randomDirection() {

		// https://mathworld.wolfram.com/SpherePointPicking.html

		const theta = Math.random() * Math.PI * 2;
		const u = Math.random() * 2 - 1;
		const c = Math.sqrt( 1 - u * u );

		this.x = c * Math.cos( theta );
		this.y = u;
		this.z = c * Math.sin( theta );

		return this;

	}
Sets this vector to a uniformly random point on a unit sphere.

@return {Vector3} A reference to this vector.