【CGAL】Region_Growing检测圆柱，保存结果并输出圆柱体参数

说明

这篇博客以代码为主，使用CGAL中的region growing方法检测圆柱体。将不同的圆柱按不同颜色保存，并输出圆柱体的中心坐标、轴方向以及半径。
region growing的具体思想网上的文章已经有很多，可以参考这个。

代码展示

#include <CGAL/Point_set_3.h>
#include <CGAL/Point_set_3/IO.h>
#include <CGAL/Simple_cartesian.h>
#include <CGAL/Shape_detection/Region_growing/Region_growing.h>
#include <CGAL/IO/read_points.h>
#include <CGAL/property_map.h>
#include <CGAL/Shape_detection/Region_growing/Point_set.h>
#include <boost/iterator/function_output_iterator.hpp>
#include <CGAL/utils.h>
#include <fstream>

// 源文件
#define src_file_path "cylinder1_dense.ply"

// 检测结果分颜色保存
#define result_path "cylinder1_dense_result.ply"

// 参数保存
#define param_path "cylinder1_dense_param.txt"


// Typedefs.
using Kernel = CGAL::Simple_cartesian<double>;
using FT = Kernel::FT;
using Point_3 = Kernel::Point_3;
using Vector_3 = Kernel::Vector_3;
using Point_set = CGAL::Point_set_3<Point_3>;
using Point_map = typename Point_set::Point_map;
//using Normal_map = typename Point_set::Vector_map;
typedef std::pair<Point_3, Vector_3> Point_with_normal;
typedef std::vector<Point_with_normal> Pwn_vector;
using Neighbor_query = CGAL::Shape_detection::Point_set::K_neighbor_query_for_point_set<Point_set>;
using Region_type = CGAL::Shape_detection::Point_set::Least_squares_cylinder_fit_region_for_point_set<Point_set>;
using Region_growing = CGAL::Shape_detection::Region_growing<Neighbor_query, Region_type>;

void detect_and_save(Point_set& point_set, Neighbor_query& neighbor_query, Region_type& region_type)
{
    // Create an instance of the region growing class.
    Region_growing region_growing(
        point_set, neighbor_query, region_type);

    // Add maps to get a colored output.
    Point_set::Property_map<unsigned char>
        red = point_set.add_property_map<unsigned char>("red", 0).first,
        green = point_set.add_property_map<unsigned char>("green", 0).first,
        blue = point_set.add_property_map<unsigned char>("blue", 0).first;
    // Run the algorithm.
    //CGAL::Random random;
    std::size_t num_cylinders = 0;

    region_growing.detect(
    boost::make_function_output_iterator(
        [&](const std::pair< Region_type::Primitive, std::vector<typename Point_set::Index> >& region) {
            // Assign a random color to each region.
            const unsigned char r = static_cast<unsigned char>(rand() % 255);
            const unsigned char g = static_cast<unsigned char>(rand() % 255);
            const unsigned char b = static_cast<unsigned char>(rand() % 255);
            for (auto id : region.second) {
                put(red, id, r);
                put(green, id, g);
                put(blue, id, b);
            }
            ++num_cylinders;
        }
    )
);

    std::cout << "* number of found cylinders: " << num_cylinders << std::endl;
    // Save regions to a file.
    std::ofstream out(src_file_path);
    CGAL::IO::set_ascii_mode(out);
    out << point_set;
}

void detect_and_print_param(Point_set& point_set, Neighbor_query& neighbor_query, Region_type& region_type)
{
    // Create an instance of the region growing class.
    Region_growing region_growing(
        point_set, neighbor_query, region_type);

    std::vector<typename Region_growing::Primitive_and_region> regions;
    region_growing.detect(std::back_inserter(regions));

    // 打开输出文件
    std::ofstream outFile(param_path);

    for (size_t i = 0; i < regions.size(); i++)
    {
        const auto& primitive_and_region = regions[i];
        //const auto& region = primitive_and_region.second;
        const auto& cylinder_param = primitive_and_region.first;

        // 获取轴的方向
        const auto& dx = cylinder_param.axis.direction().dx();
        const auto& dy = cylinder_param.axis.direction().dy();
        const auto& dz = cylinder_param.axis.direction().dz();

        // 获取圆柱中心位置
        const auto& cx = cylinder_param.axis.point(0).x();
        const auto& cy = cylinder_param.axis.point(0).y();
        const auto& cz = cylinder_param.axis.point(0).z();

        // 获取圆柱半径
        const auto& r = cylinder_param.radius;

        outFile << r << " " << dx << " " << dy << " " << dz << " " << cx << " " << cy << " " << cz << "\n";

        std::cout << "圆柱半径：" << r << std::endl;
        std::cout << "圆柱轴方向：" << dx << ", " << dy << ", " << dz << std::endl;
        std::cout << "圆柱中心：" << cx << ", " << cy << ", " << cz << std::endl;
    }

    outFile.close();
}


int main(int argc, char** argv) {
    // Load ply data either from a local folder or a user-provided file.

    const std::string input_file = src_file_path;

    std::ifstream in(CGAL::data_file_path(input_file));
    CGAL::IO::set_ascii_mode(in);
    //CGAL::IO::set_binary_mode(in);
    if (!in) {
        std::cerr << "ERROR: cannot read the input file!" << std::endl;
        return EXIT_FAILURE;
    }
    Point_set point_set;
    in >> point_set;
    in.close();
    std::cout << "* number of input points: " << point_set.size() << std::endl;
    //assert(!is_default_input || point_set.size() == 1813);
    assert(point_set.has_normal_map()); // input should have normals
    // Default parameter values for the data file cuble.pwn.
    const std::size_t k = 10;
    const FT          max_distance = FT(1) / FT(500);
    const FT          max_angle = FT(60);
    const std::size_t min_region_size = 200;
    // Create instances of the classes Neighbor_query and Region_type.
    Neighbor_query neighbor_query = CGAL::Shape_detection::Point_set::make_k_neighbor_query(point_set, CGAL::parameters::k_neighbors(k));
    Region_type region_type = CGAL::Shape_detection::Point_set::make_least_squares_cylinder_fit_region(
        point_set,
        CGAL::parameters::
        maximum_distance(max_distance).
        maximum_angle(max_angle).
        minimum_region_size(min_region_size));
    
    // 检测圆柱，对属于不同圆柱的点赋予不同颜色
    //detect_and_save(point_set, neighbor_query, region_type);

    // 检测圆柱，输出每个圆柱的参数
    detect_and_print_param(point_set, neighbor_query, region_type);

    return EXIT_SUCCESS;
}