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124 lines
4.0 KiB
124 lines
4.0 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 <igl/slice.h>
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#include "ear_clipping.h"
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#include "point_inside_convex_polygon.h"
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#include "predicates.h"
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template <typename DerivedP, typename DerivedRT,
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typename DerivedF, typename DerivedI>
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IGL_INLINE void igl::predicates::ear_clipping(
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const Eigen::MatrixBase<DerivedP>& P,
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const Eigen::MatrixBase<DerivedRT>& RT,
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Eigen::PlainObjectBase<DerivedI>& I,
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Eigen::PlainObjectBase<DerivedF>& eF,
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Eigen::PlainObjectBase<DerivedP>& nP
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){
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typedef typename DerivedF::Scalar Index;
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typedef typename DerivedP::Scalar Scalar;
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static_assert(std::is_same<typename DerivedI::Scalar,
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typename DerivedF::Scalar>::value,
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"index type should be consistent");
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// check whether vertex i is an ear
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auto is_ear = [](
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const Eigen::MatrixBase<DerivedP>& P,
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const Eigen::MatrixBase<DerivedRT>& RT,
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const Eigen::Matrix<Index,Eigen::Dynamic,1>& L,
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const Eigen::Matrix<Index,Eigen::Dynamic,1>& R,
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const Index i
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){
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Index a = L(i), b = R(i);
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if(RT(i) != 0 || RT(a) != 0 || RT(b) != 0) return false;
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Eigen::Matrix<Scalar,1,2> pa = P.row(a);
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Eigen::Matrix<Scalar,1,2> pb = P.row(b);
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Eigen::Matrix<Scalar,1,2> pi = P.row(i);
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auto r = igl::predicates::orient2d(pa,pi,pb);
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if(r == igl::predicates::Orientation::NEGATIVE ||
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r == igl::predicates::Orientation::COLLINEAR) return false;
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// check if any vertex is lying inside triangle (a,b,i);
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Index k=R(b);
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while(k!=a){
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Eigen::Matrix<Scalar,-1,2> T(3,2);
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T<<P.row(a),P.row(i),P.row(b);
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Eigen::Matrix<Scalar,1,2> q=P.row(k);
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if(igl::predicates::point_inside_convex_polygon(T,q))
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return false;
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k=R(k);
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}
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return true;
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};
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Eigen::Matrix<Index,Eigen::Dynamic,1> L(P.rows());
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Eigen::Matrix<Index,Eigen::Dynamic,1> R(P.rows());
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for(int i=0;i<P.rows();i++){
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L(i) = Index((i-1+P.rows())%P.rows());
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R(i) = Index((i+1)%P.rows());
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}
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Eigen::Matrix<Index,Eigen::Dynamic,1> ears; // mark ears
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Eigen::Matrix<Index,Eigen::Dynamic,1> X; // clipped vertices
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ears.setZero(P.rows());
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X.setZero(P.rows());
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// initialize ears
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for(int i=0;i<P.rows();i++){
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ears(i) = is_ear(P,RT,L,R,i);
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}
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// clip ears until none left
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while(ears.maxCoeff()==1){
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// find the first ear
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Index e = 0;
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while(e<ears.rows()&&ears(e)!=1) e++;
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// find valid neighbors
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Index a = L(e), b = R(e);
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if(a == b) break;
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// clip ear and store face
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eF.conservativeResize(eF.rows()+1,3);
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eF.bottomRows(1)<<a,e,b;
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L(b) = a;
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L(e) = -1;
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R(a) = b;
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R(e) = -1;
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ears(e) = 0; // mark vertex e as non-ear
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// update neighbor's ear status
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ears(a) = is_ear(P,RT,L,R,a);
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ears(b) = is_ear(P,RT,L,R,b);
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X(e) = 1;
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// when only one edge left
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// mark the endpoints as clipped
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if(L(a)==b && R(b)==a){
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X(a) = 1;
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X(b) = 1;
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}
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}
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// collect remaining vertices if theres any
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for(int i=0;i<X.rows();i++)
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X(i) = 1-X(i);
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I.resize(X.sum());
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Index j=0;
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for(Index i=0;i<X.rows();i++)
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if(X(i)==1){
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I(j++) = i;
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}
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igl::slice(P,I,1,nP);
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}
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#ifdef IGL_STATIC_LIBRARY
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template void igl::predicates::ear_clipping<Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::Matrix<int, -1, 1, 0, -1, 1>, Eigen::Matrix<int, -1, -1, 0, -1, -1>, Eigen::Matrix<int, -1, 1, 0, -1, 1> >(Eigen::MatrixBase<Eigen::Matrix<double, -1, -1, 0, -1, -1> > const&, Eigen::MatrixBase<Eigen::Matrix<int, -1, 1, 0, -1, 1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, 1, 0, -1, 1> >&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> >&, Eigen::PlainObjectBase<Eigen::Matrix<double, -1, -1, 0, -1, -1> >&);
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#endif
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