POV-Ray : Newsgroups : povray.binaries.images : Calibrated spectral colors : Re: Calibrated spectral colors Server Time
2 Dec 2023 20:05:12 EST (-0500)
  Re: Calibrated spectral colors  
From: BayashiPascal
Date: 6 Aug 2023 00:10:00
Message: <web.64cf1cc96ed655f18f8c74531749e915@news.povray.org>
Cousin Ricky <ric### [at] yahoocom> wrote:
> A few years ago I created a macro that returns reflective spectral power
> distribution (SPD) curves, but I hesitated to publish it due to its poor
> correspondence with RGB colors.  But over the past couple of months, I
> developed a filter that solves this problem: you submit an RGB spec, and
> it figures out what to tell the SPD generator.  For good measure, I also
> threw in a true RGB generator.
>   https://github.com/CousinRicky/POV-MakeSpectrum
> The illustrations show three examples of X11/SVG colors passed through
> my library.  For each illustration, the large spheres were pigmented
> with SPDs converted to colors using Lightsys IV.  The left SPD was built
> from individual red, green, and blue curves, and the right SPD is from
> my original SPD generator (albeit tweaked over the years), which was
> designed to generate reflective SPDs resembling those bundled with
> Lightsys IV and SpectralRender.  The small sphere at the center was
> simply pigmented with the straight sRGB color.
> The sphere colors are all reduced to 62.5% value, corresponding to a
> finish diffuse of 0.625.  The scene has the recommended assumed_gamma 1:
> the library handles sRGB and gamma issues.

Hi Cousin Ricky,

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.

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) ?


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