# Using Geometry Nodes to manipulate curves / spirals including extending specific vertices

I'm a geometry nodes newbie but love the coding/puzzle aspect of it alongside how powerful it can be. I'm hoping to be able to take a spiral, and extend certain vertices to create new shapes. then be able to convert it to mesh etc.

So i did this in simple blender mode. Added spiral, grabbed some vertices and then extruded etc.

What i think i should be able to do is start with a sinlge vertex (e.g. the right hand vertex), extrude it set direction, then merge into a spiral. As bonus, subdivide the "straight line" part and extrude a branch at a certain angle.

For final piece i'm hoping to animate these spirals "growing out"

I think it must be achievable, but i'm not too sure how from a shape you can extract information and then manipulate individual vertices.

Any help would be great.

R

UPDATE: So looking at the advice below i've created a spiral and got these nodes. Spiral node --> Curve to mesh to get the original spiral. I've then extruded the final vector using Index and COmpare as suggested. However, it's now extruding along normal.

Any ideas how i can change the angle of extrusion?

• ID node -> Compare node integer equal to Commented Nov 23, 2022 at 21:05
• I saw something like that on another example of a cube.... They could change position of one corner. However I couldn't tell how they selected that one corner over the others. For example of I had a straight line with three vertices, how would I differentiate them with nodes Commented Nov 23, 2022 at 21:45
• blender.stackexchange.com/a/258333/110840 - This is the answer that helped me the most. Note that you can calculate proximity to other parts of your node tree. Commented Nov 25, 2022 at 4:46
• This may help blender.stackexchange.com/questions/276171/… Commented Apr 12, 2023 at 21:04