Home Reference Source

scripts/exporters/GLTFExporter.js

var THREE = require( 'three' );
/**
 * @author fernandojsg / http://fernandojsg.com
 * @author Don McCurdy / https://www.donmccurdy.com
 * @author Takahiro / https://github.com/takahirox
 */

//------------------------------------------------------------------------------
//Constants
//------------------------------------------------------------------------------
var WEBGL_CONSTANTS = {
		POINTS: 0x0000,
		LINES: 0x0001,
		LINE_LOOP: 0x0002,
		LINE_STRIP: 0x0003,
		TRIANGLES: 0x0004,
		TRIANGLE_STRIP: 0x0005,
		TRIANGLE_FAN: 0x0006,

		UNSIGNED_BYTE: 0x1401,
		UNSIGNED_SHORT: 0x1403,
		FLOAT: 0x1406,
		UNSIGNED_INT: 0x1405,
		ARRAY_BUFFER: 0x8892,
		ELEMENT_ARRAY_BUFFER: 0x8893,

		NEAREST: 0x2600,
		LINEAR: 0x2601,
		NEAREST_MIPMAP_NEAREST: 0x2700,
		LINEAR_MIPMAP_NEAREST: 0x2701,
		NEAREST_MIPMAP_LINEAR: 0x2702,
		LINEAR_MIPMAP_LINEAR: 0x2703
};

var THREE_TO_WEBGL = {
		// @TODO Replace with computed property name [THREE.*] when available on
		// es6
		1003: WEBGL_CONSTANTS.NEAREST,
		1004: WEBGL_CONSTANTS.NEAREST_MIPMAP_NEAREST,
		1005: WEBGL_CONSTANTS.NEAREST_MIPMAP_LINEAR,
		1006: WEBGL_CONSTANTS.LINEAR,
		1007: WEBGL_CONSTANTS.LINEAR_MIPMAP_NEAREST,
		1008: WEBGL_CONSTANTS.LINEAR_MIPMAP_LINEAR
};

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


var _GLTFExporter = (function(){
//	------------------------------------------------------------------------------
//	GLTF Exporter
//	------------------------------------------------------------------------------
	function GLTFExporter() {}

	GLTFExporter.prototype = {

			constructor: GLTFExporter,

			/**
			 * Parse scenes and generate GLTF output
			 * 
			 * @param {THREE.Scene
			 *            or [THREE.Scenes]} input THREE.Scene or Array of
			 *            THREE.Scenes
			 * @param {Function}
			 *            onDone Callback on completed
			 * @param {Object}
			 *            options options
			 */
			parse: function ( input, onDone, options ) {

				var DEFAULT_OPTIONS = {
						binary: false,
						trs: false,
						onlyVisible: true,
						truncateDrawRange: true,
						embedImages: true,
						animations: [],
						forceIndices: false,
						forcePowerOfTwoTextures: false
				};

				options = Object.assign( {}, DEFAULT_OPTIONS, options );

				if ( options.animations.length > 0 ) {

					// Only TRS properties, and not matrices, may be targeted by
					// animation.
					options.trs = true;

				}

				var outputJSON = {

						asset: {

							version: "2.0",
							generator: "THREE.GLTFExporter"

						}

				};

				var byteOffset = 0;
				var buffers = [];
				var pending = [];
				var nodeMap = new Map();
				var skins = [];
				var extensionsUsed = {};
				var cachedData = {

						attributes: new Map(),
						materials: new Map(),
						textures: new Map(),
						images: new Map()

				};

				var cachedCanvas;

				/**
				 * Compare two arrays
				 */
				/**
				 * Compare two arrays
				 * 
				 * @param {Array}
				 *            array1 Array 1 to compare
				 * @param {Array}
				 *            array2 Array 2 to compare
				 * @return {Boolean} Returns true if both arrays are equal
				 */
				function equalArray( array1, array2 ) {

					return ( array1.length === array2.length ) && array1.every( function ( element, index ) {

						return element === array2[ index ];

					} );

				}

				/**
				 * Converts a string to an ArrayBuffer.
				 * 
				 * @param {string}
				 *            text
				 * @return {ArrayBuffer}
				 */
				function stringToArrayBuffer( text ) {

					if ( window.TextEncoder !== undefined ) {

						return new TextEncoder().encode( text ).buffer;

					}

					var array = new Uint8Array( new ArrayBuffer( text.length ) );

