Just place a slab of any kind on the upper side of a block many times, and you'll sometime get one that converts to being on the bottom side of a block.
Description from MC-89850
When placing top- or bottom aligned blocks like slabs and stairs server and client disagree about the alignment of placed blocks
Doesn't happen in single player (or isn't visible), but on dedicated server or Realms.
Steps to reproduce:
Place a block with a well defined center (e.g. stone bricks) at ca. eye level
Take a stair or slab
Aim slightly above the center of the block
Place block
The results:
Client places the block at the correct top alignment
Server overwrites the block a split second later at incorrect bottom alignment
Screenshots show before and after placement (the in-between position is quite difficult to capture)
Code analysis by @unknown in this comment.
Related issues
is duplicated by
MC-8
Slabs and Stairs Placed Wrong
MC-9269
When building a bridge out of top-slabs, some will randomly turn into bottom-slabs (SMP)
MC-36953
slabs placed against upside-down slabs aren't upside-down
MC-44810
Half slabs placing glitch
MC-50554
Placing bottom slabs sometimes doesn't work when you're in the top half of the block
MC-81379
Slabs placed on top layer flip to bottom layer
MC-89850
Server and client disagree about correct alignment of placed blocks
MC-96283
Top slabs glitch and become bottom slabs
MC-97569
Half-slab wrong placement
MC-101712
Slabs flip positon randomly when placed on multiplayer servers or realms
MC-102884
Stairs and slabs placement detection wrong
MC-104739
Slabs placing on the wrong half of the block
relates to
Attachments
Comments
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And you're absolutely sure the point of the block you were pointing at didn't change slightly while you were moving so you pointed at the lower half of the block?
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Yes, it has happened when I placed it aside another half-slab that was placed correctly.
It happened to myself and it keep happening to pretty much every youtuber I'm watching.
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Confirmed in 13w03a on multiplayer. Aiming at the very bottom of an upper slab like in the screenshot places the upcoming slab as lower slab.
Edit: Works fine in singleplayer.
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Agh, this is so annoying for the non-host when bridging with half-slabs in LAN play.
edit: Version 1.6.2 pre-release.
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bug is still in the game please release a fix 😉
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Extremely annoying. This really shouldn't be able to happen because there is no way of selecting the bottom half of the block if you are placing it against another slab. Please fix it.
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I'm experiencing the same problem with 1.7.5 multi-player. It's annoying for building with slabs.
Nonetheless, this does not seem to happen with single-player modes (confirmed in 1.7.5 and 14w11b).
I have no idea on what could cause this bug. Just a guess, would be this related to kind of floating-point round-off errors or server-client synchronization issues?
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This happens when you place a slab on the bottom row of pixels on a upside down slab
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.
KnightMiner
Fixed in 1.8 or before
Ezekiel
Resolved as fixed in 1.8.1
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Nope, not fixed at all.
This happened when I was playing on my new server two months ago. Both server and client were running vanilla 1.8.3. I was recording at the time, so I have video proof.
I haven't tested it in 1.8.4, but more likely than not it hasn't been fixed.
EDIT: I tested it on my server just now, and the bug is still there! Please reopen and add 1.8.3/1.8.4 to the affected versions.
EDIT again: The affected versions have been updated, but this wasn't reopened.
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Still present in 1.8.5 and 1.8.6.
kumasasa
Confirmed for 15w44b: MC-89850
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1.8.9 too
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Not fixed in 1.9.2
JUE13
Confirmed for 1.9.4
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Confirmed for 16w20a
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The easiest way to replicate this is by placing a top slab, then place the cursor as low on the side of the slab as possible. Finally, place a new slab and quickly move the cursor downwards.
BTW: confirmed for 1.10.1 and 1.10.2
FaRo1
Can anyone confirm that this happens only in multiplayer and/or that this is always lag/latency related? If not, could then please someone provide a teleport command including rotation to reproduce this?
I've seen this often in videos, I think it might have always been on servers, but I'm not sure. I think it never happened to me, but I'm also not sure of that.
kumasasa
This happens only in Multiplayer but is not lag dependant.
Panda4994
I came across this issue when looking into MC-4 and found that it basically has the same cause.
When you place a block the packet CPacketPlayerTryUseItemOnBlock is sent to the server. It encodes the facing into bytes to transmit them which causes this inaccuracy.
The packet is just send when the player right clicks on a block holding an item, so it probably isn't an issue to just change the transmission of these values to floats.
It would probably be good to add this to the description 🙂
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Wrongly marked. This is a duplicate of MC-8
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It is not, this contains more details.
pokechu22
@@unknown MC-8 can be a duplicate of this report because this one was created with more details, details that allowed the devs to actually fix the issue. Just because MC-8 was created first doesn't mean it's the best dupe-target for similar issues.
In some cases the content from the newer report will be moved to the older report if the fact that there is an older issue that is the same thing is found, but (especially if there are a lot of linked issues on the newer one and the older one is basically abandoned for 3 years) it won't usually be changed. It doesn't matter, anyways - the issue number is insignificant for most purposes. If having the smallest issue ID mattered, then one could just constantly replace old dupes with other unrelated issues - not necessary and generally a waste of time.
Erik Broes