GLTFLoader.js

/**
 * @author Rich Tibbett / https://github.com/richtr
 * @author mrdoob / http://mrdoob.com/
 * @author Tony Parisi / http://www.tonyparisi.com/
 * @author Takahiro / https://github.com/takahirox
 * @author Don McCurdy / https://www.donmccurdy.com
 */

THREE.GLTFLoader = ( function () {

	function GLTFLoader( manager ) {

		this.manager = ( manager !== undefined ) ? manager : THREE.DefaultLoadingManager;
		this.dracoLoader = null;
		this.userExtensions = {};
	}

	GLTFLoader.prototype = {

		constructor: GLTFLoader,

		crossOrigin: 'anonymous',

		load: function ( url, onLoad, onProgress, onError ) {

			var scope = this;

			var resourcePath;

			if ( this.resourcePath !== undefined ) {

				resourcePath = this.resourcePath;

			} else if ( this.path !== undefined ) {

				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.
			scope.manager.itemStart( url );

			var _onError = function ( e ) {

				if ( onError ) {

					onError( e );

				} else {

					console.error( e );

				}

				scope.manager.itemError( url );
				scope.manager.itemEnd( url );

			};

			var loader = new THREE.FileLoader( scope.manager );

			loader.setPath( this.path );
			loader.setResponseType( 'arraybuffer' );

			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 );

		},

		setCrossOrigin: function ( value ) {

			this.crossOrigin = value;
			return this;

		},

		setPath: function ( value ) {

			this.path = value;
			return this;

		},

		setResourcePath: function ( value ) {

			this.resourcePath = value;
			return this;

		},

		setDRACOLoader: function ( dracoLoader ) {

			this.dracoLoader = dracoLoader;
			return this;

		},

		registerExtension: function ( name, factory ) {

			if(typeof factory !== 'function') {
				throw new Error('THREE:GLTFLoader: factory must be a function that returns a extension instance');
			}

			// check if an user extension with the same name is already registered
			if( this.userExtensions[name] ) {
				throw new Error('THREE:GLTFLoader: Trying to overwrite already registered userExtension');
			}

			// check the name is already used by internally defined extensions
			for( var key in EXTENSIONS ) {
				if( EXTENSIONS.hasOwnProperty(key) && EXTENSIONS[key] === name ) {
					throw new Error('THREE.GLTFLoader: Trying to add custom extension with internally registered name');
				}
			}

			this.userExtensions[name] = {
				factory: factory
			};

			return this;
		},

		parse: function ( data, path, onLoad, onError ) {

			var content;
			var extensions = {};

			if ( typeof data === 'string' ) {

				content = data;

			} else {

				var 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;

					}

					content = extensions[ EXTENSIONS.KHR_BINARY_GLTF ].content;

				} else {

					content = THREE.LoaderUtils.decodeText( new Uint8Array( data ) );

				}

			}

			var json = JSON.parse( content );

			if ( json.asset === undefined || json.asset.version[ 0 ] < 2 ) {

				if ( onError ) onError( new Error( 'THREE.GLTFLoader: Unsupported asset. glTF versions >=2.0 are supported. Use LegacyGLTFLoader instead.' ) );
				return;

			}

			if ( json.extensionsUsed ) {

				for ( var i = 0; i < json.extensionsUsed.length; ++ i ) {

					var extensionName = json.extensionsUsed[ i ];
					var extensionsRequired = json.extensionsRequired || [];

					switch ( extensionName ) {

						case EXTENSIONS.KHR_LIGHTS_PUNCTUAL:
							extensions[ extensionName ] = new GLTFLightsExtension( json );
							break;

						case EXTENSIONS.KHR_MATERIALS_UNLIT:
							extensions[ extensionName ] = new GLTFMaterialsUnlitExtension( json );
							break;

						case EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS:
							extensions[ extensionName ] = new GLTFMaterialsPbrSpecularGlossinessExtension( json );
							break;

						case EXTENSIONS.KHR_DRACO_MESH_COMPRESSION:
							extensions[ extensionName ] = new GLTFDracoMeshCompressionExtension( json, this.dracoLoader );
							break;

						case EXTENSIONS.MSFT_TEXTURE_DDS:
							extensions[ EXTENSIONS.MSFT_TEXTURE_DDS ] = new GLTFTextureDDSExtension();
							break;

						case EXTENSIONS.KHR_TEXTURE_TRANSFORM:
							extensions[ EXTENSIONS.KHR_TEXTURE_TRANSFORM ] = new GLTFTextureTransformExtension( json );
							break;

						default:

							if( this.userExtensions[extensionName] ) {

								// todo maybe add more than the json ?
								var instance = this.userExtensions[extensionName].factory( json );
								instance.isUserExtension = true;
								extensions[ extensionName ] = instance;
								
								break;
								
							}

							if ( extensionsRequired.indexOf( extensionName ) >= 0 ) {

								console.warn( 'THREE.GLTFLoader: Unknown extension "' + extensionName + '".' );

							}

					}

				}

			}

			var parser = new GLTFParser( json, extensions, {

				path: path || this.resourcePath || '',
				crossOrigin: this.crossOrigin,
				manager: this.manager

			} );

			parser.parse( function ( scene, scenes, cameras, animations, json ) {

				var glTF = {
					scene: scene,
					scenes: scenes,
					cameras: cameras,
					animations: animations,
					asset: json.asset,
					parser: parser,
					userData: {}
				};

				addUnknownExtensionsToUserData( extensions, glTF, json );

				onLoad( glTF );

			}, onError );

		}

	};

	/* GLTFREGISTRY */

	function GLTFRegistry() {

		var 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 ***********/
	/*********************************/

	var EXTENSIONS = {
		KHR_BINARY_GLTF: 'KHR_binary_glTF',
		KHR_DRACO_MESH_COMPRESSION: 'KHR_draco_mesh_compression',
		KHR_LIGHTS_PUNCTUAL: 'KHR_lights_punctual',
		KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS: 'KHR_materials_pbrSpecularGlossiness',
		KHR_MATERIALS_UNLIT: 'KHR_materials_unlit',
		KHR_TEXTURE_TRANSFORM: 'KHR_texture_transform',
		MSFT_TEXTURE_DDS: 'MSFT_texture_dds'
	};

	/**
	 * DDS Texture Extension
	 *
	 * Specification:
	 * https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/MSFT_texture_dds
	 *
	 */
	function GLTFTextureDDSExtension() {

		if ( ! THREE.DDSLoader ) {

			throw new Error( 'THREE.GLTFLoader: Attempting to load .dds texture without importing THREE.DDSLoader' );

		}

		this.name = EXTENSIONS.MSFT_TEXTURE_DDS;
		this.ddsLoader = new THREE.DDSLoader();

	}

	/**
	 * Lights Extension
	 *
	 * Specification: PENDING
	 */
	function GLTFLightsExtension( json ) {

		this.name = EXTENSIONS.KHR_LIGHTS_PUNCTUAL;

		var extension = ( json.extensions && json.extensions[ EXTENSIONS.KHR_LIGHTS_PUNCTUAL ] ) || {};
		this.lightDefs = extension.lights || [];

	}

	GLTFLightsExtension.prototype.loadLight = function ( lightIndex ) {

		var lightDef = this.lightDefs[ lightIndex ];
		var lightNode;

		var color = new THREE.Color( 0xffffff );
		if ( lightDef.color !== undefined ) color.fromArray( lightDef.color );

		var 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;

		if ( lightDef.intensity !== undefined ) lightNode.intensity = lightDef.intensity;

		lightNode.name = lightDef.name || ( 'light_' + lightIndex );

		return Promise.resolve( lightNode );

	};

	/**
	 * Unlit Materials Extension (pending)
	 *
	 * PR: https://github.com/KhronosGroup/glTF/pull/1163
	 */
	function GLTFMaterialsUnlitExtension( json ) {

		this.name = EXTENSIONS.KHR_MATERIALS_UNLIT;

	}

	GLTFMaterialsUnlitExtension.prototype.getMaterialType = function ( material ) {

		return THREE.MeshBasicMaterial;

	};

	GLTFMaterialsUnlitExtension.prototype.extendParams = function ( materialParams, material, parser ) {

		var pending = [];

		materialParams.color = new THREE.Color( 1.0, 1.0, 1.0 );
		materialParams.opacity = 1.0;

		var metallicRoughness = material.pbrMetallicRoughness;

		if ( metallicRoughness ) {

			if ( Array.isArray( metallicRoughness.baseColorFactor ) ) {

				var array = metallicRoughness.baseColorFactor;

				materialParams.color.fromArray( array );
				materialParams.opacity = array[ 3 ];

			}

			if ( metallicRoughness.baseColorTexture !== undefined ) {

				pending.push( parser.assignTexture( materialParams, 'map', metallicRoughness.baseColorTexture ) );

			}

		}

		return Promise.all( pending );

	};

	/* BINARY EXTENSION */

	var BINARY_EXTENSION_BUFFER_NAME = 'binary_glTF';
	var BINARY_EXTENSION_HEADER_MAGIC = 'glTF';
	var BINARY_EXTENSION_HEADER_LENGTH = 12;
	var BINARY_EXTENSION_CHUNK_TYPES = { JSON: 0x4E4F534A, BIN: 0x004E4942 };

	function GLTFBinaryExtension( data ) {

		this.name = EXTENSIONS.KHR_BINARY_GLTF;
		this.content = null;
		this.body = null;

		var 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. Use LegacyGLTFLoader instead.' );

