What is an alpha channel?
When objects are painted, they are normally defined as having red, green, and blue values.
There is another value, however, that can be associated with pixels, known as an alpha
channel. The alpha value for a pixel is a measure of the pixel's transparency. This
allows objects such as glass, water, or smoke to be easily rendered.
How about an example?
Sure. Imagine for a minute that you are looking at an icicle on a cold, wintery morning.
You see that light is passing through the icicle, but it is not the same intensity as
the rest of the light because this icicle is cloudy. With alpha blending,
the color of light behind the icicle is combined with the icicle's color and transparency.
This allows a realistic object to be drawn, as the blending effect is the same as that which occurs
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