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 ); end if ( 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 ); return end