function polygonal_surface_display ( node_file_name, triangle_file_name )

%% TRI_MESH_DISPLAY displays a 3D triangular mesh.
%
%  Modified:
%
%    26 February 2007
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, string NODE_FILE_NAME, the name of the node file.
%
%    Input, string TRIANGLE_FILE_NAME, the name of the triangle file.
%
  timestamp;

  fprintf ( 1, '\n' );
  fprintf ( 1, 'TRI_MESH_DISPLAY\n' );
  fprintf ( 1, '  Read the nodes and triangles defining\n' );
  fprintf ( 1, '  a triangulated 3D surface and display the object\n' );
  fprintf ( 1, '  as a MATLAB shape.\n' );
%
%  If at least one command line argument, it's the node file name.
%
  if ( nargin < 1 )

    fprintf ( 1, '\n' );
    fprintf ( 1, 'TRI_MESH_DISPLAY:\n' );
    node_file_name = input ( 'Enter the name of the node file:' );

  end
%
%  If at least two command line arguments, it's the triangle file name.
%
  if ( nargin < 2 )

    fprintf ( 1, '\n' );
    fprintf ( 1, 'TRI_MESH_DISPLAY:\n' );
    triangle_file_name = input ( 'Enter the name of the triangle file:' );

  end
%
%  Read the node data.
%
  [ dim_num, node_num ] = dtable_header_read ( node_file_name );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Spatial dimension of nodes = %d\n', dim_num );
  fprintf ( 1, '  Number of nodes =            %d\n', node_num );

  if ( dim_num ~= 3 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'TRI_MESH_DISPLAY - Fatal error!\n' );
    fprintf ( 1, '  The nodes do not have dimension 3.\n' );
    error ( 'TRI_MESH_DISPLAY - Fatal error!\n' );
  end

  node_xyz = dtable_data_read ( node_file_name, dim_num, node_num );

  r8mat_transpose_print_some ( dim_num, node_num, node_xyz, ...
    1, 1, dim_num, 5, '  First five nodes:' );
%
%  Read the triangle data.
%
  [ triangle_order, triangle_num ] = itable_header_read ( triangle_file_name );

  fprintf ( 1, '\n' );
  fprintf ( 1, '  Order of triangles =  %d\n', triangle_order );
  fprintf ( 1, '  Number of triangles = %d\n', triangle_num );

  if ( triangle_order ~= 3 )
    fprintf ( 1, '\n' );
    fprintf ( 1, 'TRI_MESH_DISPLAY - Fatal error!\n' );
    fprintf ( 1, '  The triangles do not have order 3.\n' );
    error ( 'TRI_MESH_DISPLAY - Fatal error!\n' );
  end

  triangle_node = itable_data_read ( triangle_file_name, triangle_order, ...
    triangle_num );

  i4mat_transpose_print_some ( triangle_order, triangle_num, triangle_node, ...
    1, 1, triangle_order, 5, '  First five triangles:' );
%
%  Display the image as a collection of polygons.
%
  trisurf ( triangle_node', node_xyz(1,:), node_xyz(2,:), node_xyz(3,:) )
% colormap ( gray )
  axis equal; 
  grid on;

  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 ( triangle_file_name );
  title ( title_string )

  fprintf ( 1, '\n' );
  fprintf ( 1, 'TRI_MESH_DISPLAY:\n' );
  fprintf ( 1, '  Normal end of execution.\n' );

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