Recursion in geometry nodes?

Question

I'm almost certain the answer is going to be no, but is there a way of a node group being recursive? That is, the node group somehow includes a copy of itself. Say you have a node group that creates a branch on a tree. The resultant branch might have sub-branches, and they might have sub-branches and so on. Without recursion you need to specifically add each of the branching levels, basically hard-coding the number of levels of sub-branch. With recursion you'd create a branching node group, and inside it you would call itself to create the sub-branches and so on, until you hit some limiting factor. Of course without some limiting factor this would inevitably lead to an out-of-memory error, which I'm guessing is maybe a reason why it doesn't exist. Of course you could have recursion limits built in, like in the Javascript engines in browsers that only let you do a few thousand levels of recursion. Given the way that geometry nodes are increasing looking like a proper programming language (somewhere someone is totally porting Doom to run on geonodes) this would be a useful feature.

Answer 1

This is an exemple of "fake" recursion achieved with "Repeat Zone" to make a fractal cubes on cube's vertices.

Key Concepts

• A stop criteria with a "switch". I used a maximum level (index), but you could use any other criteria. If stop criteria reached, output the original geometry for this iteration, else, output your node setup
• A separate output for the "current geometry" and the "full geometry".
• We work with the "current geometry" and join the results into the full geometry

---

Alternative storing recursion levels

This might be useful in some cases, but not for this simple example.

• We can store at each geometry the recursion level at which it was generated, for selection, inspection and other uses.