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I am trying to create some lichen like, differential growth style animation, where the open edges of a mesh extrude outwards and "subdivide" (by extruding individually and scaling the extrusion by zero, then extruding the "gaps")

Here is some demonstration: Picture

Extrude, Scale to 0, extrude again, flatten the extrusion so first and second extrusion line up. Then theres also the possibility of diverting the direction for a third extrusion by not lining them up exactly. I hope you get what I mean.

Since there is no way to extrude Edges individually (if there is a hack please let me know!) and setting the offset direction is more straightforward for face Extrude, I first extruded the flat object to get a side attribute, from where I can now extrude these sides as faces. Of course i now have unnecessary geometry and need two things:

  1. A way to capture only the flat "side"faces, not the sides of the extrusion pointing up and down (in this example) to select the next extrusion

  2. A way to select the created faces on the underside to delete them (either after every extrusion or in the end.

I wanted to ask if there is any elegant solution to this? for 1.: I could maybe make a selection based on if the difference between edges of every face is above a certain threshold, to just select these narrow and wide faces? But there might be a better way... It bugs me that it seems not possible to propagate an attribute from the edge of the face you extrude from to the face corners of the newly created extrusion (?)

I will upload the current .blend file for anyone interested, its a bit messy right now...

the current setup: Main GeoNodes Inside Nodegroup in Repeat Zone

Best wishes,

Todesdigga

Edit: Here is the Blend File:

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Not totally sure that meets all you need, as your final goal is not evident to me.

enter image description here

Make the half icosphere and flatten it.

Extrudes edges to the outer side (normal cross their vertices), for edges that have one face (boundaries).

Split the side edges of the extrusion.

Scale the top.

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  • $\begingroup$ Oh thank you so much, this is great! Now that the approach to use Extrude Mesh in Face Mode is obsolete, and storing old attributes is also not needed anymore, this should maybe be the answer to something like "how to Extrude Edges individually in Geometry Nodes", I don't know if this is still possible? Either way thank you again lemon! $\endgroup$ Feb 16 at 17:06
  • $\begingroup$ About "top and side", this is immediatly available when extruding, so... $\endgroup$
    – lemon
    Feb 16 at 17:08
  • $\begingroup$ Yeah, when working with Edges this is no problem as in this case I always want to extrude from the Outer Edges, it was just a problem when trying to only extrude Faces on the "rim", which are a mix of Top Faces from the former Extrusion and some Side Faces, but not the ones pointing up and thus adding to the new main area of the "Lichen". But directly using edges has only advantages, now that I know you can also do it individually and also scale by their individual centers $\endgroup$ Feb 16 at 17:16

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