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52 lines
2.1 KiB
52 lines
2.1 KiB
// This file is part of libigl, a simple c++ geometry processing library.
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//
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// Copyright (C) 2019 Hanxiao Shen <hanxiao@cs.nyu.edu>
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//
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// This Source Code Form is subject to the terms of the Mozilla Public License
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// v. 2.0. If a copy of the MPL was not distributed with this file, You can
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// obtain one at http://mozilla.org/MPL/2.0/.
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#include "segment_segment_intersect.h"
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// https://www.geeksforgeeks.org/check-if-two-given-line-segments-intersect/
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template <typename DerivedP>
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IGL_INLINE bool igl::predicates::segment_segment_intersect(
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const Eigen::MatrixBase<DerivedP>& a,
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const Eigen::MatrixBase<DerivedP>& b,
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const Eigen::MatrixBase<DerivedP>& c,
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const Eigen::MatrixBase<DerivedP>& d
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)
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{
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typename DerivedP::Scalar Scalar;
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auto t1 = igl::predicates::orient2d(a,b,c);
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auto t2 = igl::predicates::orient2d(b,c,d);
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auto t3 = igl::predicates::orient2d(a,b,d);
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auto t4 = igl::predicates::orient2d(a,c,d);
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// assume m,n,p are colinear, check whether p is in range [m,n]
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auto on_segment = [](
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const Eigen::MatrixBase<DerivedP>& m,
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const Eigen::MatrixBase<DerivedP>& n,
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const Eigen::MatrixBase<DerivedP>& p
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){
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return ((p(0) >= std::min(m(0),n(0))) &&
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(p(0) <= std::max(m(0),n(0))) &&
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(p(1) >= std::min(m(1),n(1))) &&
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(p(1) <= std::max(m(1),n(1))));
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};
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// colinear case
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if((t1 == igl::predicates::Orientation::COLLINEAR && on_segment(a,b,c)) ||
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(t2 == igl::predicates::Orientation::COLLINEAR && on_segment(c,d,b)) ||
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(t3 == igl::predicates::Orientation::COLLINEAR && on_segment(a,b,d)) ||
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(t4 == igl::predicates::Orientation::COLLINEAR && on_segment(c,d,a)))
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return true;
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// ordinary case
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return (t1 != t3 && t2 != t4);
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}
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#ifdef IGL_STATIC_LIBRARY
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template bool igl::predicates::segment_segment_intersect<Eigen::Matrix<double, 1, 2, 1, 1, 2> >(Eigen::MatrixBase<Eigen::Matrix<double, 1, 2, 1, 1, 2> > const&, Eigen::MatrixBase<Eigen::Matrix<double, 1, 2, 1, 1, 2> > const&, Eigen::MatrixBase<Eigen::Matrix<double, 1, 2, 1, 1, 2> > const&, Eigen::MatrixBase<Eigen::Matrix<double, 1, 2, 1, 1, 2> > const&);
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#endif
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