POV-Ray : Newsgroups : povray.binaries.images : Calibrated spectral colors : Re: Calibrated spectral colors Server Time
2 Dec 2023 19:42:26 EST (-0500)
  Re: Calibrated spectral colors  
From: Cousin Ricky
Date: 6 Aug 2023 16:34:09
Message: <64d003c1@news.povray.org>
On 2023-08-06 00:08 (-4), BayashiPascal wrote:
> Your post attracted my attention as I've spent some time working with spectral
> power distribution myself. I had a look at your library and Ive's work (which I
> didn't knew about), but couldn't check Lightsys as the link is broken.

I have reposted Lightsys 4d in p.binaries.scene-files.

> If I understand well, your macros are intended to be used as a conversion tool
> from RGB values to SPDs to be used in Ive's macros. Could you explain what are
> the advantages of using your macros over Ive's D_RGB macro (which seems to me to
> have the same function) ?
I had two issues with D_RGB().  The first, as Ive made clear in the
documentation, is that it does not match the RGB colors that we are used
to.  This makes matching colors more difficult, and this task is indeed
the reason I held up publishing MakeSpectrum for so long.

The second issue is that some RGB combinations create pigments that
reflect/transmit more light than than they receive at some wavelengths.
This can be seen in the attached illustration.

I am currently looking at a potential third issue: whether or not
generating SPDs by naively combining primary colors will lead to the
same fade_color/absorption primary color bias than RGB rendering has,
but I do not have results on that yet.

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