Lumenj

Lumenj is an open-source software toolkit designed to model, simulate, and visualize luminous flux and lighting performance in architectural and entertainment contexts. It provides a data model for photometric measurements, a scene graph for arranging light sources, surfaces, and materials, and algorithms for calculating illuminance, luminance, and color metrics across virtual spaces. The project emphasizes interoperability, supporting import of common photometric formats such as IES and EULUMDAT, as well as export to JSON and XML schemas. It includes a lightweight rendering engine and bindings for popular languages, enabling both browser-based visualization and desktop workflows.

Lumenj is organized around modular components: a core runtime, a plugin system for light sources and materials, and adapters for data sources and renderers. The design aims to be accessible to students and professionals while remaining suitable for research. The project promotes reproducible workflows, with example datasets and notebooks that demonstrate daylight simulations, artificial lighting calculations, and retrofit analyses.

Development is community-driven, with an open governance model and contributions tracked in a public repository. Since its initial release, Lumenj has been adopted by universities and small design studios as a teaching and prototyping tool, while remaining complementary to commercial lighting software. Limitations include performance constraints for very large scenes and the need for careful validation when used for critical design decisions.