Pulsar Lighting Engine

Pulsar

Pulsar is an async lighting engine for CleanroomLoader. It reimplements Starlight-style lighting algorithms for 1.12.2 and moves most server-side block-light and sky-light propagation off the main server thread.

Unlike vanilla and Alfheim, Pulsar performs most propagation work on dedicated worker threads. Its goal is to provide an actively developed Cleanroom-native alternative to lighting engines such as Alfheim and Phosphor.

Requirements

• Cleanroom 0.5.17-alpha or newer

Features

Pulsar is designed to reduce server-thread stalls when lighting has a large amount of work to resolve, such as during chunk generation, explosions, large building-tool operations, or machine-driven block changes.

• Runs server-side block-light and sky-light propagation on dedicated worker threads.
• Batches large groups of block changes instead of lighting every edit separately.
• Stores completed Pulsar light data in each chunk's NBT, avoiding unnecessary full relights when valid cached chunks are loaded again.
• Keeps Minecraft's standard block-light and sky-light data synchronized, so the additional Pulsar cache can be discarded safely if Pulsar is removed.
• Fixes vanilla propagation and rendering problems involving stairs, slabs, liquids, emissive blocks, paintings, empty sections, and chunk borders.

The largest gains appear under heavy lighting load. At lighter loads, Pulsar's main benefit is lower light-update latency rather than higher TPS.

Fixed Vanilla Issues

Pulsar includes fixes for the following vanilla lighting and rendering issues:

• MC-92
• MC-1531 — smooth lighting across painting tile boundaries. Only paintings are covered; item frames are not.
• MC-3329
• MC-80966
• MC-104532
• MC-116690
• MC-117067
• MC-117094
• MC-249343

Compatibility

Pulsar should work with most biome, cave, world-generation, and dimension mods that use Minecraft's standard chunk and world APIs. Please report combinations that do not work as expected.

Supported integrations

• Celeritas, including face-aware lighting for stairs and slabs.
• Fluidlogged API, including the opacity and emission of fluids stored inside fluidlogged blocks.
• Depths Update, including dimensions that extend below Y=0 or above Y=255.
• JSON Paintings,

Incompatible

• Alfheim
• Phosphor for Forge
• Hesperus
• Any other mod that replaces or rewrites the lighting engine
• The standard edition of The Aether II, which bundles Phosphor. Use The Aether II: Phosphor Not Included instead.

Performance

In controlled Lightbench tests, Pulsar recorded the lowest server-side light-completion latency in all four measured block-edit workloads. In a separate fresh-generation test, it completed the workload 13.5% sooner than vanilla and performed broadly similarly to Alfheim.

These results are specific to the tested machine and workloads. They do not represent equivalent improvements to FPS, TPS, or overall game performance.

Light-update benchmark

Each edit was measured until server-side lighting completed.

Circles represent vanilla, diamonds represent Alfheim, and squares represent Pulsar. The horizontal lines show the fastest-to-slowest result across three independent Minecraft restarts.

Open the light-update graph at full size.

Fresh chunk generation benchmark

Pulsar completed the 10,404-chunk workload in a median of 48.831 seconds, compared with 56.461 seconds for vanilla: 13.5% less elapsed time on the test system.

Alfheim completed it in 49.615 seconds, and its measured range overlapped with Pulsar's, so the two should be considered broadly similar in this workload.

The colored bars show the median total time. The horizontal lines show the fastest-to-slowest result across three independent Minecraft launches.

This test includes terrain generation and lighting. It is not a pure light-propagation benchmark.

Open the chunk-generation graph at full size.

See the complete methodology, individual runs, limitations, and raw data on GitHub.

Credits

• Starlight by Spottedleaf, for the architecture and core algorithms on which Pulsar is based
• SuperNova by GTNewHorizons, a Minecraft 1.7.10 port of Starlight that served as the basis for early versions of Pulsar
• Alfheim by Red Studio, as a reference for fixing MC-92
• CleanroomModTemplate by CleanroomMC