Hey great, I understood that very well.
No sky_sphere huh, okay, I had one. 8 bits? Okay again, I set that to
more in case it was going to need more over the usual 24-bit image
capacity, I'll go back and try this out.
Thanks so much.


Thorsten Froehlich wrote:
> 
> In article <371### [at] aolcom> , Bob Hughes <inv### [at] aolcom>
> wrote:
> 
> > I only just recently tried alpha channel output +UA as a png file and
> > then used that as an image file and saw nothing different.
> 
> Did you use a sky_sphere? The alpha-channel will only work with background.
> 
> > Yes, transmit and filter were applied to 'all'. Maybe it did, maybe it
> > didn't change it, I was looking for the obvious.
> > Opening the file with PSP showed the image to definately have Alpha as
> > compared to a non-Alpha png. Thing is PSP couldn't show anything there,
> > just black or blank, even if I added a second channel in with PSP
> > itself.
> > I also used Bits_per_Color to increase the "bandwith" so to speak to
> > make room for 8 bits of transparency info in that Alpha Channel.
> > I never understood it to begin with, and now I know why. I agree, the
> > only way to learn is if others have used it and can manage a
> > tutorial-like explanation or a word of sense about it at least.
> 
> Well, actually it is easy:
> 
> An alpha-channel is a fourth component saved with each pixel. It determines
> how much of the background behind an image comes through. This is usually
> useful for editing the image later in Paint Shop Pro, Photoshop or Gimp(?)
> and combine it with other images.
> In POV-Ray you need to do some setup to get an alpha-channel output:
> - Set the alpha-channel option +UA or Output_Alpha=true.
> - To get a full alpha-channel, make sure Bits_per_Color is set to 8.
> - Make sure you don't use sky_shpere {}. The alpha-channel will only be
> visible when using background {}. During rendering you will still see the
> background, no alpha-channel (except on POV-Ray Mac which can preview the
> alpha-channel).
> - To make objects (half) transparent in the alpha-channel use the transmit
> color component - filter won't work. A value 1.0 is full transparency.
> 
> I hope this explains how to use it. :-)
> 
>     Thorsten
> 
> ____________________________________________________
> Thorsten Froehlich, Duisburg, Germany
> e-mail: Tho### [at] csicom
> 
> Visit POV-Ray on the web: http://mac.povray.org

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