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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 adj = meshAdjacencyMatrix(faces, varargin)
%MESHADJACENCYMATRIX Compute adjacency matrix of a mesh from set of faces.
%
% ADJMAT = meshAdjacencyMatrix(FACES)
% Returns a sparse NV-by-NV matrix (NV being the largest vertex index)
% containing vertex adjacency of the mesh represented by FACES.
% FACES is either a NF-by-3, a NF-by-4 index array, or a Nf-by-1 cell
% array.
%
% Example
% [v f] = createCube;
% adj = meshAdjacencyMatrix(f);
%
% See also
% meshes3d, triangulateFaces, smoothMesh
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2013-04-30, using Matlab 7.9.0.529 (R2009b)
% Copyright 2013-2023 INRA - Cepia Software Platform
% Ensures faces is a N-by-3 or N-by-4 array
if iscell(faces) || (isnumeric(faces) && size(faces, 2) > 4)
faces = triangulateFaces(faces);
end
% forces faces to be floating point array, for sparse function
if ~isfloat(faces)
faces = double(faces);
end
nv = max(faces(:));
% populate a sparse matrix
if size(faces, 2) == 3
adj = sparse(...
[faces(:,1); faces(:,1); faces(:,2); faces(:,2); faces(:,3); faces(:,3)], ...
[faces(:,3); faces(:,2); faces(:,1); faces(:,3); faces(:,2); faces(:,1)], ...
1.0, nv, nv);
elseif size(faces, 2) == 4
adj = sparse(...
[faces(:,1); faces(:,1); faces(:,2); faces(:,2); faces(:,3); faces(:,3); faces(:,4); faces(:,4)], ...
[faces(:,4); faces(:,2); faces(:,1); faces(:,3); faces(:,2); faces(:,4); faces(:,3); faces(:,1)], ...
1.0, nv, nv);
end
% remove double adjacencies
adj = min(adj, 1);
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