text: ( function () {
  
  	class GLTFExporter {
  
  		constructor() {
  
  			this.pluginCallbacks = [];
  			this.register( function ( writer ) {
  
  				return new GLTFLightExtension( writer );
  
  			} );
  			this.register( function ( writer ) {
  
  				return new GLTFMaterialsUnlitExtension( writer );
  
  			} );
  			this.register( function ( writer ) {
  
  				return new GLTFMaterialsPBRSpecularGlossiness( writer );
  
  			} );
  
  		}
  
  		register( callback ) {
  
  			if ( this.pluginCallbacks.indexOf( callback ) === - 1 ) {
  
  				this.pluginCallbacks.push( callback );
  
  			}
  
  			return this;
  
  		}
  
  		unregister( callback ) {
  
  			if ( this.pluginCallbacks.indexOf( callback ) !== - 1 ) {
  
  				this.pluginCallbacks.splice( this.pluginCallbacks.indexOf( callback ), 1 );
  
  			}
  
  			return this;
  
  		}
  		/**
     * Parse scenes and generate GLTF output
     * @param  {Scene or [THREE.Scenes]} input   THREE.Scene or Array of THREE.Scenes
     * @param  {Function} onDone  Callback on completed
     * @param  {Object} options options
     */
  
  
  		parse( input, onDone, options ) {
  
  			const writer = new GLTFWriter();
  			const plugins = [];
  
  			for ( let i = 0, il = this.pluginCallbacks.length; i < il; i ++ ) {
  
  				plugins.push( this.pluginCallbacks[ i ]( writer ) );
  
  			}
  
  			writer.setPlugins( plugins );
  			writer.write( input, onDone, options );
  
  		}
  
  	} //------------------------------------------------------------------------------
  	// Constants
  	//------------------------------------------------------------------------------
  
  
  	const WEBGL_CONSTANTS = {
  		POINTS: 0x0000,
  		LINES: 0x0001,
  		LINE_LOOP: 0x0002,
  		LINE_STRIP: 0x0003,
  		TRIANGLES: 0x0004,
  		TRIANGLE_STRIP: 0x0005,
  		TRIANGLE_FAN: 0x0006,
  		UNSIGNED_BYTE: 0x1401,
  		UNSIGNED_SHORT: 0x1403,
  		FLOAT: 0x1406,
  		UNSIGNED_INT: 0x1405,
  		ARRAY_BUFFER: 0x8892,
  		ELEMENT_ARRAY_BUFFER: 0x8893,
  		NEAREST: 0x2600,
  		LINEAR: 0x2601,
  		NEAREST_MIPMAP_NEAREST: 0x2700,
  		LINEAR_MIPMAP_NEAREST: 0x2701,
  		NEAREST_MIPMAP_LINEAR: 0x2702,
  		LINEAR_MIPMAP_LINEAR: 0x2703,
  		CLAMP_TO_EDGE: 33071,
  		MIRRORED_REPEAT: 33648,
  		REPEAT: 10497
  	};
  	const THREE_TO_WEBGL = {};
  	THREE_TO_WEBGL[ THREE.NearestFilter ] = WEBGL_CONSTANTS.NEAREST;
  	THREE_TO_WEBGL[ THREE.NearestMipmapNearestFilter ] = WEBGL_CONSTANTS.NEAREST_MIPMAP_NEAREST;
  	THREE_TO_WEBGL[ THREE.NearestMipmapLinearFilter ] = WEBGL_CONSTANTS.NEAREST_MIPMAP_LINEAR;
  	THREE_TO_WEBGL[ THREE.LinearFilter ] = WEBGL_CONSTANTS.LINEAR;
  	THREE_TO_WEBGL[ THREE.LinearMipmapNearestFilter ] = WEBGL_CONSTANTS.LINEAR_MIPMAP_NEAREST;
  	THREE_TO_WEBGL[ THREE.LinearMipmapLinearFilter ] = WEBGL_CONSTANTS.LINEAR_MIPMAP_LINEAR;
  	THREE_TO_WEBGL[ THREE.ClampToEdgeWrapping ] = WEBGL_CONSTANTS.CLAMP_TO_EDGE;
  	THREE_TO_WEBGL[ THREE.RepeatWrapping ] = WEBGL_CONSTANTS.REPEAT;
  	THREE_TO_WEBGL[ THREE.MirroredRepeatWrapping ] = WEBGL_CONSTANTS.MIRRORED_REPEAT;
  	const PATH_PROPERTIES = {
  		scale: 'scale',
  		position: 'translation',
  		quaternion: 'rotation',
  		morphTargetInfluences: 'weights'
  	}; // GLB constants
  	// https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#glb-file-format-specification
  
  	const GLB_HEADER_BYTES = 12;
  	const GLB_HEADER_MAGIC = 0x46546C67;
  	const GLB_VERSION = 2;
  	const GLB_CHUNK_PREFIX_BYTES = 8;
  	const GLB_CHUNK_TYPE_JSON = 0x4E4F534A;
  	const GLB_CHUNK_TYPE_BIN = 0x004E4942; //------------------------------------------------------------------------------
  	// Utility functions
  	//------------------------------------------------------------------------------
  
  	/**
   * Compare two arrays
   * @param  {Array} array1 Array 1 to compare
   * @param  {Array} array2 Array 2 to compare
   * @return {Boolean}        Returns true if both arrays are equal
   */
  
  	function equalArray( array1, array2 ) {
  
  		return array1.length === array2.length && array1.every( function ( element, index ) {
  
  			return element === array2[ index ];
  
  		} );
  
  	}
  	/**
   * Converts a string to an ArrayBuffer.
   * @param  {string} text
   * @return {ArrayBuffer}
   */
  
  
  	function stringToArrayBuffer( text ) {
  
  		if ( window.TextEncoder !== undefined ) {
  
  			return new TextEncoder().encode( text ).buffer;
  
  		}
  
  		const array = new Uint8Array( new ArrayBuffer( text.length ) );
  
  		for ( let i = 0, il = text.length; i < il; i ++ ) {
  
  			const value = text.charCodeAt( i ); // Replacing multi-byte character with space(0x20).
  
  			array[ i ] = value > 0xFF ? 0x20 : value;
  
  		}
  
  		return array.buffer;
  
  	}
  	/**
   * Is identity matrix
   *
   * @param {Matrix4} matrix
   * @returns {Boolean} Returns true, if parameter is identity matrix
   */
  
  
  	function isIdentityMatrix( matrix ) {
  
  		return equalArray( matrix.elements, [ 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1 ] );
  
  	}
  	/**
   * Get the min and max vectors from the given attribute
   * @param  {BufferAttribute} attribute Attribute to find the min/max in range from start to start + count
   * @param  {Integer} start
   * @param  {Integer} count
   * @return {Object} Object containing the `min` and `max` values (As an array of attribute.itemSize components)
   */
  
  
  	function getMinMax( attribute, start, count ) {
  
  		const output = {
  			min: new Array( attribute.itemSize ).fill( Number.POSITIVE_INFINITY ),
  			max: new Array( attribute.itemSize ).fill( Number.NEGATIVE_INFINITY )
  		};
  
  		for ( let i = start; i < start + count; i ++ ) {
  
  			for ( let a = 0; a < attribute.itemSize; a ++ ) {
  
  				let value;
  
  				if ( attribute.itemSize > 4 ) {
  
  					// no support for interleaved data for itemSize > 4
  					value = attribute.array[ i * attribute.itemSize + a ];
  
  				} else {
  
  					if ( a === 0 ) value = attribute.getX( i ); else if ( a === 1 ) value = attribute.getY( i ); else if ( a === 2 ) value = attribute.getZ( i ); else if ( a === 3 ) value = attribute.getW( i );
  
  				}
  
  				output.min[ a ] = Math.min( output.min[ a ], value );
  				output.max[ a ] = Math.max( output.max[ a ], value );
  
  			}
  
  		}
  
  		return output;
  
  	}
  	/**
   * Get the required size + padding for a buffer, rounded to the next 4-byte boundary.
   * https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#data-alignment
   *
   * @param {Integer} bufferSize The size the original buffer.
   * @returns {Integer} new buffer size with required padding.
   *
   */
  
  
  	function getPaddedBufferSize( bufferSize ) {
  
  		return Math.ceil( bufferSize / 4 ) * 4;
  
  	}
  	/**
   * Returns a buffer aligned to 4-byte boundary.
   *
   * @param {ArrayBuffer} arrayBuffer Buffer to pad
   * @param {Integer} paddingByte (Optional)
   * @returns {ArrayBuffer} The same buffer if it's already aligned to 4-byte boundary or a new buffer
   */
  
  
  	function getPaddedArrayBuffer( arrayBuffer, paddingByte = 0 ) {
  
  		const paddedLength = getPaddedBufferSize( arrayBuffer.byteLength );
  
  		if ( paddedLength !== arrayBuffer.byteLength ) {
  
  			const array = new Uint8Array( paddedLength );
  			array.set( new Uint8Array( arrayBuffer ) );
  
  			if ( paddingByte !== 0 ) {
  
  				for ( let i = arrayBuffer.byteLength; i < paddedLength; i ++ ) {
  
  					array[ i ] = paddingByte;
  
