vendor/libigl/tutorial/101_FileIO/main.cpp

#include <igl/readOFF.h>
#include <igl/writeOBJ.h>
#include <iostream>

Eigen::MatrixXd V;
Eigen::MatrixXi F;

int main(int argc, char *argv[])

{
  // Load a mesh in OFF format
  igl::readOFF(TUTORIAL_SHARED_PATH  "/cube.off", V, F);

  // Print the vertices and faces matrices
  std::cout << "Vertices: " << std::endl << V << std::endl;
  std::cout << "Faces:    " << std::endl << F << std::endl;

  // Save the mesh in OBJ format
  igl::writeOBJ("cube.obj",V,F);
}