Pulsar Lighting Engine

Overview

Pulsar is a lighting engine mod for Cleanroom, based on Starlight and SuperNova. It replaces Minecraft's vanilla lighting engine with queue-based breadth-first search (BFS) light propagation derived from Starlight. It offers a non-colored SCALAR lighting mode like Starlight and a full RGB colored lighting mode like SuperNova.

Features

• RGB colored lighting: Calculates block light and sky light per RGB channel, accounting for light source colors and filtering through blocks such as stained glass.
• SCALAR mode: Uses conventional, non-colored lighting calculations, like Starlight.
• Asynchronous and parallel processing: Runs server-side light propagation on separate worker threads.
• Batched lighting updates: Groups lighting updates caused by large numbers of block changes.
• Light data caching: Saves calculated light data in chunk NBT to avoid recalculation when chunks are loaded.
• Various additional bug fixes and quality-of-life improvements not listed here.
• Natural lighting for Thaumcraft crystals.

Fixed Bugs

• MC-92
• MC-1531
• MC-3329
• MC-80966
• MC-104532
• MC-116690
• MC-117067
• MC-117094
• MC-249343

Compatibility

• JSON Paintings: Applies smooth lighting to paintings added by the mod.
• SpongeForge: Includes compatibility support for asynchronous lighting.
• Fluidlogged API: Accounts for the opacity and light emission of fluids stored inside blocks.
• CBMultipart: Standard microblocks inherit their materials' light source colors. Custom parts retain neutral emission unless handled by a dedicated integration.
• ProjectRed: RGB emission for full-block lamps, multipart fixtures, light buttons, and light microblock materials, preserving their actual brightness and power state.
• Depths Update: Supports extended world height ranges.
• Thaumcraft: Adds smooth lighting to crystals.
• Celeritas: Supports its rendering pipeline.
• Demonica Shader: Tested and confirmed working with Complementary Reimagined.
  • Compatibility with forks such as Actinium, Pintonium, and Impetus is not guaranteed.

Incompatibilities

Pulsar completely replaces the lighting engine and is incompatible with other lighting engine mods.

• Alfheim
• Phosphor
• Hesperus
• Starlight-1.12
• OptiFine: Use Celeritas instead. Demonica Shader provides shader support, while Celeritas Extra and Celeritas Leaf Culling should cover the additional video options.
• The Aether II: Use The Aether II: Phosphor Not Included instead.

Configuration

• config/pulsar.cfg: Selects the lighting mode and configures additional features.
  • lightingMode: RGB (default, RGB colored lighting) or SCALAR (conventional, non-colored lighting).
  • rgbGameplayLight: RGB_MAX (default, uses the brightest RGB component as gameplay brightness; per-channel attenuation affects light checks such as mob spawning) or VANILLA (calculates non-colored lighting separately for gameplay light checks).
  • rgbBlendMode: Includes an optional MAXIMUM mode that combines block and sky light by taking the brightest value per channel. Full daylight stays neutral around colored sources. This controls normal rendering; shader packs handle their own shading.
  • debug.traceLightUpdates: Opt-in diagnostics for lighting queues, render requests, and Celeritas rebuilds. Logs a bounded summary every 200 client ticks; caller and position samples cover 1 in 64 requests.
• config/pulsar-colors.cfg: Defines light source colors.
• config/pulsar-filters.cfg: Defines attenuation for each RGB channel.

API

Pulsar provides APIs for other mods to define light source colors and light transmission properties.

• ColoredLightSource / PositionalColoredLightSource: Define RGB emission based on block state or position.
• ColoredTranslucency / PositionalColoredTranslucency: Define per-channel RGB transmittance.
• FaceLightOcclusion: Define light opacity for individual block faces.
• BlockLightColors / BlockLightFilters: Register light source colors and minimum per-channel absorption for blocks or block states.
• RegisterLightPropertiesEvent: Forge event for registering light source colors and filters.
• PackedLightColor: Pack and unpack 0xRGB values with components from 0 to 15, and convert to and from SuperNova's format.
• LightColors: Provides basic color constants.
• ExtendedChunk / ExtendedWorld: Query chunk lighting readiness and pending world lighting updates.

See the API documentation and integration example for details.

Benchmarks

Measured on 2026-10-30 with Minecraft 1.12.2 / Cleanroom 0.6.13-alpha, comparing vanilla lighting, Alfheim 1.6, and Pulsar 0.6.0 in SCALAR and RGB (RGB_MAX) modes.

The charts measure dedicated-server latency from a block change through completed lighting, including the completion adapter. Each value is the median of four fresh-JVM run means; whiskers show the minimum and maximum. The CPU is a Ryzen AI MAX+ 395, with Java 25 and a fixed 4 GiB heap. Lower is better; axes use a logarithmic scale.

Vanilla passes the open-sky block-light test, but fails the roof fixture's initial stored sky-light validation, so no vanilla sky-update time is scored. RGB computes additional colored-light information. These repeated, individually awaited updates do not measure FPS, chunk generation, or concurrent update throughput.

See the measured values and run ranges and raw measurement results for the full comparison.

See lighting validation notes for compatibility probes and the opt-in empty-section experiment.

Credits

• Starlight: The foundation for the lighting engine's architecture and core algorithms.
• SuperNova: The source of the ported lighting engine, per-world task management, and packed RGB propagation code.
• Alfheim: A reference for various lighting bug fixes.
• CleanroomModTemplate: An excellent mod development template for Cleanroom.
• CleanroomVersioning: Build plugin for version management.
• TokenEnvoy: Build plugin for embedding metadata at build time.

LLM Usage

LLMs are used to help write some of Pulsar's code and documentation.

License

Pulsar is licensed under LGPL-3.0.