constructor( radius = 1, phi = 0, theta = 0 ) {

    		this.radius = radius;
    		this.phi = phi; // polar angle
    		this.theta = theta; // azimuthal angle

    		return this;

    	}
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-axis.