google3/third_party/libigl/include/igl/orient_halfedges.cpp

// This file is part of libigl, a simple c++ geometry processing library.
//
// Copyright (C) 2020 Oded Stein <oded.stein@columbia.edu>
//
// This Source Code Form is subject to the terms of the Mozilla Public License
// v. 2.0. If a copy of the MPL was not distributed with this file, You can
// obtain one at http://mozilla.org/MPL/2.0/.
#include "orient_halfedges.h"

#include "oriented_facets.h"
#include "unique_simplices.h"


template <typename DerivedF, typename DerivedE, typename DerivedOE>
IGL_INLINE void
igl::orient_halfedges(
  const Eigen::MatrixBase<DerivedF>& F,
  Eigen::PlainObjectBase<DerivedE>& E,
  Eigen::PlainObjectBase<DerivedOE>& oE)
{
  assert(F.cols()==3 && "This only works for triangle meshes.");
  
  using Int = typename DerivedF::Scalar;
  
  const Eigen::Index m = F.rows();
  
  DerivedE allE, EE;
  oriented_facets(F, allE);
  Eigen::Matrix<Int, Eigen::Dynamic, 1> IA, IC;
  unique_simplices(allE, EE, IA, IC);
  
  E.resize(m, 3);
  oE.resize(m, 3);
  for(Eigen::Index f=0; f<m; ++f) {
    for(int e=0; e<3; ++e) {
      const Int ind = f + m*e;
      E(f,e) = IC(ind);
      assert((EE(E(f,e),0)==allE(ind,0) || EE(E(f,e),0)==allE(ind,1)) &&
       "Something is wrong in the edge matrix.");
      oE(f,e) = EE(E(f,e),0)==allE(ind,0) ? 1 : -1;
    }
  }
}

#ifdef IGL_STATIC_LIBRARY
// Explicit template instantiation
template void igl::orient_halfedges<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<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> >&);
#endif