		}

		var chunkView = new DataView( data, BINARY_EXTENSION_HEADER_LENGTH );
		var chunkIndex = 0;

		while ( chunkIndex < chunkView.byteLength ) {

			var chunkLength = chunkView.getUint32( chunkIndex, true );
			chunkIndex += 4;

			var chunkType = chunkView.getUint32( chunkIndex, true );
			chunkIndex += 4;

			if ( chunkType === BINARY_EXTENSION_CHUNK_TYPES.JSON ) {

				var contentArray = new Uint8Array( data, BINARY_EXTENSION_HEADER_LENGTH + chunkIndex, chunkLength );
				this.content = THREE.LoaderUtils.decodeText( contentArray );

			} else if ( chunkType === BINARY_EXTENSION_CHUNK_TYPES.BIN ) {

				var byteOffset = BINARY_EXTENSION_HEADER_LENGTH + chunkIndex;
				this.body = data.slice( byteOffset, byteOffset + chunkLength );

			}

			// Clients must ignore chunks with unknown types.

			chunkIndex += chunkLength;

		}

		if ( this.content === null ) {

			throw new Error( 'THREE.GLTFLoader: JSON content not found.' );

		}

	}

	/**
	 * DRACO Mesh Compression Extension
	 *
	 * Specification: https://github.com/KhronosGroup/glTF/pull/874
	 */
	function GLTFDracoMeshCompressionExtension( 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;
		THREE.DRACOLoader.getDecoderModule();

	}

	GLTFDracoMeshCompressionExtension.prototype.decodePrimitive = function ( primitive, parser ) {

		var json = this.json;
		var dracoLoader = this.dracoLoader;
		var bufferViewIndex = primitive.extensions[ this.name ].bufferView;
		var gltfAttributeMap = primitive.extensions[ this.name ].attributes;
		var threeAttributeMap = {};
		var attributeNormalizedMap = {};
		var attributeTypeMap = {};

		for ( var attributeName in gltfAttributeMap ) {

			if ( ! ( attributeName in ATTRIBUTES ) ) continue;

			threeAttributeMap[ ATTRIBUTES[ attributeName ] ] = gltfAttributeMap[ attributeName ];

		}

		for ( attributeName in primitive.attributes ) {

			if ( ATTRIBUTES[ attributeName ] !== undefined && gltfAttributeMap[ attributeName ] !== undefined ) {

				var accessorDef = json.accessors[ primitive.attributes[ attributeName ] ];
				var componentType = WEBGL_COMPONENT_TYPES[ accessorDef.componentType ];

				attributeTypeMap[ ATTRIBUTES[ attributeName ] ] = componentType;
				attributeNormalizedMap[ ATTRIBUTES[ attributeName ] ] = accessorDef.normalized === true;

			}

		}

		return parser.getDependency( 'bufferView', bufferViewIndex ).then( function ( bufferView ) {

			return new Promise( function ( resolve ) {

				dracoLoader.decodeDracoFile( bufferView, function ( geometry ) {

					for ( var attributeName in geometry.attributes ) {

						var attribute = geometry.attributes[ attributeName ];
						var normalized = attributeNormalizedMap[ attributeName ];

						if ( normalized !== undefined ) attribute.normalized = normalized;

					}

					resolve( geometry );

				}, threeAttributeMap, attributeTypeMap );

			} );

		} );

	};

	/**
	 * Texture Transform Extension
	 *
	 * Specification:
	 */
	function GLTFTextureTransformExtension( json ) {

		this.name = EXTENSIONS.KHR_TEXTURE_TRANSFORM;

	}

	GLTFTextureTransformExtension.prototype.extendTexture = function ( texture, transform ) {

		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 );

		}

		if ( transform.texCoord !== undefined ) {

			console.warn( 'THREE.GLTFLoader: Custom UV sets in "' + this.name + '" extension not yet supported.' );

		}

		texture.needsUpdate = true;

		return texture;

	};

	/**
	 * Specular-Glossiness Extension
	 *
	 * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_pbrSpecularGlossiness
	 */
	function GLTFMaterialsPbrSpecularGlossinessExtension() {

		return {

			name: EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS,

			specularGlossinessParams: [
				'color',
				'map',
				'lightMap',
				'lightMapIntensity',
				'aoMap',
				'aoMapIntensity',
				'emissive',
				'emissiveIntensity',
				'emissiveMap',
				'bumpMap',
				'bumpScale',
				'normalMap',
				'displacementMap',
				'displacementScale',
				'displacementBias',
				'specularMap',
				'specular',
				'glossinessMap',
				'glossiness',
				'alphaMap',
				'envMap',
				'envMapIntensity',
				'refractionRatio',
			],

			getMaterialType: function () {

				return THREE.ShaderMaterial;

			},

			extendParams: function ( params, material, parser ) {

				var pbrSpecularGlossiness = material.extensions[ this.name ];

				var shader = THREE.ShaderLib[ 'standard' ];

				var uniforms = THREE.UniformsUtils.clone( shader.uniforms );

				var specularMapParsFragmentChunk = [
					'#ifdef USE_SPECULARMAP',
					'	uniform sampler2D specularMap;',
					'#endif'
				].join( '\n' );

				var glossinessMapParsFragmentChunk = [
					'#ifdef USE_GLOSSINESSMAP',
					'	uniform sampler2D glossinessMap;',
					'#endif'
				].join( '\n' );

				var specularMapFragmentChunk = [
					'vec3 specularFactor = specular;',
					'#ifdef USE_SPECULARMAP',
					'	vec4 texelSpecular = texture2D( specularMap, vUv );',
					'	texelSpecular = sRGBToLinear( texelSpecular );',
					'	// reads channel RGB, compatible with a glTF Specular-Glossiness (RGBA) texture',
					'	specularFactor *= texelSpecular.rgb;',
					'#endif'
				].join( '\n' );

				var 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' );

				var lightPhysicalFragmentChunk = [
					'PhysicalMaterial material;',
					'material.diffuseColor = diffuseColor.rgb;',
					'material.specularRoughness = clamp( 1.0 - glossinessFactor, 0.04, 1.0 );',
					'material.specularColor = specularFactor.rgb;',
				].join( '\n' );

				var 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 );

				delete uniforms.roughness;
				delete uniforms.metalness;
				delete uniforms.roughnessMap;
				delete uniforms.metalnessMap;

				uniforms.specular = { value: new THREE.Color().setHex( 0x111111 ) };
				uniforms.glossiness = { value: 0.5 };
				uniforms.specularMap = { value: null };
				uniforms.glossinessMap = { value: null };

				params.vertexShader = shader.vertexShader;
				params.fragmentShader = fragmentShader;
				params.uniforms = uniforms;
				params.defines = { 'STANDARD': '' };

				params.color = new THREE.Color( 1.0, 1.0, 1.0 );
				params.opacity = 1.0;

				var pending = [];

				if ( Array.isArray( pbrSpecularGlossiness.diffuseFactor ) ) {

					var array = pbrSpecularGlossiness.diffuseFactor;

					params.color.fromArray( array );
					params.opacity = array[ 3 ];

				}

				if ( pbrSpecularGlossiness.diffuseTexture !== undefined ) {

					pending.push( parser.assignTexture( params, 'map', pbrSpecularGlossiness.diffuseTexture ) );

				}

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

				if ( Array.isArray( pbrSpecularGlossiness.specularFactor ) ) {

					params.specular.fromArray( pbrSpecularGlossiness.specularFactor );

				}

				if ( pbrSpecularGlossiness.specularGlossinessTexture !== undefined ) {

					var specGlossMapDef = pbrSpecularGlossiness.specularGlossinessTexture;
					pending.push( parser.assignTexture( params, 'glossinessMap', specGlossMapDef ) );
					pending.push( parser.assignTexture( params, 'specularMap', specGlossMapDef ) );

				}

				return Promise.all( pending );

			},

			createMaterial: function ( params ) {

				// setup material properties based on MeshStandardMaterial for Specular-Glossiness

				var material = new THREE.ShaderMaterial( {
					defines: params.defines,
					vertexShader: params.vertexShader,
					fragmentShader: params.fragmentShader,
					uniforms: params.uniforms,
					fog: true,
					lights: true,
					opacity: params.opacity,
					transparent: params.transparent
				} );

				material.isGLTFSpecularGlossinessMaterial = true;

				material.color = params.color;

				material.map = params.map === undefined ? null : params.map;

				material.lightMap = null;
				material.lightMapIntensity = 1.0;

				material.aoMap = params.aoMap === undefined ? null : params.aoMap;
				material.aoMapIntensity = 1.0;

				material.emissive = params.emissive;
				material.emissiveIntensity = 1.0;
				material.emissiveMap = params.emissiveMap === undefined ? null : params.emissiveMap;

				material.bumpMap = params.bumpMap === undefined ? null : params.bumpMap;
				material.bumpScale = 1;

				material.normalMap = params.normalMap === undefined ? null : params.normalMap;
				if ( params.normalScale ) material.normalScale = params.normalScale;

				material.displacementMap = null;
				material.displacementScale = 1;
				material.displacementBias = 0;

				material.specularMap = params.specularMap === undefined ? null : params.specularMap;
				material.specular = params.specular;

				material.glossinessMap = params.glossinessMap === undefined ? null : params.glossinessMap;
				material.glossiness = params.glossiness;

				material.alphaMap = null;

				material.envMap = params.envMap === undefined ? null : params.envMap;
				material.envMapIntensity = 1.0;

				material.refractionRatio = 0.98;

				material.extensions.derivatives = true;

				return material;

			},

			/**
			 * Clones a GLTFSpecularGlossinessMaterial instance. The ShaderMaterial.copy() method can
			 * copy only properties it knows about or inherits, and misses many properties that would
			 * normally be defined by MeshStandardMaterial.
			 *
			 * This method allows GLTFSpecularGlossinessMaterials to be cloned in the process of
			 * loading a glTF model, but cloning later (e.g. by the user) would require these changes
			 * AND also updating `.onBeforeRender` on the parent mesh.
			 *
			 * @param  {THREE.ShaderMaterial} source
			 * @return {THREE.ShaderMaterial}
			 */
			cloneMaterial: function ( source ) {

				var target = source.clone();

				target.isGLTFSpecularGlossinessMaterial = true;

				var params = this.specularGlossinessParams;

				for ( var i = 0, il = params.length; i < il; i ++ ) {

					target[ params[ i ] ] = source[ params[ i ] ];

				}

				return target;

			},

			// Here's based on refreshUniformsCommon() and refreshUniformsStandard() in WebGLRenderer.
			refreshUniforms: function ( renderer, scene, camera, geometry, material, group ) {

				if ( material.isGLTFSpecularGlossinessMaterial !== true ) {

					return;

				}

				var uniforms = material.uniforms;
				var defines = material.defines;

				uniforms.opacity.value = material.opacity;

				uniforms.diffuse.value.copy( material.color );
				uniforms.emissive.value.copy( material.emissive ).multiplyScalar( material.emissiveIntensity );

				uniforms.map.value = material.map;
				uniforms.specularMap.value = material.specularMap;
				uniforms.alphaMap.value = material.alphaMap;

				uniforms.lightMap.value = material.lightMap;
				uniforms.lightMapIntensity.value = material.lightMapIntensity;

				uniforms.aoMap.value = material.aoMap;
				uniforms.aoMapIntensity.value = material.aoMapIntensity;

				// uv repeat and offset setting priorities
				// 1. color map
				// 2. specular map
				// 3. normal map
				// 4. bump map
				// 5. alpha map
				// 6. emissive map

				var uvScaleMap;

				if ( material.map ) {

					uvScaleMap = material.map;

				} else if ( material.specularMap ) {

					uvScaleMap = material.specularMap;

				} else if ( material.displacementMap ) {

					uvScaleMap = material.displacementMap;

				} else if ( material.normalMap ) {

					uvScaleMap = material.normalMap;

				} else if ( material.bumpMap ) {

					uvScaleMap = material.bumpMap;

				} else if ( material.glossinessMap ) {

					uvScaleMap = material.glossinessMap;

				} else if ( material.alphaMap ) {

					uvScaleMap = material.alphaMap;

				} else if ( material.emissiveMap ) {

					uvScaleMap = material.emissiveMap;

				}

				if ( uvScaleMap !== undefined ) {

					// backwards compatibility
					if ( uvScaleMap.isWebGLRenderTarget ) {

						uvScaleMap = uvScaleMap.texture;

					}

					if ( uvScaleMap.matrixAutoUpdate === true ) {

						uvScaleMap.updateMatrix();

					}

					uniforms.uvTransform.value.copy( uvScaleMap.matrix );

				}

				if ( material.envMap ) {

					uniforms.envMap.value = material.envMap;
					uniforms.envMapIntensity.value = material.envMapIntensity;

					// don't flip CubeTexture envMaps, flip everything else:
					//  WebGLRenderTargetCube will be flipped for backwards compatibility
					//  WebGLRenderTargetCube.texture will be flipped because it's a Texture and NOT a CubeTexture
					// this check must be handled differently, or removed entirely, if WebGLRenderTargetCube uses a CubeTexture in the future
					uniforms.flipEnvMap.value = material.envMap.isCubeTexture ? - 1 : 1;

					uniforms.reflectivity.value = material.reflectivity;
					uniforms.refractionRatio.value = material.refractionRatio;

					uniforms.maxMipLevel.value = renderer.properties.get( material.envMap ).__maxMipLevel;

				}

				uniforms.specular.value.copy( material.specular );
				uniforms.glossiness.value = material.glossiness;

				uniforms.glossinessMap.value = material.glossinessMap;

				uniforms.emissiveMap.value = material.emissiveMap;
				uniforms.bumpMap.value = material.bumpMap;
				uniforms.normalMap.value = material.normalMap;

				uniforms.displacementMap.value = material.displacementMap;
				uniforms.displacementScale.value = material.displacementScale;
				uniforms.displacementBias.value = material.displacementBias;

				if ( uniforms.glossinessMap.value !== null && defines.USE_GLOSSINESSMAP === undefined ) {

					defines.USE_GLOSSINESSMAP = '';
					// set USE_ROUGHNESSMAP to enable vUv
					defines.USE_ROUGHNESSMAP = '';

				}

				if ( uniforms.glossinessMap.value === null && defines.USE_GLOSSINESSMAP !== undefined ) {

					delete defines.USE_GLOSSINESSMAP;
					delete defines.USE_ROUGHNESSMAP;

				}

			}

		};

	}

	/*********************************/
	/********** INTERPOLATION ********/
	/*********************************/

	// Spline Interpolation
	// Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#appendix-c-spline-interpolation
	function GLTFCubicSplineInterpolant( parameterPositions, sampleValues, sampleSize, resultBuffer ) {

		THREE.Interpolant.call( this, parameterPositions, sampleValues, sampleSize, resultBuffer );

	}

	GLTFCubicSplineInterpolant.prototype = Object.create( THREE.Interpolant.prototype );
	GLTFCubicSplineInterpolant.prototype.constructor = GLTFCubicSplineInterpolant;

	GLTFCubicSplineInterpolant.prototype.copySampleValue_ = function ( index ) {

		// Copies a sample value to the result buffer. See description of glTF
		// CUBICSPLINE values layout in interpolate_() function below.

		var result = this.resultBuffer,
			values = this.sampleValues,
			valueSize = this.valueSize,
			offset = index * valueSize * 3 + valueSize;

		for ( var i = 0; i !== valueSize; i ++ ) {

			result[ i ] = values[ offset + i ];

		}

		return result;

	};

	GLTFCubicSplineInterpolant.prototype.beforeStart_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;

	GLTFCubicSplineInterpolant.prototype.afterEnd_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;

	GLTFCubicSplineInterpolant.prototype.interpolate_ = function ( i1, t0, t, t1 ) {

		var result = this.resultBuffer;
		var values = this.sampleValues;
		var stride = this.valueSize;

		var stride2 = stride * 2;
		var stride3 = stride * 3;

		var td = t1 - t0;

		var p = ( t - t0 ) / td;
		var pp = p * p;
		var ppp = pp * p;

		var offset1 = i1 * stride3;
		var offset0 = offset1 - stride3;

		var s2 = - 2 * ppp + 3 * pp;
		var s3 = ppp - pp;
		var s0 = 1 - s2;
		var s1 = s3 - pp + p;

		// Layout of keyframe output values for CUBICSPLINE animations:
		//   [ inTangent_1, splineVertex_1, outTangent_1, inTangent_2, splineVertex_2, ... ]
		for ( var i = 0; i !== stride; i ++ ) {

			var p0 = values[ offset0 + i + stride ]; // splineVertex_k
			var m0 = values[ offset0 + i + stride2 ] * td; // outTangent_k * (t_k+1 - t_k)
			var p1 = values[ offset1 + i + stride ]; // splineVertex_k+1
			var 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;

	};

