ceph/src/boost/libs/math/example/catmull_rom_example.cpp

   1 // Copyright Nick Thompson, 2017
   2
   3 // Distributed under the Boost Software License, Version 1.0.
   4 // (See accompanying file LICENSE_1_0.txt or
   5 // copy at http://www.boost.org/LICENSE_1_0.txt).
   6
   7 #include <iostream>
   8 #include <vector>
   9 #include <array>
  10 #include <cmath>
  11 #include <boost/math/interpolators/catmull_rom.hpp>
  12 #include <boost/math/constants/constants.hpp>
  13
  14 using std::sin;
  15 using std::cos;
  16 using boost::math::catmull_rom;
  17
  18 int main()
  19 {
  20     std::cout << "This shows how to use Boost's Catmull-Rom spline to create an Archimedean spiral.\n";
  21
  22     // The Archimedean spiral is given by r = a*theta. We have set a = 1.
  23     std::vector<std::array<double, 2>> spiral_points(500);
  24     double theta_max = boost::math::constants::pi<double>();
  25     for (size_t i = 0; i < spiral_points.size(); ++i)
  26     {
  27         double theta = ((double) i/ (double) spiral_points.size())*theta_max;
  28         spiral_points[i] = {theta*cos(theta), theta*sin(theta)};
  29     }
  30
  31     auto archimedean = catmull_rom<std::array<double,2>>(std::move(spiral_points));
  32     double max_s = archimedean.max_parameter();
  33     std::cout << "Max s = " << max_s << std::endl;
  34     for (double s = 0; s < max_s; s += 0.01)
  35     {
  36         auto p = archimedean(s);
  37         double x = p[0];
  38         double y = p[1];
  39         double r = sqrt(x*x + y*y);
  40         double theta = atan2(y/r, x/r);
  41         std::cout << "r = " << r << ", theta = " << theta << ", r - theta = " << r - theta << std::endl;
  42     }
  43
  44     return 0;
  45 }