You can look up the formulas e.g. here
http://en.wikipedia.org/wiki/Spherical_coordinate_system
and it's straightforward to implement:
/******************************//**
* \brief Conversion from cartesian to spherical coordinates (if the
* resulting radius is 0 also the azimutal and inclination
* angles get set to 0).
*
* @param r Reference to return the radius
* @param theta Reference to return the inclination angle (in radian)
* @param phi Reference to return the azimutal angle (in radian)
* @param x x coordinate
* @param y y coordinate
* @param z z coordinate
******************************/
void
cartesianToSpherical( double & r,
double & theta,
double & phi,
double x,
double y,
double z )
{
if ( ( r = sqrt( x * x + y * y + z * z ) ) != 0.0 )
{
theta = acos( z / r );
phi = atan2( y, x );
}
else
theta = phi = 0.0;
}
/******************************//**
* \brief Conversion from spherical to cartesian coordinates
*
* @param x Reference to return the x coordinate
* @param y Reference to return the y coordinate
* @param z Reference to return the z coordinate
* @param r Radius (must be non-negative)
* @param theta Inclination angle (in radian)
* @param phi Azimutal angle (in radian)
******************************/
void
sphericalToCartesian( double & x,
double & y,
double & z,
double r,
double theta,
double phi )
{
if ( r < 0.0 )
throw "Negative radius in sphericalToCartesian()";
x = r * sin( theta ) * cos( phi );
y = r * sin( theta ) * sin( phi );
z = r * cos( theta );
}
Regards, Jens
