[MC-7809] Aiming at the very bottom of a side of an upper slab/stair places slabs/stairs right-side up in multiplayer Created: 18/Jan/13  Updated: 05/Nov/16  Resolved: 30/Sep/16

Status: Resolved
Project: Minecraft: Java Edition
Component/s: None
Affects Version/s: Minecraft 1.4.7, Snapshot 13w03a, Minecraft 1.5, Snapshot 13w11a, Minecraft 1.5.1, Minecraft 1.6.4, Minecraft 13w42b, Minecraft 13w43a, Minecraft 1.7.1, Minecraft 1.7.2, Minecraft 1.8.1, Minecraft 1.8.3, Minecraft 1.8.4, Minecraft 1.8.5, Minecraft 1.8.6, Minecraft 1.8.7, Minecraft 1.8.8, Minecraft 15w44b, Minecraft 1.8.9, Minecraft 1.9.2, Minecraft 1.9.4, Minecraft 16w20a, Minecraft 1.10.2
Fix Version/s: Minecraft 1.8, Minecraft 16w39c

Type: Bug
Reporter: Halgdp Halgdp Assignee: [Mojang] Grum (Erik Broes)
Resolution: Fixed Votes: 36
Labels: block

Attachments: PNG File 2013-01-20_00.38.51.png     PNG File 2015-10-05_00.57.38.png     PNG File 2015-10-05_00.57.51.png    
Issue Links:
Duplicate
is duplicated by MC-9269 When building a bridge out of top-sla... Resolved
is duplicated by MC-36953 slabs placed against upside-down slab... Resolved
is duplicated by MC-44810 Half slabs placing glitch Resolved
is duplicated by MC-50554 Placing bottom slabs sometimes doesn'... Resolved
is duplicated by MC-81379 Slabs placed on top layer flip to bot... Resolved
is duplicated by MC-89850 Server and client disagree about corr... Resolved
is duplicated by MC-96283 Top slabs glitch and become bottom slabs Resolved
is duplicated by MC-97569 Half-slab wrong placement Resolved
is duplicated by MC-101712 Slabs flip positon randomly when plac... Resolved
is duplicated by MC-102884 Stairs and slabs placement detection ... Resolved
is duplicated by MC-104739 Slabs placing on the wrong half of th... Resolved
is duplicated by MC-8 Slabs and Stairs Placed Wrong Resolved
Relates
relates to MC-90022 Movement packets arrive too late Resolved
CHK:
Confirmation Status: Confirmed

 Description   

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 Panda4994 in this comment.



 Comments   
Comment by [Mod] Pokechu22 [ 05/Nov/16 ]

@TheRedstoneRazor 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.

Comment by Mustek [ 05/Nov/16 ]

It is not, this contains more details.

Comment by Nope. [ 05/Nov/16 ]

Wrongly marked. This is a duplicate of MC-8

Comment by [Mojang] Panda [ 15/Aug/16 ]

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

Comment by Kumasasa [ 31/Jul/16 ]

This happens only in Multiplayer but is not lag dependant.

Comment by Fabian Röling [ 31/Jul/16 ]

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.

Comment by tomatitus1 [ 28/Jun/16 ]

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

Comment by fdagpigj [ 20/May/16 ]

Confirmed for 16w20a

Comment by user33 [ 11/May/16 ]

Confirmed for 1.9.4

Comment by Nicolas Mayora [ 08/May/16 ]

Not fixed in 1.9.2

Comment by PancakeMan77 [ 29/Jan/16 ]

1.8.9 too

Comment by Kumasasa [ 04/Nov/15 ]

Confirmed for 15w44b: MC-89850

Comment by BoxFigs [ 28/May/15 ]

Still present in 1.8.5 and 1.8.6.

Comment by BoxFigs [ 22/Apr/15 ]

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.

Comment by [Mod] Ezekiel (ezfe) [ 06/Jan/15 ]

Resolved as fixed in 1.8.1

Comment by KnightMiner [ 30/Oct/14 ]

Fixed in 1.8 or before

Comment by Galaxy_2Alex [ 25/Oct/14 ]

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.

Comment by David Wheatley [ 07/Aug/14 ]

This happens when you place a slab on the bottom row of pixels on a upside down slab

Comment by Joongi Kim [ 22/Mar/14 ]

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?

Comment by ComputerKing [ 18/Jan/14 ]

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.

Comment by Djfe [ 16/Nov/13 ]

bug is still in the game please release a fix

Comment by Tim Gunderson [ 08/Jul/13 ]

Agh, this is so annoying for the non-host when bridging with half-slabs in LAN play.

edit: Version 1.6.2 pre-release.

Comment by ItsMartin [ 07/Feb/13 ]

Discussion of this bug on /r/minecraft

SethBling's gif showing the bug

Comment by Tails [ 19/Jan/13 ]

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.

Comment by Halgdp Halgdp [ 19/Jan/13 ]

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.

Comment by Anorma [ 18/Jan/13 ]

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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