copy( v ) {

		this.x = v.x;
		this.y = v.y;
		this.z = v.z;
		this.w = ( v.w !== undefined ) ? v.w : 1;

		return this;

	}
Copies the values of the given vector to this instance.

@param {Vector3|Vector4} v - The vector to copy.
@return {Vector4} A reference to this vector.