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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 polyList = meshBoundary(varargin)
%MESHBOUNDARY Boundary of a mesh as a collection of 3D line strings.
%
% CURVES = meshBoundary(V, F)
%
% Example
% % Example 1
% % create centered icosahedron
% [v, f] = createIcosahedron;
% v(:,3) = v(:,3) - mean(v(:,3));
% % convert to simili-sphere
% [v2, f2] = subdivideMesh(v, f, 3);
% v3 = normalizeVector3d(v2);
% % clip with plane
% plane = createPlane([0 0 0], [-1 -2 3]);
% [vc, fc] = clipMeshVertices(v3, f2, plane, 'shape', 'plane');
% figure; drawMesh(vc, fc); axis equal; view(3);
% % draw mesh boundary
% curves = meshBoundary(vc, fc);
% hold on; drawPolygon3d(curves{1}, 'linewidth', 2, 'color', 'b');
%
% % Example 2
% mesh = readMesh('mushroom.off');
% plane = createPlane([0 0 0.7], [-1 -2 3]);
% mesh = clipMeshVertices(mesh, plane, 'shape', 'plane');
% curves = meshBoundary(mesh);
% figure; drawMesh(mesh); axis equal; view(3);
% cellfun(@(x) drawPolygon3d(x, 'linewidth', 2, 'color', 'b'), curves)
%
% See also
% meshes3d, meshBoundaryEdgeIndices, meshBoundaryVertexIndices
%
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2019-05-01, using Matlab 8.6.0.267246 (R2015b)
% Copyright 2019-2023 INRA - Cepia Software Platform
[vertices, edges, faces] = parseMeshData(varargin{:});
% Compute edge-vertex map if not specified
if isempty(edges)
edges = meshEdges(vertices, faces);
end
bndEdgeInds = meshBoundaryEdgeIndices(vertices, edges, faces);
bndEdges = edges(bndEdgeInds, :);
if isempty(bndEdgeInds)
polyList = {};
return;
end
% allocate empty array
polyList = {};
nPolys = 0;
while ~isempty(bndEdges)
nPolys = nPolys + 1;
% current edge
edge = bndEdges(1, :);
% initialize new polyline at first vertex
ind0 = edge(1);
vertexInds = ind0;
% current vertex
index = edge(2);
bndEdges(1, :) = [];
% iterate over edges until current vertex becomes ind0
while index ~= ind0
% append current vertex to list of indices for current polygon
vertexInds = [vertexInds ; index]; %#ok<AGROW>
% index of the next edge containing current vertex
edgeInd = find(sum(bndEdges == index, 2) > 0);
% check validity
if isempty(edgeInd)
error('could not find next edge for vertex index %d', index);
end
if length(edgeInd) > 1
error('two many edges contains vertex index %d', index);
end
% remove current edge from the list of edges to process
edge = bndEdges(edgeInd, :);
bndEdges(edgeInd, :) = [];
% % check if current edge closes current polygon
% if index == ind0
% break;
% end
% identify the next index
index = edge(edge ~= index);
end
% create the 3D polyline
polyList{nPolys} = vertices(vertexInds, :); %#ok<AGROW>
end
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