# What do geometry node inputs that you cannot edit do? e. g. index node. (3.x if that matters)

I started to learn geometry nodes and everything is somewhat understandable except un-editable inputs. Workflow, to my understanding, moves only in one way, so what you connect e.g. index node to shouldn't change indexes, so what does it even too? I can get behind value node because it actually has a numerical value and I can control it.

Following pictures are to illustrate my comment on the answer. With position node connected

Without position node connected.

Input nodes like Normal, Position, and Index etc. let you extract related attribute data from geometries and manipulate them. Say you distributed some points on a surface and placed instances on those points—branches on a tree trunk. By default, all your instances will simply be duplicated as they are, without any changes to their rotations or scale, which means all your branches are now pointing towards the same direction. How would you tell Geometry Nodes to orientate the branches so they stick directly out from the trunk's surface? You could capture the Normal information of your trunk faces, and align the Euler rotations of your branches to those normals:

It is impossible to overstate the importance of these input nodes for Geometry Nodes, and there are a million ways you could use them, but here are some other simple examples.

Transfer the Position information of two joined spirals to a grid of faces so you can make a spiral ramp (example taken from a previous answer):

Extrude the faces of a mesh, say, except every third face, by modulating their index numbers:

Control the scales of the instances you've arrayed on a curve (like beads on a necklace) via the radius of that curve's control points:

• Thank you. It has been a great help however when trying out your position node example the position node didn't change the mesh in any way. I don't know how to put pictures in the comments so it's going to be edited in the post itself. Commented Mar 15, 2022 at 20:42
• Yeah, my bad sorry, that's a bad example. Since I'm using the Set Position node, "Position" information is already being considered so it's redundant. Hopefully the general concept is still clear. Commented Mar 15, 2022 at 20:52
• @Mandota Replaced that example with a better one from a previous question I had answered. Commented Mar 16, 2022 at 8:24