text: import {
  	AnimationClip,
  	Bone,
  	Box3,
  	BufferAttribute,
  	BufferGeometry,
  	ClampToEdgeWrapping,
  	Color,
  	DirectionalLight,
  	DoubleSide,
  	FileLoader,
  	FrontSide,
  	Group,
  	ImageBitmapLoader,
  	InterleavedBuffer,
  	InterleavedBufferAttribute,
  	Interpolant,
  	InterpolateDiscrete,
  	InterpolateLinear,
  	Line,
  	LineBasicMaterial,
  	LineLoop,
  	LineSegments,
  	LinearFilter,
  	LinearMipmapLinearFilter,
  	LinearMipmapNearestFilter,
  	Loader,
  	LoaderUtils,
  	Material,
  	MathUtils,
  	Matrix4,
  	Mesh,
  	MeshBasicMaterial,
  	MeshPhysicalMaterial,
  	MeshStandardMaterial,
  	MirroredRepeatWrapping,
  	NearestFilter,
  	NearestMipmapLinearFilter,
  	NearestMipmapNearestFilter,
  	NumberKeyframeTrack,
  	Object3D,
  	OrthographicCamera,
  	PerspectiveCamera,
  	PointLight,
  	Points,
  	PointsMaterial,
  	PropertyBinding,
  	Quaternion,
  	QuaternionKeyframeTrack,
  	RepeatWrapping,
  	Skeleton,
  	SkinnedMesh,
  	Sphere,
  	SpotLight,
  	TangentSpaceNormalMap,
  	Texture,
  	TextureLoader,
  	TriangleFanDrawMode,
  	TriangleStripDrawMode,
  	Vector2,
  	Vector3,
  	VectorKeyframeTrack,
  	sRGBEncoding
  } from './build/three.module.js';
  
  class GLTFLoader extends Loader {
  
  	constructor( manager ) {
  
  		super( manager );
  
  		this.dracoLoader = null;
  		this.ktx2Loader = null;
  		this.meshoptDecoder = null;
  
  		this.pluginCallbacks = [];
  
  		this.register( function ( parser ) {
  
  			return new GLTFMaterialsClearcoatExtension( parser );
  
  		} );
  
  		this.register( function ( parser ) {
  
  			return new GLTFTextureBasisUExtension( parser );
  
  		} );
  
  		this.register( function ( parser ) {
  
  			return new GLTFTextureWebPExtension( parser );
  
  		} );
  
  		this.register( function ( parser ) {
  
  			return new GLTFMaterialsSheenExtension( parser );
  
  		} );
  
  		this.register( function ( parser ) {
  
  			return new GLTFMaterialsTransmissionExtension( parser );
  
  		} );
  
  		this.register( function ( parser ) {
  
  			return new GLTFMaterialsVolumeExtension( parser );
  
  		} );
  
  		this.register( function ( parser ) {
  
  			return new GLTFMaterialsIorExtension( parser );
  
  		} );
  
  		this.register( function ( parser ) {
  
  			return new GLTFMaterialsSpecularExtension( parser );
  
  		} );
  
  		this.register( function ( parser ) {
  
  			return new GLTFLightsExtension( parser );
  
  		} );
  
  		this.register( function ( parser ) {
  
  			return new GLTFMeshoptCompression( parser );
  
  		} );
  
  	}
  
  	load( url, onLoad, onProgress, onError ) {
  
  		const scope = this;
  
  		let resourcePath;
  
  		if ( this.resourcePath !== '' ) {
  
  			resourcePath = this.resourcePath;
  
  		} else if ( this.path !== '' ) {
  
  			resourcePath = this.path;
  
  		} else {
  
  			resourcePath = LoaderUtils.extractUrlBase( url );
  
  		}
  
  		// Tells the LoadingManager to track an extra item, which resolves after
  		// the model is fully loaded. This means the count of items loaded will
  		// be incorrect, but ensures manager.onLoad() does not fire early.
  		this.manager.itemStart( url );
  
  		const _onError = function ( e ) {
  
  			if ( onError ) {
  
  				onError( e );
  
  			} else {
  
  				console.error( e );
  
  			}
  
  			scope.manager.itemError( url );
  			scope.manager.itemEnd( url );
  
  		};
  
  		const loader = new FileLoader( this.manager );
  
  		loader.setPath( this.path );
  		loader.setResponseType( 'arraybuffer' );
  		loader.setRequestHeader( this.requestHeader );
  		loader.setWithCredentials( this.withCredentials );
  
  		loader.load( url, function ( data ) {
  
  			try {
  
  				scope.parse( data, resourcePath, function ( gltf ) {
  
  					onLoad( gltf );
  
  					scope.manager.itemEnd( url );
  
  				}, _onError );
  
  			} catch ( e ) {
  
  				_onError( e );
  
  			}
  
  		}, onProgress, _onError );
  
  	}
  
  	setDRACOLoader( dracoLoader ) {
  
  		this.dracoLoader = dracoLoader;
  		return this;
  
  	}
  
  	setDDSLoader() {
  
  		throw new Error(
  
  			'THREE.GLTFLoader: "MSFT_texture_dds" no longer supported. Please update to "KHR_texture_basisu".'
  
  		);
  
  	}
  
  	setKTX2Loader( ktx2Loader ) {
  
  		this.ktx2Loader = ktx2Loader;
  		return this;
  
  	}
  
  	setMeshoptDecoder( meshoptDecoder ) {
  
  		this.meshoptDecoder = meshoptDecoder;
  		return this;
  
  	}
  
  	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( data, path, onLoad, onError ) {
  
  		let content;
  		const extensions = {};
  		const plugins = {};
  
  		if ( typeof data === 'string' ) {
  
  			content = data;
  
  		} else {
  
  			const magic = LoaderUtils.decodeText( new Uint8Array( data, 0, 4 ) );
  
  			if ( magic === BINARY_EXTENSION_HEADER_MAGIC ) {
  
  				try {
  
  					extensions[ EXTENSIONS.KHR_BINARY_GLTF ] = new GLTFBinaryExtension( data );
  
  				} catch ( error ) {
  
  					if ( onError ) onError( error );
  					return;
  
  				}
  
  				content = extensions[ EXTENSIONS.KHR_BINARY_GLTF ].content;
  
  			} else {
  
  				content = LoaderUtils.decodeText( new Uint8Array( data ) );
  
  			}
  
  		}
  
  		const json = JSON.parse( content );
  
  		if ( json.asset === undefined || json.asset.version[ 0 ] < 2 ) {
  
  			if ( onError ) onError( new Error( 'THREE.GLTFLoader: Unsupported asset. glTF versions >=2.0 are supported.' ) );
  			return;
  
  		}
  
  		const parser = new GLTFParser( json, {
  
  			path: path || this.resourcePath || '',
  			crossOrigin: this.crossOrigin,
  			requestHeader: this.requestHeader,
  			manager: this.manager,
  			ktx2Loader: this.ktx2Loader,
  			meshoptDecoder: this.meshoptDecoder
  
  		} );
  
  		parser.fileLoader.setRequestHeader( this.requestHeader );
  
  		for ( let i = 0; i < this.pluginCallbacks.length; i ++ ) {
  
  			const plugin = this.pluginCallbacks[ i ]( parser );
  			plugins[ plugin.name ] = plugin;
  
  			// Workaround to avoid determining as unknown extension
  			// in addUnknownExtensionsToUserData().
  			// Remove this workaround if we move all the existing
  			// extension handlers to plugin system
  			extensions[ plugin.name ] = true;
  
  		}
  
  		if ( json.extensionsUsed ) {
  
  			for ( let i = 0; i < json.extensionsUsed.length; ++ i ) {
  
  				const extensionName = json.extensionsUsed[ i ];
  				const extensionsRequired = json.extensionsRequired || [];
  
  				switch ( extensionName ) {
  
  					case EXTENSIONS.KHR_MATERIALS_UNLIT:
  						extensions[ extensionName ] = new GLTFMaterialsUnlitExtension();
  						break;
  
  					case EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS:
  						extensions[ extensionName ] = new GLTFMaterialsPbrSpecularGlossinessExtension();
  						break;
  
  					case EXTENSIONS.KHR_DRACO_MESH_COMPRESSION:
  						extensions[ extensionName ] = new GLTFDracoMeshCompressionExtension( json, this.dracoLoader );
  						break;
  
  					case EXTENSIONS.KHR_TEXTURE_TRANSFORM:
  						extensions[ extensionName ] = new GLTFTextureTransformExtension();
  						break;
  
  					case EXTENSIONS.KHR_MESH_QUANTIZATION:
  						extensions[ extensionName ] = new GLTFMeshQuantizationExtension();
  						break;
  
  					default:
  
  						if ( extensionsRequired.indexOf( extensionName ) >= 0 && plugins[ extensionName ] === undefined ) {
  
  							console.warn( 'THREE.GLTFLoader: Unknown extension "' + extensionName + '".' );
  
  						}
  
  				}
  
  			}
  
  		}
  
  		parser.setExtensions( extensions );
  		parser.setPlugins( plugins );
  		parser.parse( onLoad, onError );
  
  	}
  
  	parseAsync( data, path ) {
  
  		const scope = this;
  
  		return new Promise( function ( resolve, reject ) {
  
  			scope.parse( data, path, resolve, reject );
  
  		} );
  
  	}
  
  }
  
  /* GLTFREGISTRY */
  
  function GLTFRegistry() {
  
  	let objects = {};
  
  	return	{
  
  		get: function ( key ) {
  
  			return objects[ key ];
  
  		},
  
  		add: function ( key, object ) {
  
  			objects[ key ] = object;
  
  		},
  
  		remove: function ( key ) {
  
  			delete objects[ key ];
  
  		},
  
  		removeAll: function () {
  
  			objects = {};
  
  		}
  
  	};
  
  }
  
  /*********************************/
  /********** EXTENSIONS ***********/
  /*********************************/
  
  const EXTENSIONS = {
  	KHR_BINARY_GLTF: 'KHR_binary_glTF',
  	KHR_DRACO_MESH_COMPRESSION: 'KHR_draco_mesh_compression',
  	KHR_LIGHTS_PUNCTUAL: 'KHR_lights_punctual',
  	KHR_MATERIALS_CLEARCOAT: 'KHR_materials_clearcoat',
  	KHR_MATERIALS_IOR: 'KHR_materials_ior',
  	KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS: 'KHR_materials_pbrSpecularGlossiness',
  	KHR_MATERIALS_SHEEN: 'KHR_materials_sheen',
  	KHR_MATERIALS_SPECULAR: 'KHR_materials_specular',
  	KHR_MATERIALS_TRANSMISSION: 'KHR_materials_transmission',
  	KHR_MATERIALS_UNLIT: 'KHR_materials_unlit',
  	KHR_MATERIALS_VOLUME: 'KHR_materials_volume',
  	KHR_TEXTURE_BASISU: 'KHR_texture_basisu',
  	KHR_TEXTURE_TRANSFORM: 'KHR_texture_transform',
  	KHR_MESH_QUANTIZATION: 'KHR_mesh_quantization',
  	EXT_TEXTURE_WEBP: 'EXT_texture_webp',
  	EXT_MESHOPT_COMPRESSION: 'EXT_meshopt_compression'
  };
  
  /**
   * Punctual Lights Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_lights_punctual
   */
  class GLTFLightsExtension {
  
  	constructor( parser ) {
  
  		this.parser = parser;
  		this.name = EXTENSIONS.KHR_LIGHTS_PUNCTUAL;
  
  		// Object3D instance caches
  		this.cache = { refs: {}, uses: {} };
  
  	}
  
  	_markDefs() {
  
  		const parser = this.parser;
  		const nodeDefs = this.parser.json.nodes || [];
  
  		for ( let nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex ++ ) {
  
  			const nodeDef = nodeDefs[ nodeIndex ];
  
  			if ( nodeDef.extensions
  					&& nodeDef.extensions[ this.name ]
  					&& nodeDef.extensions[ this.name ].light !== undefined ) {
  
  				parser._addNodeRef( this.cache, nodeDef.extensions[ this.name ].light );
  
  			}
  
  		}
  
  	}
  
  	_loadLight( lightIndex ) {
  
  		const parser = this.parser;
  		const cacheKey = 'light:' + lightIndex;
  		let dependency = parser.cache.get( cacheKey );
  
  		if ( dependency ) return dependency;
  
  		const json = parser.json;
  		const extensions = ( json.extensions && json.extensions[ this.name ] ) || {};
  		const lightDefs = extensions.lights || [];
  		const lightDef = lightDefs[ lightIndex ];
  		let lightNode;
  
  		const color = new Color( 0xffffff );
  
  		if ( lightDef.color !== undefined ) color.fromArray( lightDef.color );
  
  		const range = lightDef.range !== undefined ? lightDef.range : 0;
  
  		switch ( lightDef.type ) {
  
  			case 'directional':
  				lightNode = new DirectionalLight( color );
  				lightNode.target.position.set( 0, 0, - 1 );
  				lightNode.add( lightNode.target );
  				break;
  
  			case 'point':
  				lightNode = new PointLight( color );
  				lightNode.distance = range;
  				break;
  
  			case 'spot':
  				lightNode = new SpotLight( color );
  				lightNode.distance = range;
  				// Handle spotlight properties.
  				lightDef.spot = lightDef.spot || {};
  				lightDef.spot.innerConeAngle = lightDef.spot.innerConeAngle !== undefined ? lightDef.spot.innerConeAngle : 0;
  				lightDef.spot.outerConeAngle = lightDef.spot.outerConeAngle !== undefined ? lightDef.spot.outerConeAngle : Math.PI / 4.0;
  				lightNode.angle = lightDef.spot.outerConeAngle;
  				lightNode.penumbra = 1.0 - lightDef.spot.innerConeAngle / lightDef.spot.outerConeAngle;
  				lightNode.target.position.set( 0, 0, - 1 );
  				lightNode.add( lightNode.target );
  				break;
  
  			default:
  				throw new Error( 'THREE.GLTFLoader: Unexpected light type: ' + lightDef.type );
  
  		}
  
  		// Some lights (e.g. spot) default to a position other than the origin. Reset the position
  		// here, because node-level parsing will only override position if explicitly specified.
  		lightNode.position.set( 0, 0, 0 );
  
  		lightNode.decay = 2;
  
  		if ( lightDef.intensity !== undefined ) lightNode.intensity = lightDef.intensity;
  
  		lightNode.name = parser.createUniqueName( lightDef.name || ( 'light_' + lightIndex ) );
  
  		dependency = Promise.resolve( lightNode );
  
  		parser.cache.add( cacheKey, dependency );
  
  		return dependency;
  
  	}
  
  	createNodeAttachment( nodeIndex ) {
  
  		const self = this;
  		const parser = this.parser;
  		const json = parser.json;
  		const nodeDef = json.nodes[ nodeIndex ];
  		const lightDef = ( nodeDef.extensions && nodeDef.extensions[ this.name ] ) || {};
  		const lightIndex = lightDef.light;
  
  		if ( lightIndex === undefined ) return null;
  
  		return this._loadLight( lightIndex ).then( function ( light ) {
  
  			return parser._getNodeRef( self.cache, lightIndex, light );
  
  		} );
  
