function tet_mesh_display ( input_node_filename, input_tetra_filename )

%% TET_MESH_DISPLAY displays a tet mesh.
%
%  Discussion:
%
%    Note that, for the 10 node case, we assume that the tetra file lists
%    the node indices in the following order:
%
%      P1 P2 P3 P4 P12 P13 P14 P23 P24 P34
%
%  Modified:
%
%    18 January 2007
%
%  Author:
%
%    John Burkardt
%
%  Usage:
%
%    tet_mesh_display ( 'node_file', 'tetra_file' )
%
%  Parameters:
%
%    Input, character INPUT_NODE_FILENAME, the name of the node file.
%
%    Input, character INPUT_TETRA_FILENAME, the name of the tetrahedron file.
%
  fprintf ( 1, '\n' );
  timestamp;

  fprintf ( 1, '\n' );
  fprintf ( 1, 'TET_MESH_DISPLAY:\n' );
  fprintf ( 1, '  MATLAB version:\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  Display a wireframe plot of a tet mesh.\n' );
%
%  First argument is the node file.
%
  if ( nargin < 1 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'TET_MESH_DISPLAY:\n' );
    input_node_filename = input ( '  Enter the name of the node file.' );
  end
%
%  Second argument is the tet mesh file.
%
  if ( nargin < 2 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'TET_MESH_DISPLAY:\n' );
    input_tetra_filename = input ( ...
      '  Enter the name of the tetrahedron file.' );
  end
%
%  Read the node data.
%
  [ dim_num, node_num ] = dtable_header_read (  input_node_filename );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Read the header of "%s".\n', input_node_filename );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  Spatial dimension DIM_NUM = %d\n', dim_num );
  fprintf ( 1, '  Number of points NODE_NUM = %d\n', node_num );

  if ( dim_num ~= 3 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'TET_MESH_DISPLAY - Fatal error!\n' );
    fprintf ( 1, '  Dataset must have spatial dimension 3.\n' );
    error ( 'TET_MESH_DISPLAY - Fatal error!' );
  end

  node_xyz = dtable_data_read ( input_node_filename, dim_num, node_num );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Read the data in "%s".\n', input_node_filename );

  r8mat_transpose_print_some ( dim_num, node_num, node_xyz, 1, 1, dim_num, 5, ...
    '  First 5 Nodes:' );
%
%  Read the tetra data.
%
  [ tetra_order, tetra_num ] = itable_header_read ( input_tetra_filename );

  if ( tetra_order ~= 4 & tetra_order ~= 10)
    fprintf ( 1, '\n' );
    fprintf ( 1, 'TET_MESH_DISPLAY - Fatal error!\n' );
    fprintf ( 1, '  Data is not for a 4 node or 10 node tet mesh.\n' );
    error ( 'TET_MESH_DISPLAY - Fatal error!' );
  end

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Read the header of "%s".\n', input_tetra_filename );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  Tetrahedron order = %d\n', tetra_order );
  fprintf ( 1, '  Number of tetras  = %d\n', tetra_num );

  tetra_node = itable_data_read ( input_tetra_filename, tetra_order, ...
    tetra_num );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Read the data in "%s".\n', input_tetra_filename );

  i4mat_transpose_print_some ( tetra_order, tetra_num, ...
    tetra_node, 1, 1, tetra_order, 5, '  First 5 tetrahedrons:' );
%
%  Make the plot.
%
  size = 40;
  color = 'r';

  scatter3 ( node_xyz(1,:), node_xyz(2,:), node_xyz(3,:), size, ...
    color, 'filled' )

  for tetra = 1 : tetra_num

    if ( tetra_order == 4 )
      t = [ tetra_node(1,tetra), tetra_node(2,tetra) ];
      line ( node_xyz(1,t), node_xyz(2,t), node_xyz(3,t) );
      t = [ tetra_node(1,tetra), tetra_node(3,tetra) ];
      line ( node_xyz(1,t), node_xyz(2,t), node_xyz(3,t) );
      t = [ tetra_node(1,tetra), tetra_node(4,tetra) ];
      line ( node_xyz(1,t), node_xyz(2,t), node_xyz(3,t) );
      t = [ tetra_node(2,tetra), tetra_node(3,tetra) ];
      line ( node_xyz(1,t), node_xyz(2,t), node_xyz(3,t) );
      t = [ tetra_node(2,tetra), tetra_node(4,tetra) ];
      line ( node_xyz(1,t), node_xyz(2,t), node_xyz(3,t) );
      t = [ tetra_node(3,tetra), tetra_node(4,tetra) ];
      line ( node_xyz(1,t), node_xyz(2,t), node_xyz(3,t) );
    elseif ( tetra_order == 10 )
      t = [ tetra_node(1,tetra), tetra_node(5,tetra), tetra_node(2,tetra) ];
      line ( node_xyz(1,t), node_xyz(2,t), node_xyz(3,t) );
      t = [ tetra_node(1,tetra), tetra_node(6,tetra), tetra_node(3,tetra) ];
      line ( node_xyz(1,t), node_xyz(2,t), node_xyz(3,t) );
      t = [ tetra_node(1,tetra), tetra_node(7,tetra), tetra_node(4,tetra) ];
      line ( node_xyz(1,t), node_xyz(2,t), node_xyz(3,t) );
      t = [ tetra_node(2,tetra), tetra_node(8,tetra), tetra_node(3,tetra) ];
      line ( node_xyz(1,t), node_xyz(2,t), node_xyz(3,t) );
      t = [ tetra_node(2,tetra), tetra_node(9,tetra), tetra_node(4,tetra) ];
      line ( node_xyz(1,t), node_xyz(2,t), node_xyz(3,t) );
      t = [ tetra_node(3,tetra), tetra_node(10,tetra), tetra_node(4,tetra) ];
      line ( node_xyz(1,t), node_xyz(2,t), node_xyz(3,t) );
    end

  end
  
  xlabel ( '--X axis--' )
  ylabel ( '--Y axis--' )
  zlabel ( '--Z axis--' )
%
%  The TITLE function will interpret underscores in the title.
%  We need to unescape such escape sequences!
%
  title_string = s_escape_tex ( input_tetra_filename );
  title ( title_string )
  
  fprintf ( 1, '\n' );
  fprintf ( 1, 'TET_MESH_DISPLAY:\n' );
  fprintf ( 1, '  Normal end of execution.\n' );

  fprintf ( 1, '\n' );
  timestamp;