% H = gui_comp_h_tet4( id, ix, x)
%-----------------------------------------------------------
% compute the heights for the nodes of selected elements
% WZ. Shan, 23/01/09
%-----------------------------------------------------------
% input:
% ix : elem. con. mat. [p1, p2, p3, p4]
% id : indices of selected elements
% nel : number of elements
% x : nodal coordinates, [x, y, z]
% output:
% H : heights [h1, h2, h3, h4]
