A group is the simplest type of subprograms, it takes some inputs and return some outputs or perform a certain task defined by the nodes encapsulated in it. A group is defined by a Group Input and a Group Output node, however, the latter can be skipped as in example 1. Unlike other subprograms, a group has to have at least one input.
One can make a group that positions the input object randomly and shade it smooth.
Notice that the group has two inputs Object and Seed, a new input can be added by creating a link from the transparent socket to the required node socket or by pressing the plus icon. This group has no outputs and is thus called an Operational Group because it returns nothing.
Had one defined the group, one can call/invoke it using the Invoke Subprogram node.
Groups saves one the trouble of not having to copy the whole node tree for each object resulting in a more efficient and organized node tree.
One can make a group that computes the dot product of two vector lists. The group takes two inputs A and B and returns an output Dot Product. A new output can be added by creating a link from the transparent socket to the required node socket or by pressing the plus icon. The Group Output node itself can be created by pressing the plus button Output Node.
The group can be similarly invoked as in example 1.
A network error is raised in three situations:
Adding a new Object Input node, connecting it to the group nodes and pressing Use Input In Network.
Adding a new Object Input node by pressing the plus button in the Group Output node.