  	}
  
  }
  
  /**
   * Unlit Materials Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_unlit
   */
  class GLTFMaterialsUnlitExtension {
  
  	constructor() {
  
  		this.name = EXTENSIONS.KHR_MATERIALS_UNLIT;
  
  	}
  
  	getMaterialType() {
  
  		return MeshBasicMaterial;
  
  	}
  
  	extendParams( materialParams, materialDef, parser ) {
  
  		const pending = [];
  
  		materialParams.color = new Color( 1.0, 1.0, 1.0 );
  		materialParams.opacity = 1.0;
  
  		const metallicRoughness = materialDef.pbrMetallicRoughness;
  
  		if ( metallicRoughness ) {
  
  			if ( Array.isArray( metallicRoughness.baseColorFactor ) ) {
  
  				const array = metallicRoughness.baseColorFactor;
  
  				materialParams.color.fromArray( array );
  				materialParams.opacity = array[ 3 ];
  
  			}
  
  			if ( metallicRoughness.baseColorTexture !== undefined ) {
  
  				pending.push( parser.assignTexture( materialParams, 'map', metallicRoughness.baseColorTexture ) );
  
  			}
  
  		}
  
  		return Promise.all( pending );
  
  	}
  
  }
  
  /**
   * Clearcoat Materials Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_clearcoat
   */
  class GLTFMaterialsClearcoatExtension {
  
  	constructor( parser ) {
  
  		this.parser = parser;
  		this.name = EXTENSIONS.KHR_MATERIALS_CLEARCOAT;
  
  	}
  
  	getMaterialType( materialIndex ) {
  
  		const parser = this.parser;
  		const materialDef = parser.json.materials[ materialIndex ];
  
  		if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
  		return MeshPhysicalMaterial;
  
  	}
  
  	extendMaterialParams( materialIndex, materialParams ) {
  
  		const parser = this.parser;
  		const materialDef = parser.json.materials[ materialIndex ];
  
  		if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
  			return Promise.resolve();
  
  		}
  
  		const pending = [];
  
  		const extension = materialDef.extensions[ this.name ];
  
  		if ( extension.clearcoatFactor !== undefined ) {
  
  			materialParams.clearcoat = extension.clearcoatFactor;
  
  		}
  
  		if ( extension.clearcoatTexture !== undefined ) {
  
  			pending.push( parser.assignTexture( materialParams, 'clearcoatMap', extension.clearcoatTexture ) );
  
  		}
  
  		if ( extension.clearcoatRoughnessFactor !== undefined ) {
  
  			materialParams.clearcoatRoughness = extension.clearcoatRoughnessFactor;
  
  		}
  
  		if ( extension.clearcoatRoughnessTexture !== undefined ) {
  
  			pending.push( parser.assignTexture( materialParams, 'clearcoatRoughnessMap', extension.clearcoatRoughnessTexture ) );
  
  		}
  
  		if ( extension.clearcoatNormalTexture !== undefined ) {
  
  			pending.push( parser.assignTexture( materialParams, 'clearcoatNormalMap', extension.clearcoatNormalTexture ) );
  
  			if ( extension.clearcoatNormalTexture.scale !== undefined ) {
  
  				const scale = extension.clearcoatNormalTexture.scale;
  
  				materialParams.clearcoatNormalScale = new Vector2( scale, scale );
  
  			}
  
  		}
  
  		return Promise.all( pending );
  
  	}
  
  }
  
  /**
   * Sheen Materials Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Khronos/KHR_materials_sheen
   */
  class GLTFMaterialsSheenExtension {
  
  	constructor( parser ) {
  
  		this.parser = parser;
  		this.name = EXTENSIONS.KHR_MATERIALS_SHEEN;
  
  	}
  
  	getMaterialType( materialIndex ) {
  
  		const parser = this.parser;
  		const materialDef = parser.json.materials[ materialIndex ];
  
  		if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
  		return MeshPhysicalMaterial;
  
  	}
  
  	extendMaterialParams( materialIndex, materialParams ) {
  
  		const parser = this.parser;
  		const materialDef = parser.json.materials[ materialIndex ];
  
  		if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
  			return Promise.resolve();
  
  		}
  
  		const pending = [];
  
  		materialParams.sheenColor = new Color( 0, 0, 0 );
  		materialParams.sheenRoughness = 0;
  		materialParams.sheen = 1;
  
  		const extension = materialDef.extensions[ this.name ];
  
  		if ( extension.sheenColorFactor !== undefined ) {
  
  			materialParams.sheenColor.fromArray( extension.sheenColorFactor );
  
  		}
  
  		if ( extension.sheenRoughnessFactor !== undefined ) {
  
  			materialParams.sheenRoughness = extension.sheenRoughnessFactor;
  
  		}
  
  		if ( extension.sheenColorTexture !== undefined ) {
  
  			pending.push( parser.assignTexture( materialParams, 'sheenColorMap', extension.sheenColorTexture ) );
  
  		}
  
  		if ( extension.sheenRoughnessTexture !== undefined ) {
  
  			pending.push( parser.assignTexture( materialParams, 'sheenRoughnessMap', extension.sheenRoughnessTexture ) );
  
  		}
  
  		return Promise.all( pending );
  
  	}
  
  }
  
  /**
   * Transmission Materials Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_transmission
   * Draft: https://github.com/KhronosGroup/glTF/pull/1698
   */
  class GLTFMaterialsTransmissionExtension {
  
  	constructor( parser ) {
  
  		this.parser = parser;
  		this.name = EXTENSIONS.KHR_MATERIALS_TRANSMISSION;
  
  	}
  
  	getMaterialType( materialIndex ) {
  
  		const parser = this.parser;
  		const materialDef = parser.json.materials[ materialIndex ];
  
  		if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
  		return MeshPhysicalMaterial;
  
  	}
  
  	extendMaterialParams( materialIndex, materialParams ) {
  
  		const parser = this.parser;
  		const materialDef = parser.json.materials[ materialIndex ];
  
  		if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
  			return Promise.resolve();
  
  		}
  
  		const pending = [];
  
  		const extension = materialDef.extensions[ this.name ];
  
  		if ( extension.transmissionFactor !== undefined ) {
  
  			materialParams.transmission = extension.transmissionFactor;
  
  		}
  
  		if ( extension.transmissionTexture !== undefined ) {
  
  			pending.push( parser.assignTexture( materialParams, 'transmissionMap', extension.transmissionTexture ) );
  
  		}
  
  		return Promise.all( pending );
  
  	}
  
  }
  
  /**
   * Materials Volume Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_volume
   */
  class GLTFMaterialsVolumeExtension {
  
  	constructor( parser ) {
  
  		this.parser = parser;
  		this.name = EXTENSIONS.KHR_MATERIALS_VOLUME;
  
  	}
  
  	getMaterialType( materialIndex ) {
  
  		const parser = this.parser;
  		const materialDef = parser.json.materials[ materialIndex ];
  
  		if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
  		return MeshPhysicalMaterial;
  
  	}
  
  	extendMaterialParams( materialIndex, materialParams ) {
  
  		const parser = this.parser;
  		const materialDef = parser.json.materials[ materialIndex ];
  
  		if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
  			return Promise.resolve();
  
  		}
  
  		const pending = [];
  
  		const extension = materialDef.extensions[ this.name ];
  
  		materialParams.thickness = extension.thicknessFactor !== undefined ? extension.thicknessFactor : 0;
  
  		if ( extension.thicknessTexture !== undefined ) {
  
  			pending.push( parser.assignTexture( materialParams, 'thicknessMap', extension.thicknessTexture ) );
  
  		}
  
  		materialParams.attenuationDistance = extension.attenuationDistance || 0;
  
  		const colorArray = extension.attenuationColor || [ 1, 1, 1 ];
  		materialParams.attenuationColor = new Color( colorArray[ 0 ], colorArray[ 1 ], colorArray[ 2 ] );
  
  		return Promise.all( pending );
  
  	}
  
  }
  
  /**
   * Materials ior Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_ior
   */
  class GLTFMaterialsIorExtension {
  
  	constructor( parser ) {
  
  		this.parser = parser;
  		this.name = EXTENSIONS.KHR_MATERIALS_IOR;
  
  	}
  
  	getMaterialType( materialIndex ) {
  
  		const parser = this.parser;
  		const materialDef = parser.json.materials[ materialIndex ];
  
  		if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
  		return MeshPhysicalMaterial;
  
  	}
  
  	extendMaterialParams( materialIndex, materialParams ) {
  
  		const parser = this.parser;
  		const materialDef = parser.json.materials[ materialIndex ];
  
  		if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
  			return Promise.resolve();
  
  		}
  
  		const extension = materialDef.extensions[ this.name ];
  
  		materialParams.ior = extension.ior !== undefined ? extension.ior : 1.5;
  
  		return Promise.resolve();
  
  	}
  
  }
  
  /**
   * Materials specular Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_specular
   */
  class GLTFMaterialsSpecularExtension {
  
  	constructor( parser ) {
  
  		this.parser = parser;
  		this.name = EXTENSIONS.KHR_MATERIALS_SPECULAR;
  
  	}
  
  	getMaterialType( materialIndex ) {
  
  		const parser = this.parser;
  		const materialDef = parser.json.materials[ materialIndex ];
  
  		if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
  
  		return MeshPhysicalMaterial;
  
  	}
  
  	extendMaterialParams( materialIndex, materialParams ) {
  
  		const parser = this.parser;
  		const materialDef = parser.json.materials[ materialIndex ];
  
  		if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {
  
  			return Promise.resolve();
  
  		}
  
  		const pending = [];
  
  		const extension = materialDef.extensions[ this.name ];
  
  		materialParams.specularIntensity = extension.specularFactor !== undefined ? extension.specularFactor : 1.0;
  
  		if ( extension.specularTexture !== undefined ) {
  
  			pending.push( parser.assignTexture( materialParams, 'specularIntensityMap', extension.specularTexture ) );
  
  		}
  
  		const colorArray = extension.specularColorFactor || [ 1, 1, 1 ];
  		materialParams.specularColor = new Color( colorArray[ 0 ], colorArray[ 1 ], colorArray[ 2 ] );
  
  		if ( extension.specularColorTexture !== undefined ) {
  
  			pending.push( parser.assignTexture( materialParams, 'specularColorMap', extension.specularColorTexture ).then( function ( texture ) {
  
  				texture.encoding = sRGBEncoding;
  
  			} ) );
  
  		}
  
  		return Promise.all( pending );
  
  	}
  
  }
  
  /**
   * BasisU Texture Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_texture_basisu
   */
  class GLTFTextureBasisUExtension {
  
  	constructor( parser ) {
  
  		this.parser = parser;
  		this.name = EXTENSIONS.KHR_TEXTURE_BASISU;
  
  	}
  
  	loadTexture( textureIndex ) {
  
  		const parser = this.parser;
  		const json = parser.json;
  
  		const textureDef = json.textures[ textureIndex ];
  
  		if ( ! textureDef.extensions || ! textureDef.extensions[ this.name ] ) {
  
  			return null;
  
  		}
  
  		const extension = textureDef.extensions[ this.name ];
  		const source = json.images[ extension.source ];
  		const loader = parser.options.ktx2Loader;
  
  		if ( ! loader ) {
  
  			if ( json.extensionsRequired && json.extensionsRequired.indexOf( this.name ) >= 0 ) {
  
  				throw new Error( 'THREE.GLTFLoader: setKTX2Loader must be called before loading KTX2 textures' );
  
  			} else {
  
  				// Assumes that the extension is optional and that a fallback texture is present
  				return null;
  
  			}
  
  		}
  
  		return parser.loadTextureImage( textureIndex, source, loader );
  
  	}
  
  }
  
  /**
   * WebP Texture Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_texture_webp
   */
  class GLTFTextureWebPExtension {
  
  	constructor( parser ) {
  
  		this.parser = parser;
  		this.name = EXTENSIONS.EXT_TEXTURE_WEBP;
  		this.isSupported = null;
  
  	}
  
  	loadTexture( textureIndex ) {
  
  		const name = this.name;
  		const parser = this.parser;
  		const json = parser.json;
  
  		const textureDef = json.textures[ textureIndex ];
  
  		if ( ! textureDef.extensions || ! textureDef.extensions[ name ] ) {
  
  			return null;
  
  		}
  
  		const extension = textureDef.extensions[ name ];
  		const source = json.images[ extension.source ];
  
  		let loader = parser.textureLoader;
  		if ( source.uri ) {
  
  			const handler = parser.options.manager.getHandler( source.uri );
  			if ( handler !== null ) loader = handler;
  
  		}
  
  		return this.detectSupport().then( function ( isSupported ) {
  
  			if ( isSupported ) return parser.loadTextureImage( textureIndex, source, loader );
  
  			if ( json.extensionsRequired && json.extensionsRequired.indexOf( name ) >= 0 ) {
  
  				throw new Error( 'THREE.GLTFLoader: WebP required by asset but unsupported.' );
  
  			}
  
  			// Fall back to PNG or JPEG.
  			return parser.loadTexture( textureIndex );
  
  		} );
  
  	}
  
  	detectSupport() {
  
  		if ( ! this.isSupported ) {
  
  			this.isSupported = new Promise( function ( resolve ) {
  
  				const image = new Image();
  
  				// Lossy test image. Support for lossy images doesn't guarantee support for all
  				// WebP images, unfortunately.
  				image.src = 'data:image/webp;base64,UklGRiIAAABXRUJQVlA4IBYAAAAwAQCdASoBAAEADsD+JaQAA3AAAAAA';
  
  				image.onload = image.onerror = function () {
  
  					resolve( image.height === 1 );
  
  				};
  
  			} );
  
  		}
  
  		return this.isSupported;
  
  	}
  
  }
  
  /**
   * meshopt BufferView Compression Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_meshopt_compression
   */
  class GLTFMeshoptCompression {
  
  	constructor( parser ) {
  
  		this.name = EXTENSIONS.EXT_MESHOPT_COMPRESSION;
  		this.parser = parser;
  
  	}
  
  	loadBufferView( index ) {
  
  		const json = this.parser.json;
  		const bufferView = json.bufferViews[ index ];
  
  		if ( bufferView.extensions && bufferView.extensions[ this.name ] ) {
  
  			const extensionDef = bufferView.extensions[ this.name ];
  
  			const buffer = this.parser.getDependency( 'buffer', extensionDef.buffer );
  			const decoder = this.parser.options.meshoptDecoder;
  
  			if ( ! decoder || ! decoder.supported ) {
  
  				if ( json.extensionsRequired && json.extensionsRequired.indexOf( this.name ) >= 0 ) {
  
  					throw new Error( 'THREE.GLTFLoader: setMeshoptDecoder must be called before loading compressed files' );
  
  				} else {
  
  					// Assumes that the extension is optional and that fallback buffer data is present
  					return null;
  
  				}
  
  			}
  
  			return Promise.all( [ buffer, decoder.ready ] ).then( function ( res ) {
  
  				const byteOffset = extensionDef.byteOffset || 0;
  				const byteLength = extensionDef.byteLength || 0;
  
  				const count = extensionDef.count;
  				const stride = extensionDef.byteStride;
  
  				const result = new ArrayBuffer( count * stride );
  				const source = new Uint8Array( res[ 0 ], byteOffset, byteLength );
  
  				decoder.decodeGltfBuffer( new Uint8Array( result ), count, stride, source, extensionDef.mode, extensionDef.filter );
  				return result;
  