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

						var value = text.charCodeAt( i );

						// Replacing multi-byte character with space(0x20).
						array[ i ] = value > 0xFF ? 0x20 : value;

					}

					return array.buffer;

				}

				/**
				 * Get the min and max vectors from the given attribute
				 * 
				 * @param {THREE.BufferAttribute}
				 *            attribute Attribute to find the min/max in range
				 *            from start to start + count
				 * @param {Integer}
				 *            start
				 * @param {Integer}
				 *            count
				 * @return {Object} Object containing the `min` and `max` values
				 *         (As an array of attribute.itemSize components)
				 */
				function getMinMax( attribute, start, count ) {

					var output = {

							min: new Array( attribute.itemSize ).fill( Number.POSITIVE_INFINITY ),
							max: new Array( attribute.itemSize ).fill( Number.NEGATIVE_INFINITY )

					};

					for ( var i = start; i < start + count; i ++ ) {

						for ( var a = 0; a < attribute.itemSize; a ++ ) {

							var value = attribute.array[ i * attribute.itemSize + a ];
							output.min[ a ] = Math.min( output.min[ a ], value );
							output.max[ a ] = Math.max( output.max[ a ], value );

						}

					}

					return output;

				}

				/**
				 * Checks if image size is POT.
				 * 
				 * @param {Image}
				 *            image The image to be checked.
				 * @returns {Boolean} Returns true if image size is POT.
				 * 
				 */
				function isPowerOfTwo( image ) {

					return THREE.Math.isPowerOfTwo( image.width ) && THREE.Math.isPowerOfTwo( image.height );

				}

				/**
				 * Checks if normal attribute values are normalized.
				 * 
				 * @param {THREE.BufferAttribute}
				 *            normal
				 * @returns {Boolean}
				 * 
				 */
				function isNormalizedNormalAttribute( normal ) {

					if ( cachedData.attributes.has( normal ) ) {

						return false;

					}

					var v = new THREE.Vector3();

					for ( var i = 0, il = normal.count; i < il; i ++ ) {

						// 0.0005 is from glTF-validator
						if ( Math.abs( v.fromArray( normal.array, i * 3 ).length() - 1.0 ) > 0.0005 ) return false;

					}

					return true;

				}

				/**
				 * Creates normalized normal buffer attribute.
				 * 
				 * @param {THREE.BufferAttribute}
				 *            normal
				 * @returns {THREE.BufferAttribute}
				 * 
				 */
				function createNormalizedNormalAttribute( normal ) {

					if ( cachedData.attributes.has( normal ) ) {

						return cachedData.attributes.get( normal );

					}

					var attribute = normal.clone();

					var v = new THREE.Vector3();

					for ( var i = 0, il = attribute.count; i < il; i ++ ) {

						v.fromArray( attribute.array, i * 3 );

						if ( v.x === 0 && v.y === 0 && v.z === 0 ) {

							// if values can't be normalized set (1, 0, 0)
							v.setX( 1.0 );

						} else {

							v.normalize();

						}

						v.toArray( attribute.array, i * 3 );

					}

					cachedData.attributes.set( normal, attribute );

					return attribute;

				}

				/**
				 * Get the required size + padding for a buffer, rounded to the
				 * next 4-byte boundary.
				 * https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#data-alignment
				 * 
				 * @param {Integer}
				 *            bufferSize The size the original buffer.
				 * @returns {Integer} new buffer size with required padding.
				 * 
				 */
				function getPaddedBufferSize( bufferSize ) {

					return Math.ceil( bufferSize / 4 ) * 4;

				}

				/**
				 * Returns a buffer aligned to 4-byte boundary.
				 * 
				 * @param {ArrayBuffer}
				 *            arrayBuffer Buffer to pad
				 * @param {Integer}
				 *            paddingByte (Optional)
				 * @returns {ArrayBuffer} The same buffer if it's already
				 *          aligned to 4-byte boundary or a new buffer
				 */
				function getPaddedArrayBuffer( arrayBuffer, paddingByte ) {

					paddingByte = paddingByte || 0;

					var paddedLength = getPaddedBufferSize( arrayBuffer.byteLength );

					if ( paddedLength !== arrayBuffer.byteLength ) {

						var array = new Uint8Array( paddedLength );
						array.set( new Uint8Array( arrayBuffer ) );

						if ( paddingByte !== 0 ) {

							for ( var i = arrayBuffer.byteLength; i < paddedLength; i ++ ) {

								array[ i ] = paddingByte;

