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MediaIn node connected to a Highlight node connected to a MediaOut node in the Fusion page.
When connecting nodes, a single node output can be connected to the inputs on multiple
nodes, which is known as “branching.” This is useful when you have a single node that you want
to feed multiple operations at the same time.
The MediaIn node’s output is branched to the inputs of two other nodes.
Using Multiple Inputs
Most nodes have two inputs, one for RGBA and another for a mask that can be optionally used
to limit the effect of that node to a particular part of the image. However, some nodes have
three or even more inputs, and it’s important to make sure you connect the correct image data
to the appropriate input to obtain the desired result. If you connect a node to another node’s
input and nothing happens, chances are you’ve connected to the wrong input.
For example, the MatteControl node has a background input and a foreground input, both of
which accept RGBA channels. However, it also has SolidMatte, GarbageMatte, and EffectsMask
inputs that accept Matte or Mask channels to modify the alpha key being extracted from the
image in different ways. If you want to perform the extremely common operation of using a
MatteControl node to attach a Polygon node for rotoscoping an image, you need to make sure
that you connect the Polygon node to the GarbageMatte input to obtain the correct result. The
GarbageMatte input is automatically set to alter the alpha channel of the foreground image. If
you connect to any other input, your Polygon mask may not produce expected results.
Polygon node connected to a MatteControl node for rotoscoping.
In another example, the DeltaKeyer node has a primary input (labeled “Input”) that accepts
RGBA channels, but it also has a CleanPlate input for attaching an RGB image with which to
clean up the background (typically the CleanPlate node). SolidMatte, GarbageMatte, and
EffectsMask inputs on the DeltaKeyer accept Matte or Mask channels to modify the alpha key
Chapter – 69 Understanding Image Channels 1386