  				}
  
  			}
  
  			return array.buffer;
  
  		}
  
  		return arrayBuffer;
  
  	}
  
  	let cachedCanvas = null;
  	/**
   * Writer
   */
  
  	class GLTFWriter {
  
  		constructor() {
  
  			this.plugins = [];
  			this.options = {};
  			this.pending = [];
  			this.buffers = [];
  			this.byteOffset = 0;
  			this.buffers = [];
  			this.nodeMap = new Map();
  			this.skins = [];
  			this.extensionsUsed = {};
  			this.uids = new Map();
  			this.uid = 0;
  			this.json = {
  				asset: {
  					version: '2.0',
  					generator: 'THREE.GLTFExporter'
  				}
  			};
  			this.cache = {
  				meshes: new Map(),
  				attributes: new Map(),
  				attributesNormalized: new Map(),
  				materials: new Map(),
  				textures: new Map(),
  				images: new Map()
  			};
  
  		}
  
  		setPlugins( plugins ) {
  
  			this.plugins = plugins;
  
  		}
  		/**
     * Parse scenes and generate GLTF output
     * @param  {Scene or [THREE.Scenes]} input   THREE.Scene or Array of THREE.Scenes
     * @param  {Function} onDone  Callback on completed
     * @param  {Object} options options
     */
  
  
  		write( input, onDone, options ) {
  
  			this.options = Object.assign( {}, {
  				// default options
  				binary: false,
  				trs: false,
  				onlyVisible: true,
  				truncateDrawRange: true,
  				embedImages: true,
  				maxTextureSize: Infinity,
  				animations: [],
  				includeCustomExtensions: false
  			}, options );
  
  			if ( this.options.animations.length > 0 ) {
  
  				// Only TRS properties, and not matrices, may be targeted by animation.
  				this.options.trs = true;
  
  			}
  
  			this.processInput( input );
  			const writer = this;
  			Promise.all( this.pending ).then( function () {
  
  				const buffers = writer.buffers;
  				const json = writer.json;
  				const options = writer.options;
  				const extensionsUsed = writer.extensionsUsed; // Merge buffers.
  
  				const blob = new Blob( buffers, {
  					type: 'application/octet-stream'
  				} ); // Declare extensions.
  
  				const extensionsUsedList = Object.keys( extensionsUsed );
  				if ( extensionsUsedList.length > 0 ) json.extensionsUsed = extensionsUsedList; // Update bytelength of the single buffer.
  
  				if ( json.buffers && json.buffers.length > 0 ) json.buffers[ 0 ].byteLength = blob.size;
  
  				if ( options.binary === true ) {
  
  					// https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#glb-file-format-specification
  					const reader = new window.FileReader();
  					reader.readAsArrayBuffer( blob );
  
  					reader.onloadend = function () {
  
  						// Binary chunk.
  						const binaryChunk = getPaddedArrayBuffer( reader.result );
  						const binaryChunkPrefix = new DataView( new ArrayBuffer( GLB_CHUNK_PREFIX_BYTES ) );
  						binaryChunkPrefix.setUint32( 0, binaryChunk.byteLength, true );
  						binaryChunkPrefix.setUint32( 4, GLB_CHUNK_TYPE_BIN, true ); // JSON chunk.
  
  						const jsonChunk = getPaddedArrayBuffer( stringToArrayBuffer( JSON.stringify( json ) ), 0x20 );
  						const jsonChunkPrefix = new DataView( new ArrayBuffer( GLB_CHUNK_PREFIX_BYTES ) );
  						jsonChunkPrefix.setUint32( 0, jsonChunk.byteLength, true );
  						jsonChunkPrefix.setUint32( 4, GLB_CHUNK_TYPE_JSON, true ); // GLB header.
  
  						const header = new ArrayBuffer( GLB_HEADER_BYTES );
  						const headerView = new DataView( header );
  						headerView.setUint32( 0, GLB_HEADER_MAGIC, true );
  						headerView.setUint32( 4, GLB_VERSION, true );
  						const totalByteLength = GLB_HEADER_BYTES + jsonChunkPrefix.byteLength + jsonChunk.byteLength + binaryChunkPrefix.byteLength + binaryChunk.byteLength;
  						headerView.setUint32( 8, totalByteLength, true );
  						const glbBlob = new Blob( [ header, jsonChunkPrefix, jsonChunk, binaryChunkPrefix, binaryChunk ], {
  							type: 'application/octet-stream'
  						} );
  						const glbReader = new window.FileReader();
  						glbReader.readAsArrayBuffer( glbBlob );
  
  						glbReader.onloadend = function () {
  
  							onDone( glbReader.result );
  
  						};
  
  					};
  
  				} else {
  
  					if ( json.buffers && json.buffers.length > 0 ) {
  
  						const reader = new window.FileReader();
  						reader.readAsDataURL( blob );
  
  						reader.onloadend = function () {
  
  							const base64data = reader.result;
  							json.buffers[ 0 ].uri = base64data;
  							onDone( json );
  
  						};
  
  					} else {
  
  						onDone( json );
  
  					}
  
  				}
  
  			} );
  
  		}
  		/**
     * Serializes a userData.
     *
     * @param {THREE.Object3D|THREE.Material} object
     * @param {Object} objectDef
     */
  
  
  		serializeUserData( object, objectDef ) {
  
  			if ( Object.keys( object.userData ).length === 0 ) return;
  			const options = this.options;
  			const extensionsUsed = this.extensionsUsed;
  
  			try {
  
  				const json = JSON.parse( JSON.stringify( object.userData ) );
  
  				if ( options.includeCustomExtensions && json.gltfExtensions ) {
  
  					if ( objectDef.extensions === undefined ) objectDef.extensions = {};
  
  					for ( const extensionName in json.gltfExtensions ) {
  
  						objectDef.extensions[ extensionName ] = json.gltfExtensions[ extensionName ];
  						extensionsUsed[ extensionName ] = true;
  
  					}
  
  					delete json.gltfExtensions;
  
  				}
  
  				if ( Object.keys( json ).length > 0 ) objectDef.extras = json;
  
  			} catch ( error ) {
  
  				console.warn( 'THREE.GLTFExporter: userData of \'' + object.name + '\' ' + 'won\'t be serialized because of JSON.stringify error - ' + error.message );
  
  			}
  
  		}
  		/**
     * Assign and return a temporal unique id for an object
     * especially which doesn't have .uuid
     * @param  {Object} object
     * @return {Integer}
     */
  
  
  		getUID( object ) {
  
  			if ( ! this.uids.has( object ) ) this.uids.set( object, this.uid ++ );
  			return this.uids.get( object );
  
  		}
  		/**
     * Checks if normal attribute values are normalized.
     *
     * @param {BufferAttribute} normal
     * @returns {Boolean}
     */
  
  
  		isNormalizedNormalAttribute( normal ) {
  
  			const cache = this.cache;
  			if ( cache.attributesNormalized.has( normal ) ) return false;
  			const v = new THREE.Vector3();
  
  			for ( let i = 0, il = normal.count; i < il; i ++ ) {
  
  				// 0.0005 is from glTF-validator
  				if ( Math.abs( v.fromBufferAttribute( normal, i ).length() - 1.0 ) > 0.0005 ) return false;
  
  			}
  
  			return true;
  
  		}
  		/**
     * Creates normalized normal buffer attribute.
     *
     * @param {BufferAttribute} normal
     * @returns {BufferAttribute}
     *
     */
  
  
  		createNormalizedNormalAttribute( normal ) {
  
  			const cache = this.cache;
  			if ( cache.attributesNormalized.has( normal ) ) return cache.attributesNormalized.get( normal );
  			const attribute = normal.clone();
  			const v = new THREE.Vector3();
  
  			for ( let i = 0, il = attribute.count; i < il; i ++ ) {
  
  				v.fromBufferAttribute( attribute, i );
  
  				if ( v.x === 0 && v.y === 0 && v.z === 0 ) {
  
  					// if values can't be normalized set (1, 0, 0)
  					v.setX( 1.0 );
  
  				} else {
  
  					v.normalize();
  
  				}
  
  				attribute.setXYZ( i, v.x, v.y, v.z );
  
  			}
  
  			cache.attributesNormalized.set( normal, attribute );
  			return attribute;
  
