POV-Ray : Newsgroups : povray.binaries.animations : CIELCHuv D65 gamut sphere : Re: CIELCHuv D65 gamut sphere Server Time
19 Apr 2024 09:31:03 EDT (-0400)
  Re: CIELCHuv D65 gamut sphere  
From: clipka
Date: 25 Mar 2017 16:19:47
Message: <58d6d0e3$1@news.povray.org>
Am 25.03.2017 um 18:36 schrieb Mike Horvath:
> On 3/25/2017 11:38 AM, clipka wrote:
>> In this HSL solid, S
>> is quite clearly measured radially from the vertical axis.
> Nope. It is from the center point too.

Just read up on HSL, and you are right: In your spherical HSL diagram,
the distance from the center of the spehere does indeed correspond to
the parameter called "Saturation" in the HSL model.

*BUT* that "Saturation" parameter differs significantly from what I'd
consider the physical definition of saturation, where only monochromatic
light would be defined as fully saturated, while white light (at any
brightness, i.e. any shade of grey if you will) would be considered
fully unsaturated, which is what the "Chroma" parameter in the CIE LCh
model corresponds to.

If you want to get anywhere close to your HSL sphere with the CIE LCh
model, you have to represent the "Chroma" parameter as distance from the
vertical axis, otherwise you'll get a torus-ish shape instead of a
sphere-ish one. I also /think/ you'd get closer to your ideal by
sticking to the fully canonical rendering, with the "Lightness"
parameter represented as distance from the bottom plane.

At any rate, publishing a non-canonical representation of the CIE LCh
model will certainly do more to confuse people about the colour model
than to educate them.

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