When working with repeaters and groups in Paragraphic each element and repeater iteration is assigned a number, or index as it’s called in Paragraphic. These different indexes can be used both for selecting what elements to apply changes to and to serve as input to generate dynamic repetitions that gradually change.
This video below covers introduces these concepts, or you can read about them below in more detail.
Group element indexes
Each element in a group in Paragraphic is assigned a number, referred to as the group index or element index. If you open the output element structure panel for a selected layer you can see the index number for each element to the left. And optionally you can toggle on the the overlay display options to show the element index in the selection overlay.
Index-based selection
In nodes that apply some change to a group of elements you can use the Apply to mode Selection to select just some elements to change. There are many different selection modes, but many of these use the index of the elements to select which ones to change. For example based on a counted pattern or just applying the change to a single element based on an index set by the Offset parameter.
Using indexes as input
You can also use the group index as a parameter input in change nodes that apply to a group of elements. You can do this by adding an Index Value input node to the parameter.
Using this input node you can also access a Relative index value, that maps the index to a 0-1 value range, and you can write simple index expressions like i+1 to instead get the index value plus one.
Repeater indexes
Each repeater node you add to a layer also gives you access to one or more Repeater index. This is the index of the current iteration/repetition of the repeater during generation, and it’s available to use as input in any node before the repeater in the node sequence. This means it can be used to generate repetitions that change dynamically with the index of the repeater.
Using this as input is very similar to how you can use the Group index, you just add an Index value input node and select the repeater index you wish to use. Like before you can also get a relative index or write simple index expressions.
Note in the index selector that each repeater index is clearly linked to a specific repeater node. If you add multiple repeaters to a layer you can select which one to use.
2D repeaters like the Grid, Area or Circle repeaters offer multiple repeater indexes from the same repeater. The default index as well as row and column.
Index function input node
A more convenient and powerful way of using element or repeater indexes in generation is the use the Index function input node. This input node allows you to select an index as input and then map this to an output value range using a function you can configure in various ways.
This makes it very easy to for example vary the count of a repetition between two values without needing to write expressions or worry about the actual index values.
That’s it for this introduction to index-based generation in Paragraphic.