<!-- SOLUV · part 49 -->
erialization.
	 * @return {Object} A JSON object representing the serialized texture.
	 * @see {@link ObjectLoader#parse}
	 */
	toJSON( meta ) {

		const isRootObject = ( meta === undefined || typeof meta === 'string' );

		if ( ! isRootObject && meta.textures[ this.uuid ] !== undefined ) {

			return meta.textures[ this.uuid ];

		}

		const output = {

			metadata: {
				version: 4.7,
				type: 'Texture',
				generator: 'Texture.toJSON'
			},

			uuid: this.uuid,
			name: this.name,

			image: this.source.toJSON( meta ).uuid,

			mapping: this.mapping,
			channel: this.channel,

			repeat: [ this.repeat.x, this.repeat.y ],
			offset: [ this.offset.x, this.offset.y ],
			center: [ this.center.x, this.center.y ],
			rotation: this.rotation,

			wrap: [ this.wrapS, this.wrapT ],

			format: this.format,
			internalFormat: this.internalFormat,
			type: this.type,
			normalized: this.normalized,
			colorSpace: this.colorSpace,

			minFilter: this.minFilter,
			magFilter: this.magFilter,
			anisotropy: this.anisotropy,

			flipY: this.flipY,

			generateMipmaps: this.generateMipmaps,
			premultiplyAlpha: this.premultiplyAlpha,
			unpackAlignment: this.unpackAlignment

		};

		if ( Object.keys( this.userData ).length > 0 ) output.userData = this.userData;

		if ( ! isRootObject ) {

			meta.textures[ this.uuid ] = output;

		}

		return output;

	}

	/**
	 * Frees the GPU-related resources allocated by this instance. Call this
	 * method whenever this instance is no longer used in your app.
	 *
	 * @fires Texture#dispose
	 */
	dispose() {

		/**
		 * Fires when the texture has been disposed of.
		 *
		 * @event Texture#dispose
		 * @type {Object}
		 */
		this.dispatchEvent( { type: 'dispose' } );

	}

	/**
	 * Transforms the given uv vector with the textures uv transformation matrix.
	 *
	 * @param {Vector2} uv - The uv vector.
	 * @return {Vector2} The transformed uv vector.
	 */
	transformUv( uv ) {

		if ( this.mapping !== UVMapping ) return uv;

		uv.applyMatrix3( this.matrix );

		if ( uv.x < 0 || uv.x > 1 ) {

			switch ( this.wrapS ) {

				case RepeatWrapping:

					uv.x = uv.x - Math.floor( uv.x );
					break;

				case ClampToEdgeWrapping:

					uv.x = uv.x < 0 ? 0 : 1;
					break;

				case MirroredRepeatWrapping:

					if ( Math.abs( Math.floor( uv.x ) % 2 ) === 1 ) {

						uv.x = Math.ceil( uv.x ) - uv.x;

					} else {

						uv.x = uv.x - Math.floor( uv.x );

					}

					break;

			}

		}

		if ( uv.y < 0 || uv.y > 1 ) {

			switch ( this.wrapT ) {

				case RepeatWrapping:

					uv.y = uv.y - Math.floor( uv.y );
					break;

				case ClampToEdgeWrapping:

					uv.y = uv.y < 0 ? 0 : 1;
					break;

				case MirroredRepeatWrapping:

					if ( Math.abs( Math.floor( uv.y ) % 2 ) === 1 ) {

						uv.y = Math.ceil( uv.y ) - uv.y;

					} else {

						uv.y = uv.y - Math.floor( uv.y );

					}

					break;

			}

		}

		if ( this.flipY ) {

			uv.y = 1 - uv.y;

		}

		return uv;

	}

	/**
	 * Setting this property to `true` indicates the engine the texture
	 * must be updated in the next render. This triggers a texture upload
	 * to the GPU and ensures correct texture parameter configuration.
	 *
	 * @type {boolean}
	 * @default false
	 * @param {boolean} value
	 */
	set needsUpdate( value ) {

		if ( value === true ) {

			this.version ++;
			this.source.needsUpdate = true;

		}

	}

	/**
	 * Setting this property to `true` indicates the engine the PMREM
	 * must be regenerated.
	 *
	 * @type {boolean}
	 * @default false
	 * @param {boolean} value
	 */
	set needsPMREMUpdate( value ) {

		if ( value === true ) {

			this.pmremVersion ++;

		}

	}

}

/**
 * The default image for all textures.
 *
 * @static
 * @type {?Image}
 * @default null
 */
Texture.DEFAULT_IMAGE = null;

/**
 * The default mapping for all textures.
 *
 * @static
 * @type {number}
 * @default UVMapping
 */
Texture.DEFAULT_MAPPING = UVMapping;

/**
 * The default anisotropy value for all textures.
 *
 * @static
 * @type {number}
 * @default 1
 */
Texture.DEFAULT_ANISOTROPY = 1;

/**
 * Class representing a 4D vector. A 4D vector is an ordered quadruplet of numbers
 * (labeled x, y, z and w), which can be used to represent a number of things, such as:
 *
 * - A point in 4D space.
 * - A direction and length in 4D space. In three.js the length will
 * always be the Euclidean distance(straight-line distance) from `(0, 0, 0, 0)` to `(x, y, z, w)`
 * and the direction is also measured from `(0, 0, 0, 0)` towards `(x, y, z, w)`.
 * - Any arbitrary ordered quadruplet of numbers.
 *
 * There are other things a 4D vector can be used to represent, however these
 * are the most common uses in *three.js*.
 *
 * Iterating through a vector instance will yield its components `(x, y, z, w)` in
 * the corresponding order.
 * ```js
 * const a = new THREE.Vector4( 0, 1, 0, 0 );
 *
 * //no arguments; will be initialised to (0, 0, 0, 1)
 * const b = new THREE.Vector4( );
 *
 * const d = a.dot( b );
 * ```
 */
class Vector4 {