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From: Mike Horvath
Subject: CIE L*C*h
Date: 20 Nov 2016 12:32:58
Message: <583197fa$1@news.povray.org>
Done.

https://commons.wikimedia.org/wiki/File:Cielch_color_solid_cylinder.png


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From: Dave Blandston
Subject: Re: CIE L*C*h
Date: 20 Nov 2016 13:55:00
Message: <web.5831aa179fcb9acd6ae7df010@news.povray.org>
Mike Horvath <mik### [at] gmailcom> wrote:
> Done.
>
> https://commons.wikimedia.org/wiki/File:Cielch_color_solid_cylinder.png

Spectacular!!!


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From: Dave Blandston
Subject: Re: CIE L*C*h
Date: 20 Nov 2016 14:30:01
Message: <web.5831b2e09fcb9acd6ae7df010@news.povray.org>
Uh-oh...

line 10: Parse Error: Cannot open include file ColorMine.inc.

Render failed


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From: Dave Blandston
Subject: Re: CIE L*C*h
Date: 20 Nov 2016 14:35:00
Message: <web.5831b3cd9fcb9acd6ae7df010@news.povray.org>
"Dave Blandston" <nomail@nomail> wrote:
> Uh-oh...
>
> line 10: Parse Error: Cannot open include file ColorMine.inc.
>
> Render failed

Nevermind... Found it in the Text Scene Files section...


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From: Mike Horvath
Subject: Re: CIE L*C*h
Date: 20 Nov 2016 16:40:04
Message: <5831d1e4$1@news.povray.org>
On 11/20/2016 8:50 AM, Dave Blandston wrote:
> Mike Horvath <mik### [at] gmailcom> wrote:
>> Done.
>>
>> https://commons.wikimedia.org/wiki/File:Cielch_color_solid_cylinder.png
>
> Spectacular!!!
>

Thanks!


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From: Mike Horvath
Subject: Re: CIE L*C*h
Date: 23 Nov 2016 07:43:50
Message: <583548b6@news.povray.org>
Now I'm trying to create an isosurface instead of a stack of blocks. I'm 
not sure both attached pictures represent the same object. But they look 
like they have a similar shape.

Mike


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Attachments:
Download 'cielch_color_solid_cylinder_isosurface_backup.png' (45 KB)
Download 'cielch_color_solid_cylinder_sectors_backup.png' (114 KB)

Preview of image 'cielch_color_solid_cylinder_isosurface_backup.png'
cielch_color_solid_cylinder_isosurface_backup.png

Preview of image 'cielch_color_solid_cylinder_sectors_backup.png'
cielch_color_solid_cylinder_sectors_backup.png


 

From: Mike Horvath
Subject: Re: CIE L*C*h
Date: 25 Nov 2016 03:26:35
Message: <5837af6b$1@news.povray.org>
In this scene I want to add some markers to show vertical and polar 
units. What would be a nice-looking way of doing this? Different 
shadings of gray? Black rings? I am open to suggestions.

Mike


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Attachments:
Download 'cielch_color_solid_cylinder_isosurface_backup_05.png' (24 KB)

Preview of image 'cielch_color_solid_cylinder_isosurface_backup_05.png'
cielch_color_solid_cylinder_isosurface_backup_05.png


 

From: Mike Horvath
Subject: Re: CIE L*C*h
Date: 26 Nov 2016 17:02:49
Message: <5839c039$1@news.povray.org>
On 11/20/2016 7:32 AM, Mike Horvath wrote:
> Done.
>
> https://commons.wikimedia.org/wiki/File:Cielch_color_solid_cylinder.png

Done again.

https://commons.wikimedia.org/wiki/File:SRGB_gamut_within_CIELCH_color_space_isosurface.png


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From: Ive
Subject: Re: CIE L*C*h
Date: 26 Nov 2016 19:28:19
Message: <5839e253$1@news.povray.org>
Am 11/26/2016 um 18:02 schrieb Mike Horvath:
> On 11/20/2016 7:32 AM, Mike Horvath wrote:
>> Done.
>>
>> https://commons.wikimedia.org/wiki/File:Cielch_color_solid_cylinder.png
>
> Done again.
>
>
https://commons.wikimedia.org/wiki/File:SRGB_gamut_within_CIELCH_color_space_isosurface.png
>

Your description on the wiki page is partial misleading and partial wrong.
It is not L*C*h, it's just LCh without asterix.
CIE LCh(uv) means the polar representation of the CIE Luv color space. 
But what you are actually calculating is CIE LCh - the polar 
representation of the CIE L*a*b color space (just for historical reasons 
with asterix).
sRGB fits very well into L*a*b and Luv as both cover the full range of 
visible colors - and there is no visa versa.
So the question is: why are small bits hanging out at the corners?
To me it indicates that there is something seriously wrong with that 
graphical representation.

