function triangulation_order3_contour ( node_file, triangle_file, ...
  solution_file )

%% TRIANGULATION_ORDER3_CONTOUR creates contour plots on an order 3 triangulation.
%
%  Discussion:
%
%    This program assumes that you have computed the value of some scalar
%    quantity (such as pressure or temperature) at a set of nodes, and that
%    these nodes have been triangulated, forming a network of triangles.
%
%    This program can read that data, and display a color contour of the 
%    solution data.
%
%    The program reads three data files:
%
%    * node_file, containing X, Y coordinates of points, 
%      one pair of coordinates per line;
%      
%    * triangle_file, containing, on each line, a list of the three nodes 
%      that make up a particular triangle;
%      
%    * solution_file, containing the value of a scalar function
%      U(X,Y) evaluated at each node.
%
%    The program first displays an image of the triangulation, then an image
%    of the data that uses a constant color over each triangle, and finally,
%    a nice looking contour plot that uses interpolation.  
%
%    The program pauses after each plot is displayed.  Aside from admiring 
%    a particular plot, you might also want to manipulate the viewing angle,
%    or save it as a JPEG file, for instance.
%
%  Modified:
%
%    21 June 2005
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, string NODE_FILE, the name of the node file.
%
%    Input, string TRIANGLE_FILE, the name of the triangle file.
%
%    Input, string SOLUTION_FILE, the name of the solution file.
%
  timestamp;
  fprintf ( 1, '\n' );
  fprintf ( 1, 'TRIANGULATION_ORDER3_CONTOUR:\n' );
  fprintf ( 1, '  MATLAB version\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  Plot a scalar U(X,Y) on a triangulated data set.\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  This program expects to find three files to read:\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  * node_file,      containing the node coordinates,\n' );
  fprintf ( 1, '  * triangle_file,  containing triples of nodes that form triangles,\n' );
  fprintf ( 1, '  * solution_file,  containing solution values.\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  It reads the files and makes plots of:\n' );
  fprintf ( 1, '\n' );
  fprintf ( 1, '  * the triangulation,\n' );
  fprintf ( 1, '  * a crude contour plot that is constant over each triangle, and\n' );
  fprintf ( 1, '  * a nicer contour plot that uses interpolation.\n' );
%
%  Read the data.
%
  p = load ( node_file );
  t = load ( triangle_file );
  u = load ( solution_file );
%
%  Display the mesh.
%
  trimesh ( t, p(:,1), p(:,2) );

  xlabel ( 'X', 'FontName', 'Helvetica', 'FontWeight', 'bold', ...
    'FontSize', 16 );

  ylabel ( 'Y', 'FontName', 'Helvetica', 'FontWeight', 'bold', ...
    'FontSize', 16, 'Rotation', 0 );

  title ( 'Triangulation', 'FontName', 'Helvetica', 'FontWeight', ...
    'bold', 'FontSize', 16 );

  xmax = max ( p(:,1) );
  xmin = min ( p(:,1) );
  ymax = max ( p(:,2) );
  ymin = min ( p(:,2) );
  scale = max ( xmax - xmin, ymax - ymin );
  xmax = xmax + 0.025 * scale;
  xmin = xmin - 0.025 * scale;
  ymax = ymax + 0.025 * scale;
  ymin = ymin - 0.025 * scale;
  
  axis ( [ xmin, xmax, ymin, ymax ] )
  axis ( 'equal' )

  fprintf ( 1, '\n' );
  fprintf ( 1, 'Press return...\n' );
  pause
%
%  Display the solution on the mesh, constant over each triangle.
%
  trisurf ( t, p(:,1), p(:,2), u )
  
  xlabel ( 'X', 'FontName', 'Helvetica', 'FontWeight', 'bold', ...
    'FontSize', 16 );

  ylabel ( 'Y', 'FontName', 'Helvetica', 'FontWeight', 'bold', ...
    'FontSize', 16, 'Rotation', 0 );

  zlabel ( 'U', 'FontName', 'Helvetica', 'FontWeight', 'bold', ...
    'FontSize', 16, 'Rotation', 0 );

  title ( 'Scalar U(X,Y)', 'FontName', 'Helvetica', 'FontWeight', ...
    'bold', 'FontSize', 16 );

  fprintf ( 1, '\n' );
  fprintf ( 1, 'Press return...\n' );
  pause
%
%  Make a nicer plot on the finer mesh by using color interpolation.
%
  trisurf ( t, p(:,1), p(:,2), u, 'FaceColor', 'interp', ...
    'EdgeColor', 'interp' )

  xlabel ( 'X', 'FontName', 'Helvetica', 'FontWeight', 'bold', ...
    'FontSize', 16 );

  ylabel ( 'Y', 'FontName', 'Helvetica', 'FontWeight', 'bold', ...
    'FontSize', 16, 'Rotation', 0 );

  zlabel ( 'U', 'FontName', 'Helvetica', 'FontWeight', 'bold', ...
    'FontSize', 16, 'Rotation', 0 );

  title ( 'Scalar U(X,Y)', 'FontName', 'Helvetica', 'FontWeight', ...
    'bold', 'FontSize', 16 );

  fprintf ( 1, '\n' );
  fprintf ( 1, 'Press return...\n' );
  pause

  fprintf ( 1, '\n' );
  fprintf ( 1, 'TRIANGULATION_ORDER3_CONTOUR:\n' );
  fprintf ( 1, '  Normal end of execution.\n' );

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