  		}
  		/**
     * Applies a texture transform, if present, to the map definition. Requires
     * the KHR_texture_transform extension.
     *
     * @param {Object} mapDef
     * @param {THREE.Texture} texture
     */
  
  
  		applyTextureTransform( mapDef, texture ) {
  
  			let didTransform = false;
  			const transformDef = {};
  
  			if ( texture.offset.x !== 0 || texture.offset.y !== 0 ) {
  
  				transformDef.offset = texture.offset.toArray();
  				didTransform = true;
  
  			}
  
  			if ( texture.rotation !== 0 ) {
  
  				transformDef.rotation = texture.rotation;
  				didTransform = true;
  
  			}
  
  			if ( texture.repeat.x !== 1 || texture.repeat.y !== 1 ) {
  
  				transformDef.scale = texture.repeat.toArray();
  				didTransform = true;
  
  			}
  
  			if ( didTransform ) {
  
  				mapDef.extensions = mapDef.extensions || {};
  				mapDef.extensions[ 'KHR_texture_transform' ] = transformDef;
  				this.extensionsUsed[ 'KHR_texture_transform' ] = true;
  
  			}
  
  		}
  		/**
     * Process a buffer to append to the default one.
     * @param  {ArrayBuffer} buffer
     * @return {Integer}
     */
  
  
  		processBuffer( buffer ) {
  
  			const json = this.json;
  			const buffers = this.buffers;
  			if ( ! json.buffers ) json.buffers = [ {
  				byteLength: 0
  			} ]; // All buffers are merged before export.
  
  			buffers.push( buffer );
  			return 0;
  
  		}
  		/**
     * Process and generate a BufferView
     * @param  {BufferAttribute} attribute
     * @param  {number} componentType
     * @param  {number} start
     * @param  {number} count
     * @param  {number} target (Optional) Target usage of the BufferView
     * @return {Object}
     */
  
  
  		processBufferView( attribute, componentType, start, count, target ) {
  
  			const json = this.json;
  			if ( ! json.bufferViews ) json.bufferViews = []; // Create a new dataview and dump the attribute's array into it
  
  			let componentSize;
  
  			if ( componentType === WEBGL_CONSTANTS.UNSIGNED_BYTE ) {
  
  				componentSize = 1;
  
  			} else if ( componentType === WEBGL_CONSTANTS.UNSIGNED_SHORT ) {
  
  				componentSize = 2;
  
  			} else {
  
  				componentSize = 4;
  
  			}
  
  			const byteLength = getPaddedBufferSize( count * attribute.itemSize * componentSize );
  			const dataView = new DataView( new ArrayBuffer( byteLength ) );
  			let offset = 0;
  
  			for ( let i = start; i < start + count; i ++ ) {
  
  				for ( let a = 0; a < attribute.itemSize; a ++ ) {
  
  					let value;
  
  					if ( attribute.itemSize > 4 ) {
  
  						// no support for interleaved data for itemSize > 4
  						value = attribute.array[ i * attribute.itemSize + a ];
  
  					} else {
  
  						if ( a === 0 ) value = attribute.getX( i ); else if ( a === 1 ) value = attribute.getY( i ); else if ( a === 2 ) value = attribute.getZ( i ); else if ( a === 3 ) value = attribute.getW( i );
  
  					}
  
  					if ( componentType === WEBGL_CONSTANTS.FLOAT ) {
  
  						dataView.setFloat32( offset, value, true );
  
  					} else if ( componentType === WEBGL_CONSTANTS.UNSIGNED_INT ) {
  
  						dataView.setUint32( offset, value, true );
  
  					} else if ( componentType === WEBGL_CONSTANTS.UNSIGNED_SHORT ) {
  
  						dataView.setUint16( offset, value, true );
  
  					} else if ( componentType === WEBGL_CONSTANTS.UNSIGNED_BYTE ) {
  
  						dataView.setUint8( offset, value );
  
  					}
  
  					offset += componentSize;
  
  				}
  
  			}
  
  			const bufferViewDef = {
  				buffer: this.processBuffer( dataView.buffer ),
  				byteOffset: this.byteOffset,
  				byteLength: byteLength
  			};
  			if ( target !== undefined ) bufferViewDef.target = target;
  
  			if ( target === WEBGL_CONSTANTS.ARRAY_BUFFER ) {
  
  				// Only define byteStride for vertex attributes.
  				bufferViewDef.byteStride = attribute.itemSize * componentSize;
  
  			}
  
  			this.byteOffset += byteLength;
  			json.bufferViews.push( bufferViewDef ); // @TODO Merge bufferViews where possible.
  
  			const output = {
  				id: json.bufferViews.length - 1,
  				byteLength: 0
  			};
  			return output;
  
  		}
  		/**
     * Process and generate a BufferView from an image Blob.
     * @param {Blob} blob
     * @return {Promise<Integer>}
     */
  
  
  		processBufferViewImage( blob ) {
  
  			const writer = this;
  			const json = writer.json;
  			if ( ! json.bufferViews ) json.bufferViews = [];
  			return new Promise( function ( resolve ) {
  
  				const reader = new window.FileReader();
  				reader.readAsArrayBuffer( blob );
  
  				reader.onloadend = function () {
  
  					const buffer = getPaddedArrayBuffer( reader.result );
  					const bufferViewDef = {
  						buffer: writer.processBuffer( buffer ),
  						byteOffset: writer.byteOffset,
  						byteLength: buffer.byteLength
  					};
  					writer.byteOffset += buffer.byteLength;
  					resolve( json.bufferViews.push( bufferViewDef ) - 1 );
  
  				};
  
  			} );
  
  		}
  		/**
     * Process attribute to generate an accessor
     * @param  {BufferAttribute} attribute Attribute to process
     * @param  {THREE.BufferGeometry} geometry (Optional) Geometry used for truncated draw range
     * @param  {Integer} start (Optional)
     * @param  {Integer} count (Optional)
     * @return {Integer|null} Index of the processed accessor on the "accessors" array
     */
  
  
  		processAccessor( attribute, geometry, start, count ) {
  
  			const options = this.options;
  			const json = this.json;
  			const types = {
  				1: 'SCALAR',
  				2: 'VEC2',
  				3: 'VEC3',
  				4: 'VEC4',
  				16: 'MAT4'
  			};
  			let componentType; // Detect the component type of the attribute array (float, uint or ushort)
  
  			if ( attribute.array.constructor === Float32Array ) {
  
  				componentType = WEBGL_CONSTANTS.FLOAT;
  
  			} else if ( attribute.array.constructor === Uint32Array ) {
  
  				componentType = WEBGL_CONSTANTS.UNSIGNED_INT;
  
  			} else if ( attribute.array.constructor === Uint16Array ) {
  
  				componentType = WEBGL_CONSTANTS.UNSIGNED_SHORT;
  
  			} else if ( attribute.array.constructor === Uint8Array ) {
  
  				componentType = WEBGL_CONSTANTS.UNSIGNED_BYTE;
  
  			} else {
  
  				throw new Error( 'THREE.GLTFExporter: Unsupported bufferAttribute component type.' );
  
  			}
  
  			if ( start === undefined ) start = 0;
  			if ( count === undefined ) count = attribute.count; // @TODO Indexed buffer geometry with drawRange not supported yet
  
  			if ( options.truncateDrawRange && geometry !== undefined && geometry.index === null ) {
  
  				const end = start + count;
  				const end2 = geometry.drawRange.count === Infinity ? attribute.count : geometry.drawRange.start + geometry.drawRange.count;
  				start = Math.max( start, geometry.drawRange.start );
  				count = Math.min( end, end2 ) - start;
  				if ( count < 0 ) count = 0;
  
  			} // Skip creating an accessor if the attribute doesn't have data to export
  
  
  			if ( count === 0 ) return null;
  			const minMax = getMinMax( attribute, start, count );
  			let bufferViewTarget; // If geometry isn't provided, don't infer the target usage of the bufferView. For
  			// animation samplers, target must not be set.
  
  			if ( geometry !== undefined ) {
  
  				bufferViewTarget = attribute === geometry.index ? WEBGL_CONSTANTS.ELEMENT_ARRAY_BUFFER : WEBGL_CONSTANTS.ARRAY_BUFFER;
  
  			}
  
  			const bufferView = this.processBufferView( attribute, componentType, start, count, bufferViewTarget );
  			const accessorDef = {
  				bufferView: bufferView.id,
  				byteOffset: bufferView.byteOffset,
  				componentType: componentType,
  				count: count,
  				max: minMax.max,
  				min: minMax.min,
  				type: types[ attribute.itemSize ]
  			};
  			if ( attribute.normalized === true ) accessorDef.normalized = true;
  			if ( ! json.accessors ) json.accessors = [];
  			return json.accessors.push( accessorDef ) - 1;
  
