title: spherical harmonic function in boost
body: <p>I would like to use spherical harmonics to represent a spherical function. I found out that the boost library provides functionality to generate the basis functions, which can be found at </p>
  
  <blockquote>
    <p>boost/math/special_functions/spheric_harmonic.hpp.</p>
  </blockquote>
  
  <p>The prototype is </p>
  
  <pre><code>spherical_harmonic_r(unsigned n, int m, T1 theta, T2 phi, const Policy&amp;);
  </code></pre>
  
  <p>I want to figure out the meaning of phi. Imagine a right-handed coordinate system same as used in OpenGL(+Y up, +X right, +Z out), is phi the angle that starts from +Z and goes counter-clockwise as seen from +Y.</p>