When you leave or enter the nether in multiplayer you don't appear at the right location for other clients.
This video shows the bug: http://youtu.be/c1zM8gFB3ro
Here is why this happens: When a player goes through a portal his x- and z-coordinate get multiplied/divided by 8. Then the entity gets spawned in to other dimension.
And after that the player gets moved into the portal where he should spawn. But the last repositioning isn't send to the other clients. Therefor they see the player at x*8, y, z*8 or x/8, y, z/8 (depending if the player left or entered the nether).
To fix this bug we either need to send the absolute coordinates to the other clients after the repositioning or to place the player in the portal before it gets spawned into the world.
Here is how I programmed the second fix with MCP:
In ServerConfigurationManager.java I changed line 507 to 510 from
par4WorldServer.spawnEntityInWorld(par1Entity); //Spawns the entity
par1Entity.setLocationAndAngles(var5, par1Entity.posY, var7, par1Entity.rotationYaw, par1Entity.rotationPitch); //Sets the position to x*8, y, z*8 or x/8, y, z/8. The values were calculated earlier
par4WorldServer.updateEntityWithOptionalForce(par1Entity, false);
par4WorldServer.getDefaultTeleporter().placeInPortal(par1Entity, var11, var13, var15, var17); //Repositions the entity into the portal
//The comments where added by meto
par1Entity.setLocationAndAngles(var5, par1Entity.posY, var7, par1Entity.rotationYaw, par1Entity.rotationPitch); //Sets the position to x*8, y, z*8 or x/8, y, z/8. The values were calculated earlier
par4WorldServer.getDefaultTeleporter().placeInPortal(par1Entity, var11, var13, var15, var17); //Repositions the entity into the portal
par4WorldServer.spawnEntityInWorld(par1Entity); //Spawns the entity
par4WorldServer.updateEntityWithOptionalForce(par1Entity, false);The screenshot is showing a player who came through the portal breaking a block. You can see him in the background due to the offset.
FOR MODERATORS:
Since the other two posts on this bug miss out on a lot of important information I decided to repost it. If you mark this bug as duplicate please make sure to make the information visible in the other posts. Thank you!
This issues was posted two times before:
https://mojang.atlassian.net/browse/MC-12608
https://mojang.atlassian.net/browse/MC-17345
Linked issues
is duplicated by 4
MC-12608
Players fly, get invisible, duplicate, when coming trough a portal
Resolved
MC-17345
Nether multiplayer lan issue
Resolved
MC-30471
nether bug
Resolved
MC-35036
my brother and i were in a LAN server. he went in a nether portal and then appeared in the over-world >10 blocks of the ground still in survival, and could walk around, but on his screen he was still in the nether. i have reproduced this 3 times.
Resolved
Attachments
Comments 7
This also occurs when players enter the End, although in this case they are always offset by one meter on the y coördinate: they appear to be floating one block above their actual position.
To correct Fenhl, this does not happen always. I would assume that a player's delay to the server has a role in whether he will get offset or not.
@Tilman Berres the thread creator panda explained it in his video:
the offset has nothing to do with the player's delay
it is caused by the different coordinatesystems
the coordinates of the nether portal are multiplied by 8, you get spawned in the world at this coordinates and then the server sets you into the portal, which can be offset by -8 to +8 in x and z and any value in y
you get spawned first and then the offset happens so that you land in the portal you have to be spawned in
but all other players' clients that are around just get to know that where you spawned without any further notification afterwards about an offset that gets applied
if the portal was created in the nether instead of the overworld then there can only be an offset in the y coordinate, if there are blocks in the way at the specific y coordinate, so it is more likely that there is no offset
but most of the time there is one...
this fix cares about the offset before the player is spawned -> fixed really easy
I was explicitly referring to fenhl's comment about the end portal position offset which happens occasionally.
I am completely aware of why the nether portal offset exists. after all it was me who figured that out by spectating what happens 😉
MC-12608 and MC-17345 resolved as duplicate of this ticket.