function Spherical( radius, phi, theta ) {

	this.radius = ( radius !== undefined ) ? radius : 1.0;
	this.phi = ( phi !== undefined ) ? phi : 0; // polar angle
	this.theta = ( theta !== undefined ) ? theta : 0; // azimuthal angle

	return this;

}
@author bhouston / http://clara.io
@author WestLangley / http://github.com/WestLangley

Ref: https://en.wikipedia.org/wiki/Spherical_coordinate_system

The polar angle (phi) is measured from the positive y-axis. The positive y-axis is up.
The azimuthal angle (theta) is measured from the positive z-axiz.