Expected behaviour (Until 1.21.4)
(See 1st attachment)
If you teleport a display entity and set its transformation value in the same tick to counteract the teleportation, the display entity should not visually move.
Observed behaviour (1.21.5)
(See 2nd attachment)
The application of the display entity transformation is delayed and plays a few frames after the teleportation (which is instantaneous).
Note that until 1.21.4, both transformation and teleportation were delayed and happened between ticks. Now, teleportation happens properly on-tick, but it’s desynced from transformations.
How to reproduce
Set up a redstone clock with 4 command blocks like in the attached videos. On one side, put these commands:
tp @e[type=minecraft:item_display] ~ ~1 ~
data merge entity @e[type=minecraft:item_display,limit=1] {transformation:{left_rotation:[0f,0f,0f,1f],right_rotation:[0f,0f,0f,1f],translation:[0f,0f,-3f],scale:[1f,1f,1f]}}On the other side, put these commands (The exact translation value will be different depending on how you built it. Use F3 as a reference):
tp @e[type=minecraft:item_display] ~ ~1 ~
data merge entity @e[type=minecraft:item_display,limit=1] {transformation:{left_rotation:[0f,0f,0f,1f],right_rotation:[0f,0f,0f,1f],translation:[0f,0f,3f],scale:[1f,1f,1f]}}
Now activate the redstone clock and see how the display entity flickers. This flickering will change if you pause & unpause (in singleplayer), indicating some sort of desync. This behaviour does not happen in versions 1.21.4 or below.
Linked issues
relates to 2
Attachments
Comments 8
This is a clip of me walking to the side (Version: 1.21.4, Rotation: 0, -90) while a display entity is teleported to my eyes every tick (view_range is normal). As you can see, it jitters a lot at the start, then calms down once I pause and unpause, only to continue jittering after doing it again.
Expected behaviour would be if the distance between the lines were constant. Note that the MSPT are at 0.6, and the game runs at a stable 120FPS, so lag isn’t the issue.
I can provide more detailed replication steps if needed.
It turns out that the issue is with teleportation itself, and not transformation.
Teleportation is not synchronized with the ticking, and it can be offset by pausing and unpausing in singleplayer.
I can’t edit the bugreport, but the name and description are wrong.
[media](I’m sorry for spamming the comments, but it doesn’t seem like I can edit previous ones.)
In 1.21.4 and below, both teleportation and transformation are applied off-tick (timing can be changed by pausing/unpausing).
[media]In 1.21.5, this bug only applies to transformation, which creates the visible desync. Ideally, both teleportation and transformation should be applied on tick.
[media]
Please attach a world file that can be used to reproduce this issue both for 1.21.4 and 1.21.5 / latest snapshot
Here you go. This world includes the command block setup shown in the previous comments, along with a command block to summon the item display.
I can confirm this still happens in Snapshot 25w19a.
The cube should remain centered, since the transformation and teleportation are happening in the same tick, but it appears as though the teleportation happens after the transformation is applied, causing the cube to jump around instead of remaining centered. Which matches the behavior described by SilicatYT in the comments.
It should be noted that changing the order of the commands does not effect the issue.
It seems that a similar bug exists in 1.21.4 and below, but instead of the transformed position being bugged, it’s the clientside position of the entity.
[media]In this clip, I have applied a datapack that reduces the display entity’s view_range, teleports it to my eyes and updates the translation accordingly so the entity appears stable.
As you can see, the entity sometimes starts to flicker (the clientside position is not updated fast enough) depending on me pausing and unpausing the game, again indicating some sort of desync.