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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 [nodes2, edges2] = clipGraphPolygon(nodes, edges, poly)
%CLIPGRAPHPOLYGON Clip a graph with a polygon.
%
% [NODES2, EDGES2] = clipGraphPolygon(NODES, EDGES, POLY)
% Clips the graph defined by nodes NODES and edges EDGES with the polygon
% given in POLY. POLY is a N-by-2 array of vertices.
% The result is a new graph containing nodes inside the polygon, as well
% as nodes created by the intersection of edges with the polygon.
%
% Example
% elli = [50 50 40 20 30];
% figure; hold on;
% drawEllipse(elli, 'k');
% poly = ellipseToPolygon(elli, 200);
% box = polygonBounds(poly);
% germs = randomPointInPolygon(poly, 100);
% drawPoint(germs, 'b.');
% [n, e, f] = boundedVoronoi2d(box, germs);
% [n2, e2] = clipGraphPolygon(n, e, poly);
% drawGraphEdges(n2, e2);
%
% See also
% graphs, drawGraph, clipGraph
%
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2012-02-24, using Matlab 7.9.0.529 (R2009b)
% Copyright 2012-2023 INRA - Cepia Software Platform
% Algorithm summary:
% * For each edge not outside do:
% * clip edge with poly
% * if no inter
% * add current edge (same vertex indices)
% * continue
% * end
% * add intersections to list, compute their indices
% * create the new edge(s)
%% Clip the nodes
% find index of nodes inside clipping window
nodeInside = isPointInPolygon(nodes, poly);
innerNodeInds = find(nodeInside);
% create correspondance between original nodes and inside nodes
nodeIndsMap = zeros(size(nodes, 1), 1);
for i = 1:length(innerNodeInds)
nodeIndsMap(innerNodeInds(i)) = i;
end
% select clipped nodes
nodes2 = nodes(innerNodeInds, :);
%% Clip the edges
insideEnds = nodeInside(edges);
% allocate memory for edges with at least one vertex inside
nEdges2 = sum(sum(insideEnds, 2) ~= 0);
% allocate memory for at least edges inside
edges2 = zeros(nEdges2, 2);
nEdges = size(edges, 1);
% index of next edge
iEdge2 = 1;
% index of next vertex
iNode2 = size(nodes2, 1) + 1;
% iterate over all edges
for iEdge = 1:nEdges
% index of edge vertices
v1 = edges(iEdge, 1);
v2 = edges(iEdge, 2);
% compute intersection(s) of current edge with boundary
edge0 = [nodes(v1,:) nodes(v2,:)];
intersects = intersectEdgePolygon(edge0, poly);
% process edges that do not cross polygon boundary
if isempty(intersects)
if nodeInside(v1) && nodeInside(v2)
% current edge is totally inside the clipping polygon
edges2(iEdge2,:) = nodeIndsMap([v1 v2]);
iEdge2 = iEdge2 + 1;
end
continue;
end
% add intersection(s) to the vertex array
nInters = size(intersects, 1);
intersectInds = iNode2:iNode2+nInters-1;
nodes2(intersectInds,:) = intersects;
iNode2 = iNode2 + nInters;
% concatenate vertex indices with indices of extremities inside poly
if nodeInside(v1)
intersectInds = [nodeIndsMap(v1) intersectInds]; %#ok<AGROW>
end
if nodeInside(v2)
intersectInds = [intersectInds nodeIndsMap(v2)]; %#ok<AGROW>
end
% create new edge for each couple of contiguous intersection
while length(intersectInds) > 1
edges2(iEdge2, :) = intersectInds(1:2);
intersectInds(1:2) = [];
iEdge2 = iEdge2 + 1;
end
if ~isempty(intersectInds)
warning('matGeom:graphs:AlgorithmicError', ...
'edge %d has odd number of intersects', iEdge);
end
end
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