Graphics Reference
In-Depth Information
Figure 9-34 Editing grouped nodes
At this point, you should have a pretty clear idea of what render passes contribute. This will be important
when you go on to apply specific compositing effects. In the next section, you'll step away from render passes
and take a look at a completely different use of the compositor.
Pulling a Green Screen Matte with Nodes
A big part of video compositing is the task of extracting elements from their original surroundings so as to be
able to composite them freely into different visual environments. There are several ways to do this, depending
on what kind of source material you have to work with. Typically, the process involves the creation of a matte ,
which is a special image used to suppress parts of the original image and allow other parts of the image to show
through.
The Blender composite node system enables you to take multiple images, videos, renders, or other 2D in-
formationsourcesasinputandthenperformawidevarietyofoperationsonthemtocombinetheminanendless
number of ways. The operations are performed in a nonlinear way and represented as nodes on a graph that
can be edited directly. In this section, you will see how this system can be used to perform the common task
of pulling a green screen matte from a live video. After you understand how to do this, many other uses of the
composite node system should become clear.
 
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