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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 points = polyhedronSlice(nodes, faces, plane)
%POLYHEDRONSLICE Intersect a convex polyhedron with a plane.
%
% SLICE = polyhedronSlice(NODES, FACES, PLANE)
% NODES: a Nx3 array
% FACES: either a cell array or a Nf*3 or Nf*4 array
% PLANE: a plane representation [x0 y0 z0 dx1 dy1 dz1 dx2 dy2 dz2].
% return the intersection polygon of the polyhedra with the plane, in the
% form of a set of ordered points.
%
% Works only for convex polyhedra.
%
% Example
% polyhedronSlice
%
% See also
% polyhedra, clipConvexPolyhedronByPlane, intersectPlaneMesh
%
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2007-09-18, using Matlab 7.4.0.287 (R2007a)
% Copyright 2007-2023 INRA - BIA PV Nantes - MIAJ Jouy-en-Josas
% if faces is a numeric array, convert it to cell array
if isnumeric(faces)
faces2 = cell(size(faces, 1), 1);
for f = 1:length(faces2)
faces2{f} = faces(f,:);
end
faces = faces2;
else
% ensure we have face with horizontal vectors...
for f = 1:length(faces)
face = faces{f};
faces{f} = face(:)';
end
end
% compute edges of the polyhedron
inds = zeros(0, 2);
for f = 1:length(faces)
face = faces{f}';
inds = [inds ; sort([face face([2:end 1])], 2)]; %#ok<AGROW>
end
inds = unique(inds, 'rows');
edges = [nodes(inds(:,1), :) nodes(inds(:,2), :)];
% intersection of edges with plane
points = intersectEdgePlane(edges, plane);
points = points(sum(isfinite(points), 2)==3, :);
if ~isempty(points)
points = angleSort3d(points);
end
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