							}

						}

						return array.buffer;

					}

					return arrayBuffer;

				}

				/**
				 * Serializes a userData.
				 * 
				 * @param {THREE.Object3D|THREE.Material}
				 *            object
				 * @returns {Object}
				 */
				function serializeUserData( object ) {

					try {

						return JSON.parse( JSON.stringify( object.userData ) );

					} catch ( error ) {

						console.warn( 'THREE.GLTFExporter: userData of \'' + object.name + '\' ' +
								'won\'t be serialized because of JSON.stringify error - ' + error.message );

						return {};

					}

				}

				/**
				 * Process a buffer to append to the default one.
				 * 
				 * @param {ArrayBuffer}
				 *            buffer
				 * @return {Integer}
				 */
				function processBuffer( buffer ) {

					if ( ! outputJSON.buffers ) {

						outputJSON.buffers = [ { byteLength: 0 } ];

					}

					// All buffers are merged before export.
					buffers.push( buffer );

					return 0;

				}

				/**
				 * Process and generate a BufferView
				 * 
				 * @param {THREE.BufferAttribute}
				 *            attribute
				 * @param {number}
				 *            componentType
				 * @param {number}
				 *            start
				 * @param {number}
				 *            count
				 * @param {number}
				 *            target (Optional) Target usage of the BufferView
				 * @return {Object}
				 */
				function processBufferView( attribute, componentType, start, count, target ) {

					if ( ! outputJSON.bufferViews ) {

						outputJSON.bufferViews = [];

					}

					// Create a new dataview and dump the attribute's array into
					// it

					var componentSize;

					if ( componentType === WEBGL_CONSTANTS.UNSIGNED_BYTE ) {

						componentSize = 1;

					} else if ( componentType === WEBGL_CONSTANTS.UNSIGNED_SHORT ) {

						componentSize = 2;

					} else {

						componentSize = 4;

					}

					var byteLength = getPaddedBufferSize( count * attribute.itemSize * componentSize );
					var dataView = new DataView( new ArrayBuffer( byteLength ) );
					var offset = 0;

					for ( var i = start; i < start + count; i ++ ) {

						for ( var a = 0; a < attribute.itemSize; a ++ ) {

							// @TODO Fails on InterleavedBufferAttribute, and
							// could probably be
							// optimized for normal BufferAttribute.
							var value = attribute.array[ i * attribute.itemSize + a ];

							if ( componentType === WEBGL_CONSTANTS.FLOAT ) {

								dataView.setFloat32( offset, value, true );

							} else if ( componentType === WEBGL_CONSTANTS.UNSIGNED_INT ) {

								dataView.setUint32( offset, value, true );

							} else if ( componentType === WEBGL_CONSTANTS.UNSIGNED_SHORT ) {

								dataView.setUint16( offset, value, true );

							} else if ( componentType === WEBGL_CONSTANTS.UNSIGNED_BYTE ) {

								dataView.setUint8( offset, value );

							}

							offset += componentSize;

						}

					}

					var gltfBufferView = {

							buffer: processBuffer( dataView.buffer ),
							byteOffset: byteOffset,
							byteLength: byteLength

					};

					if ( target !== undefined ) gltfBufferView.target = target;

					if ( target === WEBGL_CONSTANTS.ARRAY_BUFFER ) {

						// Only define byteStride for vertex attributes.
						gltfBufferView.byteStride = attribute.itemSize * componentSize;

					}

					byteOffset += byteLength;

					outputJSON.bufferViews.push( gltfBufferView );

					// @TODO Merge bufferViews where possible.
					var output = {

							id: outputJSON.bufferViews.length - 1,
							byteLength: 0

					};

					return output;

				}

				/**
				 * Process and generate a BufferView from an image Blob.
				 * 
				 * @param {Blob}
				 *            blob
				 * @return {Promise<Integer>}
				 */
				function processBufferViewImage( blob ) {

					if ( ! outputJSON.bufferViews ) {

						outputJSON.bufferViews = [];

					}

					return new Promise( function ( resolve ) {

						var reader = new window.FileReader();
						reader.readAsArrayBuffer( blob );
						reader.onloadend = function () {

							var buffer = getPaddedArrayBuffer( reader.result );

							var bufferView = {
									buffer: processBuffer( buffer ),
									byteOffset: byteOffset,
									byteLength: buffer.byteLength
							};

							byteOffset += buffer.byteLength;

							outputJSON.bufferViews.push( bufferView );

							resolve( outputJSON.bufferViews.length - 1 );