  		}
  		/**
     * Process image
     * @param  {Image} image to process
     * @param  {Integer} format of the image (e.g. THREE.RGBFormat, THREE.RGBAFormat etc)
     * @param  {Boolean} flipY before writing out the image
     * @return {Integer}     Index of the processed texture in the "images" array
     */
  
  
  		processImage( image, format, flipY ) {
  
  			const writer = this;
  			const cache = writer.cache;
  			const json = writer.json;
  			const options = writer.options;
  			const pending = writer.pending;
  			if ( ! cache.images.has( image ) ) cache.images.set( image, {} );
  			const cachedImages = cache.images.get( image );
  			const mimeType = format === THREE.RGBAFormat ? 'image/png' : 'image/jpeg';
  			const key = mimeType + ':flipY/' + flipY.toString();
  			if ( cachedImages[ key ] !== undefined ) return cachedImages[ key ];
  			if ( ! json.images ) json.images = [];
  			const imageDef = {
  				mimeType: mimeType
  			};
  
  			if ( options.embedImages ) {
  
  				const canvas = cachedCanvas = cachedCanvas || document.createElement( 'canvas' );
  				canvas.width = Math.min( image.width, options.maxTextureSize );
  				canvas.height = Math.min( image.height, options.maxTextureSize );
  				const ctx = canvas.getContext( '2d' );
  
  				if ( flipY === true ) {
  
  					ctx.translate( 0, canvas.height );
  					ctx.scale( 1, - 1 );
  
  				}
  
  				if ( typeof HTMLImageElement !== 'undefined' && image instanceof HTMLImageElement || typeof HTMLCanvasElement !== 'undefined' && image instanceof HTMLCanvasElement || typeof OffscreenCanvas !== 'undefined' && image instanceof OffscreenCanvas || typeof ImageBitmap !== 'undefined' && image instanceof ImageBitmap ) {
  
  					ctx.drawImage( image, 0, 0, canvas.width, canvas.height );
  
  				} else {
  
  					if ( format !== THREE.RGBAFormat && format !== THREE.RGBFormat ) {
  
  						console.error( 'GLTFExporter: Only RGB and RGBA formats are supported.' );
  
  					}
  
  					if ( image.width > options.maxTextureSize || image.height > options.maxTextureSize ) {
  
  						console.warn( 'GLTFExporter: Image size is bigger than maxTextureSize', image );
  
  					}
  
  					const data = new Uint8ClampedArray( image.height * image.width * 4 );
  
  					if ( format === THREE.RGBAFormat ) {
  
  						for ( let i = 0; i < data.length; i += 4 ) {
  
  							data[ i + 0 ] = image.data[ i + 0 ];
  							data[ i + 1 ] = image.data[ i + 1 ];
  							data[ i + 2 ] = image.data[ i + 2 ];
  							data[ i + 3 ] = image.data[ i + 3 ];
  
  						}
  
  					} else {
  
  						for ( let i = 0, j = 0; i < data.length; i += 4, j += 3 ) {
  
  							data[ i + 0 ] = image.data[ j + 0 ];
  							data[ i + 1 ] = image.data[ j + 1 ];
  							data[ i + 2 ] = image.data[ j + 2 ];
  							data[ i + 3 ] = 255;
  
  						}
  
  					}
  
  					ctx.putImageData( new ImageData( data, image.width, image.height ), 0, 0 );
  
  				}
  
  				if ( options.binary === true ) {
  
  					pending.push( new Promise( function ( resolve ) {
  
  						canvas.toBlob( function ( blob ) {
  
  							writer.processBufferViewImage( blob ).then( function ( bufferViewIndex ) {
  
  								imageDef.bufferView = bufferViewIndex;
  								resolve();
  
  							} );
  
  						}, mimeType );
  
  					} ) );
  
  				} else {
  
  					imageDef.uri = canvas.toDataURL( mimeType );
  
  				}
  
  			} else {
  
  				imageDef.uri = image.src;
  
  			}
  
  			const index = json.images.push( imageDef ) - 1;
  			cachedImages[ key ] = index;
  			return index;
  
  		}
  		/**
     * Process sampler
     * @param  {Texture} map Texture to process
     * @return {Integer}     Index of the processed texture in the "samplers" array
     */
  
  
  		processSampler( map ) {
  
  			const json = this.json;
  			if ( ! json.samplers ) json.samplers = [];
  			const samplerDef = {
  				magFilter: THREE_TO_WEBGL[ map.magFilter ],
  				minFilter: THREE_TO_WEBGL[ map.minFilter ],
  				wrapS: THREE_TO_WEBGL[ map.wrapS ],
  				wrapT: THREE_TO_WEBGL[ map.wrapT ]
  			};
  			return json.samplers.push( samplerDef ) - 1;
  
  		}
  		/**
     * Process texture
     * @param  {Texture} map Map to process
     * @return {Integer} Index of the processed texture in the "textures" array
     */
  
  
  		processTexture( map ) {
  
  			const cache = this.cache;
  			const json = this.json;
  			if ( cache.textures.has( map ) ) return cache.textures.get( map );
  			if ( ! json.textures ) json.textures = [];
  			const textureDef = {
  				sampler: this.processSampler( map ),
  				source: this.processImage( map.image, map.format, map.flipY )
  			};
  			if ( map.name ) textureDef.name = map.name;
  
  			this._invokeAll( function ( ext ) {
  
  				ext.writeTexture && ext.writeTexture( map, textureDef );
  
  			} );
  
  			const index = json.textures.push( textureDef ) - 1;
  			cache.textures.set( map, index );
  			return index;
  
  		}
  		/**
     * Process material
     * @param  {THREE.Material} material Material to process
     * @return {Integer|null} Index of the processed material in the "materials" array
     */
  
  
  		processMaterial( material ) {
  
  			const cache = this.cache;
  			const json = this.json;
  			if ( cache.materials.has( material ) ) return cache.materials.get( material );
  
  			if ( material.isShaderMaterial ) {
  
  				console.warn( 'GLTFExporter: THREE.ShaderMaterial not supported.' );
  				return null;
  
  			}
  
  			if ( ! json.materials ) json.materials = []; // @QUESTION Should we avoid including any attribute that has the default value?
  
  			const materialDef = {
  				pbrMetallicRoughness: {}
  			};
  
  			if ( material.isMeshStandardMaterial !== true && material.isMeshBasicMaterial !== true ) {
  
  				console.warn( 'GLTFExporter: Use MeshStandardMaterial or MeshBasicMaterial for best results.' );
  
  			} // pbrMetallicRoughness.baseColorFactor
  
  
  			const color = material.color.toArray().concat( [ material.opacity ] );
  
  			if ( ! equalArray( color, [ 1, 1, 1, 1 ] ) ) {
  
  				materialDef.pbrMetallicRoughness.baseColorFactor = color;
  
  			}
  
  			if ( material.isMeshStandardMaterial ) {
  
  				materialDef.pbrMetallicRoughness.metallicFactor = material.metalness;
  				materialDef.pbrMetallicRoughness.roughnessFactor = material.roughness;
  
  			} else {
  
  				materialDef.pbrMetallicRoughness.metallicFactor = 0.5;
  				materialDef.pbrMetallicRoughness.roughnessFactor = 0.5;
  
  			} // pbrMetallicRoughness.metallicRoughnessTexture
  
  
  			if ( material.metalnessMap || material.roughnessMap ) {
  
  				if ( material.metalnessMap === material.roughnessMap ) {
  
  					const metalRoughMapDef = {
  						index: this.processTexture( material.metalnessMap )
  					};
  					this.applyTextureTransform( metalRoughMapDef, material.metalnessMap );
  					materialDef.pbrMetallicRoughness.metallicRoughnessTexture = metalRoughMapDef;
  
  				} else {
  
  					console.warn( 'THREE.GLTFExporter: Ignoring metalnessMap and roughnessMap because they are not the same Texture.' );
  
  				}
  
  			} // pbrMetallicRoughness.baseColorTexture or pbrSpecularGlossiness diffuseTexture
  
  
  			if ( material.map ) {
  
  				const baseColorMapDef = {
  					index: this.processTexture( material.map )
  				};
  				this.applyTextureTransform( baseColorMapDef, material.map );
  				materialDef.pbrMetallicRoughness.baseColorTexture = baseColorMapDef;
  
  			}
  
  			if ( material.emissive ) {
  
  				// note: emissive components are limited to stay within the 0 - 1 range to accommodate glTF spec. see #21849 and #22000.
  				const emissive = material.emissive.clone().multiplyScalar( material.emissiveIntensity );
  				const maxEmissiveComponent = Math.max( emissive.r, emissive.g, emissive.b );
  
  				if ( maxEmissiveComponent > 1 ) {
  
  					emissive.multiplyScalar( 1 / maxEmissiveComponent );
  
  					console.warn( 'THREE.GLTFExporter: Some emissive components exceed 1; emissive has been limited' );
  
  				}
  
  				if ( maxEmissiveComponent > 0 ) {
  
  					materialDef.emissiveFactor = emissive.toArray();
  
