POV-Ray : Newsgroups : povray.binaries.animations : CIELCH sphere Server Time 4 Dec 2022 07:30:40 EST (-0500)
 CIELCH sphere (Message 1 to 6 of 6)
 From: Mike Horvath Subject: CIELCH sphere Date: 30 Nov 2016 15:36:51 Message: <583f3863@news.povray.org>
```
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I've attached a short movie and the scene file. Compare to this for a
general idea of what I'm trying to do:

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

Things I am unsure about:

1. The blue part is the largest. Shouldn't the green part be biggest
since because are eyes are more sensitive to greens?
2. The blue part sticks out of the sphere a tiny bit. Is the following
formula appropriate?

#declare fC = function(x,y,z) {sqrt(x*x+y*y+z*z)*128}

Isn't the hypotenuse longer than x, y or z by themselves? I mean, if
X, y or z is no more than 1, shouldn't the radius also be no more
than 1?
3. The isosurface is awfully flat at the bottom. This makes me
suspicious.

Mike
```

Attachments:

 From: Mike Horvath Subject: Re: CIELCH sphere Date: 30 Nov 2016 15:52:22 Message: <583f3c06\$1@news.povray.org>
```
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"dateCreated": "2016-11-30T20:52:22+00:00",
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On 11/30/2016 3:36 PM, Mike Horvath wrote:
> I've attached a short movie and the scene file. Compare to this for a
> general idea of what I'm trying to do:
>
> https://commons.wikimedia.org/wiki/File:HSLSphere.svg
>

Here's another view of what I'm attempting:

https://commons.wikimedia.org/wiki/File:Munsell_1929_color_solid_spherical_coordinates.png

This one is of the Munsell system instead of LCH or HSL.

Mike
```
 From: clipka Subject: Re: CIELCH sphere Date: 30 Nov 2016 16:04:27 Message: <583f3edb\$1@news.povray.org>
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Am 30.11.2016 um 21:36 schrieb Mike Horvath:
> I've attached a short movie and the scene file. Compare to this for a
> general idea of what I'm trying to do:
>
> https://commons.wikimedia.org/wiki/File:HSLSphere.svg
...
> 3. The isosurface is awfully flat at the bottom. This makes me
>    suspicious.

The whole shape makes me suspicious. Unfortunately I'm unfamiliar with
the colour space you're trying to render, so I have no idea whether
you're doing the right thing or not.

The term "CIELCH" is certainly wrong for this shape, as that would
simply be the cylindrical parameterization of the CIELAB or CIELUV
colour space you've already dealt with.

As a matter of fact I'm not aware of any LCH-based colour space that is
commonly represented in a fully spherical interpretation of those
parameters.
```
 From: Mike Horvath Subject: Re: CIELCH sphere Date: 30 Nov 2016 20:07:36 Message: <583f77d8\$1@news.povray.org>
```
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"dateCreated": "2016-12-01T01:07:36+00:00",
"datePublished": "2016-12-01T01:07:36+00:00",
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On 11/30/2016 4:04 PM, clipka wrote:
> Am 30.11.2016 um 21:36 schrieb Mike Horvath:
>> I've attached a short movie and the scene file. Compare to this for a
>> general idea of what I'm trying to do:
>>
>> https://commons.wikimedia.org/wiki/File:HSLSphere.svg
> ...
>> 3. The isosurface is awfully flat at the bottom. This makes me
>>    suspicious.
>
> The whole shape makes me suspicious. Unfortunately I'm unfamiliar with
> the colour space you're trying to render, so I have no idea whether
> you're doing the right thing or not.
>
> The term "CIELCH" is certainly wrong for this shape, as that would
> simply be the cylindrical parameterization of the CIELAB or CIELUV
> colour space you've already dealt with.
>
> As a matter of fact I'm not aware of any LCH-based colour space that is
> commonly represented in a fully spherical interpretation of those
> parameters.
>

I was curious how the shape would look like.

Mike
```
 From: Mike Horvath Subject: Re: CIELCH sphere Date: 2 Dec 2016 03:59:21 Message: <584137e9@news.povray.org>
```
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On 11/30/2016 3:36 PM, Mike Horvath wrote:
> I've attached a short movie and the scene file. Compare to this for a
> general idea of what I'm trying to do:
>
> https://commons.wikimedia.org/wiki/File:HSLSphere.svg
>
> Things I am unsure about:
>
> 1. The blue part is the largest. Shouldn't the green part be biggest
>    since because are eyes are more sensitive to greens?
> 2. The blue part sticks out of the sphere a tiny bit. Is the following
>    formula appropriate?
>
>     #declare fC = function(x,y,z) {sqrt(x*x+y*y+z*z)*128}
>
>    Isn't the hypotenuse longer than x, y or z by themselves? I mean, if
>    X, y or z is no more than 1, shouldn't the radius also be no more
>    than 1?
> 3. The isosurface is awfully flat at the bottom. This makes me
>    suspicious.
>
> Mike

Okay, the flatness was an error on my part. I forgot to change the
dimensions of the contained_by clause of the isosurface. This caused the
entire underside of the isosurface to get clipped.

The shape is not as interesting as I had hoped.

Mike
```

Attachments:

Preview of image 'cielch_color_solid_sphere_isosurface_backup_03.png'

 From: Mike Horvath Subject: Re: CIELCH sphere Date: 2 Dec 2016 10:46:07 Message: <5841973f@news.povray.org>
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"dateCreated": "2016-12-02T15:46:07+00:00",
"datePublished": "2016-12-02T15:46:07+00:00",
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New version. Not sure if the coordinate axes are oriented properly.
Should the numbers increase clockwise or counter-clockwise? Not 100%
sure they match up with the colors shown in the images.

Mike
```

Attachments: