three.js/examples/js/loaders/GLTFLoader.js

( function () {

	class GLTFLoader extends THREE.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 GLTFMaterialsEmissiveStrengthExtension( parser );

			} );
			this.register( function ( parser ) {

				return new GLTFMaterialsSpecularExtension( parser );

			} );
			this.register( function ( parser ) {

				return new GLTFMaterialsIridescenceExtension( parser );

			} );
			this.register( function ( parser ) {

				return new GLTFLightsExtension( parser );

			} );
			this.register( function ( parser ) {

				return new GLTFMeshoptCompression( parser );

			} );
			this.register( function ( parser ) {

				return new GLTFMeshGpuInstancing( 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 = THREE.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 THREE.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 json;
			const extensions = {};
			const plugins = {};
			if ( typeof data === 'string' ) {

				json = JSON.parse( data );

			} else if ( data instanceof ArrayBuffer ) {

				const magic = THREE.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;

					}

					json = JSON.parse( extensions[ EXTENSIONS.KHR_BINARY_GLTF ].content );

				} else {

					json = JSON.parse( THREE.LoaderUtils.decodeText( new Uint8Array( data ) ) );

				}

			} else {

				json = data;

			}

			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_IRIDESCENCE: 'KHR_materials_iridescence',
		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',
		KHR_MATERIALS_EMISSIVE_STRENGTH: 'KHR_materials_emissive_strength',
		EXT_TEXTURE_WEBP: 'EXT_texture_webp',
		EXT_MESHOPT_COMPRESSION: 'EXT_meshopt_compression',
		EXT_MESH_GPU_INSTANCING: 'EXT_mesh_gpu_instancing'
	};

	/**
 * 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;

			// THREE.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 THREE.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 THREE.DirectionalLight( color );
					lightNode.target.position.set( 0, 0, - 1 );
					lightNode.add( lightNode.target );
					break;
				case 'point':
					lightNode = new THREE.PointLight( color );
					lightNode.distance = range;
					break;
				case 'spot':
					lightNode = new THREE.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;
			assignExtrasToUserData( lightNode, lightDef );
			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;

		}
		getDependency( type, index ) {

			if ( type !== 'light' ) return;
			return this._loadLight( index );

		}
		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 THREE.MeshBasicMaterial;

		}
		extendParams( materialParams, materialDef, parser ) {

			const pending = [];
			materialParams.color = new THREE.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, THREE.sRGBEncoding ) );

				}

			}

			return Promise.all( pending );

		}

	}

	/**
 * Materials Emissive Strength Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/blob/5768b3ce0ef32bc39cdf1bef10b948586635ead3/extensions/2.0/Khronos/KHR_materials_emissive_strength/README.md
 */
	class GLTFMaterialsEmissiveStrengthExtension {

		constructor( parser ) {

			this.parser = parser;
			this.name = EXTENSIONS.KHR_MATERIALS_EMISSIVE_STRENGTH;

		}
		extendMaterialParams( materialIndex, materialParams ) {

			const parser = this.parser;
			const materialDef = parser.json.materials[ materialIndex ];
			if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {

				return Promise.resolve();

			}

			const emissiveStrength = materialDef.extensions[ this.name ].emissiveStrength;
			if ( emissiveStrength !== undefined ) {

				materialParams.emissiveIntensity = emissiveStrength;

			}

			return Promise.resolve();

		}

	}

	/**
 * 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 THREE.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 THREE.Vector2( scale, scale );

				}

			}

			return Promise.all( pending );

		}

	}

	/**
 * Iridescence Materials Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_iridescence
 */
	class GLTFMaterialsIridescenceExtension {

		constructor( parser ) {

			this.parser = parser;
			this.name = EXTENSIONS.KHR_MATERIALS_IRIDESCENCE;

		}
		getMaterialType( materialIndex ) {

			const parser = this.parser;
			const materialDef = parser.json.materials[ materialIndex ];
			if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;
			return THREE.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.iridescenceFactor !== undefined ) {

				materialParams.iridescence = extension.iridescenceFactor;

			}

			if ( extension.iridescenceTexture !== undefined ) {

				pending.push( parser.assignTexture( materialParams, 'iridescenceMap', extension.iridescenceTexture ) );

