an encyclopedia of finite element definitions

Some elements are defined on a barycentric dual grid. This grid is defined by taking a mesh of triangles:

Lines are then added connecting every vertex of each triangle to the midpoint of the opposite edge:

The cells in the dual grid are then defined as the union of all the triangles adjacent to one of the vertices in the original mesh:

In DefElement, regular polygons centred at the origin are used as reference elements of the dual grid.