Orthtree/octree_traversal_custom.cpp

#include <fstream>
#include <iostream>
 
#include <CGAL/Simple_cartesian.h>
#include <CGAL/Octree.h>
#include <CGAL/Orthtree/IO.h>
#include <CGAL/Point_set_3.h>
#include <CGAL/Point_set_3/IO.h>
 
// Type Declarations
using Kernel = CGAL::Simple_cartesian<double>;
using Point = Kernel::Point_3;
using Point_set = CGAL::Point_set_3<Point>;
using Point_map = Point_set::Point_map;
using Octree = CGAL::Octree<Kernel, Point_set, Point_map>;
 
template <typename Tree>
struct First_branch_traversal {
 
  using Node_index = typename Tree::Node_index;
 
  const Tree& m_orthtree;
 
  explicit First_branch_traversal(const Tree& orthtree) : m_orthtree(orthtree) {}
 
  Node_index first_index() const {
    return m_orthtree.root();
  }
 
  std::optional<Node_index> next_index(Node_index n) const {
 
    // Stop when we reach the base of the tree
    if (m_orthtree.is_leaf(n))
      return {};
 
    // Always descend the first child
    return m_orthtree.child(n, 0);
  }
};
 
int main(int argc, char** argv) {
 
  // Point set will be used to hold our points
  Point_set points;
 
  // Load points from a file.
  std::ifstream stream((argc > 1) ? argv[1] : CGAL::data_file_path("points_3/cube.pwn"));
  stream >> points;
  if (0 == points.number_of_points()) {
 
    std::cerr << "Error: cannot read file" << std::endl;
    return EXIT_FAILURE;
  }
  std::cout << "loaded " << points.number_of_points() << " points\n" << std::endl;
 
  // Create an octree from the points
  Octree octree(points, points.point_map());
 
  // Build the octree
  octree.refine();
 
  // Print out the first branch using custom traversal
  for (auto node: octree.traverse<First_branch_traversal<Octree>>()) {
    std::cout << octree.to_string(node) << std::endl;
  }
 
  return EXIT_SUCCESS;
}