			}

			if ( extension.iridescenceIor !== undefined ) {

				materialParams.iridescenceIOR = extension.iridescenceIor;

			}

			if ( materialParams.iridescenceThicknessRange === undefined ) {

				materialParams.iridescenceThicknessRange = [ 100, 400 ];

			}

			if ( extension.iridescenceThicknessMinimum !== undefined ) {

				materialParams.iridescenceThicknessRange[ 0 ] = extension.iridescenceThicknessMinimum;

			}

			if ( extension.iridescenceThicknessMaximum !== undefined ) {

				materialParams.iridescenceThicknessRange[ 1 ] = extension.iridescenceThicknessMaximum;

			}

			if ( extension.iridescenceThicknessTexture !== undefined ) {

				pending.push( parser.assignTexture( materialParams, 'iridescenceThicknessMap', extension.iridescenceThicknessTexture ) );

			}

			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 THREE.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 THREE.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, THREE.sRGBEncoding ) );

			}

			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 THREE.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 THREE.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 || Infinity;
			const colorArray = extension.attenuationColor || [ 1, 1, 1 ];
			materialParams.attenuationColor = new THREE.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 THREE.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 THREE.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 THREE.Color( colorArray[ 0 ], colorArray[ 1 ], colorArray[ 2 ] );
			if ( extension.specularColorTexture !== undefined ) {

				pending.push( parser.assignTexture( materialParams, 'specularColorMap', extension.specularColorTexture, THREE.sRGBEncoding ) );

			}

			return Promise.all( pending );

		}

	}

	/**
 * BasisU THREE.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 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, extension.source, loader );

		}

	}

	/**
 * WebP THREE.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, extension.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 buffer.then( function ( res ) {

					const byteOffset = extensionDef.byteOffset || 0;
					const byteLength = extensionDef.byteLength || 0;
					const count = extensionDef.count;
					const stride = extensionDef.byteStride;
					const source = new Uint8Array( res, byteOffset, byteLength );
					if ( decoder.decodeGltfBufferAsync ) {

						return decoder.decodeGltfBufferAsync( count, stride, source, extensionDef.mode, extensionDef.filter ).then( function ( res ) {

							return res.buffer;

						} );

					} else {

						// Support for MeshoptDecoder 0.18 or earlier, without decodeGltfBufferAsync
						return decoder.ready.then( function () {

							const result = new ArrayBuffer( count * stride );
							decoder.decodeGltfBuffer( new Uint8Array( result ), count, stride, source, extensionDef.mode, extensionDef.filter );
							return result;

						} );

					}

				} );

			} else {

				return null;

			}

		}

	}

	/**
 * GPU Instancing Extension
 *
 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_mesh_gpu_instancing
 *
 */
	class GLTFMeshGpuInstancing {

		constructor( parser ) {

			this.name = EXTENSIONS.EXT_MESH_GPU_INSTANCING;
			this.parser = parser;

		}
		createNodeMesh( nodeIndex ) {

			const json = this.parser.json;
			const nodeDef = json.nodes[ nodeIndex ];
			if ( ! nodeDef.extensions || ! nodeDef.extensions[ this.name ] || nodeDef.mesh === undefined ) {

				return null;

			}

			const meshDef = json.meshes[ nodeDef.mesh ];

			// No THREE.Points or Lines + Instancing support yet

			for ( const primitive of meshDef.primitives ) {

				if ( primitive.mode !== WEBGL_CONSTANTS.TRIANGLES && primitive.mode !== WEBGL_CONSTANTS.TRIANGLE_STRIP && primitive.mode !== WEBGL_CONSTANTS.TRIANGLE_FAN && primitive.mode !== undefined ) {

					return null;

				}

			}

			const extensionDef = nodeDef.extensions[ this.name ];
			const attributesDef = extensionDef.attributes;

			// @TODO: Can we support THREE.InstancedMesh + THREE.SkinnedMesh?

			const pending = [];
			const attributes = {};
			for ( const key in attributesDef ) {

				pending.push( this.parser.getDependency( 'accessor', attributesDef[ key ] ).then( accessor => {

					attributes[ key ] = accessor;
					return attributes[ key ];

				} ) );

			}

			if ( pending.length < 1 ) {

				return null;

