User Manual

As you can see, the node tree that comprises each composition is a schematic of operations
with tremendous flexibility. Additionally, the node tree structure facilitates compositing by giving
you the ability to direct each node’s output into separate branches, which can be independently
processed and later recombined in many different ways, to create increasingly complex
composites while eliminating the need to precompose, nest, or otherwise compound layers
together, which would impair the legibility of your composition.
In the following example, several graphics layers are individually transformed and combined
with a series of Merge nodes. The result of the last Merge node is then transformed, allowing
you to move the entire collection of previous layers around at once. Because each of these
operations is clearly represented via the node tree, it’s easy to see everything that’s
happening, and why.
The output of five Text nodes being combined using Merge
nodes is modified by a single Transform node.
Upstream and Downstream Nodes
Since nodes can be positioned anywhere in the Node Editor, and added in any direction, nodes
are referred to as being upstream and downstream of one another. Once you select a node, all
other nodes that directly or indirectly connect to its input are considered to be upstream. Any
other nodes that are directly or indirectly connected to the output are said to be downstream.
This is an important distinction to make because, unlike layer-based systems, the visual
positioning of nodes in your node tree has no bearing on the order of operations in that
composition. The only thing that matters is whether nodes are upstream or downstream of
each other.
Tools upstream (left) and downstream (right) of the Merge node.
TIP: To help you stay organized, there are Select > Upstream/Downstream commands
in the Node Editor contextual menu for selecting all upstream or downstream nodes to
move them, group them, or perform other organizational tasks.
Chapter – 56 Working in the Node Editor 1084