When I press A key on the render window I get the alpha ! Great! Now how do I save that image… and concurrently how do I save it as an animation of alphas ???
As far as I know there’s no way to save just the alpha, but…
In the render settings, if you make sure RGBA is clicked, and you select an image format like Targa that supports an alpha channel, then when you save the image, the alpha channel will be saved in that file, so you can open it up in Photoshop and in your channels palette you can edit the alpha channel.
To save an animated sequence of alpha images, you’ll have to animate it as an image sequence, not as an AVI or quicktime. Then in your compositing software you can use the alpha channels of the image sequence.
I hope this makes sense…
Actually there are some quicktime codecs that support alpha in a .mov, such as the lossless Animation code. Just select Millions of Colours+ for the colour depth in the options dialog.
There are a lot of advantages to the “file per frame” format, at least when initially preparing the piece. When the computer goes :o <<frotz>> :o … as it is wot to do about three minutes from the end of a four-hour render … you only lose one frame.