meshEdges

MESHEDGES Computes array of edge vertex indices from face array.

   EDGES = meshEdges(FACES);

   Example
     meshEdges

   See also
     meshes3d, meshEdgeFaces, meshFaceEdges

0001 function edges = meshEdges(faces, varargin)
0002 %MESHEDGES Computes array of edge vertex indices from face array.
0003 %
0004 %   EDGES = meshEdges(FACES);
0005 %
0006 %   Example
0007 %     meshEdges
0008 %
0009 %   See also
0010 %     meshes3d, meshEdgeFaces, meshFaceEdges
0011 
0012 % ------
0013 % Author: David Legland
0014 % e-mail: david.legland@grignon.inra.fr
0015 % Created: 2011-06-28,    using Matlab 7.9.0.529 (R2009b)
0016 % Copyright 2011 INRA - Cepia Software Platform.
0017 
0018 %   HISTORY
0019 %   2013-08-22 rename from computeMeshEdges to meshEdges, add more control
0020 %       on inputs
0021 
0022 %% Process input arguments
0023 
0024 if isstruct(faces) && isfield(faces, 'faces')
0025     % if input is a mesh structure, extract the 'faces' field
0026     faces = faces.faces;
0027 elseif nargin > 1
0028     % if two arguments are given, keep the second one
0029     faces = varargin{1};
0030 end
0031 
0032 
0033 if ~iscell(faces)
0034     %% Process faces given as numeric array
0035     % all faces have same number of vertices, stored in nVF variable
0036     
0037     % compute total number of edges
0038     nFaces  = size(faces, 1);
0039     nVF     = size(faces, 2);
0040     nEdges  = nFaces * nVF;
0041     
0042     % create all edges (with double ones)
0043     edges = zeros(nEdges, 2);
0044     for i = 1:nFaces
0045         f = faces(i, :);
0046         edges(((i-1)*nVF+1):i*nVF, :) = [f' f([2:end 1])'];
0047     end
0048     
0049 else
0050     %% faces are given as a cell array
0051     % faces may have different number of vertices
0052     
0053     % number of faces
0054     nFaces  = length(faces);
0055     
0056     % compute the number of edges
0057     nEdges = 0;
0058     for i = nFaces
0059         nEdges = nEdges + length(faces{i});
0060     end
0061     
0062     % allocate memory
0063     edges = zeros(nEdges, 2);
0064     ind = 0;
0065     
0066     % fillup edge array
0067     for i = 1:nFaces
0068         % get vertex indices, ensuring horizontal array
0069         f = faces{i}(:)';
0070         nVF = length(f);
0071         edges(ind+1:ind+nVF, :) = [f' f([2:end 1])'];
0072         ind = ind + nVF;
0073     end
0074     
0075 end
0076 
0077 % keep only unique edges, and return sorted result
0078 edges = sortrows(unique(sort(edges, 2), 'rows'));