slabs, which the client thinks the orbs can climb over, while the server disagrees (this might or might not be the only problem).

Video demo: http://youtu.be/oVwu3LOgS14

Related issues

MC-4639 Suffocated after save, went back to pick up items, experience orbs were with items and just float around me MC-11764 XP orbs float around your head without being collected until server restart MC-12499 Experience Orbs Ghosting. MC-12958 exp orbs float around and do not get absorbed MC-14655 Spirits (XP and items) twitch, move around like crazy, and sometimes spawn and fall off things constantly MC-24524 Client Server orb desync problem MC-31443 Experience Balls Not finalising MC-38419 Hoppers preventing EXP orbs from being collected MC-76071 Experience Orbs occasionally can't pass through upside-down half slabs, but their animations can MC-117183 XP Is Glitched MC-117244 XP spawns randomly MC-117515 constant visual exp orbs with hoppers MC-119761 xp collection bug MC-137161 XP Orbs stuck in hopper generates infinite dummy orbs MC-769 Fake XP orbs

Attachments

Comments

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Ezekiel

label this desync please

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This is a screenshot of the uncollectable orb, one of several dropped after killing some silverfish.

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Proof that the orb behaves like a normal orb, except is never collected. It had been orbiting me for nearly a full minute when I took this screenshot.

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These two screenshots are both from a Hardcore SSP world, vanilla 1.4.2

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One other note that might be relavant. When I left and reentered the world, I was on the surface, but at the same x and z coordinates that I'd had underground before leaving the world. When I went back down, there was no XP orb to be found.

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Happens to me on my client SMP games every once in a while.

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I have noticed this since 1.2.5. Very annoying when you throw a bottle of enchanting.

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Yes i've noticed this since 1.4.5. Experience orbs swirling in front of face that can't be collected. Playing on PC, single player survival, no mods. Quite rare and don't know what triggers it. Sometimes they appear just after loading a world.

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The cause is simple. The orb "moves" towards the player, and the player "collects". But this is only client side.
The orb itself has not moved, and is still at it's original drop location.
Unless the player walks over that particular location / block, the "collected" orb stays flying around the player.
The quick "fix" is to walk around all the blocks where the orbs were, to make sure you've collected them all.

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Seems to be related to MC-4.

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In 1.5.1, the orb position seems to be synced once every second or so.

Which makes it really easy to demonstrate that there is problem with halfslabs. The client seems to think that the orbs can travel up a halfslab, while the server thinks not.

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With 1.5.1 SSP, I have an xp grinder that uses half-slabs. On the sides where the half-slabs are on the top half of a block, the exp orbs are able to pass beneath the half-slabs and are absorbed normally. On sides where the half-slabs are on the bottom of the block, the exp orbs travel toward me, circle around, then reappear inside the grinder and repeat this cycle in an infinite loop (or until they despawn, I suppose.) If I break any of the lower half-slabs on the side I'm facing, or if I move around to another side of the grinder where the half-slabs are on the upper half of their block, the orbs immediately travel through the lower gap and are absorbed. I believe the credit for the exp does appear on the HUD the first time the orbs exit the grinder; it is only the visual orb entity that fails to disappear. Thus it seems orbs are able to travel through the lower half of a block, but not the upper half.

If all of the half-slabs are on the bottom of their blocks, then the orbs never get absorbed and will continue to cycle in and out of the grinder until they despawn. Walking around the grinder has no effect and it does not matter where I walk or stand.

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Tested 1.3.2, 1.4.7, and 1.5.2. Definitely happens much more often in 1.4 and 1.5 than in 1.3

Jeuv

Still in 1.7.2.

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Just updated to 1.7.4 and it seems to be worse than ever. Most of the orbs keeps flying around your head (I'm getting sea sick)

Ezekiel

Is this still a concern in the latest Minecraft version 14w21b? 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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Many bugs in Minecraft are cause by the internal server system, if Mojang back to the old singleplayer that was great, a lots of bugs in Minecraft can be fixed, examples: singleplayer lag, mob clipping, dropped items clipping, strange mob moves, missing travel.ogg sound, etc... It's only a suggestion, I would be very grateful if Mojang decide to remove the internal servers (or make it optional).