	/*********************************/
	/********** INTERNALS ************/
	/*********************************/

	/* CONSTANTS */

	var 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
	};

	var WEBGL_TYPE = {
		5126: Number,
		//35674: THREE.Matrix2,
		35675: THREE.Matrix3,
		35676: THREE.Matrix4,
		35664: THREE.Vector2,
		35665: THREE.Vector3,
		35666: THREE.Vector4,
		35678: THREE.Texture
	};

	var WEBGL_COMPONENT_TYPES = {
		5120: Int8Array,
		5121: Uint8Array,
		5122: Int16Array,
		5123: Uint16Array,
		5125: Uint32Array,
		5126: Float32Array
	};

	var WEBGL_FILTERS = {
		9728: THREE.NearestFilter,
		9729: THREE.LinearFilter,
		9984: THREE.NearestMipMapNearestFilter,
		9985: THREE.LinearMipMapNearestFilter,
		9986: THREE.NearestMipMapLinearFilter,
		9987: THREE.LinearMipMapLinearFilter
	};

	var WEBGL_WRAPPINGS = {
		33071: THREE.ClampToEdgeWrapping,
		33648: THREE.MirroredRepeatWrapping,
		10497: THREE.RepeatWrapping
	};

	var WEBGL_SIDES = {
		1028: THREE.BackSide, // Culling front
		1029: THREE.FrontSide // Culling back
		//1032: THREE.NoSide   // Culling front and back, what to do?
	};

	var WEBGL_DEPTH_FUNCS = {
		512: THREE.NeverDepth,
		513: THREE.LessDepth,
		514: THREE.EqualDepth,
		515: THREE.LessEqualDepth,
		516: THREE.GreaterEqualDepth,
		517: THREE.NotEqualDepth,
		518: THREE.GreaterEqualDepth,
		519: THREE.AlwaysDepth
	};

	var WEBGL_BLEND_EQUATIONS = {
		32774: THREE.AddEquation,
		32778: THREE.SubtractEquation,
		32779: THREE.ReverseSubtractEquation
	};

	var WEBGL_BLEND_FUNCS = {
		0: THREE.ZeroFactor,
		1: THREE.OneFactor,
		768: THREE.SrcColorFactor,
		769: THREE.OneMinusSrcColorFactor,
		770: THREE.SrcAlphaFactor,
		771: THREE.OneMinusSrcAlphaFactor,
		772: THREE.DstAlphaFactor,
		773: THREE.OneMinusDstAlphaFactor,
		774: THREE.DstColorFactor,
		775: THREE.OneMinusDstColorFactor,
		776: THREE.SrcAlphaSaturateFactor
		// The followings are not supported by Three.js yet
		//32769: CONSTANT_COLOR,
		//32770: ONE_MINUS_CONSTANT_COLOR,
		//32771: CONSTANT_ALPHA,
		//32772: ONE_MINUS_CONSTANT_COLOR
	};

	var WEBGL_TYPE_SIZES = {
		'SCALAR': 1,
		'VEC2': 2,
		'VEC3': 3,
		'VEC4': 4,
		'MAT2': 4,
		'MAT3': 9,
		'MAT4': 16
	};

	var ATTRIBUTES = {
		POSITION: 'position',
		NORMAL: 'normal',
		TANGENT: 'tangent',
		TEXCOORD_0: 'uv',
		TEXCOORD_1: 'uv2',
		COLOR_0: 'color',
		WEIGHTS_0: 'skinWeight',
		JOINTS_0: 'skinIndex',
	};

	var PATH_PROPERTIES = {
		scale: 'scale',
		translation: 'position',
		rotation: 'quaternion',
		weights: 'morphTargetInfluences'
	};

	var INTERPOLATION = {
		CUBICSPLINE: THREE.InterpolateSmooth, // We use custom interpolation GLTFCubicSplineInterpolation for CUBICSPLINE.
		                                      // KeyframeTrack.optimize() can't handle glTF Cubic Spline output values layout,
		                                      // using THREE.InterpolateSmooth for KeyframeTrack instantiation to prevent optimization.
		                                      // See KeyframeTrack.optimize() for the detail.
		LINEAR: THREE.InterpolateLinear,
		STEP: THREE.InterpolateDiscrete
	};

	var STATES_ENABLES = {
		2884: 'CULL_FACE',
		2929: 'DEPTH_TEST',
		3042: 'BLEND',
		3089: 'SCISSOR_TEST',
		32823: 'POLYGON_OFFSET_FILL',
		32926: 'SAMPLE_ALPHA_TO_COVERAGE'
	};

	var ALPHA_MODES = {
		OPAQUE: 'OPAQUE',
		MASK: 'MASK',
		BLEND: 'BLEND'
	};

	var MIME_TYPE_FORMATS = {
		'image/png': THREE.RGBAFormat,
		'image/jpeg': THREE.RGBFormat
	};

	/* UTILITY FUNCTIONS */

	function resolveURL( url, path ) {

		// Invalid URL
		if ( typeof url !== 'string' || url === '' ) return '';

		// Absolute URL http://,https://,//
		if ( /^(https?:)?\/\//i.test( url ) ) return url;

		// Data URI
		if ( /^data:.*,.*$/i.test( url ) ) return url;

		// Blob URL
		if ( /^blob:.*$/i.test( url ) ) return url;

		// Relative URL
		return path + url;

	}

	var defaultMaterial;

	/**
	 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#default-material
	 */
	function createDefaultMaterial() {

		defaultMaterial = defaultMaterial || new THREE.MeshStandardMaterial( {
			color: 0xFFFFFF,
			emissive: 0x000000,
			metalness: 1,
			roughness: 1,
			transparent: false,
			depthTest: true,
			side: THREE.FrontSide
		} );

		return defaultMaterial;

	}

	function addUnknownExtensionsToUserData( knownExtensions, object, objectDef ) {

		// Add unknown glTF extensions to an object's userData.

		for ( var name in objectDef.extensions ) {

			if ( knownExtensions[ name ] === undefined ) {

				object.userData.gltfExtensions = object.userData.gltfExtensions || {};
				object.userData.gltfExtensions[ name ] = objectDef.extensions[ name ];

			}

		}

	}

	/**
	 * @param {THREE.Object3D|THREE.Material|THREE.BufferGeometry} object
	 * @param {GLTF.definition} gltfDef
	 */
	function assignExtrasToUserData( object, gltfDef ) {

		if ( gltfDef.extras !== undefined ) {

			if ( typeof gltfDef.extras === 'object' ) {

				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 {THREE.BufferGeometry} geometry
	 * @param {Array<GLTF.Target>} targets
	 * @param {GLTFParser} parser
	 * @return {Promise<THREE.BufferGeometry>}
	 */
	function addMorphTargets( geometry, targets, parser ) {

		var hasMorphPosition = false;
		var hasMorphNormal = false;

		for ( var i = 0, il = targets.length; i < il; i ++ ) {

			var target = targets[ i ];

			if ( target.POSITION !== undefined ) hasMorphPosition = true;
			if ( target.NORMAL !== undefined ) hasMorphNormal = true;

			if ( hasMorphPosition && hasMorphNormal ) break;

		}

		if ( ! hasMorphPosition && ! hasMorphNormal ) return Promise.resolve( geometry );

		var pendingPositionAccessors = [];
		var pendingNormalAccessors = [];

		for ( var i = 0, il = targets.length; i < il; i ++ ) {

			var target = targets[ i ];

			if ( hasMorphPosition ) {

				// TODO: Error-prone use of a callback inside a loop.
				var accessor = target.POSITION !== undefined
					? parser.getDependency( 'accessor', target.POSITION )
						.then( function ( accessor ) {

							// Cloning not to pollute original accessor below
							return cloneBufferAttribute( accessor );

						} )
					: geometry.attributes.position;

				pendingPositionAccessors.push( accessor );

			}

			if ( hasMorphNormal ) {

				// TODO: Error-prone use of a callback inside a loop.
				var accessor = target.NORMAL !== undefined
					? parser.getDependency( 'accessor', target.NORMAL )
						.then( function ( accessor ) {

							return cloneBufferAttribute( accessor );

						} )
					: geometry.attributes.normal;

				pendingNormalAccessors.push( accessor );

			}

		}

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

			var morphPositions = accessors[ 0 ];
			var morphNormals = accessors[ 1 ];

			for ( var i = 0, il = targets.length; i < il; i ++ ) {

				var target = targets[ i ];
				var attributeName = 'morphTarget' + i;

				if ( hasMorphPosition ) {

					// Three.js morph position is absolute value. The formula is
					//   basePosition
					//     + weight0 * ( morphPosition0 - basePosition )
					//     + weight1 * ( morphPosition1 - basePosition )
					//     ...
					// while the glTF one is relative
					//   basePosition
					//     + weight0 * glTFmorphPosition0
					//     + weight1 * glTFmorphPosition1
					//     ...
					// then we need to convert from relative to absolute here.

					if ( target.POSITION !== undefined ) {

						var positionAttribute = morphPositions[ i ];
						positionAttribute.name = attributeName;

						var position = geometry.attributes.position;

						for ( var j = 0, jl = positionAttribute.count; j < jl; j ++ ) {

							positionAttribute.setXYZ(
								j,
								positionAttribute.getX( j ) + position.getX( j ),
								positionAttribute.getY( j ) + position.getY( j ),
								positionAttribute.getZ( j ) + position.getZ( j )
							);

						}

					}

				}

				if ( hasMorphNormal ) {

					// see target.POSITION's comment

					if ( target.NORMAL !== undefined ) {

						var normalAttribute = morphNormals[ i ];
						normalAttribute.name = attributeName;

						var normal = geometry.attributes.normal;

						for ( var j = 0, jl = normalAttribute.count; j < jl; j ++ ) {

							normalAttribute.setXYZ(
								j,
								normalAttribute.getX( j ) + normal.getX( j ),
								normalAttribute.getY( j ) + normal.getY( j ),
								normalAttribute.getZ( j ) + normal.getZ( j )
							);

						}

					}

				}

			}

			if ( hasMorphPosition ) geometry.morphAttributes.position = morphPositions;
			if ( hasMorphNormal ) geometry.morphAttributes.normal = morphNormals;

			return geometry;

		} );

	}

	/**
	 * @param {THREE.Mesh} mesh
	 * @param {GLTF.Mesh} meshDef
	 */
	function updateMorphTargets( mesh, meshDef ) {

		mesh.updateMorphTargets();

		if ( meshDef.weights !== undefined ) {

			for ( var 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 ) ) {

			var targetNames = meshDef.extras.targetNames;

			if ( mesh.morphTargetInfluences.length === targetNames.length ) {

				mesh.morphTargetDictionary = {};

				for ( var 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 isObjectEqual( a, b ) {

		if ( Object.keys( a ).length !== Object.keys( b ).length ) return false;

		for ( var key in a ) {

			if ( a[ key ] !== b[ key ] ) return false;