  			} );
  
  		} else {
  
  			return null;
  
  		}
  
  	}
  
  }
  
  /* BINARY EXTENSION */
  const BINARY_EXTENSION_HEADER_MAGIC = 'glTF';
  const BINARY_EXTENSION_HEADER_LENGTH = 12;
  const BINARY_EXTENSION_CHUNK_TYPES = { JSON: 0x4E4F534A, BIN: 0x004E4942 };
  
  class GLTFBinaryExtension {
  
  	constructor( data ) {
  
  		this.name = EXTENSIONS.KHR_BINARY_GLTF;
  		this.content = null;
  		this.body = null;
  
  		const headerView = new DataView( data, 0, BINARY_EXTENSION_HEADER_LENGTH );
  
  		this.header = {
  			magic: LoaderUtils.decodeText( new Uint8Array( data.slice( 0, 4 ) ) ),
  			version: headerView.getUint32( 4, true ),
  			length: headerView.getUint32( 8, true )
  		};
  
  		if ( this.header.magic !== BINARY_EXTENSION_HEADER_MAGIC ) {
  
  			throw new Error( 'THREE.GLTFLoader: Unsupported glTF-Binary header.' );
  
  		} else if ( this.header.version < 2.0 ) {
  
  			throw new Error( 'THREE.GLTFLoader: Legacy binary file detected.' );
  
  		}
  
  		const chunkContentsLength = this.header.length - BINARY_EXTENSION_HEADER_LENGTH;
  		const chunkView = new DataView( data, BINARY_EXTENSION_HEADER_LENGTH );
  		let chunkIndex = 0;
  
  		while ( chunkIndex < chunkContentsLength ) {
  
  			const chunkLength = chunkView.getUint32( chunkIndex, true );
  			chunkIndex += 4;
  
  			const chunkType = chunkView.getUint32( chunkIndex, true );
  			chunkIndex += 4;
  
  			if ( chunkType === BINARY_EXTENSION_CHUNK_TYPES.JSON ) {
  
  				const contentArray = new Uint8Array( data, BINARY_EXTENSION_HEADER_LENGTH + chunkIndex, chunkLength );
  				this.content = LoaderUtils.decodeText( contentArray );
  
  			} else if ( chunkType === BINARY_EXTENSION_CHUNK_TYPES.BIN ) {
  
  				const byteOffset = BINARY_EXTENSION_HEADER_LENGTH + chunkIndex;
  				this.body = data.slice( byteOffset, byteOffset + chunkLength );
  
  			}
  
  			// Clients must ignore chunks with unknown types.
  
  			chunkIndex += chunkLength;
  
  		}
  
  		if ( this.content === null ) {
  
  			throw new Error( 'THREE.GLTFLoader: JSON content not found.' );
  
  		}
  
  	}
  
  }
  
  /**
   * DRACO Mesh Compression Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_draco_mesh_compression
   */
  class GLTFDracoMeshCompressionExtension {
  
  	constructor( json, dracoLoader ) {
  
  		if ( ! dracoLoader ) {
  
  			throw new Error( 'THREE.GLTFLoader: No DRACOLoader instance provided.' );
  
  		}
  
  		this.name = EXTENSIONS.KHR_DRACO_MESH_COMPRESSION;
  		this.json = json;
  		this.dracoLoader = dracoLoader;
  		this.dracoLoader.preload();
  
  	}
  
  	decodePrimitive( primitive, parser ) {
  
  		const json = this.json;
  		const dracoLoader = this.dracoLoader;
  		const bufferViewIndex = primitive.extensions[ this.name ].bufferView;
  		const gltfAttributeMap = primitive.extensions[ this.name ].attributes;
  		const threeAttributeMap = {};
  		const attributeNormalizedMap = {};
  		const attributeTypeMap = {};
  
  		for ( const attributeName in gltfAttributeMap ) {
  
  			const threeAttributeName = ATTRIBUTES[ attributeName ] || attributeName.toLowerCase();
  
  			threeAttributeMap[ threeAttributeName ] = gltfAttributeMap[ attributeName ];
  
  		}
  
  		for ( const attributeName in primitive.attributes ) {
  
  			const threeAttributeName = ATTRIBUTES[ attributeName ] || attributeName.toLowerCase();
  
  			if ( gltfAttributeMap[ attributeName ] !== undefined ) {
  
  				const accessorDef = json.accessors[ primitive.attributes[ attributeName ] ];
  				const componentType = WEBGL_COMPONENT_TYPES[ accessorDef.componentType ];
  
  				attributeTypeMap[ threeAttributeName ] = componentType;
  				attributeNormalizedMap[ threeAttributeName ] = accessorDef.normalized === true;
  
  			}
  
  		}
  
  		return parser.getDependency( 'bufferView', bufferViewIndex ).then( function ( bufferView ) {
  
  			return new Promise( function ( resolve ) {
  
  				dracoLoader.decodeDracoFile( bufferView, function ( geometry ) {
  
  					for ( const attributeName in geometry.attributes ) {
  
  						const attribute = geometry.attributes[ attributeName ];
  						const normalized = attributeNormalizedMap[ attributeName ];
  
  						if ( normalized !== undefined ) attribute.normalized = normalized;
  
  					}
  
  					resolve( geometry );
  
  				}, threeAttributeMap, attributeTypeMap );
  
  			} );
  
  		} );
  
  	}
  
  }
  
  /**
   * Texture Transform Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_texture_transform
   */
  class GLTFTextureTransformExtension {
  
  	constructor() {
  
  		this.name = EXTENSIONS.KHR_TEXTURE_TRANSFORM;
  
  	}
  
  	extendTexture( texture, transform ) {
  
  		if ( transform.texCoord !== undefined ) {
  
  			console.warn( 'THREE.GLTFLoader: Custom UV sets in "' + this.name + '" extension not yet supported.' );
  
  		}
  
  		if ( transform.offset === undefined && transform.rotation === undefined && transform.scale === undefined ) {
  
  			// See https://github.com/mrdoob/three.js/issues/21819.
  			return texture;
  
  		}
  
  		texture = texture.clone();
  
  		if ( transform.offset !== undefined ) {
  
  			texture.offset.fromArray( transform.offset );
  
  		}
  
  		if ( transform.rotation !== undefined ) {
  
  			texture.rotation = transform.rotation;
  
  		}
  
  		if ( transform.scale !== undefined ) {
  
  			texture.repeat.fromArray( transform.scale );
  
  		}
  
  		texture.needsUpdate = true;
  
  		return texture;
  
  	}
  
  }
  
  /**
   * Specular-Glossiness Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Archived/KHR_materials_pbrSpecularGlossiness
   */
  
  /**
   * A sub class of StandardMaterial with some of the functionality
   * changed via the `onBeforeCompile` callback
   * @pailhead
   */
  class GLTFMeshStandardSGMaterial extends MeshStandardMaterial {
  
  	constructor( params ) {
  
  		super();
  
  		this.isGLTFSpecularGlossinessMaterial = true;
  
  		//various chunks that need replacing
  		const specularMapParsFragmentChunk = [
  			'#ifdef USE_SPECULARMAP',
  			'	uniform sampler2D specularMap;',
  			'#endif'
  		].join( '\n' );
  
  		const glossinessMapParsFragmentChunk = [
  			'#ifdef USE_GLOSSINESSMAP',
  			'	uniform sampler2D glossinessMap;',
  			'#endif'
  		].join( '\n' );
  
  		const specularMapFragmentChunk = [
  			'vec3 specularFactor = specular;',
  			'#ifdef USE_SPECULARMAP',
  			'	vec4 texelSpecular = texture2D( specularMap, vUv );',
  			'	// reads channel RGB, compatible with a glTF Specular-Glossiness (RGBA) texture',
  			'	specularFactor *= texelSpecular.rgb;',
  			'#endif'
  		].join( '\n' );
  
  		const glossinessMapFragmentChunk = [
  			'float glossinessFactor = glossiness;',
  			'#ifdef USE_GLOSSINESSMAP',
  			'	vec4 texelGlossiness = texture2D( glossinessMap, vUv );',
  			'	// reads channel A, compatible with a glTF Specular-Glossiness (RGBA) texture',
  			'	glossinessFactor *= texelGlossiness.a;',
  			'#endif'
  		].join( '\n' );
  
  		const lightPhysicalFragmentChunk = [
  			'PhysicalMaterial material;',
  			'material.diffuseColor = diffuseColor.rgb * ( 1. - max( specularFactor.r, max( specularFactor.g, specularFactor.b ) ) );',
  			'vec3 dxy = max( abs( dFdx( geometryNormal ) ), abs( dFdy( geometryNormal ) ) );',
  			'float geometryRoughness = max( max( dxy.x, dxy.y ), dxy.z );',
  			'material.roughness = max( 1.0 - glossinessFactor, 0.0525 ); // 0.0525 corresponds to the base mip of a 256 cubemap.',
  			'material.roughness += geometryRoughness;',
  			'material.roughness = min( material.roughness, 1.0 );',
  			'material.specularColor = specularFactor;',
  		].join( '\n' );
  
  		const uniforms = {
  			specular: { value: new Color().setHex( 0xffffff ) },
  			glossiness: { value: 1 },
  			specularMap: { value: null },
  			glossinessMap: { value: null }
  		};
  
  		this._extraUniforms = uniforms;
  
  		this.onBeforeCompile = function ( shader ) {
  
  			for ( const uniformName in uniforms ) {
  
  				shader.uniforms[ uniformName ] = uniforms[ uniformName ];
  
  			}
  
  			shader.fragmentShader = shader.fragmentShader
  				.replace( 'uniform float roughness;', 'uniform vec3 specular;' )
  				.replace( 'uniform float metalness;', 'uniform float glossiness;' )
  				.replace( '#include <roughnessmap_pars_fragment>', specularMapParsFragmentChunk )
  				.replace( '#include <metalnessmap_pars_fragment>', glossinessMapParsFragmentChunk )
  				.replace( '#include <roughnessmap_fragment>', specularMapFragmentChunk )
  				.replace( '#include <metalnessmap_fragment>', glossinessMapFragmentChunk )
  				.replace( '#include <lights_physical_fragment>', lightPhysicalFragmentChunk );
  
  		};
  
  		Object.defineProperties( this, {
  
  			specular: {
  				get: function () {
  
  					return uniforms.specular.value;
  
  				},
  				set: function ( v ) {
  
  					uniforms.specular.value = v;
  
  				}
  			},
  
  			specularMap: {
  				get: function () {
  
  					return uniforms.specularMap.value;
  
  				},
  				set: function ( v ) {
  
  					uniforms.specularMap.value = v;
  
  					if ( v ) {
  
  						this.defines.USE_SPECULARMAP = ''; // USE_UV is set by the renderer for specular maps
  
  					} else {
  
  						delete this.defines.USE_SPECULARMAP;
  
  					}
  
  				}
  			},
  
  			glossiness: {
  				get: function () {
  
  					return uniforms.glossiness.value;
  
  				},
  				set: function ( v ) {
  
  					uniforms.glossiness.value = v;
  
  				}
  			},
  
  			glossinessMap: {
  				get: function () {
  
  					return uniforms.glossinessMap.value;
  
  				},
  				set: function ( v ) {
  
  					uniforms.glossinessMap.value = v;
  
  					if ( v ) {
  
  						this.defines.USE_GLOSSINESSMAP = '';
  						this.defines.USE_UV = '';
  
  					} else {
  
  						delete this.defines.USE_GLOSSINESSMAP;
  						delete this.defines.USE_UV;
  
  					}
  
  				}
  			}
  
  		} );
  
  		delete this.metalness;
  		delete this.roughness;
  		delete this.metalnessMap;
  		delete this.roughnessMap;
  
  		this.setValues( params );
  
  	}
  
  	copy( source ) {
  
  		super.copy( source );
  
  		this.specularMap = source.specularMap;
  		this.specular.copy( source.specular );
  		this.glossinessMap = source.glossinessMap;
  		this.glossiness = source.glossiness;
  		delete this.metalness;
  		delete this.roughness;
  		delete this.metalnessMap;
  		delete this.roughnessMap;
  		return this;
  
  	}
  
  }
  
  
  class GLTFMaterialsPbrSpecularGlossinessExtension {
  
  	constructor() {
  
  		this.name = EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS;
  
  		this.specularGlossinessParams = [
  			'color',
  			'map',
  			'lightMap',
  			'lightMapIntensity',
  			'aoMap',
  			'aoMapIntensity',
  			'emissive',
  			'emissiveIntensity',
  			'emissiveMap',
  			'bumpMap',
  			'bumpScale',
  			'normalMap',
  			'normalMapType',
  			'displacementMap',
  			'displacementScale',
  			'displacementBias',
  			'specularMap',
  			'specular',
  			'glossinessMap',
  			'glossiness',
  			'alphaMap',
  			'envMap',
  			'envMapIntensity',
  			'refractionRatio',
  		];
  
  	}
  
  	getMaterialType() {
  
  		return GLTFMeshStandardSGMaterial;
  
  	}
  
  	extendParams( materialParams, materialDef, parser ) {
  
  		const pbrSpecularGlossiness = materialDef.extensions[ this.name ];
  
  		materialParams.color = new Color( 1.0, 1.0, 1.0 );
  		materialParams.opacity = 1.0;
  
  		const pending = [];
  
  		if ( Array.isArray( pbrSpecularGlossiness.diffuseFactor ) ) {
  
  			const array = pbrSpecularGlossiness.diffuseFactor;
  
  			materialParams.color.fromArray( array );
  			materialParams.opacity = array[ 3 ];
  
  		}
  
  		if ( pbrSpecularGlossiness.diffuseTexture !== undefined ) {
  
  			pending.push( parser.assignTexture( materialParams, 'map', pbrSpecularGlossiness.diffuseTexture ) );
  
  		}
  
  		materialParams.emissive = new Color( 0.0, 0.0, 0.0 );
  		materialParams.glossiness = pbrSpecularGlossiness.glossinessFactor !== undefined ? pbrSpecularGlossiness.glossinessFactor : 1.0;
  		materialParams.specular = new Color( 1.0, 1.0, 1.0 );
  
  		if ( Array.isArray( pbrSpecularGlossiness.specularFactor ) ) {
  
  			materialParams.specular.fromArray( pbrSpecularGlossiness.specularFactor );
  
  		}
  
  		if ( pbrSpecularGlossiness.specularGlossinessTexture !== undefined ) {
  
  			const specGlossMapDef = pbrSpecularGlossiness.specularGlossinessTexture;
  			pending.push( parser.assignTexture( materialParams, 'glossinessMap', specGlossMapDef ) );
  			pending.push( parser.assignTexture( materialParams, 'specularMap', specGlossMapDef ) );
  
  		}
  
  		return Promise.all( pending );
  
