Nodes and Edges

The class Node is an abstract index into cell-centered locations. It corresponds to a combination of a CellLib CellFrag and a BoxLib IntVect. The class Edge is an abstract index into edge-centered locations. It is characterized by the pair of Nodes that are connected by the Edge. The possible range of values that can be taken on by a Node or an Edge is determined by the index space containing the Node. For that reason, access to the internal state of Node and Edge is read-only, except by the index space to which they belong. Furthermore, The index space to which a Node or Edge belongs is part of that internal state.

• If n is a Node , n.gridIndex() returns an IntVect which is the grid index of the rectangular cell containing the Node.
• The Boolean infix operators == , != , are used to determine whether or not Node s , are equal.
• n.volFrac() returns the volume fraction (area fraction in 2D) of the cell fragment indexed by n.
• For e an Edge , e.lowNode(), e.highNode() returns the Node s connected by the Edge . The function e.direction() returns the integer coordinate direction = 0 ... d-1 that is perpendicular to the Edge . The geometric interpretation of Node and Edge imposes the requirement that

  e.highNode().gridIndex() - e.lowNode().gridIndex()

  be equal to the unit vector in the e.direction() direction.

• Each Node n has member functions n.lowEdge(int idir), n.highEdge(int idir), that returns a Vector<Edge>Vector<Edge>containing the Edge s that abut n on the low and high sides in the idir = 0 ... d-1 coordinate directions.
• e.areaFrac() returns the area fraction (length fraction in 2D) of the edge fragment indexed by e.