		}

		return true;

	}

	function createPrimitiveKey( primitiveDef ) {

		var dracoExtension = primitiveDef.extensions && primitiveDef.extensions[ EXTENSIONS.KHR_DRACO_MESH_COMPRESSION ];
		var 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 ) {

		var attributesKey = '';

		var keys = Object.keys( attributes ).sort();

		for ( var i = 0, il = keys.length; i < il; i ++ ) {

			attributesKey += keys[ i ] + ':' + attributes[ keys[ i ] ] + ';';

		}

		return attributesKey;

	}

	function cloneBufferAttribute( attribute ) {

		if ( attribute.isInterleavedBufferAttribute ) {

			var count = attribute.count;
			var itemSize = attribute.itemSize;
			var array = attribute.array.slice( 0, count * itemSize );

			for ( var i = 0, j = 0; i < count; ++ i ) {

				array[ j ++ ] = attribute.getX( i );
				if ( itemSize >= 2 ) array[ j ++ ] = attribute.getY( i );
				if ( itemSize >= 3 ) array[ j ++ ] = attribute.getZ( i );
				if ( itemSize >= 4 ) array[ j ++ ] = attribute.getW( i );

			}

			return new THREE.BufferAttribute( array, itemSize, attribute.normalized );

		}

		return attribute.clone();

	}

	/* GLTF PARSER */

	function GLTFParser( json, extensions, options ) {

		this.json = json || {};
		this.extensions = extensions || {};
		this.options = options || {};

		// loader object cache
		this.cache = new GLTFRegistry();

		// BufferGeometry caching
		this.primitiveCache = {};

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

		this.fileLoader = new THREE.FileLoader( this.options.manager );
		this.fileLoader.setResponseType( 'arraybuffer' );

	}

	GLTFParser.prototype.parse = function ( onLoad, onError ) {

		var json = this.json;

		// Clear the loader cache
		this.cache.removeAll();

		// Mark the special nodes/meshes in json for efficient parse
		this.markDefs();

		// Fire the callback on complete
		this.getMultiDependencies( [

			'scene',
			'animation',
			'camera'

		] ).then( function ( dependencies ) {

			var scenes = dependencies.scenes || [];
			var scene = scenes[ json.scene || 0 ];
			var animations = dependencies.animations || [];
			var cameras = dependencies.cameras || [];

			onLoad( scene, scenes, cameras, animations, json );

		} ).catch( onError );

	};

	GLTFParser.prototype.acceptUserExtensions = function ( eventType, objectDef, object ) {

		var modifiedObject = object;

		for( var name in this.extensions ) {

			if( this.extensions.hasOwnProperty(name) ) {
				var extension = this.extensions[name];

				if( extension.isUserExtension // only if extension is registered as user extension
				 	&& typeof extension[eventType] === 'function' // if the type function exists
				 	&& objectDef.extensions && objectDef.extensions[name] !== undefined ) {

					modifiedObject = extension[eventType](objectDef, object);
					
					if( modifiedObject === undefined ) {

						// reassign old object if nothing was returned
						modifiedObject = object;
					}

				}

			}

		}

		return modifiedObject;

	};

	/**
	 * Marks the special nodes/meshes in json for efficient parse.
	 */
	GLTFParser.prototype.markDefs = function () {

		var nodeDefs = this.json.nodes || [];
		var skinDefs = this.json.skins || [];
		var meshDefs = this.json.meshes || [];

		var meshReferences = {};
		var meshUses = {};

		// Nothing in the node definition indicates whether it is a Bone or an
		// Object3D. Use the skins' joint references to mark bones.
		for ( var skinIndex = 0, skinLength = skinDefs.length; skinIndex < skinLength; skinIndex ++ ) {

			var joints = skinDefs[ skinIndex ].joints;

			for ( var i = 0, il = joints.length; i < il; i ++ ) {

				nodeDefs[ joints[ i ] ].isBone = true;

			}

		}

		// Meshes can (and should) be reused by multiple nodes in a glTF asset. To
		// avoid having more than one THREE.Mesh with the same name, count
		// references and rename instances below.
		//
		// Example: CesiumMilkTruck sample model reuses "Wheel" meshes.
		for ( var nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex ++ ) {

			var nodeDef = nodeDefs[ nodeIndex ];

			if ( nodeDef.mesh !== undefined ) {

				if ( meshReferences[ nodeDef.mesh ] === undefined ) {

					meshReferences[ nodeDef.mesh ] = meshUses[ nodeDef.mesh ] = 0;

				}

				meshReferences[ nodeDef.mesh ] ++;

				// Nothing in the mesh definition indicates whether it is
				// a SkinnedMesh or Mesh. Use the node's mesh reference
				// to mark SkinnedMesh if node has skin.
				if ( nodeDef.skin !== undefined ) {

					meshDefs[ nodeDef.mesh ].isSkinnedMesh = true;

				}

			}

		}

		this.json.meshReferences = meshReferences;
		this.json.meshUses = meshUses;

	};

	/**
	 * Requests the specified dependency asynchronously, with caching.
	 * @param {string} type
	 * @param {number} index
	 * @return {Promise<THREE.Object3D|THREE.Material|THREE.Texture|THREE.AnimationClip|ArrayBuffer|Object>}
	 */
	GLTFParser.prototype.getDependency = function ( type, index ) {

		var cacheKey = type + ':' + index;
		var 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.loadMesh( index );
					break;

				case 'accessor':
					dependency = this.loadAccessor( index );
					break;

				case 'bufferView':
					dependency = this.loadBufferView( index );
					break;

				case 'buffer':
					dependency = this.loadBuffer( index );
					break;

				case 'material':
					dependency = this.loadMaterial( index );
					break;

				case 'texture':
					dependency = this.loadTexture( index );
					break;

				case 'skin':
					dependency = this.loadSkin( index );
					break;

				case 'animation':
					dependency = this.loadAnimation( index );
					break;

				case 'camera':
					dependency = this.loadCamera( index );
					break;

				case 'light':
					dependency = this.extensions[ EXTENSIONS.KHR_LIGHTS_PUNCTUAL ].loadLight( index );
					break;

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

			}

			this.cache.add( cacheKey, dependency );

		}

		return dependency;

	};

	/**
	 * Requests all dependencies of the specified type asynchronously, with caching.
	 * @param {string} type
	 * @return {Promise<Array<Object>>}
	 */
	GLTFParser.prototype.getDependencies = function ( type ) {

		var dependencies = this.cache.get( type );

		if ( ! dependencies ) {

			var parser = this;
			var 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;

	};

	/**
	 * Requests all multiple dependencies of the specified types asynchronously, with caching.
	 * @param {Array<string>} types
	 * @return {Promise<Object<Array<Object>>>}
	 */
	GLTFParser.prototype.getMultiDependencies = function ( types ) {

		var results = {};
		var pending = [];

		for ( var i = 0, il = types.length; i < il; i ++ ) {

			var type = types[ i ];
			var value = this.getDependencies( type );

			// TODO: Error-prone use of a callback inside a loop.
			value = value.then( function ( key, value ) {

				results[ key ] = value;

			}.bind( this, type + ( type === 'mesh' ? 'es' : 's' ) ) );

			pending.push( value );

		}

		return Promise.all( pending ).then( function () {

			return results;

		} );

	};

	/**
	 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
	 * @param {number} bufferIndex
	 * @return {Promise<ArrayBuffer>}
	 */
	GLTFParser.prototype.loadBuffer = function ( bufferIndex ) {

		var bufferDef = this.json.buffers[ bufferIndex ];
		var 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.acceptUserExtensions('onBuffer', bufferDef, this.extensions[ EXTENSIONS.KHR_BINARY_GLTF ].body)  );

		}

		var options = this.options;

		return new Promise( function ( resolve, reject ) {

			loader.load( 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>}
	 */
	GLTFParser.prototype.loadBufferView = function ( bufferViewIndex ) {

		var bufferViewDef = this.json.bufferViews[ bufferViewIndex ];
		var parser = this;

		return this.getDependency( 'buffer', bufferViewDef.buffer ).then( function ( buffer ) {

			var byteLength = bufferViewDef.byteLength || 0;
			var byteOffset = bufferViewDef.byteOffset || 0;

			return parser.acceptUserExtensions('onBufferView', bufferViewDef, buffer.slice( byteOffset, byteOffset + byteLength ));

		} );

	};

	/**
	 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#accessors
	 * @param {number} accessorIndex
	 * @return {Promise<THREE.BufferAttribute|THREE.InterleavedBufferAttribute>}
	 */
	GLTFParser.prototype.loadAccessor = function ( accessorIndex ) {

		var parser = this;
		var json = this.json;

		var accessorDef = this.json.accessors[ accessorIndex ];

		if ( accessorDef.bufferView === undefined && accessorDef.sparse === undefined ) {

			// Ignore empty accessors, which may be used to declare runtime
			// information about attributes coming from another source (e.g. Draco
			// compression extension).
			return Promise.resolve( null );

