POV-Ray : Newsgroups : povray.binaries.images : Colors from golds.inc and metals.inc : Re: Colors from golds.inc and metals.inc Server Time
29 Feb 2024 11:37:54 EST (-0500)
  Re: Colors from golds.inc and metals.inc  
From: Cousin Ricky
Date: 27 Feb 2022 12:09:58
Message: <621bb066@news.povray.org>
On 2022-02-22 09:36 (-4), Cousin Ricky wrote:
> 
> One question that must be answered is should we assume that the colors
> are gamma pre-encoded?  Image stock_metal_gamma-srgb.jpg assumes that
> they are, and uses the srgbft keyword to decode them.  Image
> stock_metal_gamma-linear.jpg assumes they are not, and just uses the
> colors as-is.  Comparing them, it seems to me that the colors were not
> pre-encoded, unlike those in colors.inc.

I discovered that the demo scenes from POV-Ray 3.0 explicitly set
assumed_gamma to 2.2, suggesting that the pigment colors were gamma
pre-encoded.  However, as the first OP image shows, this results in
metals that are too dark when used with a realistic finish.  It appears
that the old finishes exaggerated the luminances of the colors while
reducing their saturations, so it seems best to leave the colors as-is,
as if they were not pre-encoded.

Not gamma-decoding the colors does result in hue drift, but I think the
drift is in a better direction.

The attached images show the old finishes without and with radiosity.
Since they were rendered with POV-Ray 3.7, the ambients were
automatically suppressed for the radiosity renders.  The radiosity image
shows that the ambients were not the only problem with the old finishes;
the reflection { metallic } introduced in POV-Ray 3.5 really makes a
difference.


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Attachments:
Download 'stock_metalc_gamma-srgb-a.jpg' (211 KB) Download 'stock_metalc_gamma-srgb-r.jpg' (211 KB)

Preview of image 'stock_metalc_gamma-srgb-a.jpg'
stock_metalc_gamma-srgb-a.jpg

Preview of image 'stock_metalc_gamma-srgb-r.jpg'
stock_metalc_gamma-srgb-r.jpg


 

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