And while I'm at it, why do you use
XYZEpsilon = 0.008856 and XYZKappa = 903.3
where the CIE recommendation is 216/24389 and 24389/27 to avoid the 
discontinuity at the junction point for the lightness function.
And why do you use D65 as reference white while e,g, the ICC, Adobe, HP 
and myself do use D50?

And finally the appearance of your images at the page
https://en.wikipedia.org/wiki/HCL_color_space
doesn't make sense as this page is about LCh(uv) and not LCh.

-Ive


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From: Mike Horvath
Subject: Re: CIE L*C*h
Date: 26 Nov 2016 22:06:15
Message: <583a0757$1@news.povray.org>
On 11/26/2016 2:28 PM, Ive wrote:
 > Am 11/26/2016 um 18:02 schrieb Mike Horvath:
 >> On 11/20/2016 7:32 AM, Mike Horvath wrote:
 >>> Done.
 >>>
 >>> https://commons.wikimedia.org/wiki/File:Cielch_color_solid_cylinder.png
 >>
 >> Done again.
 >>
 >> 
https://commons.wikimedia.org/wiki/File:SRGB_gamut_within_CIELCH_color_space_isosurface.png
 >>
 >>
 >
 > Your description on the wiki page is partial misleading and partial 
wrong.
 > It is not L*C*h, it's just LCh without asterix.
 > CIE LCh(uv) means the polar representation of the CIE Luv color space.
 > But what you are actually calculating is CIE LCh - the polar
 > representation of the CIE L*a*b color space (just for historical reasons
 > with asterix).
 > sRGB fits very well into L*a*b and Luv as both cover the full range of
 > visible colors - and there is no visa versa.
 > So the question is: why are small bits hanging out at the corners?
 > To me it indicates that there is something seriously wrong with that
 > graphical representation.
 >
 > And while I'm at it, why do you use
 > XYZEpsilon = 0.008856 and XYZKappa = 903.3
 > where the CIE recommendation is 216/24389 and 24389/27 to avoid the
 > discontinuity at the junction point for the lightness function.
 > And why do you use D65 as reference white while e,g, the ICC, Adobe, HP
 > and myself do use D50?
 >
 > And finally the appearance of your images at the page
 > https://en.wikipedia.org/wiki/HCL_color_space
 > doesn't make sense as this page is about LCh(uv) and not LCh.
 >
 > -Ive
 >
 >
 >

Thanks for clarifying the acronyms! There are so many of them...

I got my conversion formulas from here:

	https://github.com/thejoezack/colormine

I also used the following color converter to double check my results:

	http://www.easyrgb.com/index.php?X=CALC

In my prior attempt I plotted individual chunks using cylindrical 
coordinates, and colored each chunk individually. As a test, I increased 
the number of chunks to 360 * 100 * 100 = 3600000 chunks. The shape was 
identical to the one in the above image, except "grainier" and less smooth.

Epsilon, kappa and white point were all gotten from here:

	https://github.com/THEjoezack/ColorMine/blob/master/ColorMine/ColorSpaces/Conversions/XyzConverter.cs

The easyrgb.com converter says the illuminant being used is D65. I 
didn't double check to make sure it's right. Here is some sample output:

	HTTP       =  #008B76
	Web safe   =  #009966
	RGB 0-255  =     0.00   139.16   117.60
	RGB 0-FF   =       00       8B       75
	RGB 0-0.1  =  0.00000  0.54573  0.46120
	CMY 0-0.1  =  1.00000  0.45427  0.53880
	CMYK %     =  100.000    0.000   15.491   45.427
	XYZ        =    9.803   18.419   20.055
	Yxy        =   18.419  0.20306  0.38152
	CIE-L*ab   =   50.000  -50.000    0.000
	CIE-L*CH   =   50.000   50.000  180.000
	CIE-L*uv   =   50.000  -54.984    6.773
	HunterLab  =   42.917  -34.332    2.336

	Illuminant =  D65
	Observer   =  2° (1931)

I'm sure it's possible to plot invalid LCH coordinates such that parts 
of the SRGB gamut fall outside it. It's just going to be a lot of work 
tracking down those values in the image.

Mike


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