topology (nodebox)

How a mesh is connected: topology.edges lists its unique edges with the faces each borders, topology.borders counts the faces along each edge, topology.boundary finds the open edges and the loops they form, topology.islands labels the connected pieces, topology.adjacency answers a neighbour relation (the points, edges or faces around a point, edge or face), and topology.convert moves a 0/1 group between the point, vertex, edge and primitive classes. Every node takes a group that limits it to the faces the group selects, chosen the way topology.participation chooses them. A node that answers a table (edges, boundary, islands, adjacency, converted) reads it back to the CPU as a Data record beside the geometry it marks.