			}

			pending.push( this.parser.createNodeMesh( nodeIndex ) );
			return Promise.all( pending ).then( results => {

				const nodeObject = results.pop();
				const meshes = nodeObject.isGroup ? nodeObject.children : [ nodeObject ];
				const count = results[ 0 ].count; // All attribute counts should be same
				const instancedMeshes = [];
				for ( const mesh of meshes ) {

					// Temporal variables
					const m = new THREE.Matrix4();
					const p = new THREE.Vector3();
					const q = new THREE.Quaternion();
					const s = new THREE.Vector3( 1, 1, 1 );
					const instancedMesh = new THREE.InstancedMesh( mesh.geometry, mesh.material, count );
					for ( let i = 0; i < count; i ++ ) {

						if ( attributes.TRANSLATION ) {

							p.fromBufferAttribute( attributes.TRANSLATION, i );

						}

						if ( attributes.ROTATION ) {

							q.fromBufferAttribute( attributes.ROTATION, i );

						}

						if ( attributes.SCALE ) {

							s.fromBufferAttribute( attributes.SCALE, i );

						}

						instancedMesh.setMatrixAt( i, m.compose( p, q, s ) );

					}

					// Add instance attributes to the geometry, excluding TRS.
					for ( const attributeName in attributes ) {

						if ( attributeName !== 'TRANSLATION' && attributeName !== 'ROTATION' && attributeName !== 'SCALE' ) {

							mesh.geometry.setAttribute( attributeName, attributes[ attributeName ] );

						}

					}

					// Just in case
					THREE.Object3D.prototype.copy.call( instancedMesh, mesh );

					// https://github.com/mrdoob/three.js/issues/18334
					instancedMesh.frustumCulled = false;
					this.parser.assignFinalMaterial( instancedMesh );
					instancedMeshes.push( instancedMesh );

				}

				if ( nodeObject.isGroup ) {

					nodeObject.clear();
					nodeObject.add( ...instancedMeshes );
					return nodeObject;

				}

				return instancedMeshes[ 0 ];

			} );

		}

	}

	/* 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: THREE.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 = THREE.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 THREE.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.name;
					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 );

				} );

			} );

		}

	}

	/**
 * THREE.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 THREE.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 THREE.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' ];

		}
		getMaterialType() {

			return GLTFMeshStandardSGMaterial;

		}
		extendParams( materialParams, materialDef, parser ) {

			const pbrSpecularGlossiness = materialDef.extensions[ this.name ];
			materialParams.color = new THREE.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, THREE.sRGBEncoding ) );

			}

			materialParams.emissive = new THREE.Color( 0.0, 0.0, 0.0 );
			materialParams.glossiness = pbrSpecularGlossiness.glossinessFactor !== undefined ? pbrSpecularGlossiness.glossinessFactor : 1.0;
			materialParams.specular = new THREE.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, THREE.sRGBEncoding ) );

			}

			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 = materialParams.emissiveIntensity === undefined ? 1.0 : materialParams.emissiveIntensity;
			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 = THREE.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;
			return material;

		}

	}

	/**
 * THREE.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 THREE.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;

		}
		interpolate_( 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 THREE.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: THREE.NearestFilter,
		9729: THREE.LinearFilter,
		9984: THREE.NearestMipmapNearestFilter,
		9985: THREE.LinearMipmapNearestFilter,
		9986: THREE.NearestMipmapLinearFilter,
		9987: THREE.LinearMipmapLinearFilter
	};
	const WEBGL_WRAPPINGS = {
		33071: THREE.ClampToEdgeWrapping,
		33648: THREE.MirroredRepeatWrapping,
		10497: THREE.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: THREE.InterpolateLinear,
		STEP: THREE.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 THREE.MeshStandardMaterial( {
				color: 0xFFFFFF,
				emissive: 0x000000,
				metalness: 1,
				roughness: 1,
				transparent: false,
				depthTest: true,
				side: THREE.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;
		let hasMorphColor = 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 ( target.COLOR_0 !== undefined ) hasMorphColor = true;
			if ( hasMorphPosition && hasMorphNormal && hasMorphColor ) break;

		}

		if ( ! hasMorphPosition && ! hasMorphNormal && ! hasMorphColor ) return Promise.resolve( geometry );
		const pendingPositionAccessors = [];
		const pendingNormalAccessors = [];
		const pendingColorAccessors = [];
		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 );

