The only applications I'm aware of that currently do spectral rendering on the fly are painting apps.

I have one called Brushwork ( https://brushworkvr.com ) that upsamples RGB from 3 to a larger number of samples spread across visible light, mixes paint in the upsampled space, and then downsamples for rendering (the upsampling approach that app uses is from Scott Burns http://scottburns.us/color-science-projects/ ). FocalPaint on iOS does something similar ( https://apps.apple.com/us/app/focalpaint/id1532688085 ).

I'm happy that tech like this will open up more apps to use spectral rendering.

I was sure it must have been invented already! I've been trying to look for this idea without knowing it's called "spectral rendering", looking for "absorptive rendering" or similar instead, which led me to dead ends. The technique is very interesting and I would love to see it together with semi-transparent materials — I have been suspecting for some time that a method like that could allow cheap OIT out of the box?

Not a ton of info on it, but ran into this graphics of a galaxy, all rendered with some form of spectral rendering. Thought it was super cool. https://bsky.app/profile/altunenes.bsky.social/post/3m5z6vr2...

Distantly reminds me the decades I spent with galaxy as my xscreensaver. https://manpages.debian.org/jessie/xscreensaver-data/galaxy....

Apparently (from a layman's perspective) the difference between conventional RGB ray tracing and spectral ray tracing is this:

RGB assumes all light sources consist of three RGB lights, where the brightness of red, green, and blue varies. E.g. a yellow light would always be a red and a green light.

In contrast, spectral rendering allows light sources with arbitrary spectra. A pure yellow light (~580 nm) is different from a red+green light.

The physical difference is this: If you shine, for example, a pure yellow light on a scene, everything looks yellow, just more or less dark. But if you shine a red+green (impure yellow) light on a scene, green objects will be green and red objects will be red. Not everything will appear as a shade of yellow. Conventional RGB rendering can only model the latter case.

This means some light sources, like high-pressure sodium lamps, cannot be accurately rendered with RGB rendering: red and green surfaces would look too bright.

(Also note that the linked post has also a part 1 and 3, accessible via "next/previous post" at the bottom.)