						};

					} );

				}

				/**
				 * Process attribute to generate an accessor
				 * 
				 * @param {THREE.BufferAttribute}
				 *            attribute Attribute to process
				 * @param {THREE.BufferGeometry}
				 *            geometry (Optional) Geometry used for truncated
				 *            draw range
				 * @param {Integer}
				 *            start (Optional)
				 * @param {Integer}
				 *            count (Optional)
				 * @return {Integer} Index of the processed accessor on the
				 *         "accessors" array
				 */
				function processAccessor( attribute, geometry, start, count ) {

					var types = {

							1: 'SCALAR',
							2: 'VEC2',
							3: 'VEC3',
							4: 'VEC4',
							16: 'MAT4'

					};

					var componentType;

					// Detect the component type of the attribute array (float,
					// uint or ushort)
					if ( attribute.array.constructor === Float32Array ) {

						componentType = WEBGL_CONSTANTS.FLOAT;

					} else if ( attribute.array.constructor === Uint32Array ) {

						componentType = WEBGL_CONSTANTS.UNSIGNED_INT;

					} else if ( attribute.array.constructor === Uint16Array ) {

						componentType = WEBGL_CONSTANTS.UNSIGNED_SHORT;

					} else if ( attribute.array.constructor === Uint8Array ) {

						componentType = WEBGL_CONSTANTS.UNSIGNED_BYTE;

					} else {

						throw new Error( 'THREE.GLTFExporter: Unsupported bufferAttribute component type.' );

					}

					if ( start === undefined ) start = 0;
					if ( count === undefined ) count = attribute.count;

					// @TODO Indexed buffer geometry with drawRange not
					// supported yet
					if ( options.truncateDrawRange && geometry !== undefined && geometry.index === null ) {

						var end = start + count;
						var end2 = geometry.drawRange.count === Infinity
						? attribute.count
								: geometry.drawRange.start + geometry.drawRange.count;

						start = Math.max( start, geometry.drawRange.start );
						count = Math.min( end, end2 ) - start;

						if ( count < 0 ) count = 0;

					}

					// Skip creating an accessor if the attribute doesn't have
					// data to export
					if ( count === 0 ) {

						return null;

					}

					var minMax = getMinMax( attribute, start, count );

					var bufferViewTarget;

					// If geometry isn't provided, don't infer the target usage
					// of the bufferView. For
					// animation samplers, target must not be set.
					if ( geometry !== undefined ) {

						bufferViewTarget = attribute === geometry.index ? WEBGL_CONSTANTS.ELEMENT_ARRAY_BUFFER : WEBGL_CONSTANTS.ARRAY_BUFFER;

					}

					var bufferView = processBufferView( attribute, componentType, start, count, bufferViewTarget );

					var gltfAccessor = {

							bufferView: bufferView.id,
							byteOffset: bufferView.byteOffset,
							componentType: componentType,
							count: count,
							max: minMax.max,
							min: minMax.min,
							type: types[ attribute.itemSize ]

					};

					if ( ! outputJSON.accessors ) {

						outputJSON.accessors = [];

					}

					outputJSON.accessors.push( gltfAccessor );

					return outputJSON.accessors.length - 1;

				}

				/**
				 * Process image
				 * 
				 * @param {Image}
				 *            image to process
				 * @param {Integer}
				 *            format of the image (e.g. THREE.RGBFormat,
				 *            THREE.RGBAFormat etc)
				 * @param {Boolean}
				 *            flipY before writing out the image
				 * @return {Integer} Index of the processed texture in the
				 *         "images" array
				 */
				function processImage( image, format, flipY ) {

					if ( ! cachedData.images.has( image ) ) {

						cachedData.images.set( image, {} );

					}

					var cachedImages = cachedData.images.get( image );
					var mimeType = format === THREE.RGBAFormat ? 'image/png' : 'image/jpeg';
					var key = mimeType + ":flipY/" + flipY.toString();

					if ( cachedImages[ key ] !== undefined ) {

						return cachedImages[ key ];

					}

					if ( ! outputJSON.images ) {

						outputJSON.images = [];

