Light Mesurment and Templates
I’d really love to see Lux (lx) and Lumen (lm) used as the standard units for lighting. Not only are these industry-standard units, but they’re also much easier to work with since you can find accurate real-world data for different light sources online. I would suggest using lx as the default for directional lights and lm for the others.
In addition, it would be incredibly useful to have a template that includes some basic light source presets, with typical intensity and color temperature values — like a candle, interior lighting, or sunlight.
It would also be great to visually present these presets in the UI, for example by showing small icons next to or beneath a slider to indicate roughly what range the current settings fall into (e.g. candle-strength, street lamp, etc.).
Unity provides a great reference:
Physical light units | High Definition RP | 14.0.12 (the link not work)
1 Comment
Discussions about this already happened here and there:
TL;DR: It's not just a simple unit conversion like multiplying meters by 3.28 to get feets. Both lumen and lux are perception-based units: they measure luminous flux (how bright light appears to the human eye), not its actual physical energy ; unlike watts, which measure the radiant flux (the energy emitted).
Making them work in a path-tracing engine would require accounting for how perceived brightness varies with wavelength (color), which would require quite some complex and careful design to avoid misleading results or breaking consistency in physically based rendering.