function p04_demo ( iteration_max, h )%*****************************************************************************80%%% P04_DEMO runs the 2D demo problem #4, with mesh size H.%%Licensing:%%(C) 2004 Per-Olof Persson. %See COPYRIGHT.TXT for details.%%Modified:%%06 February 2006%%Reference:%%Per-Olof Persson and Gilbert Strang,%A Simple Mesh Generator in MATLAB,%SIAM Review,%Volume 46, Number 2, June 2004, pages 329-345.%%Parameters:%%Input, integer ITERATION_MAX, the maximum number of iterations that DISTMESH%should take.(The program might take fewer iterations if it detects convergence.)%%Input, real H, the mesh spacing parameter.%if ( nargin < 1 )iteration_max = 200;fprintf ( 1, '\n' );fprintf ( 1, 'P04_DEMO - Note:\n' );fprintf ( 1, 'No value of ITERATION_MAX was supplied.\n' );fprintf ( 1, 'The default value ITERATION_MAX = %d will be used.\n', ...iteration_max );endif ( nargin < 2 )h = 0.1;fprintf ( 1, '\n' );fprintf ( 1, 'P04_DEMO - Note:\n' );fprintf ( 1, 'No value of H was supplied.\n' );fprintf ( 1, 'The default value H = %f will be used.\n', h );end%%Put the random number generator into a fixed initial state.%rand ( 'state', 111 );%%Set the rendering method for the current figure to Z-buffering.%set ( gcf, 'rend', 'z' );fprintf ( 1, '\n' );fprintf ( 1, 'Problem 4:\n' );fprintf ( 1, 'Hexagon with a hexagonal hole, h = %f\n', h )fd = @p04_fd;fh = @p04_fh;box = [ -1.0, -1.0; 1.0, 1.0 ];n = 6;phi = 2 * pi * (0:2:2*(n-1))' / ( 2 * n );outer = [ cos(phi), sin(phi) ];phi = 2 * pi * (1:2:2*(n-1)+1)' / ( 2 * n );inner = 0.5 * [ cos(phi), sin(phi) ];fixed = [ inner; outer ];[ p, t ] = distmesh_2d ( fd, fh, h, box, iteration_max, fixed );post_2d ( p, t, fh )%%Write a PostScript image of the triangulation.%[ node_num, junk ] = size ( p );[ tri_num, junk ] = size ( t );p = p';t = t';node_show = 0;triangle_show = 1;triangulation_order3_plot ( 'p04_mesh.eps', node_num, p, tri_num, ...t, node_show, triangle_show );%%Write a text file containing the nodes.%r8mat_write ( 'p04_nodes.txt', 2, node_num, p );%%Write a text file containing the triangles.%i4mat_write ( 'p04_elements.txt', 3, tri_num, t );returnend