예제 #1
0
/*! Print the given envelope diagram. */
void print_diagram (const Diagram_1& diag)
{
  Diagram_1::Edge_const_handle     e = diag.leftmost();
  Diagram_1::Vertex_const_handle   v;

  while (e != diag.rightmost())
  {
    std::cout << "Edge: ";
    if (! e->is_empty())
    {
      Circle_2      circ = e->curve().supporting_circle();
      std::cout << " (x - " << CGAL::to_double(circ.center().x()) << ")^2 +"
                << " (y - " << CGAL::to_double(circ.center().y()) << ")^2 = "
                << CGAL::to_double(circ.squared_radius()) << std::endl;
    }
    else
      std::cout << " [empty]" << std::endl;

    v = e->right();
    std::cout << "Vertex (" << CGAL::to_double(v->point().x()) << ' '
              << CGAL::to_double(v->point().y()) << ')' << std::endl;

    e = v->right();
  }
  CGAL_assertion (e->is_empty());
  std::cout << "Edge: [empty]" << std::endl;

  return;
}
예제 #2
0
파일: convex_hull.cpp 프로젝트: FMX/CGAL
int main (int argc, char* argv[])
{
  // Read the points from the input file.
  const char* filename = (argc > 1) ? argv[1] : "ch_points.dat";
  std::ifstream in_file(filename);
  if (!in_file.is_open()) {
    std::cerr << "Failed to open " << filename << " ..." << std::endl;
    return -1;
  }

  // Read the points from the file, and construct their dual lines.
  std::list<Dual_line_2>  dual_lines;

  unsigned int            n;
  in_file >> n;
  std::vector<Point_2>    points;
  points.resize(n);

  for (unsigned int k = 0; k < n; ++k) {
    int px, py;
    in_file >> px >> py;
    points[k] = Point_2 (px, py);

    // The line dual to the point (p_x, p_y) is y = p_x*x - p_y,
    // or: p_x*x - y - p_y = 0:
    Line_2 line = Line_2 (Number_type(px), Number_type(-1), Number_type(-py));

    // Generate the x-monotone curve based on the line and the point index.
    dual_lines.push_back (Dual_line_2 (line, k));
  }
  in_file.close();

  // Compute the lower envelope of dual lines, which corresponds to the upper
  // part of the convex hull, and their upper envelope, which corresponds to
  // the lower part of the convex hull.
  Diagram_1              min_diag;
  Diagram_1              max_diag;
  lower_envelope_x_monotone_2(dual_lines.begin(), dual_lines.end(), min_diag);
  upper_envelope_x_monotone_2(dual_lines.begin(), dual_lines.end(), max_diag);

  // Output the points along the boundary convex hull in counterclockwise
  // order. We start by traversing the minimization diagram from left to
  // right, then the maximization diagram from right to left.
  std::cout << "The convex hull of " << points.size() << " input points:";
  Diagram_1::Edge_const_handle  e = min_diag.leftmost();
  while (e != min_diag.rightmost()) {
    std::cout << " (" << points[e->curve().data()] << ')';
    e = e->right()->right();
  }

  // Handle the degenerate case of a vertical convex hull edge:
  if (e->curve().data() != max_diag.leftmost()->curve().data())
    std::cout << " (" << points[e->curve().data()] << ')';
  
  e = max_diag.leftmost();
  while (e != max_diag.rightmost()) {
    std::cout << " (" << points[e->curve().data()] << ')';
    e = e->right()->right();
  }
  std::cout << std::endl;

  return 0;
}