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From: Lars W 
Subject: Re: Shadows without Objects
Date: 17 Feb 1999 16:43:28
Message: <36CB3848.B14FBA5D@snafu.de>
Yes i read all this, and i tried TGA and PNG, both deliver only a 1 bit
palette, and i don't know why.

can anybody confirm that he has a more than 1 bit Alpha with POV 3.1 ?

Spider schrieb:

> POV-help is here !
>
> Output_Alpha=bool       Sets alpha output on/off
> Bits_Per_Color=n        Sets file output bits/color to n
> The default type of image file depends on which platform you are using.
> MS-DOS and most others default to 24-bit uncompressed Targa. See your
> platform-specific documentation to see what your default file type is.
> You may select one of several different file types using
> Output_File_Type=x or +Fx where x is one of the following...
>
> +FN     New PNG (portable network graphics) format
> (this isn't very interesting)
> Most of these formats output 24 bits per pixel with 8 bits for each of
> red, green and blue data. PNG allows you to optionally specify the
> output bit depth from 5 to 16 bits for each of the red, green, and blue
> colors, giving from 15 to 48 bits of color information per pixel. The
> default output depth for all formats is 8 bits/color (16 million
> possible colors), but this may be changed for PNG format files by
> setting Bits_Per_Color=n or by specifying +FNn, where n is the desired
> bit depth.
>
> -------(THIS IS INTERESTING)
> Targa format also allows 8 bits of alpha transparency data to be output,
> while PNG format allows 5 to 16 bits of alpha transparency data,
> depending on the color bit depth as specified above. You may turn this
> option on with Output_Alpha=on or +UA. The default is off or -UA. See
> section "Using the Alpha Channel" for further details on transparency.
>
> all this from the doc's -
>
> --
> //Spider
> ( spi### [at] bahnhofse ) [ http://www.bahnhof.se/~spider/ ]
> #declare life = rand(seed(42))*sqrt(-1);


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From: Ron Parker
Subject: Re: Shadows without Objects
Date: 18 Feb 1999 08:38:20
Message: <36cc17cc.0@news.povray.org>
On Wed, 17 Feb 1999 22:44:41 +0100, Lars W. <lar### [at] snafude> wrote:
>
>Yes i read all this, and i tried TGA and PNG, both deliver only a 1 bit
>palette, and i don't know why.
>
>can anybody confirm that he has a more than 1 bit Alpha with POV 3.1 ?

I do when I output it as an 8-bit PNG and load it into Photoshop.
Perhaps the problem lies with DTA?


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From: Thorsten Froehlich
Subject: Re: Shadows without Objects
Date: 18 Feb 1999 10:43:36
Message: <36cc3528.0@news.povray.org>
In article <36CB2CB3.1D9C7925@snafu.de> , "Lars W." <lar### [at] snafude>
wrote:

> Does POV-Ray only supports 1 bit Alpha Channels, or is there a Trick to use
> more then 1 bit, maybe 8 or 16
> or am i so blind, and it has more than one bit, cause the compositing Programm
> DTA ( Daves Targa Animator 3.0 beta ) converts
> the alpha channel only to an black and White image, even when there are
> transparencies in there ( i removed any Skyspheres for
> testing that ).

The alpha channels should be eight bit for all true color images. If you use
16 per color PNG images you should even get a 16 bit alpha channel. To see
the difference, change the transmit value of the second sphere to something
else, i.e. 0.5. However, the sphere is still a real object for POV-Ray and
it will start calcualtiong all the standard effects for it, so you will see
a high-light in the alpha channel in this case, and the first sphere will
change its color, too.  If you need different alpha channel values for the
easiest way to go might be to simply render the image several times with
different objects being invisible just to get more than one alpha channel.
Adjust the alpha channels and combine them to get one alpha channel.
However, you might need a more powerful tool to do this, a lot of programs
only allow one bit alpha channels.


    Thorsten


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From: Psychomek
Subject: Re: Shadows without Objects
Date: 19 Feb 1999 04:45:13
Message: <36CD3235.AC9477A3@cyberhighway.net>
Ron Parker wrote:

> On Wed, 17 Feb 1999 22:44:41 +0100, Lars W. <lar### [at] snafude> wrote:
> >
> >Yes i read all this, and i tried TGA and PNG, both deliver only a 1 bit
> >palette, and i don't know why.
> >
> >can anybody confirm that he has a more than 1 bit Alpha with POV 3.1 ?
>
> I do when I output it as an 8-bit PNG and load it into Photoshop.
> Perhaps the problem lies with DTA?

When ever i try and load a PNG file from PovRay to Paintshop it says
unrecognized color or something to that effect......  but i use a different
program to convert PNG to JPG then use paintshop to resize, resample, then
resave in a slightly higher compression rate... (Usually about 5-10% higher).


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