POV-Ray : Newsgroups : povray.general : Alpha channel? Server Time
1 Aug 2024 10:15:53 EDT (-0400)
  Alpha channel? (Message 1 to 3 of 3)  
From: Tim Nikias
Subject: Alpha channel?
Date: 14 Dec 2005 19:00:12
Message: <43a0b20c@news.povray.org>
I'm experimenting a bit with image-based pigments and such, trying to create
my own little SDL Compositing Tool... :-)

Now, BMP's don't come with alpha, PNG and TGA do, and PNG even comes with
inbuilt Gamma (which'll get gamma-corrected automatically by POV-Ray).

Anyways, POV-Ray uses the alpha-channel of images for transparency. I've
looked around the Docs and found use_alpha, but I haven't found an inverse
of that, e.g. which would turn an image with alpha into a pigment without
transparency. Any pointers? Otherwise I'd probably run it through a function
to extract red, green and blue.

Regards,
Tim

-- 
aka "Tim Nikias v2.0"
Homepage: <http://www.nolights.de>


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From: Warp
Subject: Re: Alpha channel?
Date: 15 Dec 2005 02:47:50
Message: <43a11fa6@news.povray.org>
Tim Nikias <JUSTTHELOWERCASE:timISNOTnikias(at)gmx.netWARE> wrote:
> which would turn an image with alpha into a pigment without
> transparency.

  Use layered textures.

-- 
                                                          - Warp


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From: Tim Nikias
Subject: Re: Alpha channel?
Date: 15 Dec 2005 11:40:53
Message: <43a19c95$1@news.povray.org>
> > which would turn an image with alpha into a pigment without
> > transparency.
>
>   Use layered textures.

Hm. Might be an option. I'll have to experiment a little how POV-Ray handles
various things with functions, pigments and image-maps to see if it does
work with the other scripts I'm trying to implement.

What I wanted to do was to create functions from images, to allow
transparency-mapping, gamma-correction, color-correction and a few basic
compositing/masking steps, so that I could do my compositing in POV-Ray. :-)

I'm not sure if layered textures will work properly with what I have in
mind, I had hoped that there was some simple way to "disable" the
alpha-channel from TGA and PNG (aside of running it through a function to
extract rgb).

Thanks anyway,
regards,
Tim


-- 
aka "Tim Nikias v2.0"
Homepage: <http://www.nolights.de>


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