Empty tiles with flat world

[Doelia]

I created a world with Minecraft 1.8.1 vanilla : "Solo / Create new world / More world Options... / World Type : Superflat", defaults settings.

Overviewer generate empty tiles.

It works with a normal world.
I try with Windows binaries and compiling from source on Debian.

No error or warning messages :

overviewer.py "world" ./render
2021-12-15 18:25:23  Welcome to Minecraft Overviewer version 0.17.40 (f6ee2cf)!
2021-12-15 18:25:23  Generating textures...
2021-12-15 18:25:42  Preprocessing...
2021-12-15 18:26:01  Rendering 581 total tiles.
 99% [======================================================================================================= ] 577 11.20t/s eta 00h 00m 00s
2021-12-15 18:26:53  Rendering complete!
2021-12-15 18:26:54  Your render has been written to '/render', open index.html to view it.

[spacegriffin]

Do superflat worlds in 1.18 generate below y=0? If so, that's the problem. Overviewer doesn't currently render blocks below y=0 or above y=256

[greatmastermario]

Yes, they generate from Y=-64 as of 1.18. This is fixed in my PR (see screenshots) #2012

[lostallmymoney]

Normal world and I get the same result on 1.18.1,
Overviewer 17.47
Might have been my mistake some other maps are aight