The bug
Block light updates don't cross chunk borders properly when updated. This can be caused by fire placed by exploding beds, using /fill to fill a large amount of light sources or other blocks, using /place to place a feature or structure with light sources, or other miscellaneous circumstances. This may also occur upon world generation with light sources, see MC-249508.
To reproduce
Create a new flatland world
/time set midnightRun
/fill ~ ~ ~ ~63 ~ ~63 sea_lanternwhile on the ground
Enable chunk border overlay (F3+G)
→ ❌ The light will not have updated properly in some placesReplace the sea lanterns with air again
/fill ~ ~ ~ ~63 ~ ~63 sea_lantern→ ❌ The light did not update properly again
Video
Original description
i was building a house and then all of a sudden i noticed that one half of the house was bright and lit while the other was mostly dark with light patches.
in the photo you can see the split. in the video i switch between the light block and dark block and they have the same light level even though they visually are different.
i had no lanterns before this and the same thing happened.
i tried updating the blocks around and it worked but then returned when i updated other areas.
you can see in the second video that it will just flicker when i try and update the blocks.
the other 2 screenshots are just other odd things that the lighting caused.
you should also know that i placed most of the roof with the /fill command if that helps
Linked issues
is duplicated by 22
MC-175181
Respawn anchor explodes doesn't update lighting
Resolved
MC-179287
Light is not updated properly at chunk borders when a structure is loaded
Resolved
MC-180378
A light square is shown when respawn anchor is exploded
Resolved
MC-183049
Lighting Glitch - No light in Certain Crevices - Placing a torch and breaking fixes the Issue
Resolved
MC-184450
Light not recalculating over chunk borders
Resolved
relates to 5
MC-197524
Border chunks do not enforce neighbors to be loaded, causing light updates to get stuck
Resolved
MCPE-58182
Light sources don't go beyond the chunk they're in
Resolved
MC-166260
Light from fire that has gone out lingers at the border of chunks
Resolved
MC-186337
The lighting of the "Client" doesn't correspond to that of the "Server"
Resolved
MC-199952
Skylight does not propagate across certain chunk borders upon world generation
Resolved
Attachments
Comments 39
Please force a crash by pressing F3 + C for 10 seconds while in-game and attach the crash report (minecraft/crash-reports/crash-<DATE>-client.txt) here.
Also, did you use structure blocks? This might or might not be the same issue as MC-179287.
I have found a good way of reproducing this bug. I don't know if there should be a new bug report because the step to reproduce are different than this post. First create a new world or update an old one to 1.18.2 (I have not tested other versions of 1.18 but I assume the same effects apply.) Then find or create a large underground cave or area and light it up enough so mobs can't spawn. After this update that world to 1.19 by optimizing and selecting the erase cached data option. Load the same world and you should be able to see the light glitches. I have had light level 0 next to torches which makes no sense when it tries to cross chunk borders. This bug is pretty bad because I have had creepers spawn and grief in places I thought were well over lit just to keep them safe from mob griefing. This bug has carried over to the later versions of 1.19.
[media]Saw this in 23w17a
-2297050722172854459
Don't know if it is relevant:
I didn't try to update light or blocks, it just generated like this
[^20200523_194614[1].mp4]
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