- added MEX tutorial example

Former-commit-id: 7ccbb909cdbe42c4d93bd4299999c4fc990b4163

tutorial/603_MEX/compileMEX.m

@@ -0,0 +1,3 @@
+mex readOBJ.cpp ...
+    -I../../include ...
+    -I/opt/local/include/eigen3 %% Change this path to point to your copy of Eigen

tutorial/603_MEX/readOBJ.cpp

@@ -0,0 +1,90 @@
+#include "mex.h"
+
+#define IGL_HEADER_ONLY
+#include <Eigen/Core>
+#include <igl/readOBJ.h>
+
+
+using namespace std;
+using namespace Eigen;
+
+extern void _main();
+
+Eigen::MatrixXd readMatrix(const mxArray* mat)
+{
+  double* ptr = mxGetPr(mat);
+
+  int m = mxGetM(mat);
+  int n = mxGetN(mat);
+
+  Eigen::MatrixXd	V;
+  V.resize(m,n);
+  for(int j=0;j<n;j++)
+    for(int i=0;i<m;++i)
+      V(i,j) = *(ptr++);
+
+  return V;
+}
+
+mxArray* writeMatrix(const MatrixXd& mat)
+{
+  mxArray* ret = 0;
+
+  if (mat.size() == 0)
+  {
+    ret =	mxCreateNumericMatrix(0, 0, mxDOUBLE_CLASS, mxREAL);
+  }
+  else
+  {
+    int M = mat.rows();
+    int N = mat.cols();
+
+    ret = mxCreateNumericMatrix(M, N, mxDOUBLE_CLASS, mxREAL);
+    double* pointer = mxGetPr(ret);
+
+    /* Copy data into the mxArray */
+    int count = 0;
+    for ( int j = 0; j < N; ++j )
+      for (int i = 0; i < M; ++i)
+        pointer[count++] = mat(i,j);
+  }
+
+  return ret;
+}
+
+void mexFunction(
+     int          nlhs,
+     mxArray      *plhs[],
+     int          nrhs,
+     const mxArray *prhs[]
+     )
+{
+  /* Check for proper number of arguments */
+
+  if (nrhs != 1) {
+  mexErrMsgIdAndTxt("MATLAB:mexcpp:nargin",
+      "readOBJ requires 1 input arguments, the path of the file to open");
+  }
+  else if (nlhs != 2) {
+  mexErrMsgIdAndTxt("MATLAB:mexcpp:nargout",
+      "readOBJ generates two output argument, V and F.");
+  }
+
+  // Read the file path
+  char* file_path = mxArrayToString(prhs[0]);
+
+  MatrixXd V;
+  MatrixXi F;
+
+  // Read the mesh
+  igl::readOBJ(file_path,V,F);
+
+  // Matlab is indexing matrices from 1
+  F = F.array() + 1;
+
+  // Return the matrices to matlab, after converting them to double
+  plhs[0] = writeMatrix(V);
+  plhs[1] = writeMatrix(F.cast<double>());
+
+  return;
+}