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## Copyright (C) 2024 David Legland
## All rights reserved.
##
## Redistribution and use in source and binary forms, with or without
## modification, are permitted provided that the following conditions are met:
##
## 1 Redistributions of source code must retain the above copyright notice,
## this list of conditions and the following disclaimer.
## 2 Redistributions in binary form must reproduce the above copyright
## notice, this list of conditions and the following disclaimer in the
## documentation and/or other materials provided with the distribution.
##
## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ''AS IS''
## AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
## IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
## ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
## ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
## DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
## SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
## CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
## OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
##
## The views and conclusions contained in the software and documentation are
## those of the authors and should not be interpreted as representing official
## policies, either expressed or implied, of the copyright holders.
function edges = meshEdges(faces, varargin)
%MESHEDGES Computes array of edge vertex indices from face array.
%
% EDGES = meshEdges(FACES);
%
% Example
% meshEdges
%
% See also
% meshes3d, meshEdgeFaces, meshFaceEdges
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2011-06-28, using Matlab 7.9.0.529 (R2009b)
% Copyright 2011-2023 INRA - Cepia Software Platform
%% Process input arguments
if isstruct(faces) && isfield(faces, 'faces')
% if input is a mesh structure, extract the 'faces' field
faces = faces.faces;
elseif nargin > 1
% if two arguments are given, keep the second one
faces = varargin{1};
end
if ~iscell(faces)
%% Process faces given as numeric array
% all faces have same number of vertices
nVF = size(faces,2);
e = nchoosek(1:nVF,2);
A = sparse(faces(:,e(:,1)),faces(:,e(:,2)),1,max(faces(:)),max(faces(:)));
[EI,EJ] = find(tril(A+A'));
edges = [EJ EI];
else
%% faces are given as a cell array
% faces may have different number of vertices
% number of faces
nFaces = length(faces);
% compute the number of edges
nEdges = 0;
for i = nFaces
nEdges = nEdges + length(faces{i});
end
% allocate memory
edges = zeros(nEdges, 2);
ind = 0;
% fillup edge array
for i = 1:nFaces
% get vertex indices, ensuring horizontal array
f = faces{i}(:)';
nVF = length(f);
edges(ind+1:ind+nVF, :) = [f' f([2:end 1])'];
ind = ind + nVF;
end
% keep only unique edges, and return sorted result
edges = sortrows(unique(sort(edges, 2), 'rows'));
end
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