		}

		var 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 ) {

			var bufferView = bufferViews[ 0 ];

			var itemSize = WEBGL_TYPE_SIZES[ accessorDef.type ];
			var TypedArray = WEBGL_COMPONENT_TYPES[ accessorDef.componentType ];

			// For VEC3: itemSize is 3, elementBytes is 4, itemBytes is 12.
			var elementBytes = TypedArray.BYTES_PER_ELEMENT;
			var itemBytes = elementBytes * itemSize;
			var byteOffset = accessorDef.byteOffset || 0;
			var byteStride = accessorDef.bufferView !== undefined ? json.bufferViews[ accessorDef.bufferView ].byteStride : undefined;
			var normalized = accessorDef.normalized === true;
			var array, bufferAttribute;

			// The buffer is not interleaved if the stride is the item size in bytes.
			if ( byteStride && byteStride !== itemBytes ) {

				var ibCacheKey = 'InterleavedBuffer:' + accessorDef.bufferView + ':' + accessorDef.componentType;
				var ib = parser.cache.get( ibCacheKey );

				if ( ! ib ) {

					// Use the full buffer if it's interleaved.
					array = new TypedArray( bufferView );

					// 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 / 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 ) {

				var itemSizeIndices = WEBGL_TYPE_SIZES.SCALAR;
				var TypedArrayIndices = WEBGL_COMPONENT_TYPES[ accessorDef.sparse.indices.componentType ];

				var byteOffsetIndices = accessorDef.sparse.indices.byteOffset || 0;
				var byteOffsetValues = accessorDef.sparse.values.byteOffset || 0;

				var sparseIndices = new TypedArrayIndices( bufferViews[ 1 ], byteOffsetIndices, accessorDef.sparse.count * itemSizeIndices );
				var 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.setArray( bufferAttribute.array.slice() );

				}

				for ( var i = 0, il = sparseIndices.length; i < il; i ++ ) {

					var index = sparseIndices[ i ];

					bufferAttribute.setX( index, sparseValues[ i * itemSize ] );
					if ( itemSize >= 2 ) bufferAttribute.setY( index, sparseValues[ i * itemSize + 1 ] );
					if ( itemSize >= 3 ) bufferAttribute.setZ( index, sparseValues[ i * itemSize + 2 ] );
					if ( itemSize >= 4 ) bufferAttribute.setW( index, sparseValues[ i * itemSize + 3 ] );
					if ( itemSize >= 5 ) throw new Error( 'THREE.GLTFLoader: Unsupported itemSize in sparse BufferAttribute.' );

				}

			}

			return parser.acceptUserExtensions('onAccessor', accessorDef, bufferAttribute);

		} );

	};

	/**
	 * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#textures
	 * @param {number} textureIndex
	 * @return {Promise<THREE.Texture>}
	 */
	GLTFParser.prototype.loadTexture = function ( textureIndex ) {

		var parser = this;
		var json = this.json;
		var options = this.options;
		var textureLoader = this.textureLoader;

		var URL = window.URL || window.webkitURL;

		var textureDef = json.textures[ textureIndex ];

		var textureExtensions = textureDef.extensions || {};

		var source;

		if ( textureExtensions[ EXTENSIONS.MSFT_TEXTURE_DDS ] ) {

			source = json.images[ textureExtensions[ EXTENSIONS.MSFT_TEXTURE_DDS ].source ];

		} else {

			source = json.images[ textureDef.source ];

		}

		var sourceURI = source.uri;
		var isObjectURL = false;

		if ( source.bufferView !== undefined ) {

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

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

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

			} );

		}

		return Promise.resolve( sourceURI ).then( function ( sourceURI ) {

			// Load Texture resource.

			var loader = THREE.Loader.Handlers.get( sourceURI );

			if ( ! loader ) {

				loader = textureExtensions[ EXTENSIONS.MSFT_TEXTURE_DDS ]
					? parser.extensions[ EXTENSIONS.MSFT_TEXTURE_DDS ].ddsLoader
					: textureLoader;

			}

			return new Promise( function ( resolve, reject ) {

				loader.load( resolveURL( sourceURI, options.path ), resolve, undefined, reject );

			} );

		} ).then( function ( texture ) {

			// Clean up resources and configure Texture.

			if ( isObjectURL === true ) {

				URL.revokeObjectURL( sourceURI );

			}

			texture.flipY = false;

			if ( textureDef.name !== undefined ) texture.name = textureDef.name;

			// Ignore unknown mime types, like DDS files.
			if ( source.mimeType in MIME_TYPE_FORMATS ) {

				texture.format = MIME_TYPE_FORMATS[ source.mimeType ];

			}

			var samplers = json.samplers || {};
			var 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;

			return parser.acceptUserExtensions('onTexture', textureDef, texture);

		} );

	};

	/**
	 * Asynchronously assigns a texture to the given material parameters.
	 * @param {Object} materialParams
	 * @param {string} mapName
	 * @param {Object} mapDef
	 * @return {Promise}
	 */
	GLTFParser.prototype.assignTexture = function ( materialParams, mapName, mapDef ) {

		var parser = this;

		return this.getDependency( 'texture', mapDef.index ).then( function ( texture ) {

			switch ( mapName ) {

				case 'aoMap':
				case 'emissiveMap':
				case 'metalnessMap':
				case 'normalMap':
				case 'roughnessMap':
					texture.format = THREE.RGBFormat;
					break;

			}

			if ( parser.extensions[ EXTENSIONS.KHR_TEXTURE_TRANSFORM ] ) {

				var transform = mapDef.extensions !== undefined ? mapDef.extensions[ EXTENSIONS.KHR_TEXTURE_TRANSFORM ] : undefined;

				if ( transform ) {

					texture = parser.extensions[ EXTENSIONS.KHR_TEXTURE_TRANSFORM ].extendTexture( texture, transform );

				}

			}

			materialParams[ mapName ] = texture;

		} );

	};

	/**
	 * Assigns final material to a Mesh, Line, or Points instance. The instance
	 * already has a material (generated from the glTF material options alone)
	 * but reuse of the same glTF material may require multiple threejs materials
	 * to accomodate different primitive types, defines, etc. New materials will
	 * be created if necessary, and reused from a cache.
	 * @param  {THREE.Object3D} mesh Mesh, Line, or Points instance.
	 */
	GLTFParser.prototype.assignFinalMaterial = function ( mesh ) {

		var geometry = mesh.geometry;
		var material = mesh.material;
		var extensions = this.extensions;

		var useVertexTangents = geometry.attributes.tangent !== undefined;
		var useVertexColors = geometry.attributes.color !== undefined;
		var useFlatShading = geometry.attributes.normal === undefined;
		var useSkinning = mesh.isSkinnedMesh === true;
		var useMorphTargets = Object.keys( geometry.morphAttributes ).length > 0;
		var useMorphNormals = useMorphTargets && geometry.morphAttributes.normal !== undefined;

		if ( mesh.isPoints ) {

			var cacheKey = 'PointsMaterial:' + material.uuid;

			var 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.lights = false; // PointsMaterial doesn't support lights yet

				this.cache.add( cacheKey, pointsMaterial );

			}

			material = pointsMaterial;

		} else if ( mesh.isLine ) {

			var cacheKey = 'LineBasicMaterial:' + material.uuid;

			var lineMaterial = this.cache.get( cacheKey );

			if ( ! lineMaterial ) {

				lineMaterial = new THREE.LineBasicMaterial();
				THREE.Material.prototype.copy.call( lineMaterial, material );
				lineMaterial.color.copy( material.color );
				lineMaterial.lights = false; // LineBasicMaterial doesn't support lights yet

				this.cache.add( cacheKey, lineMaterial );

			}

			material = lineMaterial;

		}

		// Clone the material if it will be modified
		if ( useVertexTangents || useVertexColors || useFlatShading || useSkinning || useMorphTargets ) {

			var cacheKey = 'ClonedMaterial:' + material.uuid + ':';

			if ( material.isGLTFSpecularGlossinessMaterial ) cacheKey += 'specular-glossiness:';
			if ( useSkinning ) cacheKey += 'skinning:';
			if ( useVertexTangents ) cacheKey += 'vertex-tangents:';
			if ( useVertexColors ) cacheKey += 'vertex-colors:';
			if ( useFlatShading ) cacheKey += 'flat-shading:';
			if ( useMorphTargets ) cacheKey += 'morph-targets:';
			if ( useMorphNormals ) cacheKey += 'morph-normals:';

			var cachedMaterial = this.cache.get( cacheKey );

			if ( ! cachedMaterial ) {

				cachedMaterial = material.isGLTFSpecularGlossinessMaterial
					? extensions[ EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS ].cloneMaterial( material )
					: material.clone();

				if ( useSkinning ) cachedMaterial.skinning = true;
				if ( useVertexTangents ) cachedMaterial.vertexTangents = true;
				if ( useVertexColors ) cachedMaterial.vertexColors = THREE.VertexColors;
				if ( useFlatShading ) cachedMaterial.flatShading = true;
				if ( useMorphTargets ) cachedMaterial.morphTargets = true;
				if ( useMorphNormals ) cachedMaterial.morphNormals = true;

				this.cache.add( cacheKey, cachedMaterial );

			}

			material = cachedMaterial;

