I understood the alpha component of a color to express the visibility of the
color. An alpha of 1.0 will render the color opaquely, an alpha of 0.0 will
make the color invisible and an alpha of 0.5 will render the color with the
background visible through the color.
So why does Quartz Composer sometimes follow the above and at other times
render an alpha of 0.0 as black.
I refer to
bersearch.com/MacOSXSoftware/TomsQCCompositions/ColorTransformation.zip
In this quick sample, I started with a Clear patch set to clear the patch to
a light gray with an alpha of 1.0. Then I added a Sprite. To the sprite, I
connected a Color Transformation. I set the initial color of the Color
Transformation to a light blue with an alpha of 1.0. Then I connected two
Interpolation patches to the Color Transformation; the first Interpolation
ranges from 0.0 to 360.0 and drives the Hue Rotation. The second
Interpolation ranges from 0.0 to 1.0 and drives the Alpha Factor. I was
expecting the Sprite to gradually fade in from totally invisible to the
color of the moment. Instead, the Sprite goes from black to the color of the
moment.
Thanks in advance.
Tom Bernard
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