					}

					var gltfImage = { mimeType: mimeType };

					if ( options.embedImages ) {

						var canvas = cachedCanvas = cachedCanvas || document.createElement( 'canvas' );

						canvas.width = image.width;
						canvas.height = image.height;

						if ( options.forcePowerOfTwoTextures && ! isPowerOfTwo( image ) ) {

							console.warn( 'GLTFExporter: Resized non-power-of-two image.', image );

							canvas.width = THREE.Math.floorPowerOfTwo( canvas.width );
							canvas.height = THREE.Math.floorPowerOfTwo( canvas.height );

						}

						var ctx = canvas.getContext( '2d' );

						if ( flipY === true ) {

							ctx.translate( 0, canvas.height );
							ctx.scale( 1, - 1 );

						}

						ctx.drawImage( image, 0, 0, canvas.width, canvas.height );

						if ( options.binary === true ) {

							pending.push( new Promise( function ( resolve ) {

								canvas.toBlob( function ( blob ) {

									processBufferViewImage( blob ).then( function ( bufferViewIndex ) {

										gltfImage.bufferView = bufferViewIndex;

										resolve();

									} );

								}, mimeType );

							} ) );

						} else {

							gltfImage.uri = canvas.toDataURL( mimeType );

						}

					} else {

						gltfImage.uri = image.src;

					}

					outputJSON.images.push( gltfImage );

					var index = outputJSON.images.length - 1;
					cachedImages[ key ] = index;

					return index;

				}

				/**
				 * Process sampler
				 * 
				 * @param {Texture}
				 *            map Texture to process
				 * @return {Integer} Index of the processed texture in the
				 *         "samplers" array
				 */
				function processSampler( map ) {

					if ( ! outputJSON.samplers ) {

						outputJSON.samplers = [];

					}

					var gltfSampler = {

							magFilter: THREE_TO_WEBGL[ map.magFilter ],
							minFilter: THREE_TO_WEBGL[ map.minFilter ],
							wrapS: THREE_TO_WEBGL[ map.wrapS ],
							wrapT: THREE_TO_WEBGL[ map.wrapT ]

					};

					outputJSON.samplers.push( gltfSampler );

					return outputJSON.samplers.length - 1;

				}

				/**
				 * Process texture
				 * 
				 * @param {Texture}
				 *            map Map to process
				 * @return {Integer} Index of the processed texture in the
				 *         "textures" array
				 */
				function processTexture( map ) {

					if ( cachedData.textures.has( map ) ) {

						return cachedData.textures.get( map );

					}

					if ( ! outputJSON.textures ) {

						outputJSON.textures = [];

					}

					var gltfTexture = {

							sampler: processSampler( map ),
							source: processImage( map.image, map.format, map.flipY )

					};

					outputJSON.textures.push( gltfTexture );

					var index = outputJSON.textures.length - 1;
					cachedData.textures.set( map, index );

					return index;

				}

				/**
				 * Process material
				 * 
				 * @param {THREE.Material}
				 *            material Material to process
				 * @return {Integer} Index of the processed material in the
				 *         "materials" array
				 */
				function processMaterial( material ) {

					if ( cachedData.materials.has( material ) ) {

						return cachedData.materials.get( material );

					}

					if ( ! outputJSON.materials ) {

						outputJSON.materials = [];

					}

					if ( material.isShaderMaterial ) {

						console.warn( 'GLTFExporter: THREE.ShaderMaterial not supported.' );
						return null;

					}

					// @QUESTION Should we avoid including any attribute that
					// has the default value?
					var gltfMaterial = {

							pbrMetallicRoughness: {}

					};

					if ( material.isMeshBasicMaterial ) {

						gltfMaterial.extensions = { KHR_materials_unlit: {} };

						extensionsUsed[ 'KHR_materials_unlit' ] = true;

					} else if ( ! material.isMeshStandardMaterial ) {

						console.warn( 'GLTFExporter: Use MeshStandardMaterial or MeshBasicMaterial for best results.' );

					}

					// pbrMetallicRoughness.baseColorFactor
					var color = material.color.toArray().concat( [ material.opacity ] );

					if ( ! equalArray( color, [ 1, 1, 1, 1 ] ) ) {

						gltfMaterial.pbrMetallicRoughness.baseColorFactor = color;

					}

					if ( material.isMeshStandardMaterial ) {

						gltfMaterial.pbrMetallicRoughness.metallicFactor = material.metalness;
						gltfMaterial.pbrMetallicRoughness.roughnessFactor = material.roughness;

