I haven't done an alpha channel image of a media. But if it doesn't work, this
is what you can do: render the media on a black background, with a
black-and-white colour map. Where the media is denser, it is brighter. Less
dense - darker. Save this at 8 bpp and you've got your alpha image.
This is untested, but it should work just fine.

Margus

Mathias Broxvall wrote:
> 
> Question: How do I circumvent this? Is this a (un)wanted feature of
> povray or a bug?
> 
> I have had some planes of calculating the alpha channel with a separate
> program
> I'll write - but would rather not have to do that. My somewhat tedious
> way of
> calculating a alpha channel would be to render the picture with two
> different
> backgrounds (rgb 0 / rgb 1) and see what pixels changed and record that
> in the
> alpha channel. I'd prefer not to have to do that....
> 
> / Mathias Broxvall

Post a reply to this message