			}

			if ( hasMorphColor ) {

				const pendingAccessor = target.COLOR_0 !== undefined ? parser.getDependency( 'accessor', target.COLOR_0 ) : geometry.attributes.color;
				pendingColorAccessors.push( pendingAccessor );

			}

		}

		return Promise.all( [ Promise.all( pendingPositionAccessors ), Promise.all( pendingNormalAccessors ), Promise.all( pendingColorAccessors ) ] ).then( function ( accessors ) {

			const morphPositions = accessors[ 0 ];
			const morphNormals = accessors[ 1 ];
			const morphColors = accessors[ 2 ];
			if ( hasMorphPosition ) geometry.morphAttributes.position = morphPositions;
			if ( hasMorphNormal ) geometry.morphAttributes.normal = morphNormals;
			if ( hasMorphColor ) geometry.morphAttributes.color = morphColors;
			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.' );

		}

	}

	function getImageURIMimeType( uri ) {

		if ( uri.search( /\.jpe?g($|\?)/i ) > 0 || uri.search( /^data\:image\/jpeg/ ) === 0 ) return 'image/jpeg';
		if ( uri.search( /\.webp($|\?)/i ) > 0 || uri.search( /^data\:image\/webp/ ) === 0 ) return 'image/webp';
		return 'image/png';

	}

	/* 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();

			// THREE.BufferGeometry caching
			this.primitiveCache = {};

			// THREE.Object3D instance caches
			this.meshCache = {
				refs: {},
				uses: {}
			};
			this.cameraCache = {
				refs: {},
				uses: {}
			};
			this.lightCache = {
				refs: {},
				uses: {}
			};
			this.sourceCache = {};
			this.textureCache = {};

			// Track node names, to ensure no duplicates
			this.nodeNamesUsed = {};

			// Use an THREE.ImageBitmapLoader if imageBitmaps are supported. Moves much of the
			// expensive work of uploading a texture to the GPU off the main thread.

			const isSafari = /^((?!chrome|android).)*safari/i.test( navigator.userAgent ) === true;
			const isFirefox = navigator.userAgent.indexOf( 'Firefox' ) > - 1;
			const firefoxVersion = isFirefox ? navigator.userAgent.match( /Firefox\/([0-9]+)\./ )[ 1 ] : - 1;
			if ( typeof createImageBitmap === 'undefined' || isSafari || isFirefox && firefoxVersion < 98 ) {

				this.textureLoader = new THREE.TextureLoader( this.options.manager );

			} else {

				this.textureLoader = new THREE.ImageBitmapLoader( this.options.manager );

			}

			this.textureLoader.setCrossOrigin( this.options.crossOrigin );
			this.textureLoader.setRequestHeader( this.options.requestHeader );
			this.fileLoader = new THREE.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 THREE.Bone or an
			// THREE.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 THREE.SkinnedMesh or THREE.Mesh. Use the node's mesh reference
					// to mark THREE.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 / THREE.Object3D resources. These resources
   * can be reused, or "instantiated", at multiple nodes in the scene
   * hierarchy. THREE.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._invokeOne( function ( ext ) {

							return ext.loadAnimation && ext.loadAnimation( index );

						} );
						break;
					case 'camera':
						dependency = this.loadCamera( index );
						break;
					default:
						dependency = this._invokeOne( function ( ext ) {

							return ext != this && ext.getDependency && ext.getDependency( type, index );

						} );
						if ( ! dependency ) {

							throw new Error( 'Unknown type: ' + type );

						}

						break;

				}

				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( THREE.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 ) {

				const itemSize = WEBGL_TYPE_SIZES[ accessorDef.type ];
				const TypedArray = WEBGL_COMPONENT_TYPES[ accessorDef.componentType ];
				const normalized = accessorDef.normalized === true;
				const array = new TypedArray( accessorDef.count * itemSize );
				return Promise.resolve( new THREE.BufferAttribute( array, itemSize, normalized ) );

			}

			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 THREE.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 THREE.InterleavedBuffer( array, byteStride / elementBytes );
						parser.cache.add( ibCacheKey, ib );

					}

					bufferAttribute = new THREE.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 THREE.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 THREE.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 THREE.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 sourceIndex = textureDef.source;
			const sourceDef = json.images[ sourceIndex ];
			let loader = this.textureLoader;
			if ( sourceDef.uri ) {

				const handler = options.manager.getHandler( sourceDef.uri );
				if ( handler !== null ) loader = handler;

