We built CircadianLab, a free in-browser tool for lighting design. It uses webGPU shaders to calculate melanopic equivalent daylight illuminance (mel-EDI, formerly EML, relevant for circadian rhythm and WELL v2 compliance), photopic illuminance, UGR glare per CIE 117, and actual daylight through windows and skylights.

It has a database of 400,000+ IES files from 81 lighting manufacturers and supports easy sharing of scenes/configs with other people.

Daylight uses the NREL Solar Position Algorithm and a Perez clear / intermediate / overcast sky model, mixed into the same radiosity solve as electric fixtures. Sun and sky are added as initial flux on every patch, then bounced through the same form-factor network. Form factors via Monte Carlo with visibility tests, then a Gauss-Seidel 3-bounce iterative solve.

  My company (Innerscene) makes "daylight" luminaires. We built CircadianLab to address a specific gap (no browser-based way to verify WELL v2 mel-EDI compliance before specifying), but it works with any IES file from any manufacturer, not just our line.  For mel-EDI you need SPDs to accurately calculate but CCT is a good proxy.

  Write-up + demo videos: https://www.innerscene.com/blog/introducing-circadian-lab

Of interest to HN crowd, there are measurable productivity/performance enhancements that can be achieved with higher mel-EDIs which is why the design community is now incorporating this into building design. If you haven't dug into any of the research before checkout: https://www.innerscene.com/research?topic=Workplace+Performa...

Here is an example scene with a classroom and sunlight coming through a window, showing foot candles as a heatmap:

3d view: https://www.innerscene.com/tools/circadian-lab?share=b104262... 2d view: https://www.innerscene.com/tools/circadian-lab?share=456ad19...

Happy to answer questions on anything related.