Ultra Fast Pregen 13

Fabric 1.20.1-13 · Forge 1.20.1-13 · NeoForge 1.21.1-13

Fixes

• Correct lighting underground. Generated chunks were lit as if the world below the surface were empty, so caves came out at full sky light, with no light from lava or glow lichen. The server's light engine only reads chunks the server holds, so it could not see chunks generated in RAM. It now reads them while they are lit, and the one-chunk halo is lit too. The light of every block now matches what Minecraft computes for the same blocks (new LIGHT_PARITY_CHECK).
• No more dark patches around players. Chunks the server was holding part-way generated lost their light data when a batch finished. They showed as black rectangles in singleplayer, or on a server with players inside the area. Light is now kept for chunks the server holds.

New

• /pregen set changes batch_size, threads and skip_existing_chunks from in game and saves them to the config file. Comments and other keys in the file are kept. A running task keeps the values it started with.
• Boss bar for ops who are online, showing overall progress %, speed and ETA. It replaces the action bar text.

Notes

• Lighting is now actually computed, so a run is somewhat slower. On the i9 test machine, 3000×3000 went from 120.6 to 113.3 chunks/s, about 6% (most of the lighting cost is hidden behind the next batch).
• Worlds generated by 1.20.1-12 or earlier keep their old light data. Those chunks are not fixed retroactively. Regenerate them with skip_existing_chunks=false, or let Minecraft relight them as players load them.
• All three builds pass the full test suite, including the new light parity check.
• The license is now LGPL-3.0 in every jar.