					} else if ( material.isMeshBasicMaterial ) {

						gltfMaterial.pbrMetallicRoughness.metallicFactor = 0.0;
						gltfMaterial.pbrMetallicRoughness.roughnessFactor = 0.9;

					} else {

						gltfMaterial.pbrMetallicRoughness.metallicFactor = 0.5;
						gltfMaterial.pbrMetallicRoughness.roughnessFactor = 0.5;

					}

					// pbrMetallicRoughness.metallicRoughnessTexture
					if ( material.metalnessMap || material.roughnessMap ) {

						if ( material.metalnessMap === material.roughnessMap ) {

							gltfMaterial.pbrMetallicRoughness.metallicRoughnessTexture = {

									index: processTexture( material.metalnessMap )

							};

						} else {

							console.warn( 'THREE.GLTFExporter: Ignoring metalnessMap and roughnessMap because they are not the same Texture.' );

						}

					}

					// pbrMetallicRoughness.baseColorTexture
					if ( material.map ) {

						gltfMaterial.pbrMetallicRoughness.baseColorTexture = {

								index: processTexture( material.map )

						};

					}

					if ( material.isMeshBasicMaterial ||
							material.isLineBasicMaterial ||
							material.isPointsMaterial ) {

					} else {

						// emissiveFactor
						var emissive = material.emissive.clone().multiplyScalar( material.emissiveIntensity ).toArray();

						if ( ! equalArray( emissive, [ 0, 0, 0 ] ) ) {

							gltfMaterial.emissiveFactor = emissive;

						}

						// emissiveTexture
						if ( material.emissiveMap ) {

							gltfMaterial.emissiveTexture = {

									index: processTexture( material.emissiveMap )

							};

						}

					}

					// normalTexture
					if ( material.normalMap ) {

						gltfMaterial.normalTexture = {

								index: processTexture( material.normalMap )

						};

						if ( material.normalScale.x !== - 1 ) {

							if ( material.normalScale.x !== material.normalScale.y ) {

								console.warn( 'THREE.GLTFExporter: Normal scale components are different, ignoring Y and exporting X.' );

							}

							gltfMaterial.normalTexture.scale = material.normalScale.x;

						}

					}

					// occlusionTexture
					if ( material.aoMap ) {

						gltfMaterial.occlusionTexture = {

								index: processTexture( material.aoMap )

						};

						if ( material.aoMapIntensity !== 1.0 ) {

							gltfMaterial.occlusionTexture.strength = material.aoMapIntensity;

						}

					}

					// alphaMode
					if ( material.transparent || material.alphaTest > 0.0 ) {

						gltfMaterial.alphaMode = material.opacity < 1.0 ? 'BLEND' : 'MASK';

						// Write alphaCutoff if it's non-zero and different from
						// the default (0.5).
						if ( material.alphaTest > 0.0 && material.alphaTest !== 0.5 ) {

							gltfMaterial.alphaCutoff = material.alphaTest;

						}

					}

					// doubleSided
					if ( material.side === THREE.DoubleSide ) {

						gltfMaterial.doubleSided = true;

					}

					if ( material.name !== '' ) {

						gltfMaterial.name = material.name;

					}

					if ( Object.keys( material.userData ).length > 0 ) {

						gltfMaterial.extras = serializeUserData( material );

					}

					outputJSON.materials.push( gltfMaterial );

					var index = outputJSON.materials.length - 1;
					cachedData.materials.set( material, index );

					return index;

				}

				/**
				 * Process mesh
				 * 
				 * @param {THREE.Mesh}
				 *            mesh Mesh to process
				 * @return {Integer} Index of the processed mesh in the "meshes"
				 *         array
				 */
				function processMesh( mesh ) {

					var geometry = mesh.geometry;

					var mode;

					// Use the correct mode
					if ( mesh.isLineSegments ) {

						mode = WEBGL_CONSTANTS.LINES;

					} else if ( mesh.isLineLoop ) {

						mode = WEBGL_CONSTANTS.LINE_LOOP;

					} else if ( mesh.isLine ) {

						mode = WEBGL_CONSTANTS.LINE_STRIP;

					} else if ( mesh.isPoints ) {

						mode = WEBGL_CONSTANTS.POINTS;

					} else {

						if ( ! geometry.isBufferGeometry ) {

							var geometryTemp = new THREE.BufferGeometry();
							geometryTemp.fromGeometry( geometry );
							geometry = geometryTemp;

