dm_2d_pt_elecs

 DM_2D_PT_ELECS: Create circle mesh (or radius 1) refined
     at points on the electrodes

 fmdl = dm_2d_circ_pt_elecs( elec_pts, pfix, spacinf, shapefn, bbox)

 elec_pts = cell fcn of N x [x,y,{z}] for each electrode
    normally one or two points are specified (at start and end of electrode)
    eg elec_pts{1} = [-.1,1;.1,1];
 pfix = any fixed points to provide to the model (default = [])

 params is a structure with fields (you can add more as required)
   params.base_spacing - edge length away from refined nodes (eg 0.1)
   params.refine_ratio - relative refinement near points (eg. 10)
   params.gradient     - transition slope of refinement (eg 0.1)

 shapefn = distmesh shapefn (calculates distance to boundary)

 bbox = bounding box of the space

 Example:
  elec_pts = {[1,0],[0,1;sin(0.2),cos(0.2)],[0.5,0.5]};
  shapefn = inline('sqrt(sum(p.^2,2))-params.rad','p','params'); % Circle
  params.rad = 1;
  params.base_spacing = 0.06;
  params.refine_ratio = 10;
  params.gradient     = 0.05;
  fmdl= dm_2d_pt_elecs( elec_pts, [], params, shapefn, [-1,-1;1,1] );

0001 function fmdl = dm_2d_pt_elecs( elec_pts, pfix, params, shapefn, bbox);
0002 % DM_2D_PT_ELECS: Create circle mesh (or radius 1) refined
0003 %     at points on the electrodes
0004 %
0005 % fmdl = dm_2d_circ_pt_elecs( elec_pts, pfix, spacinf, shapefn, bbox)
0006 %
0007 % elec_pts = cell fcn of N x [x,y,{z}] for each electrode
0008 %    normally one or two points are specified (at start and end of electrode)
0009 %    eg elec_pts{1} = [-.1,1;.1,1];
0010 % pfix = any fixed points to provide to the model (default = [])
0011 %
0012 % params is a structure with fields (you can add more as required)
0013 %   params.base_spacing - edge length away from refined nodes (eg 0.1)
0014 %   params.refine_ratio - relative refinement near points (eg. 10)
0015 %   params.gradient     - transition slope of refinement (eg 0.1)
0016 %
0017 % shapefn = distmesh shapefn (calculates distance to boundary)
0018 %
0019 % bbox = bounding box of the space
0020 %
0021 % Example:
0022 %  elec_pts = {[1,0],[0,1;sin(0.2),cos(0.2)],[0.5,0.5]};
0023 %  shapefn = inline('sqrt(sum(p.^2,2))-params.rad','p','params'); % Circle
0024 %  params.rad = 1;
0025 %  params.base_spacing = 0.06;
0026 %  params.refine_ratio = 10;
0027 %  params.gradient     = 0.05;
0028 %  fmdl= dm_2d_pt_elecs( elec_pts, [], params, shapefn, [-1,-1;1,1] );
0029 
0030 % (C) 2009 Andy Adler. License: GPL version 2 or version 3
0031 % $Id: dm_2d_pt_elecs.m 6926 2024-05-31 15:34:13Z bgrychtol $
0032 
0033 if ischar(elec_pts) && strcmp(elec_pts,'UNIT_TEST'), do_unit_test; return; end
0034 
0035 epfix = vertcat(elec_pts{:});
0036 params.refine_pts   = epfix;
0037 
0038 [p,t] = distmeshnd(shapefn,@dm_refine_points,params.base_spacing/2,  ...
0039            bbox,[pfix;epfix],params);
0040 
0041 bdy = find_boundary(t);
0042 ubn = unique(bdy(:));
0043 
0044 for i=1:length(elec_pts);
0045    nodesi = get_elec_nodes(elec_pts{i}, p, ubn);
0046    if isempty(nodesi);
0047       % If not on boundary, try all nodes
0048       nodesi = get_elec_nodes(elec_pts{i}, p, (1:size(p,1))');
0049    end
0050    electrode(i).nodes     = nodesi;
0051    electrode(i).z_contact = 0.01; % nominal
0052 end
0053 
0054 fmdl.nodes= p;
0055 fmdl.elems= t;
0056 fmdl.boundary = bdy;
0057 fmdl.name = 'dm_2d_pt_elec';
0058 fmdl.electrode = electrode;
0059 fmdl.gnd_node=           1;
0060 
0061 fmdl = eidors_obj('fwd_model', fmdl);
0062 
0063 % Find the nodes associated with a given electrode
0064 %   electrode(i).nodes = get_elec_nodes(elec_pts{i}, p, ubn);
0065 % electrode points are no further from each end point
0066 %   than the elecs are from each other
0067 function nodes= get_elec_nodes( epts, p, ubn);
0068    tol = 1e-6;
0069    nodes = ubn;
0070    bp    = p(ubn,:); % Unique points on the boundary
0071    lep = size(epts,1);
0072    oep = ones(lep,1);
0073    onp = ones(size(ubn,1),1);
0074    for i=1:lep
0075       el = epts(i,:);
0076       % Distance to other electrodes
0077       de = oep*el - epts;
0078       de = sqrt( sum( de.^2,2 ));
0079       mde= max(de);
0080       % Distance to other points
0081       dp = onp*el - bp;
0082       dp = sqrt( sum( dp.^2,2 ));
0083       % Zero outside points
0084       nodes( dp > mde+tol ) = 0;
0085    end
0086    nodes = nodes( nodes>0 );
0087 
0088 function do_unit_test
0089  elec_pts = {[1,0],[0,1;sin(0.2),cos(0.2)],[0.5,0.5]};
0090  shapefn = inline('sqrt(sum(p.^2,2))-params.rad','p','params'); % Circle
0091  params.rad = 1;
0092  params.base_spacing = 0.06;
0093  params.refine_ratio = 10;
0094  params.gradient     = 0.05;
0095  fmdl= dm_2d_pt_elecs( elec_pts, [], params, shapefn, [-1,-1;1,1] );
0096  show_fem(fmdl);