xyz = [3, 1, 6; -5, 2, 1];
[fens,gcells] = mesh_hexahedron(xyz,12,3,4);
%     [fens,gcells1,gcells2] = merge_meshes(fens1, gcells1, fens2, gcells2, eps);
%     gcells= cat(2,gcells1,gcells2);
    % drawmesh({fens,gcells},'gcells','nodes','facecolor','red')
    drawmesh({fens,gcells},'gcells','facecolor','red'); hold on
%     drawmesh({fens,gcells2},'gcells','facecolor','Green'); hold on
    % ix =gcell_select(fens,bg,...
    %     struct ('box',[-100 100 -100 0 -100 0],'inflate', 0.5))
    % drawmesh({fens,bg(ix)},'facecolor','red','shrink', 1.0)