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On Mon, 14 Jun 1999 18:54:43 -0600, Nobot <vip### [at] powersurfr com>
wrote:
>i've never gotten anything to ouput to the alpha chan any one wanna help
>me did i miss somthing? what would normaly be there?
The alpha channel stores transparency. In POV, it is white where there
are objects and black where there are not, anti-aliased if need be.
The alpha channes is used in paint / anim programs as a mask or
selection to make blending images easier. If you have your scene but
think it could use a better background, you can do this in a paint
program.
To turn alpha channel on, use the +ua setting and either png or tga
output filetypes.
Here are some tips:
1. A sky_sphere is considered an object, so if you use one your alpha
channel will be all white and therefore of no use
2. Media absorption and scattering as well as fog do not affect the
alpha channel
3. Semitransparent / refracting objects give pure white (totally
opaque) in the alpha channel
4. Floor planes just get in the way most of the times, so be prepared
to comment them out and render a +q0 scene just to get the alpha
channel right
5. You can do more advanced stuff like focal blur, distance fade /
desaturation or assembly of several images, but unfortunately POV's
alpha channel support is too limited. You can still use POV to
generate a grayscale image and use it as an alpha channel, if you have
experience with paint programs.
I hope this helps. If you have more interest in the subject, I'll be
glad to help.
Peter Popov
ICQ: 15002700
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