<!-- SOLUV · part 35 -->
labeled x, y and z), which can be used to represent a number of things, such as:
 *
 * - A point in 3D space.
 * - A direction and length in 3D space. In three.js the length will
 * always be the Euclidean distance(straight-line distance) from `(0, 0, 0)` to `(x, y, z)`
 * and the direction is also measured from `(0, 0, 0)` towards `(x, y, z)`.
 * - Any arbitrary ordered triplet of numbers.
 *
 * There are other things a 3D vector can be used to represent, such as
 * momentum vectors and so on, however these are the most
 * common uses in three.js.
 *
 * Iterating through a vector instance will yield its components `(x, y, z)` in
 * the corresponding order.
 * ```js
 * const a = new THREE.Vector3( 0, 1, 0 );
 *
 * //no arguments; will be initialised to (0, 0, 0)
 * const b = new THREE.Vector3( );
 *
 * const d = a.distanceTo( b );
 * ```
 */
class Vector3 {

	static {

		/**
		 * This flag can be used for type testing.
		 *
		 * @type {boolean}
		 * @readonly
		 * @default true
		 */
		Vector3.prototype.isVector3 = true;

	}

	/**
	 * Constructs a new 3D vector.
	 *
	 * @param {number} [x=0] - The x value of this vector.
	 * @param {number} [y=0] - The y value of this vector.
	 * @param {number} [z=0] - The z value of this vector.
	 */
	constructor( x = 0, y = 0, z = 0 ) {

		/**
		 * The x value of this vector.
		 *
		 * @type {number}
		 */
		this.x = x;

		/**
		 * The y value of this vector.
		 *
		 * @type {number}
		 */
		this.y = y;

		/**
		 * The z value of this vector.
		 *
		 * @type {number}
		 */
		this.z = z;

	}

	/**
	 * Sets the vector components.
	 *
	 * @param {number} x - The value of the x component.
	 * @param {number} y - The value of the y component.
	 * @param {number} z - The value of the z component.
	 * @return {Vector3} A reference to this vector.
	 */
	set( x, y, z ) {

		if ( z === undefined ) z = this.z; // sprite.scale.set(x,y)

		this.x = x;
		this.y = y;
		this.z = z;

		return this;

	}

	/**
	 * Sets the vector components to the same value.
	 *
	 * @param {number} scalar - The value to set for all vector components.
	 * @return {Vector3} A reference to this vector.
	 */
	setScalar( scalar ) {

		this.x = scalar;
		this.y = scalar;
		this.z = scalar;

		return this;

	}

	/**
	 * Sets the vector's x component to the given value.
	 *
	 * @param {number} x - The value to set.
	 * @return {Vector3} A reference to this vector.
	 */
	setX( x ) {

		this.x = x;

		return this;

	}

	/**
	 * Sets the vector's y component to the given value.
	 *
	 * @param {number} y - The value to set.
	 * @return {Vector3} A reference to this vector.
	 */
	setY( y ) {

		this.y = y;

		return this;

	}

	/**
	 * Sets the vector's z component to the given value.
	 *
	 * @param {number} z - The value to set.
	 * @return {Vector3} A reference to this vector.
	 */
	setZ( z ) {

		this.z = z;

		return this;

	}

	/**
	 * Allows to set a vector component with an index.
	 *
	 * @param {number} index - The component index. `0` equals to x, `1` equals to y, `2` equals to z.
	 * @param {number} value - The value to set.
	 * @return {Vector3} A reference to this vector.
	 */
	setComponent( index, value ) {

		switch ( index ) {

			case 0: this.x = value; break;
			case 1: this.y = value; break;
			case 2: this.z = value; break;
			default: throw new Error( 'THREE.Vector3: index is out of range: ' + index );

		}

		return this;

	}

	/**
	 * Returns the value of the vector component which matches the given index.
	 *
	 * @param {number} index - The component index. `0` equals to x, `1` equals to y, `2` equals to z.
	 * @return {number} A vector component value.
	 */
	getComponent( index ) {

		switch ( index ) {

			case 0: return this.x;
			case 1: return this.y;
			case 2: return this.z;
			default: throw new Error( 'THREE.Vector3: index is out of range: ' + index );

		}

	}

	/**
	 * Returns a new vector with copied values from this instance.
	 *
	 * @return {Vector3} A clone of this instance.
	 */
	clone() {

		return new this.constructor( this.x, this.y, this.z );

	}

	/**
	 * Copies the values of the given vector to this instance.
	 *
	 * @param {Vector3} v - The vector to copy.
	 * @return {Vector3} A reference to this vector.
	 */
	copy( v ) {

		this.x = v.x;
		this.y = v.y;
		this.z = v.z;

		return this;

	}

	/**
	 * Adds the given vector to this instance.
	 *
	 * @param {Vector3} v - The vector to add.
	 * @return {Vector3} A reference to this vector.
	 */
	add( v ) {

		this.x += v.x;
		this.y += v.y;
		this.z += v.z;

		return this;

	}

	/**
	 * Adds the given scalar value to all components of this instance.
	 *
	 * @param {number} s - The scalar to add.
	 * @return {Vector3} A reference to this vector.
	 */
	addScalar( s ) {

		this.x += s;
		this.y += s;
		this.z += s;

		return this;

	}

	/**
	 * Adds the given vectors and stores the result in this instance.
	 *
	 * @param {Vector3} a - The first vector.
	 * @param {Vector3} b - The second vector.
	 * @r