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#include <igl/readOFF.h>
#include <igl/cotmatrix.h>
#include <igl/matlab/matlabinterface.h>
#include <igl/opengl/glfw/Viewer.h>
#include <iostream>
// On mac you may need to issue something like:
//
// PATH=$PATH:/Applications/MATLAB_R2019a.app/bin/ ./tutorial/602_Matlab_bin
// Base mesh
Eigen::MatrixXd V;
Eigen::MatrixXi F;
// Matlab instance
Engine* engine;
// Eigenvectors of the laplacian
Eigen::MatrixXd EV;
// This function is called every time a keyboard button is pressed
bool key_down(igl::opengl::glfw::Viewer& viewer, unsigned char key, int modifier)
{
if (key >= '1' && key <= '9')
{
viewer.data().set_data(EV.col((key - '1') + 1));
}
return false;
}
int main(int argc, char *argv[])
{
// Load a mesh in OFF format
igl::readOFF(TUTORIAL_SHARED_PATH "/3holes.off", V, F);
// Launch MATLAB
igl::matlab::mlinit(&engine);
// Compute the discrete Laplacian operator
Eigen::SparseMatrix<double> L;
igl::cotmatrix(V,F,L);
// Send Laplacian matrix to matlab
igl::matlab::mlsetmatrix(&engine,"L",L);
// Plot the laplacian matrix using matlab spy
igl::matlab::mleval(&engine,"spy(L)");
// Extract the first 10 eigenvectors
igl::matlab::mleval(&engine,"[EV,~] = eigs(-L,10,'sm')");
// Plot the size of EV (only for demonstration purposes)
std::cerr << igl::matlab::mleval(&engine,"size(EV)") << std::endl;
// Retrieve the result
igl::matlab::mlgetmatrix(&engine,"EV",EV);
// Plot the mesh
igl::opengl::glfw::Viewer viewer;
viewer.callback_key_down = &key_down;
viewer.data().set_mesh(V, F);
// Plot the first non-trivial eigenvector
viewer.data().set_data(EV.col(1));
// Launch the viewer
viewer.launch();
}
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