  	}
  
  	createMaterial( materialParams ) {
  
  		const material = new GLTFMeshStandardSGMaterial( materialParams );
  		material.fog = true;
  
  		material.color = materialParams.color;
  
  		material.map = materialParams.map === undefined ? null : materialParams.map;
  
  		material.lightMap = null;
  		material.lightMapIntensity = 1.0;
  
  		material.aoMap = materialParams.aoMap === undefined ? null : materialParams.aoMap;
  		material.aoMapIntensity = 1.0;
  
  		material.emissive = materialParams.emissive;
  		material.emissiveIntensity = 1.0;
  		material.emissiveMap = materialParams.emissiveMap === undefined ? null : materialParams.emissiveMap;
  
  		material.bumpMap = materialParams.bumpMap === undefined ? null : materialParams.bumpMap;
  		material.bumpScale = 1;
  
  		material.normalMap = materialParams.normalMap === undefined ? null : materialParams.normalMap;
  		material.normalMapType = TangentSpaceNormalMap;
  
  		if ( materialParams.normalScale ) material.normalScale = materialParams.normalScale;
  
  		material.displacementMap = null;
  		material.displacementScale = 1;
  		material.displacementBias = 0;
  
  		material.specularMap = materialParams.specularMap === undefined ? null : materialParams.specularMap;
  		material.specular = materialParams.specular;
  
  		material.glossinessMap = materialParams.glossinessMap === undefined ? null : materialParams.glossinessMap;
  		material.glossiness = materialParams.glossiness;
  
  		material.alphaMap = null;
  
  		material.envMap = materialParams.envMap === undefined ? null : materialParams.envMap;
  		material.envMapIntensity = 1.0;
  
  		material.refractionRatio = 0.98;
  
  		return material;
  
  	}
  
  }
  
  /**
   * Mesh Quantization Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_mesh_quantization
   */
  class GLTFMeshQuantizationExtension {
  
  	constructor() {
  
  		this.name = EXTENSIONS.KHR_MESH_QUANTIZATION;
  
  	}
  
  }
  
  /*********************************/
  /********** INTERPOLATION ********/
  /*********************************/
  
  // Spline Interpolation
  // Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#appendix-c-spline-interpolation
  class GLTFCubicSplineInterpolant extends Interpolant {
  
  	constructor( parameterPositions, sampleValues, sampleSize, resultBuffer ) {
  
  		super( parameterPositions, sampleValues, sampleSize, resultBuffer );
  
  	}
  
  	copySampleValue_( index ) {
  
  		// Copies a sample value to the result buffer. See description of glTF
  		// CUBICSPLINE values layout in interpolate_() function below.
  
  		const result = this.resultBuffer,
  			values = this.sampleValues,
  			valueSize = this.valueSize,
  			offset = index * valueSize * 3 + valueSize;
  
  		for ( let i = 0; i !== valueSize; i ++ ) {
  
  			result[ i ] = values[ offset + i ];
  
  		}
  
  		return result;
  
  	}
  
  }
  
  GLTFCubicSplineInterpolant.prototype.beforeStart_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;
  
  GLTFCubicSplineInterpolant.prototype.afterEnd_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;
  
  GLTFCubicSplineInterpolant.prototype.interpolate_ = function ( i1, t0, t, t1 ) {
  
  	const result = this.resultBuffer;
  	const values = this.sampleValues;
  	const stride = this.valueSize;
  
  	const stride2 = stride * 2;
  	const stride3 = stride * 3;
  
  	const td = t1 - t0;
  
  	const p = ( t - t0 ) / td;
  	const pp = p * p;
  	const ppp = pp * p;
  
  	const offset1 = i1 * stride3;
  	const offset0 = offset1 - stride3;
  
  	const s2 = - 2 * ppp + 3 * pp;
  	const s3 = ppp - pp;
  	const s0 = 1 - s2;
  	const s1 = s3 - pp + p;
  
  	// Layout of keyframe output values for CUBICSPLINE animations:
  	//   [ inTangent_1, splineVertex_1, outTangent_1, inTangent_2, splineVertex_2, ... ]
  	for ( let i = 0; i !== stride; i ++ ) {
  
  		const p0 = values[ offset0 + i + stride ]; // splineVertex_k
  		const m0 = values[ offset0 + i + stride2 ] * td; // outTangent_k * (t_k+1 - t_k)
  		const p1 = values[ offset1 + i + stride ]; // splineVertex_k+1
  		const m1 = values[ offset1 + i ] * td; // inTangent_k+1 * (t_k+1 - t_k)
  
  		result[ i ] = s0 * p0 + s1 * m0 + s2 * p1 + s3 * m1;
  
  	}
  
  	return result;
  
  };
  
  const _q = new Quaternion();
  
  class GLTFCubicSplineQuaternionInterpolant extends GLTFCubicSplineInterpolant {
  
  	interpolate_( i1, t0, t, t1 ) {
  
  		const result = super.interpolate_( i1, t0, t, t1 );
  
  		_q.fromArray( result ).normalize().toArray( result );
  
  		return result;
  
  	}
  
  }
  
  
  /*********************************/
  /********** INTERNALS ************/
  /*********************************/
  
  /* CONSTANTS */
  
  const WEBGL_CONSTANTS = {
  	FLOAT: 5126,
  	//FLOAT_MAT2: 35674,
  	FLOAT_MAT3: 35675,
  	FLOAT_MAT4: 35676,
  	FLOAT_VEC2: 35664,
  	FLOAT_VEC3: 35665,
  	FLOAT_VEC4: 35666,
  	LINEAR: 9729,
  	REPEAT: 10497,
  	SAMPLER_2D: 35678,
  	POINTS: 0,
  	LINES: 1,
  	LINE_LOOP: 2,
  	LINE_STRIP: 3,
  	TRIANGLES: 4,
  	TRIANGLE_STRIP: 5,
  	TRIANGLE_FAN: 6,
  	UNSIGNED_BYTE: 5121,
  	UNSIGNED_SHORT: 5123
  };
  
  const WEBGL_COMPONENT_TYPES = {
  	5120: Int8Array,
  	5121: Uint8Array,
  	5122: Int16Array,
  	5123: Uint16Array,
  	5125: Uint32Array,
  	5126: Float32Array
  };
  
  const WEBGL_FILTERS = {
  	9728: NearestFilter,
  	9729: LinearFilter,
  	9984: NearestMipmapNearestFilter,
  	9985: LinearMipmapNearestFilter,
  	9986: NearestMipmapLinearFilter,
  	9987: LinearMipmapLinearFilter
  };
  
  const WEBGL_WRAPPINGS = {
  	33071: ClampToEdgeWrapping,
  	33648: MirroredRepeatWrapping,
  	10497: RepeatWrapping
  };
  
  const WEBGL_TYPE_SIZES = {
  	'SCALAR': 1,
  	'VEC2': 2,
  	'VEC3': 3,
  	'VEC4': 4,
  	'MAT2': 4,
  	'MAT3': 9,
  	'MAT4': 16
  };
  
  const ATTRIBUTES = {
  	POSITION: 'position',
  	NORMAL: 'normal',
  	TANGENT: 'tangent',
  	TEXCOORD_0: 'uv',
  	TEXCOORD_1: 'uv2',
  	COLOR_0: 'color',
  	WEIGHTS_0: 'skinWeight',
  	JOINTS_0: 'skinIndex',
  };
  
  const PATH_PROPERTIES = {
  	scale: 'scale',
  	translation: 'position',
  	rotation: 'quaternion',
  	weights: 'morphTargetInfluences'
  };
  
  const INTERPOLATION = {
  	CUBICSPLINE: undefined, // We use a custom interpolant (GLTFCubicSplineInterpolation) for CUBICSPLINE tracks. Each
  		                        // keyframe track will be initialized with a default interpolation type, then modified.
  	LINEAR: InterpolateLinear,
  	STEP: InterpolateDiscrete
  };
  
  const ALPHA_MODES = {
  	OPAQUE: 'OPAQUE',
  	MASK: 'MASK',
  	BLEND: 'BLEND'
  };
  
  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#default-material
   */
  function createDefaultMaterial( cache ) {
  
  	if ( cache[ 'DefaultMaterial' ] === undefined ) {
  
  		cache[ 'DefaultMaterial' ] = new MeshStandardMaterial( {
  			color: 0xFFFFFF,
  			emissive: 0x000000,
  			metalness: 1,
  			roughness: 1,
  			transparent: false,
  			depthTest: true,
  			side: FrontSide
  		} );
  
  	}
  
  	return cache[ 'DefaultMaterial' ];
  
  }
  
  function addUnknownExtensionsToUserData( knownExtensions, object, objectDef ) {
  
  	// Add unknown glTF extensions to an object's userData.
  
  	for ( const name in objectDef.extensions ) {
  
  		if ( knownExtensions[ name ] === undefined ) {
  
  			object.userData.gltfExtensions = object.userData.gltfExtensions || {};
  			object.userData.gltfExtensions[ name ] = objectDef.extensions[ name ];
  
  		}
  
  	}
  
  }
  
  /**
   * @param {Object3D|Material|BufferGeometry} object
   * @param {GLTF.definition} gltfDef
   */
  function assignExtrasToUserData( object, gltfDef ) {
  
  	if ( gltfDef.extras !== undefined ) {
  
  		if ( typeof gltfDef.extras === 'object' ) {
  
  			Object.assign( object.userData, gltfDef.extras );
  
  		} else {
  
  			console.warn( 'THREE.GLTFLoader: Ignoring primitive type .extras, ' + gltfDef.extras );
  
  		}
  
  	}
  
  }
  
  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#morph-targets
   *
   * @param {BufferGeometry} geometry
   * @param {Array<GLTF.Target>} targets
   * @param {GLTFParser} parser
   * @return {Promise<BufferGeometry>}
   */
  function addMorphTargets( geometry, targets, parser ) {
  
  	let hasMorphPosition = false;
  	let hasMorphNormal = false;
  
  	for ( let i = 0, il = targets.length; i < il; i ++ ) {
  
  		const target = targets[ i ];
  
  		if ( target.POSITION !== undefined ) hasMorphPosition = true;
  		if ( target.NORMAL !== undefined ) hasMorphNormal = true;
  
  		if ( hasMorphPosition && hasMorphNormal ) break;
  
  	}
  
  	if ( ! hasMorphPosition && ! hasMorphNormal ) return Promise.resolve( geometry );
  
  	const pendingPositionAccessors = [];
  	const pendingNormalAccessors = [];
  
  	for ( let i = 0, il = targets.length; i < il; i ++ ) {
  
  		const target = targets[ i ];
  
  		if ( hasMorphPosition ) {
  
  			const pendingAccessor = target.POSITION !== undefined
  				? parser.getDependency( 'accessor', target.POSITION )
  				: geometry.attributes.position;
  
  			pendingPositionAccessors.push( pendingAccessor );
  
  		}
  
  		if ( hasMorphNormal ) {
  
  			const pendingAccessor = target.NORMAL !== undefined
  				? parser.getDependency( 'accessor', target.NORMAL )
  				: geometry.attributes.normal;
  
  			pendingNormalAccessors.push( pendingAccessor );
  
  		}
  
  	}
  
  	return Promise.all( [
  		Promise.all( pendingPositionAccessors ),
  		Promise.all( pendingNormalAccessors )
  	] ).then( function ( accessors ) {
  
  		const morphPositions = accessors[ 0 ];
  		const morphNormals = accessors[ 1 ];
  
  		if ( hasMorphPosition ) geometry.morphAttributes.position = morphPositions;
  		if ( hasMorphNormal ) geometry.morphAttributes.normal = morphNormals;
  		geometry.morphTargetsRelative = true;
  
  		return geometry;
  
  	} );
  
  }
  
  /**
   * @param {Mesh} mesh
   * @param {GLTF.Mesh} meshDef
   */
  function updateMorphTargets( mesh, meshDef ) {
  
  	mesh.updateMorphTargets();
  
  	if ( meshDef.weights !== undefined ) {
  
  		for ( let i = 0, il = meshDef.weights.length; i < il; i ++ ) {
  
  			mesh.morphTargetInfluences[ i ] = meshDef.weights[ i ];
  
  		}
  
  	}
  
  	// .extras has user-defined data, so check that .extras.targetNames is an array.
  	if ( meshDef.extras && Array.isArray( meshDef.extras.targetNames ) ) {
  
  		const targetNames = meshDef.extras.targetNames;
  
  		if ( mesh.morphTargetInfluences.length === targetNames.length ) {
  
  			mesh.morphTargetDictionary = {};
  
  			for ( let i = 0, il = targetNames.length; i < il; i ++ ) {
  
  				mesh.morphTargetDictionary[ targetNames[ i ] ] = i;
  
  			}
  
  		} else {
  
  			console.warn( 'THREE.GLTFLoader: Invalid extras.targetNames length. Ignoring names.' );
  
  		}
  
  	}
  
  }
  
  function createPrimitiveKey( primitiveDef ) {
  
  	const dracoExtension = primitiveDef.extensions && primitiveDef.extensions[ EXTENSIONS.KHR_DRACO_MESH_COMPRESSION ];
  	let geometryKey;
  
  	if ( dracoExtension ) {
  
  		geometryKey = 'draco:' + dracoExtension.bufferView
  				+ ':' + dracoExtension.indices
  				+ ':' + createAttributesKey( dracoExtension.attributes );
  
  	} else {
  
  		geometryKey = primitiveDef.indices + ':' + createAttributesKey( primitiveDef.attributes ) + ':' + primitiveDef.mode;
  
  	}
  
  	return geometryKey;
  
  }
  
  function createAttributesKey( attributes ) {
  
  	let attributesKey = '';
  
  	const keys = Object.keys( attributes ).sort();
  
  	for ( let i = 0, il = keys.length; i < il; i ++ ) {
  
  		attributesKey += keys[ i ] + ':' + attributes[ keys[ i ] ] + ';';
  
  	}
  
  	return attributesKey;
  
  }
  
  function getNormalizedComponentScale( constructor ) {
  
  	// Reference:
  	// https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_mesh_quantization#encoding-quantized-data
  
  	switch ( constructor ) {
  
  		case Int8Array:
  			return 1 / 127;
  
  		case Uint8Array:
  			return 1 / 255;
  
  		case Int16Array:
  			return 1 / 32767;
  
  		case Uint16Array:
  			return 1 / 65535;
  
  		default:
  			throw new Error( 'THREE.GLTFLoader: Unsupported normalized accessor component type.' );
  
  	}
  
  }
  
  /* GLTF PARSER */
  
  class GLTFParser {
  
  	constructor( json = {}, options = {} ) {
  
  		this.json = json;
  		this.extensions = {};
  		this.plugins = {};
  		this.options = options;
  
  		// loader object cache
  		this.cache = new GLTFRegistry();
  
  		// associations between Three.js objects and glTF elements
  		this.associations = new Map();
  
  		// BufferGeometry caching
  		this.primitiveCache = {};
  
  		// Object3D instance caches
  		this.meshCache = { refs: {}, uses: {} };
  		this.cameraCache = { refs: {}, uses: {} };
  		this.lightCache = { refs: {}, uses: {} };
  
  		this.textureCache = {};
  
  		// Track node names, to ensure no duplicates
  		this.nodeNamesUsed = {};
  
