Assigns a background shader. This is stored as an “ai:background” option
in Gaffer’s globals, and translated onto the
Container for user-defined plugs. Nodes should never make their own plugs here, so users are free to do as they wish.
The processed output scene.
The on/off state of the node. When it is off, the node outputs the input scene unchanged.
The input scene
The shader to be assigned. This will be stored as an option within the scene globals.