libigl_Martin/faces_first.cpp

#include "faces_first.h"

#include <vector>
#include <Eigen/Dense>

template <typename MatV, typename MatF, typename VecI>
IGL_INLINE void igl::faces_first(
  const MatV & V, 
  const MatF & F, 
  MatV & RV, 
  MatF & RF, 
  VecI & IM)
{
  using namespace std;
  using namespace Eigen;
  vector<bool> in_face(V.rows());
  for(int i = 0; i<F.rows(); i++)
  {
    for(int j = 0; j<F.cols(); j++)
    {
      in_face[F(i,j)] = true;
    }
  }
  // count number of vertices not in faces
  int num_in_F = 0;
  for(int i = 0;i<V.rows();i++)
  {
    num_in_F += (in_face[i]?1:0);
  }
  // list of unique vertices that occur in F
  VectorXi U(num_in_F);
  // list of unique vertices that do not occur in F
  VectorXi NU(V.rows()-num_in_F);
  int Ui = 0;
  int NUi = 0;
  // loop over vertices
  for(int i = 0;i<V.rows();i++)
  {
    if(in_face[i])
    {
      U(Ui) = i;
      Ui++;
    }else
    {
      NU(NUi) = i;
      NUi++;
    }
  }
  IM.resize(V.rows());
  // reindex vertices that occur in faces to be first
  for(int i = 0;i<U.size();i++)
  {
    IM(U(i)) = i;
  }
  // reindex vertices that do not occur in faces to come after those that do
  for(int i = 0;i<NU.size();i++)
  {
    IM(NU(i)) = i+U.size();
  }
  RF.resize(F.rows(),F.cols());
  // Reindex faces
  for(int i = 0; i<F.rows(); i++)
  {
    for(int j = 0; j<F.cols(); j++)
    {
      RF(i,j) = IM(F(i,j));
    }
  }
  RV.resize(V.rows(),V.cols());
  // Reorder vertices
  for(int i = 0;i<V.rows();i++)
  {
    RV.row(IM(i)) = V.row(i);
  }
}

#ifndef IGL_HEADER_ONLY
// Explicit template specialization
#endif