			}

			return this.loadTextureImage( textureIndex, sourceIndex, loader );

		}
		loadTextureImage( textureIndex, sourceIndex, loader ) {

			const parser = this;
			const json = this.json;
			const textureDef = json.textures[ textureIndex ];
			const sourceDef = json.images[ sourceIndex ];
			const cacheKey = ( sourceDef.uri || sourceDef.bufferView ) + ':' + textureDef.sampler;
			if ( this.textureCache[ cacheKey ] ) {

				// See https://github.com/mrdoob/three.js/issues/21559.
				return this.textureCache[ cacheKey ];

			}

			const promise = this.loadImageSource( sourceIndex, loader ).then( function ( texture ) {

				texture.flipY = false;
				texture.name = textureDef.name || sourceDef.name || '';
				const samplers = json.samplers || {};
				const sampler = samplers[ textureDef.sampler ] || {};
				texture.magFilter = WEBGL_FILTERS[ sampler.magFilter ] || THREE.LinearFilter;
				texture.minFilter = WEBGL_FILTERS[ sampler.minFilter ] || THREE.LinearMipmapLinearFilter;
				texture.wrapS = WEBGL_WRAPPINGS[ sampler.wrapS ] || THREE.RepeatWrapping;
				texture.wrapT = WEBGL_WRAPPINGS[ sampler.wrapT ] || THREE.RepeatWrapping;
				parser.associations.set( texture, {
					textures: textureIndex
				} );
				return texture;

			} ).catch( function () {

				return null;

			} );
			this.textureCache[ cacheKey ] = promise;
			return promise;

		}
		loadImageSource( sourceIndex, loader ) {

			const parser = this;
			const json = this.json;
			const options = this.options;
			if ( this.sourceCache[ sourceIndex ] !== undefined ) {

				return this.sourceCache[ sourceIndex ].then( texture => texture.clone() );

			}

			const sourceDef = json.images[ sourceIndex ];
			const URL = self.URL || self.webkitURL;
			let sourceURI = sourceDef.uri || '';
			let isObjectURL = false;
			if ( sourceDef.bufferView !== undefined ) {

				// Load binary image data from bufferView, if provided.

				sourceURI = parser.getDependency( 'bufferView', sourceDef.bufferView ).then( function ( bufferView ) {

					isObjectURL = true;
					const blob = new Blob( [ bufferView ], {
						type: sourceDef.mimeType
					} );
					sourceURI = URL.createObjectURL( blob );
					return sourceURI;

				} );

			} else if ( sourceDef.uri === undefined ) {

				throw new Error( 'THREE.GLTFLoader: Image ' + sourceIndex + ' 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 THREE.Texture( imageBitmap );
							texture.needsUpdate = true;
							resolve( texture );

						};

					}

					loader.load( THREE.LoaderUtils.resolveURL( sourceURI, options.path ), onLoad, undefined, reject );

				} );

			} ).then( function ( texture ) {

				// Clean up resources and configure THREE.Texture.

				if ( isObjectURL === true ) {

					URL.revokeObjectURL( sourceURI );

				}

				texture.userData.mimeType = sourceDef.mimeType || getImageURIMimeType( sourceDef.uri );
				return texture;

			} ).catch( function ( error ) {

				console.error( 'THREE.GLTFLoader: Couldn\'t load texture', sourceURI );
				throw error;

			} );
			this.sourceCache[ sourceIndex ] = 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, encoding ) {

			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 );

					}

				}

				if ( encoding !== undefined ) {

					texture.encoding = encoding;

				}

				materialParams[ mapName ] = texture;
				return texture;

			} );

		}

		/**
   * Assigns final material to a THREE.Mesh, THREE.Line, or THREE.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 THREE.Mesh, THREE.Line, or THREE.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 THREE.PointsMaterial();
					THREE.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 THREE.LineBasicMaterial();
					THREE.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() {

			return THREE.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 THREE.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, THREE.sRGBEncoding ) );

