The bug
For whatever reason, the lighting system for magma blocks acts weirdly, in that it seems to give off darkness rather than light like its supposed to.
As far as I know, this only affects magma blocks; glowstone, torches, and other blocks still properly give off light.
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migrated
migrated
Thank you for your report!
We're actually already tracking this issue at MC-138211, so we will resolve and link this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
muzikbike
That's a completely different issue. I can confirm that magma blocks appear to darken the area around them unnecessarily much.
muzikbike
May relate to MC-139621
wobst.michael
I think it's fixed now in 19w14a. Can you re-check?
migrated
This issue does not seem to be fixed in the latest snapshot. It seems to behave the exact same way it does in 19w09a, 19w12b, and 19w13b.
Fry