  				} // emissiveTexture
  
  
  				if ( material.emissiveMap ) {
  
  					const emissiveMapDef = {
  						index: this.processTexture( material.emissiveMap )
  					};
  					this.applyTextureTransform( emissiveMapDef, material.emissiveMap );
  					materialDef.emissiveTexture = emissiveMapDef;
  
  				}
  
  			} // normalTexture
  
  
  			if ( material.normalMap ) {
  
  				const normalMapDef = {
  					index: this.processTexture( material.normalMap )
  				};
  
  				if ( material.normalScale && material.normalScale.x !== - 1 ) {
  
  					if ( material.normalScale.x !== material.normalScale.y ) {
  
  						console.warn( 'THREE.GLTFExporter: Normal scale components are different, ignoring Y and exporting X.' );
  
  					}
  
  					normalMapDef.scale = material.normalScale.x;
  
  				}
  
  				this.applyTextureTransform( normalMapDef, material.normalMap );
  				materialDef.normalTexture = normalMapDef;
  
  			} // occlusionTexture
  
  
  			if ( material.aoMap ) {
  
  				const occlusionMapDef = {
  					index: this.processTexture( material.aoMap ),
  					texCoord: 1
  				};
  
  				if ( material.aoMapIntensity !== 1.0 ) {
  
  					occlusionMapDef.strength = material.aoMapIntensity;
  
  				}
  
  				this.applyTextureTransform( occlusionMapDef, material.aoMap );
  				materialDef.occlusionTexture = occlusionMapDef;
  
  			} // alphaMode
  
  
  			if ( material.transparent ) {
  
  				materialDef.alphaMode = 'BLEND';
  
  			} else {
  
  				if ( material.alphaTest > 0.0 ) {
  
  					materialDef.alphaMode = 'MASK';
  					materialDef.alphaCutoff = material.alphaTest;
  
  				}
  
  			} // doubleSided
  
  
  			if ( material.side === THREE.DoubleSide ) materialDef.doubleSided = true;
  			if ( material.name !== '' ) materialDef.name = material.name;
  			this.serializeUserData( material, materialDef );
  
  			this._invokeAll( function ( ext ) {
  
  				ext.writeMaterial && ext.writeMaterial( material, materialDef );
  
  			} );
  
  			const index = json.materials.push( materialDef ) - 1;
  			cache.materials.set( material, index );
  			return index;
  
  		}
  		/**
     * Process mesh
     * @param  {THREE.Mesh} mesh Mesh to process
     * @return {Integer|null} Index of the processed mesh in the "meshes" array
     */
  
  
  		processMesh( mesh ) {
  
  			const cache = this.cache;
  			const json = this.json;
  			const meshCacheKeyParts = [ mesh.geometry.uuid ];
  
  			if ( Array.isArray( mesh.material ) ) {
  
  				for ( let i = 0, l = mesh.material.length; i < l; i ++ ) {
  
  					meshCacheKeyParts.push( mesh.material[ i ].uuid );
  
  				}
  
  			} else {
  
  				meshCacheKeyParts.push( mesh.material.uuid );
  
  			}
  
  			const meshCacheKey = meshCacheKeyParts.join( ':' );
  			if ( cache.meshes.has( meshCacheKey ) ) return cache.meshes.get( meshCacheKey );
  			const geometry = mesh.geometry;
  			let mode; // Use the correct mode
  
  			if ( mesh.isLineSegments ) {
  
  				mode = WEBGL_CONSTANTS.LINES;
  
  			} else if ( mesh.isLineLoop ) {
  
  				mode = WEBGL_CONSTANTS.LINE_LOOP;
  
  			} else if ( mesh.isLine ) {
  
  				mode = WEBGL_CONSTANTS.LINE_STRIP;
  
  			} else if ( mesh.isPoints ) {
  
  				mode = WEBGL_CONSTANTS.POINTS;
  
  			} else {
  
  				mode = mesh.material.wireframe ? WEBGL_CONSTANTS.LINES : WEBGL_CONSTANTS.TRIANGLES;
  
  			}
  
  			if ( geometry.isBufferGeometry !== true ) {
  
  				throw new Error( 'THREE.GLTFExporter: Geometry is not of type THREE.BufferGeometry.' );
  
  			}
  
  			const meshDef = {};
  			const attributes = {};
  			const primitives = [];
  			const targets = []; // Conversion between attributes names in threejs and gltf spec
  
  			const nameConversion = {
  				uv: 'TEXCOORD_0',
  				uv2: 'TEXCOORD_1',
  				color: 'COLOR_0',
  				skinWeight: 'WEIGHTS_0',
  				skinIndex: 'JOINTS_0'
  			};
  			const originalNormal = geometry.getAttribute( 'normal' );
  
  			if ( originalNormal !== undefined && ! this.isNormalizedNormalAttribute( originalNormal ) ) {
  
  				console.warn( 'THREE.GLTFExporter: Creating normalized normal attribute from the non-normalized one.' );
  				geometry.setAttribute( 'normal', this.createNormalizedNormalAttribute( originalNormal ) );
  
  			} // @QUESTION Detect if .vertexColors = true?
  			// For every attribute create an accessor
  
  
  			let modifiedAttribute = null;
  
  			for ( let attributeName in geometry.attributes ) {
  
  				// Ignore morph target attributes, which are exported later.
  				if ( attributeName.substr( 0, 5 ) === 'morph' ) continue;
  				const attribute = geometry.attributes[ attributeName ];
  				attributeName = nameConversion[ attributeName ] || attributeName.toUpperCase(); // Prefix all geometry attributes except the ones specifically
  				// listed in the spec; non-spec attributes are considered custom.
  
  				const validVertexAttributes = /^(POSITION|NORMAL|TANGENT|TEXCOORD_\d+|COLOR_\d+|JOINTS_\d+|WEIGHTS_\d+)$/;
  				if ( ! validVertexAttributes.test( attributeName ) ) attributeName = '_' + attributeName;
  
  				if ( cache.attributes.has( this.getUID( attribute ) ) ) {
  
  					attributes[ attributeName ] = cache.attributes.get( this.getUID( attribute ) );
  					continue;
  
  				} // JOINTS_0 must be UNSIGNED_BYTE or UNSIGNED_SHORT.
  
  
  				modifiedAttribute = null;
  				const array = attribute.array;
  
  				if ( attributeName === 'JOINTS_0' && ! ( array instanceof Uint16Array ) && ! ( array instanceof Uint8Array ) ) {
  
  					console.warn( 'GLTFExporter: Attribute "skinIndex" converted to type UNSIGNED_SHORT.' );
  					modifiedAttribute = new THREE.BufferAttribute( new Uint16Array( array ), attribute.itemSize, attribute.normalized );
  
  				}
  
  				const accessor = this.processAccessor( modifiedAttribute || attribute, geometry );
  
  				if ( accessor !== null ) {
  
  					attributes[ attributeName ] = accessor;
  					cache.attributes.set( this.getUID( attribute ), accessor );
  
  				}
  
  			}
  
  			if ( originalNormal !== undefined ) geometry.setAttribute( 'normal', originalNormal ); // Skip if no exportable attributes found
  
  			if ( Object.keys( attributes ).length === 0 ) return null; // Morph targets
  
  			if ( mesh.morphTargetInfluences !== undefined && mesh.morphTargetInfluences.length > 0 ) {
  
  				const weights = [];
  				const targetNames = [];
  				const reverseDictionary = {};
  
  				if ( mesh.morphTargetDictionary !== undefined ) {
  
  					for ( const key in mesh.morphTargetDictionary ) {
  
  						reverseDictionary[ mesh.morphTargetDictionary[ key ] ] = key;
  
  					}
  
  				}
  
  				for ( let i = 0; i < mesh.morphTargetInfluences.length; ++ i ) {
  
  					const target = {};
  					let warned = false;
  
  					for ( const attributeName in geometry.morphAttributes ) {
  
  						// glTF 2.0 morph supports only POSITION/NORMAL/TANGENT.
  						// Three.js doesn't support TANGENT yet.
  						if ( attributeName !== 'position' && attributeName !== 'normal' ) {
  
  							if ( ! warned ) {
  
  								console.warn( 'GLTFExporter: Only POSITION and NORMAL morph are supported.' );
  								warned = true;
  
  							}
  
  							continue;
  
  						}
  
  						const attribute = geometry.morphAttributes[ attributeName ][ i ];
  						const gltfAttributeName = attributeName.toUpperCase(); // Three.js morph attribute has absolute values while the one of glTF has relative values.
  						//
  						// glTF 2.0 Specification:
  						// https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#morph-targets
  
  						const baseAttribute = geometry.attributes[ attributeName ];
  
  						if ( cache.attributes.has( this.getUID( attribute ) ) ) {
  
  							target[ gltfAttributeName ] = cache.attributes.get( this.getUID( attribute ) );
  							continue;
  
