angleTo( v ) {

		const denominator = Math.sqrt( this.lengthSq() * v.lengthSq() );

		if ( denominator === 0 ) return Math.PI / 2;

		const theta = this.dot( v ) / denominator;

		// clamp, to handle numerical problems

		return Math.acos( clamp( theta, - 1, 1 ) );

	}
Returns the angle between the given vector and this instance in radians.

@param {Vector3} v - The vector to compute the angle with.
@return {number} The angle in radians.