DOLFIN User Manual - FEniCS Project

DOLFIN User ManualHoffman, Jansson, Logg, WellsA.3.2Ordering among mesh entitiesWith each mesh entity, there can be associated zero or more nodes and thenodes are ordered locally and globally based on the topological dimension ofthe mesh entity with which they are associated. Thus, any nodes associatedwith vertices are ordered first and nodes associated with cells last.If more than one node is associated with a single mesh entity, the internalordering of the nodes associated with the mesh entity becomes important, inparticular for edges and faces, where the nodes of two adjacent cells sharinga common edge or face must line up.A.3.3Internal ordering on edgesFor edges containing more than one node, the nodes are ordered in the directionfrom the first vertex (v 0 e) of the edge to the second vertex (v 1 e) of theedge as in Figure A.5.v 1 e21PSfrag replacements0v 0 eFigure A.5: Internal ordering of nodes on edges.93