Lighting bug with light-emitting liquids

[Ekdohibs]

After removal of a light-emitting liquid, there are sometimes nodes that still stay lit while there is no light source.

To reproduce:

• go to a place with no light
• dig a 2x1 hole; the hole should be in the north/south direction
• place a lava block in one of the nodes of the hole, and wait for it to spread
• remove the lava block with a bucket (do not replace it with another node)
• result:

[est31]

Can't reproduce. Are you sure its not the fault of being in a cave which has its own lightning? But yes, there are some bugs with lightning I agree.

[est31]

Perhaps its because its at a mapblock border? your z coordinate sais 47.7. 48 == 16 * 3

[est31]

Yes, I can confirm it at a mapblock border

[est31]

Also, its a server bug, not in client prediction. Its still there at re-login.

[est31]

I've thought it was an easy bug, seems it needs more work, removing it from the milestone as its not critical.

[C1ffisme]

I had a similar bug in the older versions of minetest, but instead of staying light, it was strangely dark once lava disappeared.

[Ekdohibs]

I can confirm the bug is still present.

[PilzAdam]

Reminds me of this: ecb024a

I can confirm that this happens in current master.

[paramat]

UpdateLighting has issues, this may be another one.
Fixer has found these bugs at block borders around lavacooling mountains on servers.

[Fixer-007]

Yes, if you are interested to see it, go to "No rules" server, I asked admin not to fix it yet. I also had this bug randomly when I dealt with huge amounts of lava.

[paramat]

Maybe fixed by #4655 ?

[Fixer-007]

I tried to reproduce it with PR4655 on 6eb6e75 on mapgen7 and only thing I seen is this:

Holes coordinates:
-111 x 64 (lava source)
-111 x 65

Looks like ghost lighting in corner of mapblock. I've seen small patches of light even in bright areas. Can you check it?

[juhdanad]

I don't know what causes this. I also see the light, but the light values of the lighting node and its 26 neighbors is zero both on the client (tested with printf()) and the server (when you quit and play again, you can't see the light).
I think this bug is in the block mesh generating code.

[paramat]

Does #4682 fix this?

[juhdanad]

Yes, #4682 fixed this. What Fixer found there #2823 (comment) is a small bug in mesh generation, but lighting is correct. If you use non-smooth lighting, you should see no issues with lava.

[sofar]

I'll close it for now. I threw lots of lava and removed it with a bucket, and it all came out fine.