  						} // Clones attribute not to override
  
  
  						const relativeAttribute = attribute.clone();
  
  						if ( ! geometry.morphTargetsRelative ) {
  
  							for ( let j = 0, jl = attribute.count; j < jl; j ++ ) {
  
  								relativeAttribute.setXYZ( j, attribute.getX( j ) - baseAttribute.getX( j ), attribute.getY( j ) - baseAttribute.getY( j ), attribute.getZ( j ) - baseAttribute.getZ( j ) );
  
  							}
  
  						}
  
  						target[ gltfAttributeName ] = this.processAccessor( relativeAttribute, geometry );
  						cache.attributes.set( this.getUID( baseAttribute ), target[ gltfAttributeName ] );
  
  					}
  
  					targets.push( target );
  					weights.push( mesh.morphTargetInfluences[ i ] );
  					if ( mesh.morphTargetDictionary !== undefined ) targetNames.push( reverseDictionary[ i ] );
  
  				}
  
  				meshDef.weights = weights;
  
  				if ( targetNames.length > 0 ) {
  
  					meshDef.extras = {};
  					meshDef.extras.targetNames = targetNames;
  
  				}
  
  			}
  
  			const isMultiMaterial = Array.isArray( mesh.material );
  			if ( isMultiMaterial && geometry.groups.length === 0 ) return null;
  			const materials = isMultiMaterial ? mesh.material : [ mesh.material ];
  			const groups = isMultiMaterial ? geometry.groups : [ {
  				materialIndex: 0,
  				start: undefined,
  				count: undefined
  			} ];
  
  			for ( let i = 0, il = groups.length; i < il; i ++ ) {
  
  				const primitive = {
  					mode: mode,
  					attributes: attributes
  				};
  				this.serializeUserData( geometry, primitive );
  				if ( targets.length > 0 ) primitive.targets = targets;
  
  				if ( geometry.index !== null ) {
  
  					let cacheKey = this.getUID( geometry.index );
  
  					if ( groups[ i ].start !== undefined || groups[ i ].count !== undefined ) {
  
  						cacheKey += ':' + groups[ i ].start + ':' + groups[ i ].count;
  
  					}
  
  					if ( cache.attributes.has( cacheKey ) ) {
  
  						primitive.indices = cache.attributes.get( cacheKey );
  
  					} else {
  
  						primitive.indices = this.processAccessor( geometry.index, geometry, groups[ i ].start, groups[ i ].count );
  						cache.attributes.set( cacheKey, primitive.indices );
  
  					}
  
  					if ( primitive.indices === null ) delete primitive.indices;
  
  				}
  
  				const material = this.processMaterial( materials[ groups[ i ].materialIndex ] );
  				if ( material !== null ) primitive.material = material;
  				primitives.push( primitive );
  
  			}
  
  			meshDef.primitives = primitives;
  			if ( ! json.meshes ) json.meshes = [];
  
  			this._invokeAll( function ( ext ) {
  
  				ext.writeMesh && ext.writeMesh( mesh, meshDef );
  
  			} );
  
  			const index = json.meshes.push( meshDef ) - 1;
  			cache.meshes.set( meshCacheKey, index );
  			return index;
  
  		}
  		/**
     * Process camera
     * @param  {THREE.Camera} camera Camera to process
     * @return {Integer}      Index of the processed mesh in the "camera" array
     */
  
  
  		processCamera( camera ) {
  
  			const json = this.json;
  			if ( ! json.cameras ) json.cameras = [];
  			const isOrtho = camera.isOrthographicCamera;
  			const cameraDef = {
  				type: isOrtho ? 'orthographic' : 'perspective'
  			};
  
  			if ( isOrtho ) {
  
  				cameraDef.orthographic = {
  					xmag: camera.right * 2,
  					ymag: camera.top * 2,
  					zfar: camera.far <= 0 ? 0.001 : camera.far,
  					znear: camera.near < 0 ? 0 : camera.near
  				};
  
  			} else {
  
  				cameraDef.perspective = {
  					aspectRatio: camera.aspect,
  					yfov: THREE.MathUtils.degToRad( camera.fov ),
  					zfar: camera.far <= 0 ? 0.001 : camera.far,
  					znear: camera.near < 0 ? 0 : camera.near
  				};
  
  			} // Question: Is saving "type" as name intentional?
  
  
  			if ( camera.name !== '' ) cameraDef.name = camera.type;
  			return json.cameras.push( cameraDef ) - 1;
  
  		}
  		/**
     * Creates glTF animation entry from AnimationClip object.
     *
     * Status:
     * - Only properties listed in PATH_PROPERTIES may be animated.
     *
     * @param {THREE.AnimationClip} clip
     * @param {THREE.Object3D} root
     * @return {number|null}
     */
  
  
  		processAnimation( clip, root ) {
  
  			const json = this.json;
  			const nodeMap = this.nodeMap;
  			if ( ! json.animations ) json.animations = [];
  			clip = GLTFExporter.Utils.mergeMorphTargetTracks( clip.clone(), root );
  			const tracks = clip.tracks;
  			const channels = [];
  			const samplers = [];
  
  			for ( let i = 0; i < tracks.length; ++ i ) {
  
  				const track = tracks[ i ];
  				const trackBinding = THREE.PropertyBinding.parseTrackName( track.name );
  				let trackNode = THREE.PropertyBinding.findNode( root, trackBinding.nodeName );
  				const trackProperty = PATH_PROPERTIES[ trackBinding.propertyName ];
  
  				if ( trackBinding.objectName === 'bones' ) {
  
  					if ( trackNode.isSkinnedMesh === true ) {
  
  						trackNode = trackNode.skeleton.getBoneByName( trackBinding.objectIndex );
  
  					} else {
  
  						trackNode = undefined;
  
  					}
  
  				}
  
  				if ( ! trackNode || ! trackProperty ) {
  
  					console.warn( 'THREE.GLTFExporter: Could not export animation track "%s".', track.name );
  					return null;
  
  				}
  
  				const inputItemSize = 1;
  				let outputItemSize = track.values.length / track.times.length;
  
  				if ( trackProperty === PATH_PROPERTIES.morphTargetInfluences ) {
  
  					outputItemSize /= trackNode.morphTargetInfluences.length;
  
  				}
  
  				let interpolation; // @TODO export CubicInterpolant(InterpolateSmooth) as CUBICSPLINE
  				// Detecting glTF cubic spline interpolant by checking factory method's special property
  				// GLTFCubicSplineInterpolant is a custom interpolant and track doesn't return
  				// valid value from .getInterpolation().
  
  				if ( track.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline === true ) {
  
  					interpolation = 'CUBICSPLINE'; // itemSize of CUBICSPLINE keyframe is 9
  					// (VEC3 * 3: inTangent, splineVertex, and outTangent)
  					// but needs to be stored as VEC3 so dividing by 3 here.
  
  					outputItemSize /= 3;
  
  				} else if ( track.getInterpolation() === THREE.InterpolateDiscrete ) {
  
  					interpolation = 'STEP';
  
  				} else {
  
  					interpolation = 'LINEAR';
  
  				}
  
  				samplers.push( {
  					input: this.processAccessor( new THREE.BufferAttribute( track.times, inputItemSize ) ),
  					output: this.processAccessor( new THREE.BufferAttribute( track.values, outputItemSize ) ),
  					interpolation: interpolation
  				} );
  				channels.push( {
  					sampler: samplers.length - 1,
  					target: {
  						node: nodeMap.get( trackNode ),
  						path: trackProperty
  					}
  				} );
  
  			}
  
  			json.animations.push( {
  				name: clip.name || 'clip_' + json.animations.length,
  				samplers: samplers,
  				channels: channels
  			} );
  			return json.animations.length - 1;
  
  		}
  		/**
     * @param {THREE.Object3D} object
     * @return {number|null}
     */
  
  
  		processSkin( object ) {
  
  			const json = this.json;
  			const nodeMap = this.nodeMap;
  			const node = json.nodes[ nodeMap.get( object ) ];
  			const skeleton = object.skeleton;
  			if ( skeleton === undefined ) return null;
  			const rootJoint = object.skeleton.bones[ 0 ];
  			if ( rootJoint === undefined ) return null;
  			const joints = [];
  			const inverseBindMatrices = new Float32Array( skeleton.bones.length * 16 );
  			const temporaryBoneInverse = new THREE.Matrix4();
  
  			for ( let i = 0; i < skeleton.bones.length; ++ i ) {
  
  				joints.push( nodeMap.get( skeleton.bones[ i ] ) );
  				temporaryBoneInverse.copy( skeleton.boneInverses[ i ] );
  				temporaryBoneInverse.multiply( object.bindMatrix ).toArray( inverseBindMatrices, i * 16 );
  
