On Thu, 09 Dec 1999 22:12:56 -0500, Steve Martin <sma### [at] usitnet>
wrote:

>> Nothing. POV treats alpha channels in the exact opposite manner to
>> what paint programs do. A POV generated image with an alpha channel
>> will work perfectly in POV but to use it properly in a paint program
>> you'll have to invert the alpha channel.
>
>Okay. Thanks. I'm glad it wasn't me. Is inverting the alpha channel
>something I can do in POV-Ray, or am I going to have to figure out
>how to do that in ImageMagick?

You can do it in POV but it will be a hack. Get all your scene in one
big union and give it a black pigment. Then render the scene. You'll
get... nothing :) Well, black is black, but at least the alpha channel
will be intact. Next thing to do is put this image on a plane of
ambient 1 and make it face an orthographic camera positioned so that
the transformed image_map fits perfectly. Put a white plane of ambient
1 behind this plane and render this scene in the resolution of the
original scene. This will make all "transparent" objects white.

If what you need is exactly the opposite (I don't remember by heart...
no, please people no, ok, I'll re-read jut leave me alooooone...
OUCH!), then the union I mentioned in the beginning should be of
pigment { White } and finish { ambient 1 } , and there should be no
need of the plane behind the image (because the default background is
black anyway).

Of course, if you're uing Linux, why not use the GIMP to do this? :)


Peter Popov
pet### [at] usanet
ICQ: 15002700

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