				}

				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 = THREE.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 !== THREE.MeshBasicMaterial ) {

				pending.push( parser.assignTexture( materialParams, 'normalMap', materialDef.normalTexture ) );
				materialParams.normalScale = new THREE.Vector2( 1, 1 );
				if ( materialDef.normalTexture.scale !== undefined ) {

					const scale = materialDef.normalTexture.scale;
					materialParams.normalScale.set( scale, scale );

				}

			}

			if ( materialDef.occlusionTexture !== undefined && materialType !== THREE.MeshBasicMaterial ) {

				pending.push( parser.assignTexture( materialParams, 'aoMap', materialDef.occlusionTexture ) );
				if ( materialDef.occlusionTexture.strength !== undefined ) {

					materialParams.aoMapIntensity = materialDef.occlusionTexture.strength;

				}

			}

			if ( materialDef.emissiveFactor !== undefined && materialType !== THREE.MeshBasicMaterial ) {

				materialParams.emissive = new THREE.Color().fromArray( materialDef.emissiveFactor );

			}

			if ( materialDef.emissiveTexture !== undefined && materialType !== THREE.MeshBasicMaterial ) {

				pending.push( parser.assignTexture( materialParams, 'emissiveMap', materialDef.emissiveTexture, THREE.sRGBEncoding ) );

			}

			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;
				assignExtrasToUserData( material, materialDef );
				parser.associations.set( material, {
					materials: materialIndex
				} );
				if ( materialDef.extensions ) addUnknownExtensionsToUserData( extensions, material, materialDef );
				return material;

			} );

		}

		/** When THREE.Object3D instances are targeted by animation, they need unique names. */
		createUniqueName( originalName ) {

			const sanitizedName = THREE.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 THREE.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 THREE.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 THREE.SkinnedMesh( geometry, material ) : new THREE.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, THREE.TriangleStripDrawMode );

						} else if ( primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ) {

							mesh.geometry = toTrianglesDrawMode( mesh.geometry, THREE.TriangleFanDrawMode );

						}

					} else if ( primitive.mode === WEBGL_CONSTANTS.LINES ) {

						mesh = new THREE.LineSegments( geometry, material );

					} else if ( primitive.mode === WEBGL_CONSTANTS.LINE_STRIP ) {

						mesh = new THREE.Line( geometry, material );

					} else if ( primitive.mode === WEBGL_CONSTANTS.LINE_LOOP ) {

						mesh = new THREE.LineLoop( geometry, material );

					} else if ( primitive.mode === WEBGL_CONSTANTS.POINTS ) {

						mesh = new THREE.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 THREE.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 THREE.PerspectiveCamera( THREE.MathUtils.radToDeg( params.yfov ), params.aspectRatio || 1, params.znear || 1, params.zfar || 2e6 );

			} else if ( cameraDef.type === 'orthographic' ) {

				camera = new THREE.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;
				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();
					let TypedKeyframeTrack;
					switch ( PATH_PROPERTIES[ target.path ] ) {

						case PATH_PROPERTIES.weights:
							TypedKeyframeTrack = THREE.NumberKeyframeTrack;
							break;
						case PATH_PROPERTIES.rotation:
							TypedKeyframeTrack = THREE.QuaternionKeyframeTrack;
							break;
						case PATH_PROPERTIES.position:
						case PATH_PROPERTIES.scale:
						default:
							TypedKeyframeTrack = THREE.VectorKeyframeTrack;
							break;

					}

					const targetName = node.name ? node.name : node.uuid;
					const interpolation = sampler.interpolation !== undefined ? INTERPOLATION[ sampler.interpolation ] : THREE.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 THREE.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 THREE.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 THREE.Bone();

				} else if ( objects.length > 1 ) {

					node = new THREE.Group();

				} else if ( objects.length === 1 ) {

					node = objects[ 0 ];

				} else {

					node = new THREE.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 THREE.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;

			// THREE.Loader returns THREE.Group, not Scene.
			// See: https://github.com/mrdoob/three.js/issues/18342#issuecomment-578981172
			const scene = new THREE.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 THREE.Material || key instanceof THREE.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 THREE.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 THREE.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 THREE.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 THREE.Vector3( min[ 0 ], min[ 1 ], min[ 2 ] ), new THREE.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 THREE.Vector3();
			const vector = new THREE.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 THREE.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 === THREE.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;

	}

	THREE.GLTFLoader = GLTFLoader;

} )();