The bug
Upon pushing or pulling a light-emitting block (see below for affected blocks), the light flickers off while it is moving. This can cause performance issues due to excessive lighting updates, as well as just be undesirable in general.
How to reproduce
Construct the contraption shown in this video if testing redstone lamps, or the simple contraption shown in this screenshot if testing Shroomlights or any other blocks
Notice how the redstone lamp flickers every time it is pushed by the piston
Replace the redstone lamp with any other light-emitting block from the list below and notice how this same behaviour is present
Affected blocks
Redstone Lamp (lit)
Shroomlight
Sea Lantern
Glowstone
Redstone Ore (lit)
Magma Block
Original description
Using the setup in the screenshot, the lamp will flicker when the lever is pulled.
Glowstone sometimes exhibits this behavior.
Related issues
Attachments
Comments
migrated
CubeTheThird
Can you post said screenshot?
Delivered.
Don't know what exactly happened, I uploaded it already.
Also happens with glowstone.
Updated.
Confirmed. The glowstone and the lamp don't appear to flicker, but you can see that the light flickers if you set the time to midnight.
Flickers on the way back down again right?
Glowstone flickers both ways, redstone lamps flicker only down.
I can't get the glowstone lamp to flicker going up. I can see the bottom redstone lamp going on a few ticks before the glowstone lamp turns on, which makes it look a little inconsistent, but the glowstone lamp only flickers for me when coming back down.
Yes, it only works when being PULLED by a piston, not pushed.
shufboyardee
In 13w07a, both these blocks flicker, and both when being pushed and pulled.
shufboyardee
also in 1.5.
galaxy_2alex
Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.
Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been deliviered.
Happens in 1.8.3 and affects sea lanterns as well as glowstone and redstone lamps. It seems that it does not matter whether the piston pushes or pulls these blocks, the flicker happens either way. I tested this using each set up in the screen shot separately. Hopefully I'm not misunderstanding this issue.
michael
While being moved by pistons, blocks do not emit light.
[Mod] markderickson
Hi! I'd like to request ownership of this report.
SunCat
The ticket is yours now
[Mod] markderickson
Thanks!
SunCat
merged with MC-123217
[Mod] markderickson