User Manual

Side by side, dropping a connection on a specific
node input. Note how the inputs rearrange themselves
afterward to keep the node tree tidy-looking.
TIP: If you hold down the Option key while you drag a connection line from one node
onto another, and you keep the Option key held down while you release the mouse
button to drop the connection, a menu appears that lets you choose which specific
input you want to connect to, by name.
Some Nodes Are Incompatible with Some Inputs
Usually, you’re prevented from connecting a node’s output to another node or node input that’s
not compatible with it. For example, if you try to connect a Merge3D node’s output directly to
the input of a regular Merge node, it won’t work; you must first connect to a Renderer3D node
that creates output appropriate for 2D compositing operations.
In other cases, connecting the wrong image data to the wrong node input won’t give you any
error; it simply fails to produce the result you were expecting, necessitating you to troubleshoot
the composition. If this happens to you, check the Fusion Effects section of this manual to see if
the node you’re trying to connect to has any limitations as to how it must be attached.
TIP: This chapter tries to cover many of the easy-to-miss exceptions to node
connections that are important for you to know, so don’t skim too fast.
Always Connect the Background Input First
Many nodes combine images in different ways, using “background” and “foreground” inputs.
This includes the Merge node, the Matte Control node, and the Channel Booleans node, to cite
common examples. The color of inputs on a node can help you make the right corrections. For
instance, background inputs are always orange, and foreground inputs are always green.
When you first connect any node’s output to a multi-input node, you usually want to connect the
background input first. This is handled for you automatically when you first drop a connection
line onto the body of a new multi-input node. The orange-colored background input is almost
always connected first (the exception is Mask nodes, which always connect to the first available
Mask input). This is good because you want to get into the habit of always connecting the
background input first.
Chapter – 69 Understanding Image Channels 1388