  			}
  
  			if ( json.skins === undefined ) json.skins = [];
  			json.skins.push( {
  				inverseBindMatrices: this.processAccessor( new THREE.BufferAttribute( inverseBindMatrices, 16 ) ),
  				joints: joints,
  				skeleton: nodeMap.get( rootJoint )
  			} );
  			const skinIndex = node.skin = json.skins.length - 1;
  			return skinIndex;
  
  		}
  		/**
     * Process Object3D node
     * @param  {THREE.Object3D} node Object3D to processNode
     * @return {Integer} Index of the node in the nodes list
     */
  
  
  		processNode( object ) {
  
  			const json = this.json;
  			const options = this.options;
  			const nodeMap = this.nodeMap;
  			if ( ! json.nodes ) json.nodes = [];
  			const nodeDef = {};
  
  			if ( options.trs ) {
  
  				const rotation = object.quaternion.toArray();
  				const position = object.position.toArray();
  				const scale = object.scale.toArray();
  
  				if ( ! equalArray( rotation, [ 0, 0, 0, 1 ] ) ) {
  
  					nodeDef.rotation = rotation;
  
  				}
  
  				if ( ! equalArray( position, [ 0, 0, 0 ] ) ) {
  
  					nodeDef.translation = position;
  
  				}
  
  				if ( ! equalArray( scale, [ 1, 1, 1 ] ) ) {
  
  					nodeDef.scale = scale;
  
  				}
  
  			} else {
  
  				if ( object.matrixAutoUpdate ) {
  
  					object.updateMatrix();
  
  				}
  
  				if ( isIdentityMatrix( object.matrix ) === false ) {
  
  					nodeDef.matrix = object.matrix.elements;
  
  				}
  
  			} // We don't export empty strings name because it represents no-name in Three.js.
  
  
  			if ( object.name !== '' ) nodeDef.name = String( object.name );
  			this.serializeUserData( object, nodeDef );
  
  			if ( object.isMesh || object.isLine || object.isPoints ) {
  
  				const meshIndex = this.processMesh( object );
  				if ( meshIndex !== null ) nodeDef.mesh = meshIndex;
  
  			} else if ( object.isCamera ) {
  
  				nodeDef.camera = this.processCamera( object );
  
  			}
  
  			if ( object.isSkinnedMesh ) this.skins.push( object );
  
  			if ( object.children.length > 0 ) {
  
  				const children = [];
  
  				for ( let i = 0, l = object.children.length; i < l; i ++ ) {
  
  					const child = object.children[ i ];
  
  					if ( child.visible || options.onlyVisible === false ) {
  
  						const nodeIndex = this.processNode( child );
  						if ( nodeIndex !== null ) children.push( nodeIndex );
  
  					}
  
  				}
  
  				if ( children.length > 0 ) nodeDef.children = children;
  
  			}
  
  			this._invokeAll( function ( ext ) {
  
  				ext.writeNode && ext.writeNode( object, nodeDef );
  
  			} );
  
  			const nodeIndex = json.nodes.push( nodeDef ) - 1;
  			nodeMap.set( object, nodeIndex );
  			return nodeIndex;
  
  		}
  		/**
     * Process THREE.Scene
     * @param  {Scene} node THREE.Scene to process
     */
  
  
  		processScene( scene ) {
  
  			const json = this.json;
  			const options = this.options;
  
  			if ( ! json.scenes ) {
  
  				json.scenes = [];
  				json.scene = 0;
  
  			}
  
  			const sceneDef = {};
  			if ( scene.name !== '' ) sceneDef.name = scene.name;
  			json.scenes.push( sceneDef );
  			const nodes = [];
  
  			for ( let i = 0, l = scene.children.length; i < l; i ++ ) {
  
  				const child = scene.children[ i ];
  
  				if ( child.visible || options.onlyVisible === false ) {
  
  					const nodeIndex = this.processNode( child );
  					if ( nodeIndex !== null ) nodes.push( nodeIndex );
  
  				}
  
  			}
  
  			if ( nodes.length > 0 ) sceneDef.nodes = nodes;
  			this.serializeUserData( scene, sceneDef );
  
  		}
  		/**
     * Creates a THREE.Scene to hold a list of objects and parse it
     * @param  {Array} objects List of objects to process
     */
  
  
  		processObjects( objects ) {
  
  			const scene = new THREE.Scene();
  			scene.name = 'AuxScene';
  
  			for ( let i = 0; i < objects.length; i ++ ) {
  
  				// We push directly to children instead of calling `add` to prevent
  				// modify the .parent and break its original scene and hierarchy
  				scene.children.push( objects[ i ] );
  
  			}
  
  			this.processScene( scene );
  
  		}
  		/**
     * @param {THREE.Object3D|Array<THREE.Object3D>} input
     */
  
  
  		processInput( input ) {
  
  			const options = this.options;
  			input = input instanceof Array ? input : [ input ];
  
  			this._invokeAll( function ( ext ) {
  
  				ext.beforeParse && ext.beforeParse( input );
  
  			} );
  
  			const objectsWithoutScene = [];
  
  			for ( let i = 0; i < input.length; i ++ ) {
  
  				if ( input[ i ] instanceof THREE.Scene ) {
  
  					this.processScene( input[ i ] );
  
  				} else {
  
  					objectsWithoutScene.push( input[ i ] );
  
  				}
  
  			}
  
  			if ( objectsWithoutScene.length > 0 ) this.processObjects( objectsWithoutScene );
  
  			for ( let i = 0; i < this.skins.length; ++ i ) {
  
  				this.processSkin( this.skins[ i ] );
  
  			}
  
  			for ( let i = 0; i < options.animations.length; ++ i ) {
  
  				this.processAnimation( options.animations[ i ], input[ 0 ] );
  
  			}
  
  			this._invokeAll( function ( ext ) {
  
  				ext.afterParse && ext.afterParse( input );
  
  			} );
  
  		}
  
  		_invokeAll( func ) {
  
  			for ( let i = 0, il = this.plugins.length; i < il; i ++ ) {
  
  				func( this.plugins[ i ] );
  
  			}
  
  		}
  
  	}
  	/**
   * Punctual Lights Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_lights_punctual
   */
  
  
  	class GLTFLightExtension {
  
  		constructor( writer ) {
  
  			this.writer = writer;
  			this.name = 'KHR_lights_punctual';
  
  		}
  
  		writeNode( light, nodeDef ) {
  
  			if ( ! light.isLight ) return;
  
  			if ( ! light.isDirectionalLight && ! light.isPointLight && ! light.isSpotLight ) {
  
  				console.warn( 'THREE.GLTFExporter: Only directional, point, and spot lights are supported.', light );
  				return;
  
  			}
  
  			const writer = this.writer;
  			const json = writer.json;
  			const extensionsUsed = writer.extensionsUsed;
  			const lightDef = {};
  			if ( light.name ) lightDef.name = light.name;
  			lightDef.color = light.color.toArray();
  			lightDef.intensity = light.intensity;
  
  			if ( light.isDirectionalLight ) {
  
  				lightDef.type = 'directional';
  
  			} else if ( light.isPointLight ) {
  
  				lightDef.type = 'point';
  				if ( light.distance > 0 ) lightDef.range = light.distance;
  
  			} else if ( light.isSpotLight ) {
  
  				lightDef.type = 'spot';
  				if ( light.distance > 0 ) lightDef.range = light.distance;
  				lightDef.spot = {};
  				lightDef.spot.innerConeAngle = ( light.penumbra - 1.0 ) * light.angle * - 1.0;
  				lightDef.spot.outerConeAngle = light.angle;
  
  			}
  
  			if ( light.decay !== undefined && light.decay !== 2 ) {
  
  				console.warn( 'THREE.GLTFExporter: Light decay may be lost. glTF is physically-based, ' + 'and expects light.decay=2.' );
  
  			}
  
  			if ( light.target && ( light.target.parent !== light || light.target.position.x !== 0 || light.target.position.y !== 0 || light.target.position.z !== - 1 ) ) {
  
  				console.warn( 'THREE.GLTFExporter: Light direction may be lost. For best results, ' + 'make light.target a child of the light with position 0,0,-1.' );
  
  			}
  
  			if ( ! extensionsUsed[ this.name ] ) {
  
  				json.extensions = json.extensions || {};
  				json.extensions[ this.name ] = {
  					lights: []
  				};
  				extensionsUsed[ this.name ] = true;
  
  			}
  
  			const lights = json.extensions[ this.name ].lights;
  			lights.push( lightDef );
  			nodeDef.extensions = nodeDef.extensions || {};
  			nodeDef.extensions[ this.name ] = {
  				light: lights.length - 1
  			};
  
  		}
  
  	}
  	/**
   * Unlit Materials Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_unlit
   */
  
  
  	class GLTFMaterialsUnlitExtension {
  
  		constructor( writer ) {
  
  			this.writer = writer;
  			this.name = 'KHR_materials_unlit';
  
