Game Development Reference
In-Depth Information
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The term keying is used to describe the process of removing
part of a layer to reveal the layers beneath it. This is usually used
to refer to the removal of a blue or green screen background for
compositing. In case you were curious, blue and green are the
colors most often used because they contrast the most with the
colors in skin tones, no matter how light or dark the skin. You
would think that after all these years of having this workfl ow that
you could now just click a button and everything blue or green
would be gone. Unfortunately, that's not the case. Keying is a
craft, sometimes requiring many tools to do the job. Thus, we
have many effects in this category, all with the same intention of
removing parts of a layer to isolate objects to be composited.
Of course, some of these effects are more important than
others. And not all work with blue or green screen. Sometimes,
you might want to use keying effects—such as the Luma Key
effect—to remove very bright or very dark areas from a layer. Or,
you may want to remove a multicolored background, in which
you might want to check out the powerful Inner/Outer Key effect.
My point is that while not all workfl ows require the removal of
blue or green screen, most workfl ows still can benefi t from some
degree of keying.
Here's an example of a recent project I did using these keying
tools. I started with some green screen footage of myself reading
a newspaper ( Fig. 10.1 ).
I started by removing the green screen using some of the
methods discussed in this chapter. I then composited this foot-
age on top of a 3D model of a subway scene, courtesy of Kymnbel
Bywater of Kymnbel created the sub-
way scene with transparency in the window. This allowed me to
add a video that my wife took while hanging a camera outside
of the window of our car on a drive up the Oregon Coast in the
background. I also masked out the stool that I was sitting on,
added a refl ection in the window, and played with the color using
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