Hi @ThomasE
All you really need here are the indices of the 2 adjacent faces for each internal edge, separated consistently into left and right when looking along the direction of the edge.
(this last part is critical to be able to tell the difference between mountain and valley folds as in origami, which was my original motivation for making this component)
This just takes a couple of lines of code, and then you can use these indices to do all sorts of things - getting signed dihedral angles, creating dual edges, getting edge normals etc.
mesh_adjacentFaces.gh (38.3 KB)
