finished src/random_points_on_mesh.cpp

include/random_points_on_mesh.h

@@ -1,6 +1,11 @@
 #ifndef RANDOM_POINTS_ON_MESH_H
 #define RANDOM_POINTS_ON_MESH_H
 #include <Eigen/Core>
+#include <iostream>
+#include <igl/doublearea.h>
+#include <igl/cumsum.h>
+#include <stdlib.h>
+
 // RANDOM_POINTS_ON_MESH Randomly sample a mesh (V,F) n times.
 //
 // Inputs:

src/random_points_on_mesh.cpp

@@ -8,6 +8,40 @@ void random_points_on_mesh(
 {
   // REPLACE WITH YOUR CODE:
   X.resize(n,3);
-  for(int i = 0;i<X.rows();i++) X.row(i) = V.row(i%V.rows());
+  Eigen::MatrixXd area;
+  Eigen::MatrixXd cumsumA;
+  igl::doublearea(V, F, area);
+  igl::cumsum(area, 1, cumsumA);
+
+  double ttl = cumsumA(cumsumA.rows() - 1, 0);
+  for(int i=0;i<n;i++) {
+  	double randx = ((double)rand()/(double)RAND_MAX) * ttl;
+  	int idx = cumsumA.rows() / 2;
+  	int gap = cumsumA.rows() / 4;
+  	//go over boundary?
+  	while(idx != 0 && idx != cumsumA.rows() - 1 && 
+  		  cumsumA(idx - 1) < randx &&
+  		  cumsumA(idx) > randx) {
+  		if (randx > cumsumA(idx - 1)) {
+  			idx += gap;
+  		}
+  		else {
+  			idx -= gap;
+  		}
+  		gap /= 2;
+  	}
+
+  	double alpha = ((double)rand()/(double)RAND_MAX);
+  	double beta = ((double)rand()/(double)RAND_MAX);
+
+  	if (alpha + beta > 1) {
+  		alpha = 1 - alpha;
+  		beta = 1 - beta;
+  	}
+
+  	X.row(i) = V.row(F(idx, 0)) + 
+  			   alpha * V.row(F(idx, 1)) +
+  			   beta * V.row(F(idx, 2));
+  }
 }