add an example for random perturbation

Polygon_mesh_processing/examples/Polygon_mesh_processing/random_perturbation_SM_example.cpp

@@ -0,0 +1,40 @@
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+#include <CGAL/Surface_mesh.h>
+
+#include <CGAL/Polygon_mesh_processing/random_perturbation.h>
+
+#include <iostream>
+#include <fstream>
+
+typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
+typedef K::Point_3 Point;
+
+typedef CGAL::Surface_mesh<Point> Surface_mesh;
+typedef boost::graph_traits<Surface_mesh>::vertex_descriptor vertex_descriptor;
+typedef boost::graph_traits<Surface_mesh>::face_descriptor   face_descriptor;
+
+int main(int argc, char* argv[])
+{
+  const char* filename = (argc > 1) ? argv[1] : "data/eight.off";
+  std::ifstream input(filename);
+
+  Surface_mesh mesh;
+  if (!input || !(input >> mesh) || mesh.is_empty()) {
+    std::cerr << "Not a valid off file." << std::endl;
+    return 1;
+  }
+
+  const double max_size = (argc > 2) ? atof(argv[2]) : 0.02;
+
+  namespace PMP = CGAL::Polygon_mesh_processing;
+  PMP::random_perturbation(
+    mesh,
+    max_size,
+    PMP::parameters::vertex_point_map(mesh.points()).geom_traits(K()));
+
+  std::ofstream out("data/eight_perturbed.off");
+  out << mesh;
+  out.close();
+
+  return 0;
+}