/usr/share/octave/packages/geometry-1.7.0/polygons2d/polygonSelfIntersections.m is in octave-geometry 1.7.0-1build1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 | ## Copyright (C) 2004-2011 David Legland <david.legland@grignon.inra.fr>
## Copyright (C) 2004-2011 INRA - CEPIA Nantes - MIAJ (Jouy-en-Josas)
## Copyright (C) 2012 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
## 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
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## -*- texinfo -*-
## @deftypefn {Function File} {@var{pts} = } polygonSelfIntersections (@var{poly})
## @deftypefnx {Function File} {[@var{pts} @var{pos1} @var{pos2}] = } polygonSelfIntersections (@var{poly})
## Find-self intersection points of a polygon
##
## Return the position of self intersection points
##
## Also return the 2 positions of each intersection point (the position
## when meeting point for first time, then position when meeting point
## for the second time).
##
## Example
## @example
## # use a '8'-shaped polygon
## poly = [10 0;0 0;0 10;20 10;20 20;10 20];
## polygonSelfIntersections(poly)
## ans =
## 10 10
## @end example
##
## @seealso{polygons2d, polylineSelfIntersections}
## @end deftypefn
function varargout = polygonSelfIntersections(poly, varargin)
tol = 1e-14;
# ensure the last point equals the first one
if sum(abs(poly(end, :)-poly(1,:)) < tol) ~= 2
poly = [poly; poly(1,:)];
end
# compute intersections by calling algo for polylines
[points pos1 pos2] = polylineSelfIntersections(poly);
# It may append that first vertex of polygon is detected as intersection,
# the following tries to detect this
n = size(poly, 1) - 1;
inds = (pos1 == 0 & pos2 == n) | (pos1 == n & pos2 == 0);
points(inds, :) = [];
pos1(inds) = [];
pos2(inds) = [];
# remove multiple intersections
[points I J] = unique(points, 'rows', 'first'); ##ok<NASGU>
pos1 = pos1(I);
pos2 = pos2(I);
## Post-processing
# process output arguments
if nargout <= 1
varargout = {points};
elseif nargout == 3
varargout = {points, pos1, pos2};
end
endfunction
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