Alpha channel
From Valve Developer Community
Revision as of 00:00, 17 March 2009 by TomEdwards (Talk | contribs)
The alpha channel is an additional color channel that doesn't define color at all. In image editing generally it is used to give images transparency, but 3D graphics engines put it to all sorts of other uses as well.
Not all image formats support alpha channels. TGA and PNG are two popular ones that do.
