CGAL包围盒计算

CGAL包围盒计算

OBB方向包围盒，不同于AABB包围盒，OBB最大特点是它的方向的任意性，这使得它可以根据被包围对象的形状特点尽可能紧密的包围对象，但同时也使得它的相交测试变得复杂。

示例

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Surface_mesh.h>

#include <CGAL/optimal_bounding_box.h>
#include <CGAL/Polygon_mesh_processing/triangulate_faces.h>
#include <CGAL/Polygon_mesh_processing/measure.h>
#include <CGAL/Polygon_mesh_processing/IO/polygon_mesh_io.h>

#include <CGAL/Real_timer.h>

#include <fstream>
#include <iostream>

namespace PMP = CGAL::Polygon_mesh_processing;

typedef CGAL::Exact_predicates_inexact_constructions_kernel    K;
typedef K::Point_3                                             Point;

typedef CGAL::Surface_mesh<Point>                              Surface_mesh;

int main(int argc, char** argv)
{
  const std::string filename = (argc > 1) ? argv[1] : CGAL::data_file_path("meshes/pig.off");

  Surface_mesh sm;
  if(!PMP::IO::read_polygon_mesh(filename, sm) || sm.is_empty())
  {
    std::cerr << "Invalid input file." << std::endl;
    return EXIT_FAILURE;
  }

  CGAL::Real_timer timer;
  timer.start();

  // Compute the extreme points of the mesh, and then a tightly fitted oriented bounding box
  std::array<Point, 8> obb_points;
  CGAL::oriented_bounding_box(sm, obb_points,
                              CGAL::parameters::use_convex_hull(true));

  std::cout << "Elapsed time: " << timer.time() << std::endl;

  // Make a mesh out of the oriented bounding box
  Surface_mesh obb_sm;
  CGAL::make_hexahedron(obb_points[0], obb_points[1], obb_points[2], obb_points[3],
                        obb_points[4], obb_points[5], obb_points[6], obb_points[7], obb_sm);
  std::ofstream("obb.off") << obb_sm;
  //三角化多边形面
  PMP::triangulate_faces(obb_sm);
  std::ofstream("obb_triangle.off") << obb_sm;
  //计算体积
  std::cout << "Volume: " << PMP::volume(obb_sm) << std::endl;

  return EXIT_SUCCESS;
}