  		}
  
  		writeMaterial( material, materialDef ) {
  
  			if ( ! material.isMeshBasicMaterial ) return;
  			const writer = this.writer;
  			const extensionsUsed = writer.extensionsUsed;
  			materialDef.extensions = materialDef.extensions || {};
  			materialDef.extensions[ this.name ] = {};
  			extensionsUsed[ this.name ] = true;
  			materialDef.pbrMetallicRoughness.metallicFactor = 0.0;
  			materialDef.pbrMetallicRoughness.roughnessFactor = 0.9;
  
  		}
  
  	}
  	/**
   * Specular-Glossiness Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_pbrSpecularGlossiness
   */
  
  
  	class GLTFMaterialsPBRSpecularGlossiness {
  
  		constructor( writer ) {
  
  			this.writer = writer;
  			this.name = 'KHR_materials_pbrSpecularGlossiness';
  
  		}
  
  		writeMaterial( material, materialDef ) {
  
  			if ( ! material.isGLTFSpecularGlossinessMaterial ) return;
  			const writer = this.writer;
  			const extensionsUsed = writer.extensionsUsed;
  			const extensionDef = {};
  
  			if ( materialDef.pbrMetallicRoughness.baseColorFactor ) {
  
  				extensionDef.diffuseFactor = materialDef.pbrMetallicRoughness.baseColorFactor;
  
  			}
  
  			const specularFactor = [ 1, 1, 1 ];
  			material.specular.toArray( specularFactor, 0 );
  			extensionDef.specularFactor = specularFactor;
  			extensionDef.glossinessFactor = material.glossiness;
  
  			if ( materialDef.pbrMetallicRoughness.baseColorTexture ) {
  
  				extensionDef.diffuseTexture = materialDef.pbrMetallicRoughness.baseColorTexture;
  
  			}
  
  			if ( material.specularMap ) {
  
  				const specularMapDef = {
  					index: writer.processTexture( material.specularMap )
  				};
  				writer.applyTextureTransform( specularMapDef, material.specularMap );
  				extensionDef.specularGlossinessTexture = specularMapDef;
  
  			}
  
  			materialDef.extensions = materialDef.extensions || {};
  			materialDef.extensions[ this.name ] = extensionDef;
  			extensionsUsed[ this.name ] = true;
  
  		}
  
  	}
  	/**
   * Static utility functions
   */
  
  
  	GLTFExporter.Utils = {
  		insertKeyframe: function ( track, time ) {
  
  			const tolerance = 0.001; // 1ms
  
  			const valueSize = track.getValueSize();
  			const times = new track.TimeBufferType( track.times.length + 1 );
  			const values = new track.ValueBufferType( track.values.length + valueSize );
  			const interpolant = track.createInterpolant( new track.ValueBufferType( valueSize ) );
  			let index;
  
  			if ( track.times.length === 0 ) {
  
  				times[ 0 ] = time;
  
  				for ( let i = 0; i < valueSize; i ++ ) {
  
  					values[ i ] = 0;
  
  				}
  
  				index = 0;
  
  			} else if ( time < track.times[ 0 ] ) {
  
  				if ( Math.abs( track.times[ 0 ] - time ) < tolerance ) return 0;
  				times[ 0 ] = time;
  				times.set( track.times, 1 );
  				values.set( interpolant.evaluate( time ), 0 );
  				values.set( track.values, valueSize );
  				index = 0;
  
  			} else if ( time > track.times[ track.times.length - 1 ] ) {
  
  				if ( Math.abs( track.times[ track.times.length - 1 ] - time ) < tolerance ) {
  
  					return track.times.length - 1;
  
  				}
  
  				times[ times.length - 1 ] = time;
  				times.set( track.times, 0 );
  				values.set( track.values, 0 );
  				values.set( interpolant.evaluate( time ), track.values.length );
  				index = times.length - 1;
  
  			} else {
  
  				for ( let i = 0; i < track.times.length; i ++ ) {
  
  					if ( Math.abs( track.times[ i ] - time ) < tolerance ) return i;
  
  					if ( track.times[ i ] < time && track.times[ i + 1 ] > time ) {
  
  						times.set( track.times.slice( 0, i + 1 ), 0 );
  						times[ i + 1 ] = time;
  						times.set( track.times.slice( i + 1 ), i + 2 );
  						values.set( track.values.slice( 0, ( i + 1 ) * valueSize ), 0 );
  						values.set( interpolant.evaluate( time ), ( i + 1 ) * valueSize );
  						values.set( track.values.slice( ( i + 1 ) * valueSize ), ( i + 2 ) * valueSize );
  						index = i + 1;
  						break;
  
  					}
  
  				}
  
  			}
  
  			track.times = times;
  			track.values = values;
  			return index;
  
  		},
  		mergeMorphTargetTracks: function ( clip, root ) {
  
  			const tracks = [];
  			const mergedTracks = {};
  			const sourceTracks = clip.tracks;
  
  			for ( let i = 0; i < sourceTracks.length; ++ i ) {
  
  				let sourceTrack = sourceTracks[ i ];
  				const sourceTrackBinding = THREE.PropertyBinding.parseTrackName( sourceTrack.name );
  				const sourceTrackNode = THREE.PropertyBinding.findNode( root, sourceTrackBinding.nodeName );
  
  				if ( sourceTrackBinding.propertyName !== 'morphTargetInfluences' || sourceTrackBinding.propertyIndex === undefined ) {
  
  					// Tracks that don't affect morph targets, or that affect all morph targets together, can be left as-is.
  					tracks.push( sourceTrack );
  					continue;
  
  				}
  
  				if ( sourceTrack.createInterpolant !== sourceTrack.InterpolantFactoryMethodDiscrete && sourceTrack.createInterpolant !== sourceTrack.InterpolantFactoryMethodLinear ) {
  
  					if ( sourceTrack.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline ) {
  
  						// This should never happen, because glTF morph target animations
  						// affect all targets already.
  						throw new Error( 'THREE.GLTFExporter: Cannot merge tracks with glTF CUBICSPLINE interpolation.' );
  
  					}
  
  					console.warn( 'THREE.GLTFExporter: Morph target interpolation mode not yet supported. Using LINEAR instead.' );
  					sourceTrack = sourceTrack.clone();
  					sourceTrack.setInterpolation( THREE.InterpolateLinear );
  
  				}
  
  				const targetCount = sourceTrackNode.morphTargetInfluences.length;
  				const targetIndex = sourceTrackNode.morphTargetDictionary[ sourceTrackBinding.propertyIndex ];
  
  				if ( targetIndex === undefined ) {
  
  					throw new Error( 'THREE.GLTFExporter: Morph target name not found: ' + sourceTrackBinding.propertyIndex );
  
  				}
  
  				let mergedTrack; // If this is the first time we've seen this object, create a new
  				// track to store merged keyframe data for each morph target.
  
  				if ( mergedTracks[ sourceTrackNode.uuid ] === undefined ) {
  
  					mergedTrack = sourceTrack.clone();
  					const values = new mergedTrack.ValueBufferType( targetCount * mergedTrack.times.length );
  
  					for ( let j = 0; j < mergedTrack.times.length; j ++ ) {
  
  						values[ j * targetCount + targetIndex ] = mergedTrack.values[ j ];
  
  					} // We need to take into consideration the intended target node
  					// of our original un-merged morphTarget animation.
  
  
  					mergedTrack.name = ( sourceTrackBinding.nodeName || '' ) + '.morphTargetInfluences';
  					mergedTrack.values = values;
  					mergedTracks[ sourceTrackNode.uuid ] = mergedTrack;
  					tracks.push( mergedTrack );
  					continue;
  
  				}
  
  				const sourceInterpolant = sourceTrack.createInterpolant( new sourceTrack.ValueBufferType( 1 ) );
  				mergedTrack = mergedTracks[ sourceTrackNode.uuid ]; // For every existing keyframe of the merged track, write a (possibly
  				// interpolated) value from the source track.
  
  				for ( let j = 0; j < mergedTrack.times.length; j ++ ) {
  
  					mergedTrack.values[ j * targetCount + targetIndex ] = sourceInterpolant.evaluate( mergedTrack.times[ j ] );
  
  				} // For every existing keyframe of the source track, write a (possibly
  				// new) keyframe to the merged track. Values from the previous loop may
  				// be written again, but keyframes are de-duplicated.
  
  
  				for ( let j = 0; j < sourceTrack.times.length; j ++ ) {
  
  					const keyframeIndex = this.insertKeyframe( mergedTrack, sourceTrack.times[ j ] );
  					mergedTrack.values[ keyframeIndex * targetCount + targetIndex ] = sourceTrack.values[ j ];
  
  				}
  
  			}
  
  			clip.tracks = tracks;
  			return clip;
  
  		}
  	};
  
  	THREE.GLTFExporter = GLTFExporter;
  
  } )();
  