  		// Use an ImageBitmapLoader if imageBitmaps are supported. Moves much of the
  		// expensive work of uploading a texture to the GPU off the main thread.
  		if ( typeof createImageBitmap !== 'undefined' && /Firefox|^((?!chrome|android).)*safari/i.test( navigator.userAgent ) === false ) {
  
  			this.textureLoader = new ImageBitmapLoader( this.options.manager );
  
  		} else {
  
  			this.textureLoader = new TextureLoader( this.options.manager );
  
  		}
  
  		this.textureLoader.setCrossOrigin( this.options.crossOrigin );
  		this.textureLoader.setRequestHeader( this.options.requestHeader );
  
  		this.fileLoader = new FileLoader( this.options.manager );
  		this.fileLoader.setResponseType( 'arraybuffer' );
  
  		if ( this.options.crossOrigin === 'use-credentials' ) {
  
  			this.fileLoader.setWithCredentials( true );
  
  		}
  
  	}
  
  	setExtensions( extensions ) {
  
  		this.extensions = extensions;
  
  	}
  
  	setPlugins( plugins ) {
  
  		this.plugins = plugins;
  
  	}
  
  	parse( onLoad, onError ) {
  
  		const parser = this;
  		const json = this.json;
  		const extensions = this.extensions;
  
  		// Clear the loader cache
  		this.cache.removeAll();
  
  		// Mark the special nodes/meshes in json for efficient parse
  		this._invokeAll( function ( ext ) {
  
  			return ext._markDefs && ext._markDefs();
  
  		} );
  
  		Promise.all( this._invokeAll( function ( ext ) {
  
  			return ext.beforeRoot && ext.beforeRoot();
  
  		} ) ).then( function () {
  
  			return Promise.all( [
  
  				parser.getDependencies( 'scene' ),
  				parser.getDependencies( 'animation' ),
  				parser.getDependencies( 'camera' ),
  
  			] );
  
  		} ).then( function ( dependencies ) {
  
  			const result = {
  				scene: dependencies[ 0 ][ json.scene || 0 ],
  				scenes: dependencies[ 0 ],
  				animations: dependencies[ 1 ],
  				cameras: dependencies[ 2 ],
  				asset: json.asset,
  				parser: parser,
  				userData: {}
  			};
  
  			addUnknownExtensionsToUserData( extensions, result, json );
  
  			assignExtrasToUserData( result, json );
  
  			Promise.all( parser._invokeAll( function ( ext ) {
  
  				return ext.afterRoot && ext.afterRoot( result );
  
  			} ) ).then( function () {
  
  				onLoad( result );
  
  			} );
  
  		} ).catch( onError );
  
  	}
  
  	/**
  	 * Marks the special nodes/meshes in json for efficient parse.
  	 */
  	_markDefs() {
  
  		const nodeDefs = this.json.nodes || [];
  		const skinDefs = this.json.skins || [];
  		const meshDefs = this.json.meshes || [];
  
  		// Nothing in the node definition indicates whether it is a Bone or an
  		// Object3D. Use the skins' joint references to mark bones.
  		for ( let skinIndex = 0, skinLength = skinDefs.length; skinIndex < skinLength; skinIndex ++ ) {
  
  			const joints = skinDefs[ skinIndex ].joints;
  
  			for ( let i = 0, il = joints.length; i < il; i ++ ) {
  
  				nodeDefs[ joints[ i ] ].isBone = true;
  
  			}
  
  		}
  
  		// Iterate over all nodes, marking references to shared resources,
  		// as well as skeleton joints.
  		for ( let nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex ++ ) {
  
  			const nodeDef = nodeDefs[ nodeIndex ];
  
  			if ( nodeDef.mesh !== undefined ) {
  
  				this._addNodeRef( this.meshCache, nodeDef.mesh );
  
  				// Nothing in the mesh definition indicates whether it is
  				// a SkinnedMesh or Mesh. Use the node's mesh reference
  				// to mark SkinnedMesh if node has skin.
  				if ( nodeDef.skin !== undefined ) {
  
  					meshDefs[ nodeDef.mesh ].isSkinnedMesh = true;
  
  				}
  
  			}
  
  			if ( nodeDef.camera !== undefined ) {
  
  				this._addNodeRef( this.cameraCache, nodeDef.camera );
  
  			}
  
  		}
  
  	}
  
  	/**
  	 * Counts references to shared node / Object3D resources. These resources
  	 * can be reused, or "instantiated", at multiple nodes in the scene
  	 * hierarchy. Mesh, Camera, and Light instances are instantiated and must
  	 * be marked. Non-scenegraph resources (like Materials, Geometries, and
  	 * Textures) can be reused directly and are not marked here.
  	 *
  	 * Example: CesiumMilkTruck sample model reuses "Wheel" meshes.
  	 */
  	_addNodeRef( cache, index ) {
  
  		if ( index === undefined ) return;
  
  		if ( cache.refs[ index ] === undefined ) {
  
  			cache.refs[ index ] = cache.uses[ index ] = 0;
  
  		}
  
  		cache.refs[ index ] ++;
  
  	}
  
  	/** Returns a reference to a shared resource, cloning it if necessary. */
  	_getNodeRef( cache, index, object ) {
  
  		if ( cache.refs[ index ] <= 1 ) return object;
  
  		const ref = object.clone();
  
  		// Propagates mappings to the cloned object, prevents mappings on the
  		// original object from being lost.
  		const updateMappings = ( original, clone ) => {
  
  			const mappings = this.associations.get( original );
  			if ( mappings != null ) {
  
  				this.associations.set( clone, mappings );
  
  			}
  
  			for ( const [ i, child ] of original.children.entries() ) {
  
  				updateMappings( child, clone.children[ i ] );
  
  			}
  
  		};
  
  		updateMappings( object, ref );
  
  		ref.name += '_instance_' + ( cache.uses[ index ] ++ );
  
  		return ref;
  
  	}
  
  	_invokeOne( func ) {
  
  		const extensions = Object.values( this.plugins );
  		extensions.push( this );
  
  		for ( let i = 0; i < extensions.length; i ++ ) {
  
  			const result = func( extensions[ i ] );
  
  			if ( result ) return result;
  
  		}
  
  		return null;
  
  	}
  
  	_invokeAll( func ) {
  
  		const extensions = Object.values( this.plugins );
  		extensions.unshift( this );
  
  		const pending = [];
  
  		for ( let i = 0; i < extensions.length; i ++ ) {
  
  			const result = func( extensions[ i ] );
  
  			if ( result ) pending.push( result );
  
  		}
  
  		return pending;
  
  	}
  
  	/**
  	 * Requests the specified dependency asynchronously, with caching.
  	 * @param {string} type
  	 * @param {number} index
  	 * @return {Promise<Object3D|Material|THREE.Texture|AnimationClip|ArrayBuffer|Object>}
  	 */
  	getDependency( type, index ) {
  
  		const cacheKey = type + ':' + index;
  		let dependency = this.cache.get( cacheKey );
  
  		if ( ! dependency ) {
  
  			switch ( type ) {
  
  				case 'scene':
  					dependency = this.loadScene( index );
  					break;
  
  				case 'node':
  					dependency = this.loadNode( index );
  					break;
  
  				case 'mesh':
  					dependency = this._invokeOne( function ( ext ) {
  
  						return ext.loadMesh && ext.loadMesh( index );
  
  					} );
  					break;
  
  				case 'accessor':
  					dependency = this.loadAccessor( index );
  					break;
  
  				case 'bufferView':
  					dependency = this._invokeOne( function ( ext ) {
  
  						return ext.loadBufferView && ext.loadBufferView( index );
  
  					} );
  					break;
  
  				case 'buffer':
  					dependency = this.loadBuffer( index );
  					break;
  
  				case 'material':
  					dependency = this._invokeOne( function ( ext ) {
  
  						return ext.loadMaterial && ext.loadMaterial( index );
  
  					} );
  					break;
  
  				case 'texture':
  					dependency = this._invokeOne( function ( ext ) {
  
  						return ext.loadTexture && ext.loadTexture( index );
  
  					} );
  					break;
  
  				case 'skin':
  					dependency = this.loadSkin( index );
  					break;
  
  				case 'animation':
  					dependency = this.loadAnimation( index );
  					break;
  
  				case 'camera':
  					dependency = this.loadCamera( index );
  					break;
  
  				default:
  					throw new Error( 'Unknown type: ' + type );
  
  			}
  
  			this.cache.add( cacheKey, dependency );
  
  		}
  
  		return dependency;
  
  	}
  
  	/**
  	 * Requests all dependencies of the specified type asynchronously, with caching.
  	 * @param {string} type
  	 * @return {Promise<Array<Object>>}
  	 */
  	getDependencies( type ) {
  
  		let dependencies = this.cache.get( type );
  
  		if ( ! dependencies ) {
  
  			const parser = this;
  			const defs = this.json[ type + ( type === 'mesh' ? 'es' : 's' ) ] || [];
  
  			dependencies = Promise.all( defs.map( function ( def, index ) {
  
  				return parser.getDependency( type, index );
  
  			} ) );
  
  			this.cache.add( type, dependencies );
  
  		}
  
  		return dependencies;
  
  	}
  
  	/**
  	 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
  	 * @param {number} bufferIndex
  	 * @return {Promise<ArrayBuffer>}
  	 */
  	loadBuffer( bufferIndex ) {
  
  		const bufferDef = this.json.buffers[ bufferIndex ];
  		const loader = this.fileLoader;
  
  		if ( bufferDef.type && bufferDef.type !== 'arraybuffer' ) {
  
  			throw new Error( 'THREE.GLTFLoader: ' + bufferDef.type + ' buffer type is not supported.' );
  
  		}
  
  		// If present, GLB container is required to be the first buffer.
  		if ( bufferDef.uri === undefined && bufferIndex === 0 ) {
  
  			return Promise.resolve( this.extensions[ EXTENSIONS.KHR_BINARY_GLTF ].body );
  
  		}
  
  		const options = this.options;
  
  		return new Promise( function ( resolve, reject ) {
  
  			loader.load( LoaderUtils.resolveURL( bufferDef.uri, options.path ), resolve, undefined, function () {
  
  				reject( new Error( 'THREE.GLTFLoader: Failed to load buffer "' + bufferDef.uri + '".' ) );
  
  			} );
  
  		} );
  
  	}
  
  	/**
  	 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
  	 * @param {number} bufferViewIndex
  	 * @return {Promise<ArrayBuffer>}
  	 */
  	loadBufferView( bufferViewIndex ) {
  
  		const bufferViewDef = this.json.bufferViews[ bufferViewIndex ];
  
  		return this.getDependency( 'buffer', bufferViewDef.buffer ).then( function ( buffer ) {
  
  			const byteLength = bufferViewDef.byteLength || 0;
  			const byteOffset = bufferViewDef.byteOffset || 0;
  			return buffer.slice( byteOffset, byteOffset + byteLength );
  
  		} );
  
  	}
  
  	/**
  	 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#accessors
  	 * @param {number} accessorIndex
  	 * @return {Promise<BufferAttribute|InterleavedBufferAttribute>}
  	 */
  	loadAccessor( accessorIndex ) {
  
  		const parser = this;
  		const json = this.json;
  
  		const accessorDef = this.json.accessors[ accessorIndex ];
  
  		if ( accessorDef.bufferView === undefined && accessorDef.sparse === undefined ) {
  
  			// Ignore empty accessors, which may be used to declare runtime
  			// information about attributes coming from another source (e.g. Draco
  			// compression extension).
  			return Promise.resolve( null );
  
  		}
  
  		const pendingBufferViews = [];
  
  		if ( accessorDef.bufferView !== undefined ) {
  
  			pendingBufferViews.push( this.getDependency( 'bufferView', accessorDef.bufferView ) );
  
  		} else {
  
  			pendingBufferViews.push( null );
  
  		}
  
  		if ( accessorDef.sparse !== undefined ) {
  
  			pendingBufferViews.push( this.getDependency( 'bufferView', accessorDef.sparse.indices.bufferView ) );
  			pendingBufferViews.push( this.getDependency( 'bufferView', accessorDef.sparse.values.bufferView ) );
  
  		}
  
  		return Promise.all( pendingBufferViews ).then( function ( bufferViews ) {
  
  			const bufferView = bufferViews[ 0 ];
  
  			const itemSize = WEBGL_TYPE_SIZES[ accessorDef.type ];
  			const TypedArray = WEBGL_COMPONENT_TYPES[ accessorDef.componentType ];
  
  			// For VEC3: itemSize is 3, elementBytes is 4, itemBytes is 12.
  			const elementBytes = TypedArray.BYTES_PER_ELEMENT;
  			const itemBytes = elementBytes * itemSize;
  			const byteOffset = accessorDef.byteOffset || 0;
  			const byteStride = accessorDef.bufferView !== undefined ? json.bufferViews[ accessorDef.bufferView ].byteStride : undefined;
  			const normalized = accessorDef.normalized === true;
  			let array, bufferAttribute;
  
  			// The buffer is not interleaved if the stride is the item size in bytes.
  			if ( byteStride && byteStride !== itemBytes ) {
  
  				// Each "slice" of the buffer, as defined by 'count' elements of 'byteStride' bytes, gets its own InterleavedBuffer
  				// This makes sure that IBA.count reflects accessor.count properly
  				const ibSlice = Math.floor( byteOffset / byteStride );
  				const ibCacheKey = 'InterleavedBuffer:' + accessorDef.bufferView + ':' + accessorDef.componentType + ':' + ibSlice + ':' + accessorDef.count;
  				let ib = parser.cache.get( ibCacheKey );
  
  				if ( ! ib ) {
  
  					array = new TypedArray( bufferView, ibSlice * byteStride, accessorDef.count * byteStride / elementBytes );
  
  					// Integer parameters to IB/IBA are in array elements, not bytes.
  					ib = new InterleavedBuffer( array, byteStride / elementBytes );
  
  					parser.cache.add( ibCacheKey, ib );
  
  				}
  
  				bufferAttribute = new InterleavedBufferAttribute( ib, itemSize, ( byteOffset % byteStride ) / elementBytes, normalized );
  
  			} else {
  
  				if ( bufferView === null ) {
  
  					array = new TypedArray( accessorDef.count * itemSize );
  
  				} else {
  
  					array = new TypedArray( bufferView, byteOffset, accessorDef.count * itemSize );
  
  				}
  
  				bufferAttribute = new BufferAttribute( array, itemSize, normalized );
  
  			}
  
  			// https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#sparse-accessors
  			if ( accessorDef.sparse !== undefined ) {
  
  				const itemSizeIndices = WEBGL_TYPE_SIZES.SCALAR;
  				const TypedArrayIndices = WEBGL_COMPONENT_TYPES[ accessorDef.sparse.indices.componentType ];
  
  				const byteOffsetIndices = accessorDef.sparse.indices.byteOffset || 0;
  				const byteOffsetValues = accessorDef.sparse.values.byteOffset || 0;
  
  				const sparseIndices = new TypedArrayIndices( bufferViews[ 1 ], byteOffsetIndices, accessorDef.sparse.count * itemSizeIndices );
  				const sparseValues = new TypedArray( bufferViews[ 2 ], byteOffsetValues, accessorDef.sparse.count * itemSize );
  
  				if ( bufferView !== null ) {
  
  					// Avoid modifying the original ArrayBuffer, if the bufferView wasn't initialized with zeroes.
  					bufferAttribute = new BufferAttribute( bufferAttribute.array.slice(), bufferAttribute.itemSize, bufferAttribute.normalized );
  
