The value of the function C at a geometrical node is the arithmetic mean of all evaluations of C on all inner elements containing this geometrical node. To compute the values of U and its derivatives at a geometrical node, the values of U at the global nodes are interpolated by a polynomial. Copyrights by Universitaet Karlsruhe 1989-1996. Copyrights by Lutz Grosz 1996. All rights reserved.
More details see vecfem .