title: How to project a point on to a sphere
body: <p>If i have a point (x,y,z) how to project it on to a sphere(x0,y0,z0,radius) (on its surface).
  My input will be the coordinates of point and sphere.
  The output should be the coordinates of the projected point on sphere.</p>
  
  <p>Just convert from cartesian to spherical coordinates?</p>