POV-Ray : Newsgroups : povray.binaries.animations : CIELCHuv D65 gamut sphere Server Time
22 Jun 2024 15:42:08 EDT (-0400)
  CIELCHuv D65 gamut sphere (Message 7 to 16 of 16)  
<<< Previous 6 Messages Goto Initial 10 Messages
From: Mike Horvath
Subject: Re: CIELCHuv D65 gamut sphere
Date: 25 Mar 2017 13:36:28
Message: <58d6aa9c@news.povray.org>
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.


Mike


Post a reply to this message

From: clipka
Subject: Re: CIELCHuv D65 gamut sphere
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.


Post a reply to this message

From: Mike Horvath
Subject: Re: CIELCHuv D65 gamut sphere
Date: 25 Mar 2017 17:38:00
Message: <58d6e338$1@news.povray.org>
On 3/25/2017 4:19 PM, clipka wrote:
> 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.
>

https://commons.wikimedia.org/wiki/File:HSLSphere.svg

Is this image easier to understand? It is missing the "donut hole" in 
the middle, however. So all the grays collapse to a point, unfortunately.


> *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.
>


Do these figures show what you are talking about?

https://en.wikipedia.org/wiki/File:Hsl-hsv_saturation-lightness_slices.svg

It seems "chroma" needs to be converted to "saturation first". Not sure 
the best way to do this, as I haven't thought of it before.

>
> 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.
>

I'm not concerned so much with the outer shape. The spherical 
parameterization is what's important to me. But "chroma" needs to be 
converted to "saturation" first, as in the above image.


> 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.
>

I labeled all the images as "original research", and nothing links to 
them except a user page.


Mike


Post a reply to this message

From: clipka
Subject: Re: CIELCHuv D65 gamut sphere
Date: 25 Mar 2017 18:14:31
Message: <58d6ebc7$1@news.povray.org>
Am 25.03.2017 um 22:38 schrieb Mike Horvath:
> On 3/25/2017 4:19 PM, clipka wrote:
>> 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.
>>
> 
> https://commons.wikimedia.org/wiki/File:HSLSphere.svg
> 
> Is this image easier to understand? It is missing the "donut hole" in
> the middle, however. So all the grays collapse to a point, unfortunately.

No, it's the HSL model's definition of "Saturation" in general that I
find counter-intuitive, not your visual representations of the HSL
colour solids.


> I labeled all the images as "original research", and nothing links to
> them except a user page.

Fair enough.


Post a reply to this message

From: Mike Horvath
Subject: Re: CIELCHuv D65 gamut sphere
Date: 25 Mar 2017 18:24:05
Message: <58d6ee05$1@news.povray.org>
On 3/25/2017 6:14 PM, clipka wrote:
> No, it's the HSL model's definition of "Saturation" in general that I
> find counter-intuitive, not your visual representations of the HSL
> colour solids.
>

This article explains several definitions/methods to convert "chroma" to 
"saturation".

https://en.wikipedia.org/wiki/HSL_and_HSV

Not sure if one of these methods is good to use, or if CIELCHab & 
CIELCHuv need something custom tailored for them. (Which is beyond me.)


Mike


Post a reply to this message

From: Jörg "Yadgar" Bleimann
Subject: Re: CIELCHuv D65 gamut sphere
Date: 28 Mar 2017 14:27:10
Message: <58daaafe$1@news.povray.org>
Hi(gh)!

On 25.03.2017 09:19, Mike Horvath wrote:
> The visible gamut under D65 illumination mapped to spherical CIELCHuv
> coordinates.

Sweet! May I C64ize/AtariSTize and re-publish it (of course crediting you)?

See you in Khyberspace!

Yadgar


Post a reply to this message

From: Mike Horvath
Subject: Re: CIELCHuv D65 gamut sphere
Date: 28 Mar 2017 23:13:04
Message: <58db2640$1@news.povray.org>
On 3/28/2017 2:27 PM, Jörg "Yadgar" Bleimann wrote:
> Hi(gh)!
>
> On 25.03.2017 09:19, Mike Horvath wrote:
>> The visible gamut under D65 illumination mapped to spherical CIELCHuv
>> coordinates.
>
> Sweet! May I C64ize/AtariSTize and re-publish it (of course crediting you)?
>
> See you in Khyberspace!
>
> Yadgar

You may. But as clipka has pointed out, in its current form it is not 
useful to anyone at all and should be forgotten.


Mike


Post a reply to this message

From: Mike Horvath
Subject: Re: CIELCHuv D65 gamut sphere
Date: 28 Mar 2017 23:51:53
Message: <58db2f59$1@news.povray.org>
There are some nicer animations here:

https://commons.wikimedia.org/wiki/User:SharkD

such as one of these:

https://commons.wikimedia.org/wiki/File:Visible_gamut_within_CIELUV_color_space_D65_whitepoint_mesh.webm
https://commons.wikimedia.org/wiki/File:Visible_gamut_within_CIELCHuv_color_space_D65_whitepoint_mesh.webm

I can provide the individual uncompressed frames of the animation if needed.


Mike


Post a reply to this message

From: Mike Horvath
Subject: Re: CIELCHuv D65 gamut sphere
Date: 29 Mar 2017 00:35:06
Message: <58db397a$1@news.povray.org>
On 3/28/2017 2:27 PM, Jörg "Yadgar" Bleimann wrote:
> Hi(gh)!
>
> On 25.03.2017 09:19, Mike Horvath wrote:
>> The visible gamut under D65 illumination mapped to spherical CIELCHuv
>> coordinates.
>
> Sweet! May I C64ize/AtariSTize and re-publish it (of course crediting you)?
>
> See you in Khyberspace!
>
> Yadgar


Here's a nice animation too, though I can only claim partial credit.

https://commons.wikimedia.org/wiki/File:Pyramid_35_spheres.gif


Mike


Post a reply to this message

From: Mike Horvath
Subject: Re: CIELCHuv D65 gamut sphere
Date: 29 Mar 2017 02:04:14
Message: <58db4e5e@news.povray.org>
On 3/29/2017 12:35 AM, Mike Horvath wrote:
> Here's a nice animation too, though I can only claim partial credit.
>
> https://commons.wikimedia.org/wiki/File:Pyramid_35_spheres.gif
>
>
> Mike

ONCE AGAIN, I can only claim partial credit, rather.

;)


Mike


Post a reply to this message

<<< Previous 6 Messages Goto Initial 10 Messages

Copyright 2003-2023 Persistence of Vision Raytracer Pty. Ltd.