  				}
  
  				for ( let i = 0, il = sparseIndices.length; i < il; i ++ ) {
  
  					const index = sparseIndices[ i ];
  
  					bufferAttribute.setX( index, sparseValues[ i * itemSize ] );
  					if ( itemSize >= 2 ) bufferAttribute.setY( index, sparseValues[ i * itemSize + 1 ] );
  					if ( itemSize >= 3 ) bufferAttribute.setZ( index, sparseValues[ i * itemSize + 2 ] );
  					if ( itemSize >= 4 ) bufferAttribute.setW( index, sparseValues[ i * itemSize + 3 ] );
  					if ( itemSize >= 5 ) throw new Error( 'THREE.GLTFLoader: Unsupported itemSize in sparse BufferAttribute.' );
  
  				}
  
  			}
  
  			return bufferAttribute;
  
  		} );
  
  	}
  
  	/**
  	 * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#textures
  	 * @param {number} textureIndex
  	 * @return {Promise<THREE.Texture>}
  	 */
  	loadTexture( textureIndex ) {
  
  		const json = this.json;
  		const options = this.options;
  		const textureDef = json.textures[ textureIndex ];
  		const source = json.images[ textureDef.source ];
  
  		let loader = this.textureLoader;
  
  		if ( source.uri ) {
  
  			const handler = options.manager.getHandler( source.uri );
  			if ( handler !== null ) loader = handler;
  
  		}
  
  		return this.loadTextureImage( textureIndex, source, loader );
  
  	}
  
  	loadTextureImage( textureIndex, source, loader ) {
  
  		const parser = this;
  		const json = this.json;
  		const options = this.options;
  
  		const textureDef = json.textures[ textureIndex ];
  
  		const cacheKey = ( source.uri || source.bufferView ) + ':' + textureDef.sampler;
  
  		if ( this.textureCache[ cacheKey ] ) {
  
  			// See https://github.com/mrdoob/three.js/issues/21559.
  			return this.textureCache[ cacheKey ];
  
  		}
  
  		const URL = self.URL || self.webkitURL;
  
  		let sourceURI = source.uri || '';
  		let isObjectURL = false;
  
  		if ( source.bufferView !== undefined ) {
  
  			// Load binary image data from bufferView, if provided.
  
  			sourceURI = parser.getDependency( 'bufferView', source.bufferView ).then( function ( bufferView ) {
  
  				isObjectURL = true;
  				const blob = new Blob( [ bufferView ], { type: source.mimeType } );
  				sourceURI = URL.createObjectURL( blob );
  				return sourceURI;
  
  			} );
  
  		} else if ( source.uri === undefined ) {
  
  			throw new Error( 'THREE.GLTFLoader: Image ' + textureIndex + ' is missing URI and bufferView' );
  
  		}
  
  		const promise = Promise.resolve( sourceURI ).then( function ( sourceURI ) {
  
  			return new Promise( function ( resolve, reject ) {
  
  				let onLoad = resolve;
  
  				if ( loader.isImageBitmapLoader === true ) {
  
  					onLoad = function ( imageBitmap ) {
  
  						const texture = new Texture( imageBitmap );
  						texture.needsUpdate = true;
  
  						resolve( texture );
  
  					};
  
  				}
  
  				loader.load( LoaderUtils.resolveURL( sourceURI, options.path ), onLoad, undefined, reject );
  
  			} );
  
  		} ).then( function ( texture ) {
  
  			// Clean up resources and configure Texture.
  
  			if ( isObjectURL === true ) {
  
  				URL.revokeObjectURL( sourceURI );
  
  			}
  
  			texture.flipY = false;
  
  			if ( textureDef.name ) texture.name = textureDef.name;
  
  			const samplers = json.samplers || {};
  			const sampler = samplers[ textureDef.sampler ] || {};
  
  			texture.magFilter = WEBGL_FILTERS[ sampler.magFilter ] || LinearFilter;
  			texture.minFilter = WEBGL_FILTERS[ sampler.minFilter ] || LinearMipmapLinearFilter;
  			texture.wrapS = WEBGL_WRAPPINGS[ sampler.wrapS ] || RepeatWrapping;
  			texture.wrapT = WEBGL_WRAPPINGS[ sampler.wrapT ] || RepeatWrapping;
  
  			parser.associations.set( texture, { textures: textureIndex } );
  
  			return texture;
  
  		} ).catch( function () {
  
  			console.error( 'THREE.GLTFLoader: Couldn\'t load texture', sourceURI );
  			return null;
  
  		} );
  
  		this.textureCache[ cacheKey ] = promise;
  
  		return promise;
  
  	}
  
  	/**
  	 * Asynchronously assigns a texture to the given material parameters.
  	 * @param {Object} materialParams
  	 * @param {string} mapName
  	 * @param {Object} mapDef
  	 * @return {Promise<Texture>}
  	 */
  	assignTexture( materialParams, mapName, mapDef ) {
  
  		const parser = this;
  
  		return this.getDependency( 'texture', mapDef.index ).then( function ( texture ) {
  
  			// Materials sample aoMap from UV set 1 and other maps from UV set 0 - this can't be configured
  			// However, we will copy UV set 0 to UV set 1 on demand for aoMap
  			if ( mapDef.texCoord !== undefined && mapDef.texCoord != 0 && ! ( mapName === 'aoMap' && mapDef.texCoord == 1 ) ) {
  
  				console.warn( 'THREE.GLTFLoader: Custom UV set ' + mapDef.texCoord + ' for texture ' + mapName + ' not yet supported.' );
  
  			}
  
  			if ( parser.extensions[ EXTENSIONS.KHR_TEXTURE_TRANSFORM ] ) {
  
  				const transform = mapDef.extensions !== undefined ? mapDef.extensions[ EXTENSIONS.KHR_TEXTURE_TRANSFORM ] : undefined;
  
  				if ( transform ) {
  
  					const gltfReference = parser.associations.get( texture );
  					texture = parser.extensions[ EXTENSIONS.KHR_TEXTURE_TRANSFORM ].extendTexture( texture, transform );
  					parser.associations.set( texture, gltfReference );
  
  				}
  
  			}
  
  			materialParams[ mapName ] = texture;
  
  			return texture;
  
  		} );
  
  	}
  
  	/**
  	 * Assigns final material to a Mesh, Line, or Points instance. The instance
  	 * already has a material (generated from the glTF material options alone)
  	 * but reuse of the same glTF material may require multiple threejs materials
  	 * to accommodate different primitive types, defines, etc. New materials will
  	 * be created if necessary, and reused from a cache.
  	 * @param  {Object3D} mesh Mesh, Line, or Points instance.
  	 */
  	assignFinalMaterial( mesh ) {
  
  		const geometry = mesh.geometry;
  		let material = mesh.material;
  
  		const useDerivativeTangents = geometry.attributes.tangent === undefined;
  		const useVertexColors = geometry.attributes.color !== undefined;
  		const useFlatShading = geometry.attributes.normal === undefined;
  
  		if ( mesh.isPoints ) {
  
  			const cacheKey = 'PointsMaterial:' + material.uuid;
  
  			let pointsMaterial = this.cache.get( cacheKey );
  
  			if ( ! pointsMaterial ) {
  
  				pointsMaterial = new PointsMaterial();
  				Material.prototype.copy.call( pointsMaterial, material );
  				pointsMaterial.color.copy( material.color );
  				pointsMaterial.map = material.map;
  				pointsMaterial.sizeAttenuation = false; // glTF spec says points should be 1px
  
  				this.cache.add( cacheKey, pointsMaterial );
  
  			}
  
  			material = pointsMaterial;
  
  		} else if ( mesh.isLine ) {
  
  			const cacheKey = 'LineBasicMaterial:' + material.uuid;
  
  			let lineMaterial = this.cache.get( cacheKey );
  
  			if ( ! lineMaterial ) {
  
  				lineMaterial = new LineBasicMaterial();
  				Material.prototype.copy.call( lineMaterial, material );
  				lineMaterial.color.copy( material.color );
  
  				this.cache.add( cacheKey, lineMaterial );
  
  			}
  
  			material = lineMaterial;
  
  		}
  
  		// Clone the material if it will be modified
  		if ( useDerivativeTangents || useVertexColors || useFlatShading ) {
  
  			let cacheKey = 'ClonedMaterial:' + material.uuid + ':';
  
  			if ( material.isGLTFSpecularGlossinessMaterial ) cacheKey += 'specular-glossiness:';
  			if ( useDerivativeTangents ) cacheKey += 'derivative-tangents:';
  			if ( useVertexColors ) cacheKey += 'vertex-colors:';
  			if ( useFlatShading ) cacheKey += 'flat-shading:';
  
  			let cachedMaterial = this.cache.get( cacheKey );
  
  			if ( ! cachedMaterial ) {
  
  				cachedMaterial = material.clone();
  
  				if ( useVertexColors ) cachedMaterial.vertexColors = true;
  				if ( useFlatShading ) cachedMaterial.flatShading = true;
  
  				if ( useDerivativeTangents ) {
  
  					// https://github.com/mrdoob/three.js/issues/11438#issuecomment-507003995
  					if ( cachedMaterial.normalScale ) cachedMaterial.normalScale.y *= - 1;
  					if ( cachedMaterial.clearcoatNormalScale ) cachedMaterial.clearcoatNormalScale.y *= - 1;
  
  				}
  
  				this.cache.add( cacheKey, cachedMaterial );
  
  				this.associations.set( cachedMaterial, this.associations.get( material ) );
  
  			}
  
  			material = cachedMaterial;
  
  		}
  
  		// workarounds for mesh and geometry
  
  		if ( material.aoMap && geometry.attributes.uv2 === undefined && geometry.attributes.uv !== undefined ) {
  
  			geometry.setAttribute( 'uv2', geometry.attributes.uv );
  
  		}
  
  		mesh.material = material;
  
  	}
  
  	getMaterialType( /* materialIndex */ ) {
  
  		return MeshStandardMaterial;
  
  	}
  
  	/**
  	 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#materials
  	 * @param {number} materialIndex
  	 * @return {Promise<Material>}
  	 */
  	loadMaterial( materialIndex ) {
  
  		const parser = this;
  		const json = this.json;
  		const extensions = this.extensions;
  		const materialDef = json.materials[ materialIndex ];
  
  		let materialType;
  		const materialParams = {};
  		const materialExtensions = materialDef.extensions || {};
  
  		const pending = [];
  
  		if ( materialExtensions[ EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS ] ) {
  
  			const sgExtension = extensions[ EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS ];
  			materialType = sgExtension.getMaterialType();
  			pending.push( sgExtension.extendParams( materialParams, materialDef, parser ) );
  
  		} else if ( materialExtensions[ EXTENSIONS.KHR_MATERIALS_UNLIT ] ) {
  
  			const kmuExtension = extensions[ EXTENSIONS.KHR_MATERIALS_UNLIT ];
  			materialType = kmuExtension.getMaterialType();
  			pending.push( kmuExtension.extendParams( materialParams, materialDef, parser ) );
  
  		} else {
  
  			// Specification:
  			// https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#metallic-roughness-material
  
  			const metallicRoughness = materialDef.pbrMetallicRoughness || {};
  
  			materialParams.color = new Color( 1.0, 1.0, 1.0 );
  			materialParams.opacity = 1.0;
  
  			if ( Array.isArray( metallicRoughness.baseColorFactor ) ) {
  
  				const array = metallicRoughness.baseColorFactor;
  
  				materialParams.color.fromArray( array );
  				materialParams.opacity = array[ 3 ];
  
  			}
  
  			if ( metallicRoughness.baseColorTexture !== undefined ) {
  
  				pending.push( parser.assignTexture( materialParams, 'map', metallicRoughness.baseColorTexture ) );
  
  			}
  
  			materialParams.metalness = metallicRoughness.metallicFactor !== undefined ? metallicRoughness.metallicFactor : 1.0;
  			materialParams.roughness = metallicRoughness.roughnessFactor !== undefined ? metallicRoughness.roughnessFactor : 1.0;
  
  			if ( metallicRoughness.metallicRoughnessTexture !== undefined ) {
  
  				pending.push( parser.assignTexture( materialParams, 'metalnessMap', metallicRoughness.metallicRoughnessTexture ) );
  				pending.push( parser.assignTexture( materialParams, 'roughnessMap', metallicRoughness.metallicRoughnessTexture ) );
  
  			}
  
  			materialType = this._invokeOne( function ( ext ) {
  
  				return ext.getMaterialType && ext.getMaterialType( materialIndex );
  
  			} );
  
  			pending.push( Promise.all( this._invokeAll( function ( ext ) {
  
  				return ext.extendMaterialParams && ext.extendMaterialParams( materialIndex, materialParams );
  
  			} ) ) );
  
  		}
  
  		if ( materialDef.doubleSided === true ) {
  
  			materialParams.side = DoubleSide;
  
  		}
  
  		const alphaMode = materialDef.alphaMode || ALPHA_MODES.OPAQUE;
  
  		if ( alphaMode === ALPHA_MODES.BLEND ) {
  
  			materialParams.transparent = true;
  
  			// See: https://github.com/mrdoob/three.js/issues/17706
  			materialParams.depthWrite = false;
  
  		} else {
  
  			materialParams.transparent = false;
  
  			if ( alphaMode === ALPHA_MODES.MASK ) {
  
  				materialParams.alphaTest = materialDef.alphaCutoff !== undefined ? materialDef.alphaCutoff : 0.5;
  
  			}
  
  		}
  
  		if ( materialDef.normalTexture !== undefined && materialType !== MeshBasicMaterial ) {
  
  			pending.push( parser.assignTexture( materialParams, 'normalMap', materialDef.normalTexture ) );
  
  			materialParams.normalScale = new Vector2( 1, 1 );
  
  			if ( materialDef.normalTexture.scale !== undefined ) {
  
  				const scale = materialDef.normalTexture.scale;
  
  				materialParams.normalScale.set( scale, scale );
  
  			}
  
  		}
  
  		if ( materialDef.occlusionTexture !== undefined && materialType !== MeshBasicMaterial ) {
  
  			pending.push( parser.assignTexture( materialParams, 'aoMap', materialDef.occlusionTexture ) );
  
  			if ( materialDef.occlusionTexture.strength !== undefined ) {
  
  				materialParams.aoMapIntensity = materialDef.occlusionTexture.strength;
  
  			}
  
  		}
  
  		if ( materialDef.emissiveFactor !== undefined && materialType !== MeshBasicMaterial ) {
  
  			materialParams.emissive = new Color().fromArray( materialDef.emissiveFactor );
  
  		}
  
  		if ( materialDef.emissiveTexture !== undefined && materialType !== MeshBasicMaterial ) {
  
  			pending.push( parser.assignTexture( materialParams, 'emissiveMap', materialDef.emissiveTexture ) );
  
  		}
  
  		return Promise.all( pending ).then( function () {
  
  			let material;
  
  			if ( materialType === GLTFMeshStandardSGMaterial ) {
  
  				material = extensions[ EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS ].createMaterial( materialParams );
  
