如何使用提升::uniform_on_sphere

How to use boost::uniform_on_sphere?

本文关键字：on sphere 何使用 uniform      更新时间：2023-10-16

我试图在单位球面上选择一个随机点，发现 boost 提供了正是这样做的分布。但是当我尝试使用它时，所有生成的值都nan.我不知道我做错了什么，你能开导我吗？这个小代码描述了我正在尝试做的事情：

#include <iostream>
#include <fstream>
#include <vector>
#include <boost/random/mersenne_twister.hpp>
#include <boost/random/uniform_on_sphere.hpp>
int main()
{
  boost::mt19937 gen;
  boost::uniform_on_sphere<float> dist(3);
  { // Seed from system random device
    std::ifstream rand_device("/dev/urandom");
    uint32_t seed;
    rand_device >> seed;
    gen.seed(seed);
  }
  while(1) {
    // Generate a point on a unit sphere
    std::vector<float> res = dist(gen);
    // Print the coordinates
    for(int i = 0; i < res.size(); ++i) {
      std::cout << res[i] << ' ';
    }
    std::cout << 'n';
  }
}

输出为：

nan nan nan 
nan nan nan 
nan nan nan 
nan nan nan

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我假设你使用的是Boost 1.49。在这种情况下，下面的方法有效。

这就是Boost有点复杂的地方。uniform_on_sphere的对象只是绘制点所需的一个组成部分，它是分布部分。您还需要按照以下工作.cpp文件的行创建一个boost::variate_generator。

请注意，这有我自己的包括使用系统时间来播种等。您应该能够对其进行修改以适合您。

// Standards, w/ctime to seed based on system time.
#include <iostream>
#include <fstream>
#include <vector>
#include <ctime>
// Boost. Requires variate_generator to actually draw the values.
#include <boost/random/mersenne_twister.hpp>
#include <boost/random/uniform_on_sphere.hpp>
#include <boost/random/variate_generator.hpp>

int main(){
    typedef boost::random::mt19937 gen_type;
    // You can seed this your way as well, but this is my quick and dirty way.
    gen_type rand_gen;
    rand_gen.seed(static_cast<unsigned int>(std::time(0)));
    // Create the distribution object.
    boost::uniform_on_sphere<float> unif_sphere(3);
    // This is what will actually supply drawn values.
    boost::variate_generator<gen_type&, boost::uniform_on_sphere<float> >    random_on_sphere(rand_gen, unif_sphere);
    // Now you can draw a vector of drawn coordinates as such:
    std::vector<float> random_sphere_point = random_on_sphere();
    // Print out the drawn sphere triple's values.
    for(int i = 0; i < random_sphere_point.size(); ++i) {
        std::cout << random_sphere_point.at(i) << ' ';
    }
    std::cout << 'n';
    return 0;
}

当我在控制台中运行它时，我得到的东西似乎是正确的：

ely@AMDESK:~/Desktop/Programming/C++/RandOnSphere$ g++ -I /usr/include/boost_1_49/ -L    /usr/include/boost_1_49/stage/lib randomOnSphere.cpp -o ros
ely@AMDESK:~/Desktop/Programming/C++/RandOnSphere$ ./ros 
0.876326 -0.0441729 0.479689 
ely@AMDESK:~/Desktop/Programming/C++/RandOnSphere$ ./ros 
-0.039037 -0.17792 0.98327 
ely@AMDESK:~/Desktop/Programming/C++/RandOnSphere$ ./ros 
-0.896734 0.419589 -0.14076
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