Do not trim mesh endpoints with Geometry Nodes

Question

I have a mesh, some edges share verts, all verts are connected. Empties on the image below show the verts that belong to only 1 edge — mesh "endpoints":

I separate the edges, convert the mesh to a curve, trim it — every segment gets trimmed. However I want to offset only the points that aren't the endpoints from the previous image. Here's the result I'm getting with the empties showing where the 4 mesh endpoints should've stayed:

Here's my node tree:

I can get curve end points with the Endpoint Selection node but converting to curves will split the mesh into several splines. I've also tried to capture the mesh endpoints with the Vertex Neighbours node before splitting the mesh to get the 1-edge verts but... I don't know what to do with them after, there's no selection I could plug them into that I can think of.

And the scene: https://www.dropbox.com/s/zfim0903q9pugla/trim_without_endpoints.blend?dl=1

Answer 1

You could solve this as follows:

• First determine the number of vertices per edge. You use this value as selection for Set Position.
• You determine the position by calculating the direction vector of an edge and scaling it with the value of your choice.
• The direction of the scaling is obtained by comparing the previously selected stand-alone point with the position of the points returned by the node Edge Vertices.

Of course, you can also turn this around by simply checking that the number of vertices equals $1$:

_{(Blender 3.1+)}