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I disagree with removal of internal server (it has made modding SO MUCH EASIER) but agree that the current state of singleplayer is quite dismal. They need to go back to 1.2.5 and play it for a little and take note of how everything wasn't broken and then try to get that back in.

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The internal server has many more upsides than downsides. It has helped to make development much faster, as the singleplayer coding and the multiplayer coding can be done simultaneously and improved the stability of servers too.

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I agree that it's very beneficial, I'm just saying that more effort should've been put in to make the internal server experience match that of 1.2.5, because it's far from doing so.

galaxy_2alex

Is this still a concern in the current Minecraft version 1.8.1 Prerelease 3 / Launcher version 1.5.3 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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This actually seems to be fixed in 1.8.1-pre3.

galaxy_2alex

Fixing it as such, thanks.

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New report in 1.8.1 from MC-76071

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still happening in 1.8.3 (http://i.imgur.com/NNkg432.png) and it's really REALLY annoying when it completely blinds you, like what seems to happen to me EVERY TIME I go mob farming

marcono1234

Confirmed for

  • 1.8.3 when you throw a bottle of enchanting, the XP orbs display first all facing south (that is not really the bug) but after this get a random direction (also not the bug) and sometimes get spread for about 5 blocks

Might relate to MC-12013

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Nah, MC-12013 is safely and completely solved (I made a mod to fix it before Vanilla patched it so I know what that bug is)
This bug is just an extension / special case of MC's entity syncing system being derpy in general (client and server still not matching some code, etc.). By extension this and the item drops appearing in wrong place bug and the boat desync bug are all the result of a derpy synchronizations system.

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This happens to me with my cave spider exp farm in 1.8.8

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Affects 15w47c

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Confirmed for 1.8.9 and 15w51b.

FaRo1

Confirmed for 1.10. I've attached a screenshot of a setup with which this can be reproduced (other ways that are mentioned in this report don't work anymore).
The top glass block on the left side is at the coordinates -120 57 2, the rest of the glass box is in the direction of negative x.
First command block (right) contains "gamemode 3 @p", then there is a repeater to a little tower with the following commands:
gamemode 1 @p
teleport @p -119 57 2 90 0
summon XPOrb -121 57 2
This positions the nearest player left of the top glass block on the left and an XP orb directly on the other side, above the water source.
Result: The XP Orb flies in a well visible bow above the player before it gets reset to its server position.

FaRo1

Confirmed for 1.10.1.

marcono1234

Attached a world with the setup you described to reproduce this

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Does this problem affect Minecraft 1.11?

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Attached an screenshot showing an easy test setup.

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Still in 1.11.2

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Screen shot shows the same bug with hoppers. The orb close to the crosshair will now track me (sideways) when i move but it will not go "over the edge" and to me. However, if i log out and back in it will start to fly to me repeatedly but it cant be picked up (since i already got it before i guess).

wobst.michael

@unknown please don't attach screenshots made with modified versions of Minecraft. These are useless to us.

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Confirmed for 1.13.1.

galaxy_2alex

I am unable to reproduce this with the attached world, both in Singleplayer and Multiplayer. Can anyone else? If not, I will set this to resolved within a week.

FaRo1

This does indeed seem to be fixed in 1.14.0, at least with the setup I commented in 2016.

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This stopped happening in a shapshot like 19w45a.

Arisa Bot

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(Unassigned)

Confirmed

(Unassigned)

desync

Minecraft 1.4.2, Minecraft 1.4.5, Minecraft 1.4.7, Minecraft 1.5, Minecraft 1.5.1, ..., Minecraft 1.12, Minecraft 1.12.1 Pre-Release 1, Minecraft 1.12.1, Minecraft 1.12.2 Pre-Release 1, Minecraft 1.13.1

Minecraft 1.8.1-pre3

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