		}

		// workarounds for mesh and geometry

		if ( material.aoMap && geometry.attributes.uv2 === undefined && geometry.attributes.uv !== undefined ) {

			console.log( 'THREE.GLTFLoader: Duplicating UVs to support aoMap.' );
			geometry.addAttribute( 'uv2', new THREE.BufferAttribute( geometry.attributes.uv.array, 2 ) );

		}

		if ( material.isGLTFSpecularGlossinessMaterial ) {

			// for GLTFSpecularGlossinessMaterial(ShaderMaterial) uniforms runtime update
			mesh.onBeforeRender = extensions[ EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS ].refreshUniforms;

		}

		mesh.material = material;

	};

	/**
	 * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#materials
	 * @param {number} materialIndex
	 * @return {Promise<THREE.Material>}
	 */
	GLTFParser.prototype.loadMaterial = function ( materialIndex ) {

		var parser = this;
		var json = this.json;
		var extensions = this.extensions;
		var materialDef = json.materials[ materialIndex ];

		var materialType;
		var materialParams = {};
		var materialExtensions = materialDef.extensions || {};

		var pending = [];

		if ( materialExtensions[ EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS ] ) {

			var sgExtension = extensions[ EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS ];
			materialType = sgExtension.getMaterialType( materialDef );
			pending.push( sgExtension.extendParams( materialParams, materialDef, parser ) );

		} else if ( materialExtensions[ EXTENSIONS.KHR_MATERIALS_UNLIT ] ) {

			var kmuExtension = extensions[ EXTENSIONS.KHR_MATERIALS_UNLIT ];
			materialType = kmuExtension.getMaterialType( materialDef );
			pending.push( kmuExtension.extendParams( materialParams, materialDef, parser ) );

		} else {

			// Specification:
			// https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#metallic-roughness-material

			materialType = THREE.MeshStandardMaterial;

			var metallicRoughness = materialDef.pbrMetallicRoughness || {};

			materialParams.color = new THREE.Color( 1.0, 1.0, 1.0 );
			materialParams.opacity = 1.0;

			if ( Array.isArray( metallicRoughness.baseColorFactor ) ) {

				var array = metallicRoughness.baseColorFactor;

				materialParams.color.fromArray( array );
				materialParams.opacity = array[ 3 ];

			}

			if ( metallicRoughness.baseColorTexture !== undefined ) {

				pending.push( parser.assignTexture( materialParams, 'map', metallicRoughness.baseColorTexture ) );

			}

			materialParams.metalness = metallicRoughness.metallicFactor !== undefined ? metallicRoughness.metallicFactor : 1.0;
			materialParams.roughness = metallicRoughness.roughnessFactor !== undefined ? metallicRoughness.roughnessFactor : 1.0;

			if ( metallicRoughness.metallicRoughnessTexture !== undefined ) {

				pending.push( parser.assignTexture( materialParams, 'metalnessMap', metallicRoughness.metallicRoughnessTexture ) );
				pending.push( parser.assignTexture( materialParams, 'roughnessMap', metallicRoughness.metallicRoughnessTexture ) );

			}

		}

		if ( materialDef.doubleSided === true ) {

			materialParams.side = THREE.DoubleSide;

		}

		var alphaMode = materialDef.alphaMode || ALPHA_MODES.OPAQUE;

		if ( alphaMode === ALPHA_MODES.BLEND ) {

			materialParams.transparent = true;

		} 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 ) {

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

		}

		return Promise.all( pending ).then( function () {

			var material;

			if ( materialType === THREE.ShaderMaterial ) {

				material = extensions[ EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS ].createMaterial( materialParams );

			} else {

				material = new materialType( materialParams );

			}

			if ( materialDef.name !== undefined ) material.name = materialDef.name;

			// baseColorTexture, emissiveTexture, and specularGlossinessTexture use sRGB encoding.
			if ( material.map ) material.map.encoding = THREE.sRGBEncoding;
			if ( material.emissiveMap ) material.emissiveMap.encoding = THREE.sRGBEncoding;
			if ( material.specularMap ) material.specularMap.encoding = THREE.sRGBEncoding;

			assignExtrasToUserData( material, materialDef );

			if ( materialDef.extensions ) addUnknownExtensionsToUserData( extensions, material, materialDef );

			return parser.acceptUserExtensions('onMaterial', materialDef, material);

		} );

	};

	/**
	 * @param {THREE.BufferGeometry} geometry
	 * @param {GLTF.Primitive} primitiveDef
	 * @param {GLTFParser} parser
	 * @return {Promise<THREE.BufferGeometry>}
	 */
	function addPrimitiveAttributes( geometry, primitiveDef, parser ) {

		var attributes = primitiveDef.attributes;

		var pending = [];

		function assignAttributeAccessor( accessorIndex, attributeName ) {

			return parser.getDependency( 'accessor', accessorIndex )
				.then( function ( accessor ) {

					geometry.addAttribute( attributeName, accessor );

				} );

		}

		for ( var gltfAttributeName in attributes ) {

			var threeAttributeName = ATTRIBUTES[ gltfAttributeName ];

			if ( ! threeAttributeName ) continue;

			// 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 ) {

			var accessor = parser.getDependency( 'accessor', primitiveDef.indices ).then( function ( accessor ) {

				geometry.setIndex( accessor );

			} );

			pending.push( accessor );

		}

		assignExtrasToUserData( geometry, primitiveDef );

		return Promise.all( pending ).then( function () {

			return primitiveDef.targets !== undefined
				? addMorphTargets( geometry, primitiveDef.targets, parser )
				: geometry;

		} );

	}

	/**
	 * 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<THREE.BufferGeometry>>}
	 */
	GLTFParser.prototype.loadGeometries = function ( primitives ) {

		var parser = this;
		var extensions = this.extensions;
		var cache = this.primitiveCache;

		function createDracoPrimitive( primitive ) {

			return extensions[ EXTENSIONS.KHR_DRACO_MESH_COMPRESSION ]
				.decodePrimitive( primitive, parser )
				.then( function ( geometry ) {

					return addPrimitiveAttributes( geometry, primitive, parser );

				} );

		}

		var pending = [];

		for ( var i = 0, il = primitives.length; i < il; i ++ ) {

			var primitive = primitives[ i ];
			var cacheKey = createPrimitiveKey( primitive );

			// See if we've already created this geometry
			var cached = cache[ cacheKey ];

			if ( cached ) {

				// Use the cached geometry if it exists
				pending.push( cached.promise );

			} else {

				var 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<THREE.Group|THREE.Mesh|THREE.SkinnedMesh>}
	 */
	GLTFParser.prototype.loadMesh = function ( meshIndex ) {

		var parser = this;
		var json = this.json;
		var extensions = this.extensions;

		var meshDef = json.meshes[ meshIndex ];
		var primitives = meshDef.primitives;

		var pending = [];

		for ( var i = 0, il = primitives.length; i < il; i ++ ) {

			var material = primitives[ i ].material === undefined
				? createDefaultMaterial()
				: this.getDependency( 'material', primitives[ i ].material );

			pending.push( material );

		}

		return Promise.all( pending ).then( function ( originalMaterials ) {

			return parser.loadGeometries( primitives ).then( function ( geometries ) {

				var meshes = [];

				for ( var i = 0, il = geometries.length; i < il; i ++ ) {

					var geometry = geometries[ i ];
					var primitive = primitives[ i ];

					// 1. create Mesh

					var mesh;

					var material = originalMaterials[ 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.normalizeSkinWeights(); // #15319

						if ( primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ) {

							mesh.drawMode = THREE.TriangleStripDrawMode;

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

							mesh.drawMode = 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 = meshDef.name || ( 'mesh_' + meshIndex );

					if ( geometries.length > 1 ) mesh.name += '_' + i;

					assignExtrasToUserData( mesh, meshDef );

					parser.assignFinalMaterial( mesh );

					meshes.push( mesh );

				}

				if ( meshes.length === 1 ) {

					return meshes[ 0 ];

				}

				var group = new THREE.Group();

				for ( var i = 0, il = meshes.length; i < il; i ++ ) {

					group.add( meshes[ i ] );

				}

				return parser.acceptUserExtensions('onMesh', meshDef, group);

			} );

		} );

	};

	/**
	 * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#cameras
	 * @param {number} cameraIndex
	 * @return {Promise<THREE.Camera>}
	 */
	GLTFParser.prototype.loadCamera = function ( cameraIndex ) {

		var camera;
		var cameraDef = this.json.cameras[ cameraIndex ];
		var params = cameraDef[ cameraDef.type ];

		if ( ! params ) {

			console.warn( 'THREE.GLTFLoader: Missing camera parameters.' );
			return;

		}

		if ( cameraDef.type === 'perspective' ) {

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

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

			camera = new THREE.OrthographicCamera( params.xmag / - 2, params.xmag / 2, params.ymag / 2, params.ymag / - 2, params.znear, params.zfar );

		}

		if ( cameraDef.name !== undefined ) camera.name = cameraDef.name;

		assignExtrasToUserData( camera, cameraDef );

		return Promise.resolve( this.acceptUserExtensions('onCamera', cameraDef, camera) );

	};

