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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 [res, inds] = polygonSubcurve(poly, t0, t1)
%POLYGONSUBCURVE Extract a portion of a polygon.
%
% POLY2 = polygonSubcurve(POLYGON, POS0, POS1)
% Create a new polyline, by keeping vertices located between positions
% POS0 and POS1, and adding points corresponding to positions POS0 and
% POS1 if they are not already vertices.
%
% [POLY2, INDS] = polygonSubcurve(POLYGON, POS0, POS1)
% Also return indices of polygon vertices comprised between POS0 and
% POS1. The array INDS may be smaller than the array POLY2.
%
% Example
% Nv = 100;
% poly = circleToPolygon([30 20 15], Nv);
% arc1 = polygonSubcurve(poly, 15, 45);
% arc2 = polygonSubcurve(poly, 90, 10); % contains polygon endpoints
% figure; axis equal, hold on; axis([0 50 0 50]);
% drawPolyline(arc1, 'linewidth', 4, 'color', 'g');
% drawPolyline(arc2, 'linewidth', 4, 'color', 'r');
% drawPolygon(poly, 'color', 'b');
%
% See also
% polygons2d, polylineSubcurve, projPointOnPolygon, polygonPoint
%
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2009-04-30, using Matlab 7.7.0.471 (R2008b)
% Copyright 2009-2023 INRAE - Cepia Software Platform
% number of vertices
Nv = size(poly, 1);
if t0 < t1
% format positions
t0 = max(t0, 0);
t1 = min(t1, Nv);
end
% indices of extreme vertices inside subcurve
ind0 = ceil(t0)+1;
ind1 = floor(t1)+1;
% get the portion of polyline between 2 extremities
if t0 < t1
% The result polyline does not contain the last vertex
if ind1 <= Nv
inds = ind0:ind1;
else
inds = 1;
end
else
% polygon contains last vertex
inds = [ind0:Nv 1:ind1];
end
res = poly(inds, :);
% add first point if it is not already a vertex
if t0 ~= ind0-1
res = [polygonPoint(poly, t0); res];
end
% add last point if it is not already a vertex
if t1 ~= ind1-1
res = [res; polygonPoint(poly, t1)];
end
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