3 ms·

I guess it mainly makes a difference for light sources that are very yellow but not very red and green (sodium lights) or very cyan but not very green and blue

I guess it mainly makes a difference for light sources that are very yellow but not very red and green (sodium lights) or very cyan but not very green and blue (no realistic example here). Considering that actual sodium lights are being largely replaced by white LEDs, which can be modeled quite well with RGB ray tracing, spectral rendering might not offer a significant advantage for most applications.

dahart 1y ago
Yeah exactly. Spectral isn’t often giving you a very different result from RGB. It rarely matters for entertainment rendering like films & games, but it’s useful for scientific predictive rendering. Sodium lights are a problem not because they’re yellow, but because they have very spiky spectra. Smooth spectra, whether it’s lights or materials, will tend to work fine in RGB regardless of the color.
- astrange 1y ago
  > Sodium lights are a problem not because they’re yellow, but because they have very spiky spectra. A side effect of this (and other low-CRI lights) is that it's hard to take pictures in them, because if you take a picture of a person you want their skin tone to look just right or else they look weird and sickly and unattractive. Regular white balance algorithms are not quite able to handle this. So you might imagine why phone cameras are motivated to do AI processing or people processing or other things that make the picture look overprocessed. Because the people are temporarily literally the wrong color in that lighting, and an AI model may be capable of knowing what color they "actually" are. (That said, the main reason photos look overprocessed is that for some reason nobody on Earth ever implements sensible sharpening algorithms. They always use frequency-based ones that cause obvious white halos. Learn about warp-sharpen and median filters, people.)
sebastianmestre 11mo ago
> very cyan but not very green and blue (no realistic example here) Very high temperature blackbody radiation perhaps?

dahart 1y ago

Yeah exactly. Spectral isn’t often giving you a very different result from RGB. It rarely matters for entertainment rendering like films & games, but it’s useful for scientific predictive rendering. Sodium lights are a problem not because they’re yellow, but because they have very spiky spectra. Smooth spectra, whether it’s lights or materials, will tend to work fine in RGB regardless of the color.

astrange 1y ago
> Sodium lights are a problem not because they’re yellow, but because they have very spiky spectra. A side effect of this (and other low-CRI lights) is that it's hard to take pictures in them, because if you take a picture of a person you want their skin tone to look just right or else they look weird and sickly and unattractive. Regular white balance algorithms are not quite able to handle this. So you might imagine why phone cameras are motivated to do AI processing or people processing or other things that make the picture look overprocessed. Because the people are temporarily literally the wrong color in that lighting, and an AI model may be capable of knowing what color they "actually" are. (That said, the main reason photos look overprocessed is that for some reason nobody on Earth ever implements sensible sharpening algorithms. They always use frequency-based ones that cause obvious white halos. Learn about warp-sharpen and median filters, people.)

sebastianmestre 11mo ago

> very cyan but not very green and blue (no realistic example here) Very high temperature blackbody radiation perhaps?