	/**
	 * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#skins
	 * @param {number} skinIndex
	 * @return {Promise<Object>}
	 */
	GLTFParser.prototype.loadSkin = function ( skinIndex ) {

		var parser = this;

		var skinDef = this.json.skins[ skinIndex ];

		var 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 parser.acceptUserExtensions('onSkin', skinDef, skinEntry);

		} );

	};

	/**
	 * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#animations
	 * @param {number} animationIndex
	 * @return {Promise<THREE.AnimationClip>}
	 */
	GLTFParser.prototype.loadAnimation = function ( animationIndex ) {

		var json = this.json;
		var parser = this;

		var animationDef = json.animations[ animationIndex ];

		var pendingNodes = [];
		var pendingInputAccessors = [];
		var pendingOutputAccessors = [];
		var pendingSamplers = [];
		var pendingTargets = [];

		for ( var i = 0, il = animationDef.channels.length; i < il; i ++ ) {

			var channel = animationDef.channels[ i ];
			var sampler = animationDef.samplers[ channel.sampler ];
			var target = channel.target;
			var name = target.node !== undefined ? target.node : target.id; // NOTE: target.id is deprecated.
			var input = animationDef.parameters !== undefined ? animationDef.parameters[ sampler.input ] : sampler.input;
			var 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 ) {

			var nodes = dependencies[ 0 ];
			var inputAccessors = dependencies[ 1 ];
			var outputAccessors = dependencies[ 2 ];
			var samplers = dependencies[ 3 ];
			var targets = dependencies[ 4 ];

			var tracks = [];

			for ( var i = 0, il = nodes.length; i < il; i ++ ) {

				var node = nodes[ i ];
				var inputAccessor = inputAccessors[ i ];
				var outputAccessor = outputAccessors[ i ];
				var sampler = samplers[ i ];
				var target = targets[ i ];

				if ( node === undefined ) continue;

				node.updateMatrix();
				node.matrixAutoUpdate = true;

				var 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;

				}

				var targetName = node.name ? node.name : node.uuid;

				var interpolation = sampler.interpolation !== undefined ? INTERPOLATION[ sampler.interpolation ] : THREE.InterpolateLinear;

				var targetNames = [];

				if ( PATH_PROPERTIES[ target.path ] === PATH_PROPERTIES.weights ) {

					// node can be THREE.Group here but
					// PATH_PROPERTIES.weights(morphTargetInfluences) should be
					// the property of a mesh object under group.

					node.traverse( function ( object ) {

						if ( object.isMesh === true && object.morphTargetInfluences ) {

							targetNames.push( object.name ? object.name : object.uuid );

						}

					} );

				} else {

					targetNames.push( targetName );

				}

				// KeyframeTrack.optimize() will modify given 'times' and 'values'
				// buffers before creating a truncated copy to keep. Because buffers may
				// be reused by other tracks, make copies here.
				for ( var j = 0, jl = targetNames.length; j < jl; j ++ ) {

					var track = new TypedKeyframeTrack(
						targetNames[ j ] + '.' + PATH_PROPERTIES[ target.path ],
						THREE.AnimationUtils.arraySlice( inputAccessor.array, 0 ),
						THREE.AnimationUtils.arraySlice( outputAccessor.array, 0 ),
						interpolation
					);

					// Here is the trick to enable custom interpolation.
					// Overrides .createInterpolant in a factory method which creates custom interpolation.
					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.

							return new GLTFCubicSplineInterpolant( this.times, this.values, this.getValueSize() / 3, result );

						};

						// Workaround, provide an alternate way to know if the interpolant type is cubis spline to track.
						// track.getInterpolation() doesn't return valid value for custom interpolant.
						track.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline = true;

					}

					tracks.push( track );

				}

			}

			var name = animationDef.name !== undefined ? animationDef.name : 'animation_' + animationIndex;

			return parser.acceptUserExtensions('onAnimation', animationDef, new THREE.AnimationClip( name, undefined, tracks ));

		} );

	};

	/**
	 * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#nodes-and-hierarchy
	 * @param {number} nodeIndex
	 * @return {Promise<THREE.Object3D>}
	 */
	GLTFParser.prototype.loadNode = function ( nodeIndex ) {

		var json = this.json;
		var extensions = this.extensions;
		var parser = this;

		var meshReferences = json.meshReferences;
		var meshUses = json.meshUses;

		var nodeDef = json.nodes[ nodeIndex ];

		return ( function () {

			// .isBone isn't in glTF spec. See .markDefs
			if ( nodeDef.isBone === true ) {

				return Promise.resolve( new THREE.Bone() );

			} else if ( nodeDef.mesh !== undefined ) {

				return parser.getDependency( 'mesh', nodeDef.mesh ).then( function ( mesh ) {

					var node;

					if ( meshReferences[ nodeDef.mesh ] > 1 ) {

						var instanceNum = meshUses[ nodeDef.mesh ] ++;

						node = mesh.clone();
						node.name += '_instance_' + instanceNum;

						// onBeforeRender copy for Specular-Glossiness
						node.onBeforeRender = mesh.onBeforeRender;

						for ( var i = 0, il = node.children.length; i < il; i ++ ) {

							node.children[ i ].name += '_instance_' + instanceNum;
							node.children[ i ].onBeforeRender = mesh.children[ i ].onBeforeRender;

						}

					} else {

						node = 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 ( var i = 0, il = nodeDef.weights.length; i < il; i ++ ) {

								o.morphTargetInfluences[ i ] = nodeDef.weights[ i ];

							}

						} );

					}

					return parser.acceptUserExtensions('onMesh', nodeDef, node);

				} );

			} else if ( nodeDef.camera !== undefined ) {

				return parser.getDependency( 'camera', nodeDef.camera );

			} else if ( nodeDef.extensions
				&& nodeDef.extensions[ EXTENSIONS.KHR_LIGHTS_PUNCTUAL ]
				&& nodeDef.extensions[ EXTENSIONS.KHR_LIGHTS_PUNCTUAL ].light !== undefined ) {

				return parser.getDependency( 'light', nodeDef.extensions[ EXTENSIONS.KHR_LIGHTS_PUNCTUAL ].light );

			} else {

				return Promise.resolve( new THREE.Object3D() );

			}

		}() ).then( function ( node ) {

			if ( nodeDef.name !== undefined ) {

				node.name = THREE.PropertyBinding.sanitizeNodeName( nodeDef.name );

			}

			assignExtrasToUserData( node, nodeDef );

			if ( nodeDef.extensions ) addUnknownExtensionsToUserData( extensions, node, nodeDef );

			if ( nodeDef.matrix !== undefined ) {

				var matrix = new THREE.Matrix4();
				matrix.fromArray( nodeDef.matrix );
				node.applyMatrix( 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 );

				}

			}

			return parser.acceptUserExtensions('onNode', nodeDef, node);

		} );

	};

	/**
	 * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#scenes
	 * @param {number} sceneIndex
	 * @return {Promise<THREE.Scene>}
	 */
	GLTFParser.prototype.loadScene = function () {

		// scene node hierachy builder

		function buildNodeHierachy( nodeId, parentObject, json, parser ) {

			var nodeDef = json.nodes[ nodeId ];

			return parser.getDependency( 'node', nodeId ).then( function ( node ) {

				if ( nodeDef.skin === undefined ) return node;

				// build skeleton here as well

				var skinEntry;

				return parser.getDependency( 'skin', nodeDef.skin ).then( function ( skin ) {

					skinEntry = skin;

					var pendingJoints = [];

					for ( var i = 0, il = skinEntry.joints.length; i < il; i ++ ) {

						pendingJoints.push( parser.getDependency( 'node', skinEntry.joints[ i ] ) );

					}

					return Promise.all( pendingJoints );

				} ).then( function ( jointNodes ) {

					var meshes = node.isGroup === true ? node.children : [ node ];

					for ( var i = 0, il = meshes.length; i < il; i ++ ) {

						var mesh = meshes[ i ];

						var bones = [];
						var boneInverses = [];

						for ( var j = 0, jl = jointNodes.length; j < jl; j ++ ) {

							var jointNode = jointNodes[ j ];

							if ( jointNode ) {

								bones.push( jointNode );

								var 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 );

				var pending = [];

				if ( nodeDef.children ) {

					var children = nodeDef.children;

					for ( var i = 0, il = children.length; i < il; i ++ ) {

						var child = children[ i ];
						pending.push( buildNodeHierachy( child, node, json, parser ) );

					}

				}

				return Promise.all( pending );

			} );

		}

		return function loadScene( sceneIndex ) {

			var json = this.json;
			var extensions = this.extensions;
			var sceneDef = this.json.scenes[ sceneIndex ];
			var parser = this;

			var scene = new THREE.Scene();
			if ( sceneDef.name !== undefined ) scene.name = sceneDef.name;

			assignExtrasToUserData( scene, sceneDef );

			if ( sceneDef.extensions ) addUnknownExtensionsToUserData( extensions, scene, sceneDef );

			var nodeIds = sceneDef.nodes || [];

			var pending = [];

			for ( var i = 0, il = nodeIds.length; i < il; i ++ ) {

				pending.push( buildNodeHierachy( nodeIds[ i ], scene, json, parser ) );

			}

			return Promise.all( pending ).then( function () {

				return parser.acceptUserExtensions('onScene', sceneDef, scene);

			} );

		};

	}();

	return GLTFLoader;

} )();