The value of the function C at a geometrical node is the arithmetic mean of all extrapolation of C on the integration nodes at the elements containing this geometrical node. The extrapolation is done by a least square approach. 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 Lutz Grosz 1999. All rights reserved.
More details see vecfem .