  			} else {
  
  				material = new materialType( materialParams );
  
  			}
  
  			if ( materialDef.name ) material.name = materialDef.name;
  
  			// baseColorTexture, emissiveTexture, and specularGlossinessTexture use sRGB encoding.
  			if ( material.map ) material.map.encoding = sRGBEncoding;
  			if ( material.emissiveMap ) material.emissiveMap.encoding = sRGBEncoding;
  
  			assignExtrasToUserData( material, materialDef );
  
  			parser.associations.set( material, { materials: materialIndex } );
  
  			if ( materialDef.extensions ) addUnknownExtensionsToUserData( extensions, material, materialDef );
  
  			return material;
  
  		} );
  
  	}
  
  	/** When Object3D instances are targeted by animation, they need unique names. */
  	createUniqueName( originalName ) {
  
  		const sanitizedName = PropertyBinding.sanitizeNodeName( originalName || '' );
  
  		let name = sanitizedName;
  
  		for ( let i = 1; this.nodeNamesUsed[ name ]; ++ i ) {
  
  			name = sanitizedName + '_' + i;
  
  		}
  
  		this.nodeNamesUsed[ name ] = true;
  
  		return name;
  
  	}
  
  	/**
  	 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#geometry
  	 *
  	 * Creates BufferGeometries from primitives.
  	 *
  	 * @param {Array<GLTF.Primitive>} primitives
  	 * @return {Promise<Array<BufferGeometry>>}
  	 */
  	loadGeometries( primitives ) {
  
  		const parser = this;
  		const extensions = this.extensions;
  		const cache = this.primitiveCache;
  
  		function createDracoPrimitive( primitive ) {
  
  			return extensions[ EXTENSIONS.KHR_DRACO_MESH_COMPRESSION ]
  				.decodePrimitive( primitive, parser )
  				.then( function ( geometry ) {
  
  					return addPrimitiveAttributes( geometry, primitive, parser );
  
  				} );
  
  		}
  
  		const pending = [];
  
  		for ( let i = 0, il = primitives.length; i < il; i ++ ) {
  
  			const primitive = primitives[ i ];
  			const cacheKey = createPrimitiveKey( primitive );
  
  			// See if we've already created this geometry
  			const cached = cache[ cacheKey ];
  
  			if ( cached ) {
  
  				// Use the cached geometry if it exists
  				pending.push( cached.promise );
  
  			} else {
  
  				let geometryPromise;
  
  				if ( primitive.extensions && primitive.extensions[ EXTENSIONS.KHR_DRACO_MESH_COMPRESSION ] ) {
  
  					// Use DRACO geometry if available
  					geometryPromise = createDracoPrimitive( primitive );
  
  				} else {
  
  					// Otherwise create a new geometry
  					geometryPromise = addPrimitiveAttributes( new BufferGeometry(), primitive, parser );
  
  				}
  
  				// Cache this geometry
  				cache[ cacheKey ] = { primitive: primitive, promise: geometryPromise };
  
  				pending.push( geometryPromise );
  
  			}
  
  		}
  
  		return Promise.all( pending );
  
  	}
  
  	/**
  	 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#meshes
  	 * @param {number} meshIndex
  	 * @return {Promise<Group|Mesh|SkinnedMesh>}
  	 */
  	loadMesh( meshIndex ) {
  
  		const parser = this;
  		const json = this.json;
  		const extensions = this.extensions;
  
  		const meshDef = json.meshes[ meshIndex ];
  		const primitives = meshDef.primitives;
  
  		const pending = [];
  
  		for ( let i = 0, il = primitives.length; i < il; i ++ ) {
  
  			const material = primitives[ i ].material === undefined
  				? createDefaultMaterial( this.cache )
  				: this.getDependency( 'material', primitives[ i ].material );
  
  			pending.push( material );
  
  		}
  
  		pending.push( parser.loadGeometries( primitives ) );
  
  		return Promise.all( pending ).then( function ( results ) {
  
  			const materials = results.slice( 0, results.length - 1 );
  			const geometries = results[ results.length - 1 ];
  
  			const meshes = [];
  
  			for ( let i = 0, il = geometries.length; i < il; i ++ ) {
  
  				const geometry = geometries[ i ];
  				const primitive = primitives[ i ];
  
  				// 1. create Mesh
  
  				let mesh;
  
  				const material = materials[ i ];
  
  				if ( primitive.mode === WEBGL_CONSTANTS.TRIANGLES ||
  						primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ||
  						primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ||
  						primitive.mode === undefined ) {
  
  					// .isSkinnedMesh isn't in glTF spec. See ._markDefs()
  					mesh = meshDef.isSkinnedMesh === true
  						? new SkinnedMesh( geometry, material )
  						: new Mesh( geometry, material );
  
  					if ( mesh.isSkinnedMesh === true && ! mesh.geometry.attributes.skinWeight.normalized ) {
  
  						// we normalize floating point skin weight array to fix malformed assets (see #15319)
  						// it's important to skip this for non-float32 data since normalizeSkinWeights assumes non-normalized inputs
  						mesh.normalizeSkinWeights();
  
  					}
  
  					if ( primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ) {
  
  						mesh.geometry = toTrianglesDrawMode( mesh.geometry, TriangleStripDrawMode );
  
  					} else if ( primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ) {
  
  						mesh.geometry = toTrianglesDrawMode( mesh.geometry, TriangleFanDrawMode );
  
  					}
  
  				} else if ( primitive.mode === WEBGL_CONSTANTS.LINES ) {
  
  					mesh = new LineSegments( geometry, material );
  
  				} else if ( primitive.mode === WEBGL_CONSTANTS.LINE_STRIP ) {
  
  					mesh = new Line( geometry, material );
  
  				} else if ( primitive.mode === WEBGL_CONSTANTS.LINE_LOOP ) {
  
  					mesh = new LineLoop( geometry, material );
  
  				} else if ( primitive.mode === WEBGL_CONSTANTS.POINTS ) {
  
  					mesh = new Points( geometry, material );
  
  				} else {
  
  					throw new Error( 'THREE.GLTFLoader: Primitive mode unsupported: ' + primitive.mode );
  
  				}
  
  				if ( Object.keys( mesh.geometry.morphAttributes ).length > 0 ) {
  
  					updateMorphTargets( mesh, meshDef );
  
  				}
  
  				mesh.name = parser.createUniqueName( meshDef.name || ( 'mesh_' + meshIndex ) );
  
  				assignExtrasToUserData( mesh, meshDef );
  
  				if ( primitive.extensions ) addUnknownExtensionsToUserData( extensions, mesh, primitive );
  
  				parser.assignFinalMaterial( mesh );
  
  				meshes.push( mesh );
  
  			}
  
  			for ( let i = 0, il = meshes.length; i < il; i ++ ) {
  
  				parser.associations.set( meshes[ i ], {
  					meshes: meshIndex,
  					primitives: i
  				} );
  
  			}
  
  			if ( meshes.length === 1 ) {
  
  				return meshes[ 0 ];
  
  			}
  
  			const group = new Group();
  
  			parser.associations.set( group, { meshes: meshIndex } );
  
  			for ( let i = 0, il = meshes.length; i < il; i ++ ) {
  
  				group.add( meshes[ i ] );
  
  			}
  
  			return group;
  
  		} );
  
  	}
  
  	/**
  	 * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#cameras
  	 * @param {number} cameraIndex
  	 * @return {Promise<THREE.Camera>}
  	 */
  	loadCamera( cameraIndex ) {
  
  		let camera;
  		const cameraDef = this.json.cameras[ cameraIndex ];
  		const params = cameraDef[ cameraDef.type ];
  
  		if ( ! params ) {
  
  			console.warn( 'THREE.GLTFLoader: Missing camera parameters.' );
  			return;
  
  		}
  
  		if ( cameraDef.type === 'perspective' ) {
  
  			camera = new PerspectiveCamera( MathUtils.radToDeg( params.yfov ), params.aspectRatio || 1, params.znear || 1, params.zfar || 2e6 );
  
  		} else if ( cameraDef.type === 'orthographic' ) {
  
  			camera = new OrthographicCamera( - params.xmag, params.xmag, params.ymag, - params.ymag, params.znear, params.zfar );
  
  		}
  
  		if ( cameraDef.name ) camera.name = this.createUniqueName( cameraDef.name );
  
  		assignExtrasToUserData( camera, cameraDef );
  
  		return Promise.resolve( camera );
  
  	}
  
  	/**
  	 * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#skins
  	 * @param {number} skinIndex
  	 * @return {Promise<Object>}
  	 */
  	loadSkin( skinIndex ) {
  
  		const skinDef = this.json.skins[ skinIndex ];
  
  		const skinEntry = { joints: skinDef.joints };
  
  		if ( skinDef.inverseBindMatrices === undefined ) {
  
  			return Promise.resolve( skinEntry );
  
  		}
  
  		return this.getDependency( 'accessor', skinDef.inverseBindMatrices ).then( function ( accessor ) {
  
  			skinEntry.inverseBindMatrices = accessor;
  
  			return skinEntry;
  
  		} );
  
  	}
  
  	/**
  	 * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#animations
  	 * @param {number} animationIndex
  	 * @return {Promise<AnimationClip>}
  	 */
  	loadAnimation( animationIndex ) {
  
  		const json = this.json;
  
  		const animationDef = json.animations[ animationIndex ];
  
  		const pendingNodes = [];
  		const pendingInputAccessors = [];
  		const pendingOutputAccessors = [];
  		const pendingSamplers = [];
  		const pendingTargets = [];
  
  		for ( let i = 0, il = animationDef.channels.length; i < il; i ++ ) {
  
  			const channel = animationDef.channels[ i ];
  			const sampler = animationDef.samplers[ channel.sampler ];
  			const target = channel.target;
  			const name = target.node !== undefined ? target.node : target.id; // NOTE: target.id is deprecated.
  			const input = animationDef.parameters !== undefined ? animationDef.parameters[ sampler.input ] : sampler.input;
  			const output = animationDef.parameters !== undefined ? animationDef.parameters[ sampler.output ] : sampler.output;
  
  			pendingNodes.push( this.getDependency( 'node', name ) );
  			pendingInputAccessors.push( this.getDependency( 'accessor', input ) );
  			pendingOutputAccessors.push( this.getDependency( 'accessor', output ) );
  			pendingSamplers.push( sampler );
  			pendingTargets.push( target );
  
  		}
  
  		return Promise.all( [
  
  			Promise.all( pendingNodes ),
  			Promise.all( pendingInputAccessors ),
  			Promise.all( pendingOutputAccessors ),
  			Promise.all( pendingSamplers ),
  			Promise.all( pendingTargets )
  
  		] ).then( function ( dependencies ) {
  
  			const nodes = dependencies[ 0 ];
  			const inputAccessors = dependencies[ 1 ];
  			const outputAccessors = dependencies[ 2 ];
  			const samplers = dependencies[ 3 ];
  			const targets = dependencies[ 4 ];
  
  			const tracks = [];
  
  			for ( let i = 0, il = nodes.length; i < il; i ++ ) {
  
  				const node = nodes[ i ];
  				const inputAccessor = inputAccessors[ i ];
  				const outputAccessor = outputAccessors[ i ];
  				const sampler = samplers[ i ];
  				const target = targets[ i ];
  
  				if ( node === undefined ) continue;
  
  				node.updateMatrix();
  				node.matrixAutoUpdate = true;
  
  				let TypedKeyframeTrack;
  
  				switch ( PATH_PROPERTIES[ target.path ] ) {
  
  					case PATH_PROPERTIES.weights:
  
  						TypedKeyframeTrack = NumberKeyframeTrack;
  						break;
  
  					case PATH_PROPERTIES.rotation:
  
  						TypedKeyframeTrack = QuaternionKeyframeTrack;
  						break;
  
  					case PATH_PROPERTIES.position:
  					case PATH_PROPERTIES.scale:
  					default:
  
  						TypedKeyframeTrack = VectorKeyframeTrack;
  						break;
  
  				}
  
  				const targetName = node.name ? node.name : node.uuid;
  
  				const interpolation = sampler.interpolation !== undefined ? INTERPOLATION[ sampler.interpolation ] : InterpolateLinear;
  
  				const targetNames = [];
  
  				if ( PATH_PROPERTIES[ target.path ] === PATH_PROPERTIES.weights ) {
  
  					node.traverse( function ( object ) {
  
  						if ( object.morphTargetInfluences ) {
  
  							targetNames.push( object.name ? object.name : object.uuid );
  
  						}
  
  					} );
  
  				} else {
  
  					targetNames.push( targetName );
  
  				}
  
  				let outputArray = outputAccessor.array;
  
  				if ( outputAccessor.normalized ) {
  
  					const scale = getNormalizedComponentScale( outputArray.constructor );
  					const scaled = new Float32Array( outputArray.length );
  
  					for ( let j = 0, jl = outputArray.length; j < jl; j ++ ) {
  
  						scaled[ j ] = outputArray[ j ] * scale;
  
  					}
  
  					outputArray = scaled;
  
  				}
  
  				for ( let j = 0, jl = targetNames.length; j < jl; j ++ ) {
  
  					const track = new TypedKeyframeTrack(
  						targetNames[ j ] + '.' + PATH_PROPERTIES[ target.path ],
  						inputAccessor.array,
  						outputArray,
  						interpolation
  					);
  
  					// Override interpolation with custom factory method.
  					if ( sampler.interpolation === 'CUBICSPLINE' ) {
  
  						track.createInterpolant = function InterpolantFactoryMethodGLTFCubicSpline( result ) {
  
  							// A CUBICSPLINE keyframe in glTF has three output values for each input value,
  							// representing inTangent, splineVertex, and outTangent. As a result, track.getValueSize()
  							// must be divided by three to get the interpolant's sampleSize argument.
  
  							const interpolantType = ( this instanceof QuaternionKeyframeTrack ) ? GLTFCubicSplineQuaternionInterpolant : GLTFCubicSplineInterpolant;
  
  							return new interpolantType( this.times, this.values, this.getValueSize() / 3, result );
  
  						};
  
  						// Mark as CUBICSPLINE. `track.getInterpolation()` doesn't support custom interpolants.
  						track.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline = true;
  
  					}
  
  					tracks.push( track );
  
  				}
  
  			}
  
  			const name = animationDef.name ? animationDef.name : 'animation_' + animationIndex;
  
  			return new AnimationClip( name, undefined, tracks );
  
  		} );
  
  	}
  
  	createNodeMesh( nodeIndex ) {
  
  		const json = this.json;
  		const parser = this;
  		const nodeDef = json.nodes[ nodeIndex ];
  
  		if ( nodeDef.mesh === undefined ) return null;
  
  		return parser.getDependency( 'mesh', nodeDef.mesh ).then( function ( mesh ) {
  
  			const node = parser._getNodeRef( parser.meshCache, nodeDef.mesh, mesh );
  
  			// if weights are provided on the node, override weights on the mesh.
  			if ( nodeDef.weights !== undefined ) {
  
  				node.traverse( function ( o ) {
  
  					if ( ! o.isMesh ) return;
  
  					for ( let i = 0, il = nodeDef.weights.length; i < il; i ++ ) {
  
  						o.morphTargetInfluences[ i ] = nodeDef.weights[ i ];
  
