Suppose you are using an Object List iterator with seven cubes (see example picture above). Now suppose you want to reposition all of the cubes except the third one. Well, just chuck the third cube out of the object list, you might suggest. That’s one solution, certainly. However, a more interesting way — and in some cases perhaps the only way — is to use an ObjectIndex node instead. Connect the Index output port to a Compare node and set the Compare node’s Function to != and its Input 2 to 2 (an index list starts with 0, hence 2 corresponds to the third cube).

Next, connect the Compare node’s output to the input port of the node that sets the position for the cubes (see above). Now, when the index reaches 2 during the iteration, the Compare node will switch off the position assignment and the third cube will not have its position changed.