POV-Ray : Newsgroups : povray.general : Color changes with declared 'finish' Server Time
4 Feb 2023 23:26:18 EST (-0500)
  Color changes with declared 'finish' (Message 1 to 9 of 9)  
From: yesbird
Subject: Color changes with declared 'finish'
Date: 25 Jan 2023 03:20:00
Message: <web.63d0e51780beb0522bff3eef10800fb2@news.povray.org>
Hi guys,

Can't figure out while I am getting different object's colors when using
definition for 'finish'  component compared to 'non-defined' 'finish'.
Could anyone please explain this behavior ?
Scene in attachment.

Thanks in advance.  


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From: jr
Subject: Re: Color changes with declared 'finish'
Date: 25 Jan 2023 06:20:00
Message: <web.63d10f9ea73171dafbdc16836cde94f1@news.povray.org>
hi,

"yesbird" <nomail@nomail> wrote:
> Can't figure out while I am getting different object's colors when using

> Could anyone please explain this behavior ?

can't, really.  best guess is that in only one of the two scenarios the colour
value(s) are subject to "rounding errors"[*].  also think, looking at the code,
that I probably would use the "full-spec" 5-vector notation for colours.

[*] <https://wiki.povray.org/content/Reference:Color_Expressions>


regards, jr.


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From: Bald Eagle
Subject: Re: Color changes with declared 'finish'
Date: 25 Jan 2023 06:40:00
Message: <web.63d113e3a73171da1f9dae3025979125@news.povray.org>
"yesbird" <nomail@nomail> wrote:
> Hi guys,
>
> Can't figure out while I am getting different object's colors when using

> Could anyone please explain this behavior ?
> Scene in attachment.
>



I can't readily see the difference - they ought to be semantically the same?

What I DO notice is that you're using color values like:
rgb <8.00, 2.00, 3.00>

and POV-Ray uses rgb channel values ranging from 0-1.  So - maybe something is
happening "under-the-hood" when those values exceed unity.  I'm suspecting it's
the "metallic" keyword coupled with the large rgb values, as it causes
reflections to multiplied by the rgb pigment values.  But why defined and
undefined are different....?

Maybe fiddle with that, and if it still doesn't work, try some other
permutations of defined and undefined texture/pigment/finish and see if anything
pops out.


Just an aside:
It would be easier for the forum readership at large to see your render issues
and review your code if you kept everything in a monolithic scene file (no
#include dependencies) and just attached the scene file and the render to your
post.

It just might make the difference between you getting a speedy, helpful answer,
or waiting a day or two before someone dowlnloads, unzips, and renders your
scene file(s)


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From: Bald Eagle
Subject: Re: Color changes with declared 'finish'
Date: 25 Jan 2023 07:05:00
Message: <web.63d11a28a73171da1f9dae3025979125@news.povray.org>
"yesbird" <nomail@nomail> wrote:
> Hi guys,
>
> Can't figure out while I am getting different object's colors when using

> Could anyone please explain this behavior ?
> Scene in attachment.
>


It's early, and I'm headed out.
I'm at the stage where I'm rendering both versions, and they look the same to
me.
I'm just commenting out the relevant code in the same code block, but switch
case break end would be a good swapping strategy for intentional "version"
switching.

no need for the "color" keyword - it's completely superfluous.

#declare finish_default = finish {phong 1 reflection {0.10 metallic 0.4} }

#declare tex_pink = texture { //Polished_Chrome
          pigment{ checker rgb <8.00, 2.00, 3.00> rgb <8.00, 2.00, 3.00>  }
          //finish {phong 1 reflection {0.10 metallic 0.4} }
          finish { finish_default }
  }

Maybe do a difference with a plane, and assign one texture version to the left
side, and the other to the right, with the inverse difference (or an
intersection with a box) and compare side by side in the same render.


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From: Bald Eagle
Subject: Re: Color changes with declared 'finish'
Date: 25 Jan 2023 07:10:00
Message: <web.63d11b2aa73171da1f9dae3025979125@news.povray.org>
> #declare tex_pink = texture { //Polished_Chrome

Aha!  It's that //Polished_Chrome that doesn't belong there for any reason.


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From: yesbird
Subject: Re: Color changes with declared 'finish'
Date: 25 Jan 2023 08:55:00
Message: <web.63d13426a73171da2bff3eef10800fb2@news.povray.org>
> Just an aside:
> ...
>
> It just might make the difference between you getting a speedy, helpful answer,
> or waiting a day or two before someone dowlnloads, unzips, and renders your
> scene file(s)
Thanks, I will take in into account.


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From: yesbird
Subject: Re: Color changes with declared 'finish'
Date: 25 Jan 2023 09:00:00
Message: <web.63d134cea73171da2bff3eef10800fb2@news.povray.org>
> ...
> I probably would use the "full-spec" 5-vector notation for colours.
>
> [*] <https://wiki.povray.org/content/Reference:Color_Expressions>
>
Thank you, I will.


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From: yesbird
Subject: Re: Color changes with declared 'finish'
Date: 25 Jan 2023 09:05:00
Message: <web.63d135ffa73171da2bff3eef10800fb2@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
> > #declare tex_pink = texture { //Polished_Chrome
>
> Aha!  It's that //Polished_Chrome that doesn't belong there for any reason.

Exactly, 'Polished_Chrome' has influence, I can fix it now.
Sorry for stupid question, probably I need examine documentation more carefully.


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From: jr
Subject: Re: Color changes with declared 'finish'
Date: 25 Jan 2023 10:35:00
Message: <web.63d14b2ba73171dafbdc16836cde94f1@news.povray.org>
hi,

"yesbird" <nomail@nomail> wrote:
> ... stupid question ...

no such thing.  stupid answers, otoh, are a different kettle of fish.  </grin>


regards, jr.


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