  					}
  
  				} );
  
  			}
  
  			return node;
  
  		} );
  
  	}
  
  	/**
  	 * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#nodes-and-hierarchy
  	 * @param {number} nodeIndex
  	 * @return {Promise<Object3D>}
  	 */
  	loadNode( nodeIndex ) {
  
  		const json = this.json;
  		const extensions = this.extensions;
  		const parser = this;
  
  		const nodeDef = json.nodes[ nodeIndex ];
  
  		// reserve node's name before its dependencies, so the root has the intended name.
  		const nodeName = nodeDef.name ? parser.createUniqueName( nodeDef.name ) : '';
  
  		return ( function () {
  
  			const pending = [];
  
  			const meshPromise = parser._invokeOne( function ( ext ) {
  
  				return ext.createNodeMesh && ext.createNodeMesh( nodeIndex );
  
  			} );
  
  			if ( meshPromise ) {
  
  				pending.push( meshPromise );
  
  			}
  
  			if ( nodeDef.camera !== undefined ) {
  
  				pending.push( parser.getDependency( 'camera', nodeDef.camera ).then( function ( camera ) {
  
  					return parser._getNodeRef( parser.cameraCache, nodeDef.camera, camera );
  
  				} ) );
  
  			}
  
  			parser._invokeAll( function ( ext ) {
  
  				return ext.createNodeAttachment && ext.createNodeAttachment( nodeIndex );
  
  			} ).forEach( function ( promise ) {
  
  				pending.push( promise );
  
  			} );
  
  			return Promise.all( pending );
  
  		}() ).then( function ( objects ) {
  
  			let node;
  
  			// .isBone isn't in glTF spec. See ._markDefs
  			if ( nodeDef.isBone === true ) {
  
  				node = new Bone();
  
  			} else if ( objects.length > 1 ) {
  
  				node = new Group();
  
  			} else if ( objects.length === 1 ) {
  
  				node = objects[ 0 ];
  
  			} else {
  
  				node = new Object3D();
  
  			}
  
  			if ( node !== objects[ 0 ] ) {
  
  				for ( let i = 0, il = objects.length; i < il; i ++ ) {
  
  					node.add( objects[ i ] );
  
  				}
  
  			}
  
  			if ( nodeDef.name ) {
  
  				node.userData.name = nodeDef.name;
  				node.name = nodeName;
  
  			}
  
  			assignExtrasToUserData( node, nodeDef );
  
  			if ( nodeDef.extensions ) addUnknownExtensionsToUserData( extensions, node, nodeDef );
  
  			if ( nodeDef.matrix !== undefined ) {
  
  				const matrix = new Matrix4();
  				matrix.fromArray( nodeDef.matrix );
  				node.applyMatrix4( matrix );
  
  			} else {
  
  				if ( nodeDef.translation !== undefined ) {
  
  					node.position.fromArray( nodeDef.translation );
  
  				}
  
  				if ( nodeDef.rotation !== undefined ) {
  
  					node.quaternion.fromArray( nodeDef.rotation );
  
  				}
  
  				if ( nodeDef.scale !== undefined ) {
  
  					node.scale.fromArray( nodeDef.scale );
  
  				}
  
  			}
  
  			if ( ! parser.associations.has( node ) ) {
  
  				parser.associations.set( node, {} );
  
  			}
  
  			parser.associations.get( node ).nodes = nodeIndex;
  
  			return node;
  
  		} );
  
  	}
  
  	/**
  	 * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#scenes
  	 * @param {number} sceneIndex
  	 * @return {Promise<Group>}
  	 */
  	loadScene( sceneIndex ) {
  
  		const json = this.json;
  		const extensions = this.extensions;
  		const sceneDef = this.json.scenes[ sceneIndex ];
  		const parser = this;
  
  		// Loader returns Group, not Scene.
  		// See: https://github.com/mrdoob/three.js/issues/18342#issuecomment-578981172
  		const scene = new Group();
  		if ( sceneDef.name ) scene.name = parser.createUniqueName( sceneDef.name );
  
  		assignExtrasToUserData( scene, sceneDef );
  
  		if ( sceneDef.extensions ) addUnknownExtensionsToUserData( extensions, scene, sceneDef );
  
  		const nodeIds = sceneDef.nodes || [];
  
  		const pending = [];
  
  		for ( let i = 0, il = nodeIds.length; i < il; i ++ ) {
  
  			pending.push( buildNodeHierarchy( nodeIds[ i ], scene, json, parser ) );
  
  		}
  
  		return Promise.all( pending ).then( function () {
  
  			// Removes dangling associations, associations that reference a node that
  			// didn't make it into the scene.
  			const reduceAssociations = ( node ) => {
  
  				const reducedAssociations = new Map();
  
  				for ( const [ key, value ] of parser.associations ) {
  
  					if ( key instanceof Material || key instanceof Texture ) {
  
  						reducedAssociations.set( key, value );
  
  					}
  
  				}
  
  				node.traverse( ( node ) => {
  
  					const mappings = parser.associations.get( node );
  
  					if ( mappings != null ) {
  
  						reducedAssociations.set( node, mappings );
  
  					}
  
  				} );
  
  				return reducedAssociations;
  
  			};
  
  			parser.associations = reduceAssociations( scene );
  
  			return scene;
  
  		} );
  
  	}
  
  }
  
  function buildNodeHierarchy( nodeId, parentObject, json, parser ) {
  
  	const nodeDef = json.nodes[ nodeId ];
  
  	return parser.getDependency( 'node', nodeId ).then( function ( node ) {
  
  		if ( nodeDef.skin === undefined ) return node;
  
  		// build skeleton here as well
  
  		let skinEntry;
  
  		return parser.getDependency( 'skin', nodeDef.skin ).then( function ( skin ) {
  
  			skinEntry = skin;
  
  			const pendingJoints = [];
  
  			for ( let i = 0, il = skinEntry.joints.length; i < il; i ++ ) {
  
  				pendingJoints.push( parser.getDependency( 'node', skinEntry.joints[ i ] ) );
  
  			}
  
  			return Promise.all( pendingJoints );
  
  		} ).then( function ( jointNodes ) {
  
  			node.traverse( function ( mesh ) {
  
  				if ( ! mesh.isMesh ) return;
  
  				const bones = [];
  				const boneInverses = [];
  
  				for ( let j = 0, jl = jointNodes.length; j < jl; j ++ ) {
  
  					const jointNode = jointNodes[ j ];
  
  					if ( jointNode ) {
  
  						bones.push( jointNode );
  
  						const mat = new Matrix4();
  
  						if ( skinEntry.inverseBindMatrices !== undefined ) {
  
  							mat.fromArray( skinEntry.inverseBindMatrices.array, j * 16 );
  
  						}
  
  						boneInverses.push( mat );
  
  					} else {
  
  						console.warn( 'THREE.GLTFLoader: Joint "%s" could not be found.', skinEntry.joints[ j ] );
  
  					}
  
  				}
  
  				mesh.bind( new Skeleton( bones, boneInverses ), mesh.matrixWorld );
  
  			} );
  
  			return node;
  
  		} );
  
  	} ).then( function ( node ) {
  
  		// build node hierachy
  
  		parentObject.add( node );
  
  		const pending = [];
  
  		if ( nodeDef.children ) {
  
  			const children = nodeDef.children;
  
  			for ( let i = 0, il = children.length; i < il; i ++ ) {
  
  				const child = children[ i ];
  				pending.push( buildNodeHierarchy( child, node, json, parser ) );
  
  			}
  
  		}
  
  		return Promise.all( pending );
  
  	} );
  
  }
  
  /**
   * @param {BufferGeometry} geometry
   * @param {GLTF.Primitive} primitiveDef
   * @param {GLTFParser} parser
   */
  function computeBounds( geometry, primitiveDef, parser ) {
  
  	const attributes = primitiveDef.attributes;
  
  	const box = new Box3();
  
  	if ( attributes.POSITION !== undefined ) {
  
  		const accessor = parser.json.accessors[ attributes.POSITION ];
  
  		const min = accessor.min;
  		const max = accessor.max;
  
  		// glTF requires 'min' and 'max', but VRM (which extends glTF) currently ignores that requirement.
  
  		if ( min !== undefined && max !== undefined ) {
  
  			box.set(
  				new Vector3( min[ 0 ], min[ 1 ], min[ 2 ] ),
  				new Vector3( max[ 0 ], max[ 1 ], max[ 2 ] )
  			);
  
  			if ( accessor.normalized ) {
  
  				const boxScale = getNormalizedComponentScale( WEBGL_COMPONENT_TYPES[ accessor.componentType ] );
  				box.min.multiplyScalar( boxScale );
  				box.max.multiplyScalar( boxScale );
  
  			}
  
  		} else {
  
  			console.warn( 'THREE.GLTFLoader: Missing min/max properties for accessor POSITION.' );
  
  			return;
  
  		}
  
  	} else {
  
  		return;
  
  	}
  
  	const targets = primitiveDef.targets;
  
  	if ( targets !== undefined ) {
  
  		const maxDisplacement = new Vector3();
  		const vector = new Vector3();
  
  		for ( let i = 0, il = targets.length; i < il; i ++ ) {
  
  			const target = targets[ i ];
  
  			if ( target.POSITION !== undefined ) {
  
  				const accessor = parser.json.accessors[ target.POSITION ];
  				const min = accessor.min;
  				const max = accessor.max;
  
  				// glTF requires 'min' and 'max', but VRM (which extends glTF) currently ignores that requirement.
  
  				if ( min !== undefined && max !== undefined ) {
  
  					// we need to get max of absolute components because target weight is [-1,1]
  					vector.setX( Math.max( Math.abs( min[ 0 ] ), Math.abs( max[ 0 ] ) ) );
  					vector.setY( Math.max( Math.abs( min[ 1 ] ), Math.abs( max[ 1 ] ) ) );
  					vector.setZ( Math.max( Math.abs( min[ 2 ] ), Math.abs( max[ 2 ] ) ) );
  
  
  					if ( accessor.normalized ) {
  
  						const boxScale = getNormalizedComponentScale( WEBGL_COMPONENT_TYPES[ accessor.componentType ] );
  						vector.multiplyScalar( boxScale );
  
  					}
  
  					// Note: this assumes that the sum of all weights is at most 1. This isn't quite correct - it's more conservative
  					// to assume that each target can have a max weight of 1. However, for some use cases - notably, when morph targets
  					// are used to implement key-frame animations and as such only two are active at a time - this results in very large
  					// boxes. So for now we make a box that's sometimes a touch too small but is hopefully mostly of reasonable size.
  					maxDisplacement.max( vector );
  
  				} else {
  
  					console.warn( 'THREE.GLTFLoader: Missing min/max properties for accessor POSITION.' );
  
  				}
  
  			}
  
  		}
  
  		// As per comment above this box isn't conservative, but has a reasonable size for a very large number of morph targets.
  		box.expandByVector( maxDisplacement );
  
  	}
  
  	geometry.boundingBox = box;
  
  	const sphere = new Sphere();
  
  	box.getCenter( sphere.center );
  	sphere.radius = box.min.distanceTo( box.max ) / 2;
  
  	geometry.boundingSphere = sphere;
  
  }
  
  /**
   * @param {BufferGeometry} geometry
   * @param {GLTF.Primitive} primitiveDef
   * @param {GLTFParser} parser
   * @return {Promise<BufferGeometry>}
   */
  function addPrimitiveAttributes( geometry, primitiveDef, parser ) {
  
  	const attributes = primitiveDef.attributes;
  
  	const pending = [];
  
  	function assignAttributeAccessor( accessorIndex, attributeName ) {
  
  		return parser.getDependency( 'accessor', accessorIndex )
  			.then( function ( accessor ) {
  
  				geometry.setAttribute( attributeName, accessor );
  
  			} );
  
  	}
  
  	for ( const gltfAttributeName in attributes ) {
  
  		const threeAttributeName = ATTRIBUTES[ gltfAttributeName ] || gltfAttributeName.toLowerCase();
  
  		// Skip attributes already provided by e.g. Draco extension.
  		if ( threeAttributeName in geometry.attributes ) continue;
  
  		pending.push( assignAttributeAccessor( attributes[ gltfAttributeName ], threeAttributeName ) );
  
  	}
  
  	if ( primitiveDef.indices !== undefined && ! geometry.index ) {
  
  		const accessor = parser.getDependency( 'accessor', primitiveDef.indices ).then( function ( accessor ) {
  
  			geometry.setIndex( accessor );
  
  		} );
  
  		pending.push( accessor );
  
  	}
  
  	assignExtrasToUserData( geometry, primitiveDef );
  
  	computeBounds( geometry, primitiveDef, parser );
  
  	return Promise.all( pending ).then( function () {
  
  		return primitiveDef.targets !== undefined
  			? addMorphTargets( geometry, primitiveDef.targets, parser )
  			: geometry;
  
  	} );
  
  }
  
  /**
   * @param {BufferGeometry} geometry
   * @param {Number} drawMode
   * @return {BufferGeometry}
   */
  function toTrianglesDrawMode( geometry, drawMode ) {
  
  	let index = geometry.getIndex();
  
  	// generate index if not present
  
  	if ( index === null ) {
  
  		const indices = [];
  
  		const position = geometry.getAttribute( 'position' );
  
  		if ( position !== undefined ) {
  
  			for ( let i = 0; i < position.count; i ++ ) {
  
  				indices.push( i );
  
  			}
  
  			geometry.setIndex( indices );
  			index = geometry.getIndex();
  
  		} else {
  
  			console.error( 'THREE.GLTFLoader.toTrianglesDrawMode(): Undefined position attribute. Processing not possible.' );
  			return geometry;
  
  		}
  
  	}
  
  	//
  
  	const numberOfTriangles = index.count - 2;
  	const newIndices = [];
  
  	if ( drawMode === TriangleFanDrawMode ) {
  
  		// gl.TRIANGLE_FAN
  
  		for ( let i = 1; i <= numberOfTriangles; i ++ ) {
  
  			newIndices.push( index.getX( 0 ) );
  			newIndices.push( index.getX( i ) );
  			newIndices.push( index.getX( i + 1 ) );
  
  		}
  
  	} else {
  
  		// gl.TRIANGLE_STRIP
  
  		for ( let i = 0; i < numberOfTriangles; i ++ ) {
  
  			if ( i % 2 === 0 ) {
  
  				newIndices.push( index.getX( i ) );
  				newIndices.push( index.getX( i + 1 ) );
  				newIndices.push( index.getX( i + 2 ) );
  
  
  			} else {
  
  				newIndices.push( index.getX( i + 2 ) );
  				newIndices.push( index.getX( i + 1 ) );
  				newIndices.push( index.getX( i ) );
  
  			}
  
  		}
  
  	}
  
  	if ( ( newIndices.length / 3 ) !== numberOfTriangles ) {
  
  		console.error( 'THREE.GLTFLoader.toTrianglesDrawMode(): Unable to generate correct amount of triangles.' );
  
  	}
  
  	// build final geometry
  
  	const newGeometry = geometry.clone();
  	newGeometry.setIndex( newIndices );
  
  	return newGeometry;
  
  }
  
  export { GLTFLoader };
  