If I understand correctly, we want to compute co-edges here. I believe there are algorithms to do this, I know SketchUp has this feature [1]; also Gmsh [2]; and

If I understand correctly, we want to compute co-edges here. I believe there are algorithms to do this, I know SketchUp has this feature [1]; also Gmsh [2]; and I remember seeing Blender plugins that do the same thing (can't seem to find them now...) (edit: Actually Blender does this without plugins: "Join" 2 intersecting objects, use the "Intersect" feature, and it will generate and select the exact co-edges.) [1] https://www.google.com/search?tbm=isch&q=site:http:%2F%2Fperso.uclouvain.be%2Fvincent.legat%2Fteaching%2Fdata%2Fmeca2170-GmshCompanion.pdf https://www.google.com/search?tbm=isch&q=site:http:%2F%2Fper... [2] https://help.sketchup.com/en/article/3000100 https://help.sketchup.com/en/article/3000100 (last figure and text in the section "Subtracting one solid from another")