mojira.dev
MC-123524

X amount of Command Blocks in a chunk glitches the chunk, structure blocks, entities, hitboxes and frame rate dramatically

Reproducing: Go inside any chunk of any map on 1.12.2 or later. Place a POWERED Empty [Command:""] Repeating Command Block AND connect to it 63 Empty Chain Command Blocks inside that SINGLE chunk.
Change a single of ANY of the commands to have an unsuccessful output (such as [Command:"Hi World"]), and the chunk will become affected.
OR you can also add a 64th empty Chain Command Block, and the chunk will also become affected.
If you have any 64 powered Chain Command Blocks, the chunk will become affected, even if all 65 Command Blocks are empty.
You can also have two Repeating Command Blocks activating 32 Chain Command Blocks each, and so on.
Conditional Chain Command Blocks don't seem to affect that count, you can have as many of them anywhere on the chain.

Whenever I LOOK directly at the Command Blocks that are affecting a chunk, I have big performance issues. Turning around and looking at them can cause a FPS drop from an average of 500 frames to an average of 100 frames, with no entities near.
Also, when I'm near those Command Blocks, I sometimes get TPS lag (visual rollback after breaking or placing blocks, world takes longer to load, player hand flickers while loading world) and also "ghost FPS lag", as my screen stutters even at 300 FPS, as if I was at 30FPS instead.
Have in mind that if I have 62 Chain Command Blocks, for example, they won't cause any noticeable lag. As soon as I place the 63rd/64th one, the issues above start happening, so it's not caused by the command amount itself, but by the bug caused from the conditions above.

Also causes entity flickering after teleports, until the entity is "refreshed" (likely by relogging or teleporting again).
A wolf is a good example. Tame a wolf and teleport towards the affected chunk using a button. The world should take longer than usual to load, your hand will also flicker during loading and after loaded the wolf that, due to his tp AI, was teleported with you will be flickering. You can still make him sit/stand, but he completely loses his collision-hitbox (can't be pushed around), and if he takes damage he becomes red until refreshed and makes an even weirder pose.

Affected Chunks:
Structure Block UI will not work properly anywhere inside affected chunks. After clicking the "Change Structure Block Mode Button", your screen will flicker and redirect you to the last screen (button will not work fully, but if you press done and reopen, you might or might not be at the next screen, based on which one you were).
Additionally, if you try to go from "LOAD" to "CORNER" mode, you will get stuck between both, on a new screen, that says "CORNER" mode, but has the "LOAD" mode's text fields. (see screenshot)
All buttons except "MODE" button in all screens will disappear after you click the "MODE" button until you reopen the UI.

Entity Flicker Example: https://www.youtube.com/watch?v=_NChbKy7kvY

Related issues

Attachments

Comments

migrated
[media][media]
pokechu22

This sounds like MC-82703 to me, but I'm not 100% sure. It's a different set of symptoms.

I will note that the wolf not teleporting the first time was probably an unloaded chunks issue – the button also didn't depress until you returned.

pokechu22

This sounds like MC-82703 to me, but I'm not 100% sure. It's a different set of symptoms.

I will note that the wolf not teleporting the first time was probably an unloaded chunks issue – the button also didn't depress until you returned.

migrated

It might be an expansion to MC-82703, or a similar issue. Not a duplicate, though.

migrated

No, not an expansion. I reproduced MC-82703, and it does only get triggered after a second fill command, unlike this one, which is unavoidable, affects structure blocks, causes FPS/other issues and doesn't get fixed after chunk reloads, as the other one seems to. Not even as similar as I though to this one, as this one is much worse.
Additionally, MC-82703 still happens in the latest snapshots, and can cause crashes, as I described into it's page. (requires updating)

migrated

Still not fixed in 18w07b. Really hoping for a fix.

migrated

Still in 18w08a

migrated

Already attached all info possible, will try to attach even more if requested. Bug seems to be present in all snapshots. Still awaiting for confirmation as of snapshot 18w19b. I believe this bug would definitely cause later issues if it came live to the 1.13 release.

 

migrated

Still waiting for confirmation...

migrated
[media]

This attachment is a Minecraft Flat World where the bug can be easily reproduced. Simply try to cycle through the Structure Block menus and you should see it doesn't work. (Currently verifying if it has been fixed in 1.13-pre6, since it can't be reproduced like that anymore in that version)

migrated

Seems fixed (or at least partially fixed) in 1.13-pre6. I'll consider it fixed unless I get further issues in the future.

pokechu22

Fixed in 18w20c; present in 18w20b.

migrated

(Unassigned)

Confirmed

block, chunk, chunk-error, chunk-updates, command_block, entity, lag, structure_block

Minecraft 1.12.2, Minecraft 18w06a, Minecraft 18w07b, Minecraft 18w08a, Minecraft 18w08b, ..., Minecraft 18w14a, Minecraft 18w14b, Minecraft 18w15a, Minecraft 18w16a, Minecraft 18w19b

Minecraft 18w20c

Retrieved