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356 Chapter 19: Video Post-Production
Edit Pseudo Alpha Compositor
Rendering menu > Video Post > Video Post window >
Select a Pseudo-Alpha Compositor. > Video Post toolbar
>EditCurrentEvent
Pseudo alpha compositing
The Pseudo-Alpha C ompositor composites a
foreground image against the background by
creating an alpha channel for the foreground image
based on the foreground image’s upper-left-corner
pixel. All pixels in the foreground image that use
this color become tr ansparent.
Because only one pixel color becomes transparent,
edges of the opaque areas in the foreground image
are aliased. Use this method when the foreground
imageisabitmapwhoseformatdoesnothavean
alpha channel.
There are no setup options for this compositor.
There is also a
Pseudo Alpha Filter Event (page
3–360)
.
Procedure
To us e the Pseudo-Alpha Compositor :
1.
Add two Scene o r Image Input events to the
queue.
2. Select both events and assign an Image
Layer event consisting of the Pseudo-Alpha
Composite Filter.
Edit Simple Additive Compositor
Rendering menu > V ideo Post > V ideo Post window >
Select a Simple Additive Compositor. > Video Post to olbar
>EditCurrentEvent
Additive compositing
TheSimpleAdditiveCompositorcompositesthe
two images using the second image’s intensit y
(HSV value) to determine transparency. Areas
of full intensity (255) are opaque; areas of
zero intensity are transparent; and areas with
intermediate tr ansparency are translucent.
Thislayereventcanbeusefulwhenthesecond
image is a bitmap whose format does not have an
alpha channel.
There are no Setup options for this compositor.
Procedure
To us e the Simple Addi tive Compositor:
1.
A dd two Scene or Image Input events to the
queue.
2. Select both events and assign an Image
Layer event consisting of the Simple Additive
Compositor.