\( \newcommand{\E}{\mathrm{E}} \) \( \newcommand{\A}{\mathrm{A}} \) \( \newcommand{\R}{\mathrm{R}} \) \( \newcommand{\N}{\mathrm{N}} \) \( \newcommand{\Q}{\mathrm{Q}} \) \( \newcommand{\Z}{\mathrm{Z}} \) \( \def\ccSum #1#2#3{ \sum_{#1}^{#2}{#3} } \def\ccProd #1#2#3{ \sum_{#1}^{#2}{#3} }\)

CGAL 4.8 - Point Set Shape Detection

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Point_set_shape_detection_3/efficient_RANSAC_point_access.cpp
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/IO/read_xyz_points.h>
#include <CGAL/Point_with_normal_3.h>
#include <CGAL/property_map.h>
#include <CGAL/Timer.h>
#include <CGAL/number_utils.h>
#include <CGAL/Shape_detection_3.h>
#include <iostream>
#include <fstream>
// Type declarations
typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;
typedef Kernel::FT FT;
typedef std::pair<Kernel::Point_3, Kernel::Vector_3> Point_with_normal;
typedef std::vector<Point_with_normal> Pwn_vector;
typedef CGAL::First_of_pair_property_map<Point_with_normal> Point_map;
typedef CGAL::Second_of_pair_property_map<Point_with_normal> Normal_map;
// In Efficient_RANSAC_traits the basic types, i.e., Point and Vector types
// as well as iterator type and property maps, are defined.
typedef CGAL::Shape_detection_3::Efficient_RANSAC_traits<Kernel,
Pwn_vector, Point_map, Normal_map> Traits;
typedef CGAL::Shape_detection_3::Efficient_RANSAC<Traits> Efficient_ransac;
typedef CGAL::Shape_detection_3::Plane<Traits> Plane;
int main()
{
// Points with normals.
Pwn_vector points;
// Loads point set from a file.
// read_xyz_points_and_normals takes an OutputIterator for storing the points
// and a property map to store the normal vector with each point.
std::ifstream stream("data/cube.pwn");
if (!stream ||
!CGAL::read_xyz_points_and_normals(stream,
std::back_inserter(points),
Point_map(),
Normal_map()))
{
std::cerr << "Error: cannot read file cube.pwn" << std::endl;
return EXIT_FAILURE;
}
// Instantiates shape detection engine.
Efficient_ransac ransac;
// Provides the input data.
ransac.set_input(points);
// Registers detection of planes
ransac.add_shape_factory<Plane>();
// Measures time before setting up the shape detection.
CGAL::Timer time;
time.start();
// Build internal data structures.
ransac.preprocess();
// Measures time after preprocessing.
time.stop();
std::cout << "preprocessing took: " << time.time() * 1000 << "ms" << std::endl;
// Perform detection several times and choose result with highest coverage.
Efficient_ransac::Shape_range shapes = ransac.shapes();
FT best_coverage = 0;
for (size_t i = 0;i<3;i++) {
// Reset timer.
time.reset();
time.start();
// Detects shapes.
ransac.detect();
// Measures time after detection.
time.stop();
// Compute coverage, i.e. ratio of the points assigned to a shape.
FT coverage = FT(points.size() - ransac.number_of_unassigned_points())
/ FT(points.size());
// Prints number of assigned shapes and unsassigned points.
std::cout << "time: " << time.time() * 1000 << "ms" << std::endl;
std::cout << ransac.shapes().end() - ransac.shapes().begin() << " primitives, "
<< coverage << " coverage" << std::endl;
// Choose result with highest coverage.
if (coverage > best_coverage) {
best_coverage = coverage;
// Efficient_ransac::shapes() provides
// an iterator range to the detected shapes.
shapes = ransac.shapes();
}
}
Efficient_ransac::Shape_range::iterator it = shapes.begin();
while (it != shapes.end()) {
boost::shared_ptr<Efficient_ransac::Shape> shape = *it;
// Using Shape_base::info() for printing
// the parameters of the detected shape.
std::cout << (*it)->info();
// Sums distances of points to detected shapes.
FT sum_distances = 0;
// Iterates through point indices assigned to each detected shape.
std::vector<std::size_t>::const_iterator
index_it = (*it)->indices_of_assigned_points().begin();
while (index_it != (*it)->indices_of_assigned_points().end()) {
// Retrieves point
const Point_with_normal &p = *(points.begin() + (*index_it));
// Adds Euclidean distance between point and shape.
sum_distances += CGAL::sqrt((*it)->squared_distance(p.first));
// Proceeds with next point.
index_it++;
}
// Computes and prints average distance.
FT average_distance = sum_distances / shape->indices_of_assigned_points().size();
std::cout << " average distance: " << average_distance << std::endl;
// Proceeds with next detected shape.
it++;
}
return EXIT_SUCCESS;
}