def METHOD_NAME(self):
    """returns the spherical coordinates from a cartesian coordinates
    using this formula:
        - http://www.math.montana.edu/frankw/ccp/multiworld/multipleIVP/spherical/body.htm#converting
    :rtype: (radius, zenith, azimuth)
    """
    eye = self.target.camera.eye - self.target.camera.center
    radius = math.sqrt(pow(eye.x, 2) + pow(eye.y, 2) + pow(eye.z, 2))
    s = math.sqrt(pow(eye.x, 2) + pow(eye.y, 2))
    if s == 0:
        s = 0.000000001
    r = radius
    if r == 0:
        r = 0.000000001
    angle_z = math.acos(eye.z / r)
    if eye.x < 0:
        angle_x = math.pi - math.asin(eye.y / s)
    else:
        angle_x = math.asin(eye.y / s)
    radius = radius / self.target.camera.get_z_eye()
    return radius, angle_z, angle_x