Solix

A slightly faster light engine for Forge 1.20.1. Built as a fork of Starlight with ScalableLux's multi-threading, and a number of optimizations of its own.

Why yet another Starlight fork?

Starlight was always a solid lighting mod & unfortunately ScalableLux is not currently available on 1.20.1 Forge. Solix adds the performance benefits of both of these mods, but adds a few more fixes as well.

¹ Server setup with parallel lighting enabled (more than one worker). Vanilla already hands off chunks to the light engine roughly closest-first; Solix also orders the light work that is already queued.

Performance gains

Updated Darkness logic:

When you place a block in a lit room, Starlight darkens the entire area behind it and then re-lights it from scratch, even though almost all of those blocks are still lit from another direction. Solix checks first and only darkens the blocks that actually lost light. As a result, far less writes are necessary.

Light is spread from the brightest level down, so every block is lit once, at its final level, instead of being lit by a dim source and then overwritten by a brighter one.

In preliminary testing, placing and breaking single blocks in a lit room took ~14–20% less light time with 47% fewer light writes overall.

Reduced overhead & fewer client re-renders:

If a section's light ends up exactly the same after an update, Solix doesn't send it to players again. Every light packet a client receives makes it re-render that area and its neighbours, so skipping them should help client FPS while others place blocks nearby.

In my initial benchmarks, roughly 10–30% of updated sections were unchanged and are no longer sent.

Forge fixes

• Working opacity cache. Starlight would originally discard the block cache after it was built, but this maintains it with some fallback for the blocks that need it (dynamic shapes, modded blocks whose light depends on block positioning).
• Faster light-source scanning. New chunks skip sections that cannot contain a light source. Starlight would just scan these regardless.
• Cheaper chunk loading. Solix adds a single 64-bit mask to each chunk It runs for every chunk lit on the server and every chunk a client receives.

Backported Starlight fixes

Additionally a number of fixes that were never backported in original Starlight have been pushed to this release. Commits 6585522, 2084f46, 2b3204b, 4d59d86, and c4d051c specifically.

Configuration Options

config/solix.toml (restart to apply):

parallel = true          # multithreaded server lighting
parallelism = 0          # worker threads, 0 = automatic (CPU threads / 4)
throttle_ms = 10         # prevents C2ME's light thread from busy-waiting
propagation = targeted   # targeted | ordered | classic (Starlight's original)

For diagnostic/benchmarking use: -Dsolix.debug.lightStats=true logs light engine statistics every 10 seconds.

Options allow for multi-threading to be disabled if desired. More a troubleshooting use in the odd chance of compatibility issue as opposed to actual performance benefit.

Compatibility

• Tested with over (500+ mods), including C2ME, ModernFix, Radium, Embeddium/Xenon, Oculus, NeoVoxy, Flywheel/Create, Mekanism and AE2.
• Can be installed on client, server, or both. Vanilla clients can join a Solix server and the other way round.
• Do not install alongside other lighting mods such as Starlight, ScalableLux or Lucis. Solix replaces them, and Forge may tell you if multiple are installed.
• Should be quite safe to install on existing worlds without issue.

Q&A

Will this improve my framerate?

Not a significant amount--it's more at scale that many of these benefits are seen, however as seen in usage with mods like C2ME, lighting bottlenecks can easily become an issue. Servers benefit far more: lighting work is lighter and spread across threads.

Will other versions be supported?

I may port to neighboring versions, currently I am more focused on polishing up the 1.20.1 version.

Credits

• Starlight by Spottedleaf: the light engine Solix is built on.
• ScalableLux by RelativityMC: multithreaded scheduling
• FlowSched by IshlandMC

Solix is licensed under LGPL-3.0.