The center point coordinates are computed by the transformation of the center point of the reference element to the element by interpolation of the assigned geometrical nodes. To compute the values of U and its derivatives on the center point 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 .