						}

						if ( mesh.drawMode === THREE.TriangleFanDrawMode ) {

							console.warn( 'GLTFExporter: TriangleFanDrawMode and wireframe incompatible.' );
							mode = WEBGL_CONSTANTS.TRIANGLE_FAN;

						} else if ( mesh.drawMode === THREE.TriangleStripDrawMode ) {

							mode = mesh.material.wireframe ? WEBGL_CONSTANTS.LINE_STRIP : WEBGL_CONSTANTS.TRIANGLE_STRIP;

						} else {

							mode = mesh.material.wireframe ? WEBGL_CONSTANTS.LINES : WEBGL_CONSTANTS.TRIANGLES;

						}

					}

					var gltfMesh = {};

					var attributes = {};
					var primitives = [];
					var targets = [];

					// Conversion between attributes names in threejs and gltf
					// spec
					var nameConversion = {

							uv: 'TEXCOORD_0',
							uv2: 'TEXCOORD_1',
							color: 'COLOR_0',
							skinWeight: 'WEIGHTS_0',
							skinIndex: 'JOINTS_0'

					};

					var originalNormal = geometry.getAttribute( 'normal' );

					if ( originalNormal !== undefined && ! isNormalizedNormalAttribute( originalNormal ) ) {

						console.warn( 'THREE.GLTFExporter: Creating normalized normal attribute from the non-normalized one.' );

						geometry.addAttribute( 'normal', createNormalizedNormalAttribute( originalNormal ) );

					}

					// @QUESTION Detect if .vertexColors = THREE.VertexColors?
					// For every attribute create an accessor
					for ( var attributeName in geometry.attributes ) {

						var attribute = geometry.attributes[ attributeName ];
						attributeName = nameConversion[ attributeName ] || attributeName.toUpperCase();

						// JOINTS_0 must be UNSIGNED_BYTE or UNSIGNED_SHORT.
						var array = attribute.array;
						if ( attributeName === 'JOINTS_0' &&
								! ( array instanceof Uint16Array ) &&
								! ( array instanceof Uint8Array ) ) {

							console.warn( 'GLTFExporter: Attribute "skinIndex" converted to type UNSIGNED_SHORT.' );
							attribute = new THREE.BufferAttribute( new Uint16Array( array ), attribute.itemSize, attribute.normalized );

						}

						if ( attributeName.substr( 0, 5 ) !== 'MORPH' ) {

							var accessor = processAccessor( attribute, geometry );
							if ( accessor !== null ) {

								attributes[ attributeName ] = accessor;

							}

						}

					}

					if ( originalNormal !== undefined ) geometry.addAttribute( 'normal', originalNormal );

					// Skip if no exportable attributes found
					if ( Object.keys( attributes ).length === 0 ) {

						return null;

					}

					// Morph targets
					if ( mesh.morphTargetInfluences !== undefined && mesh.morphTargetInfluences.length > 0 ) {

						var weights = [];
						var targetNames = [];
						var reverseDictionary = {};

						if ( mesh.morphTargetDictionary !== undefined ) {

							for ( var key in mesh.morphTargetDictionary ) {

								reverseDictionary[ mesh.morphTargetDictionary[ key ] ] = key;

							}

						}

						for ( var i = 0; i < mesh.morphTargetInfluences.length; ++ i ) {

							var target = {};

							var warned = false;

							for ( var attributeName in geometry.morphAttributes ) {

								// glTF 2.0 morph supports only
								// POSITION/NORMAL/TANGENT.
								// Three.js doesn't support TANGENT yet.

								if ( attributeName !== 'position' && attributeName !== 'normal' ) {

									if ( ! warned ) {

										console.warn( 'GLTFExporter: Only POSITION and NORMAL morph are supported.' );
										warned = true;

									}

									continue;

								}

								var attribute = geometry.morphAttributes[ attributeName ][ i ];

								// Three.js morph attribute has absolute values
								// while the one of glTF has relative values.
								//
								// glTF 2.0 Specification:
								// https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#morph-targets

								var baseAttribute = geometry.attributes[ attributeName ];
								// Clones attribute not to override
								var relativeAttribute = attribute.clone();

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

									relativeAttribute.setXYZ(
											j,
											attribute.getX( j ) - baseAttribute.getX( j ),
											attribute.getY( j ) - baseAttribute.getY( j ),
											attribute.getZ( j ) - baseAttribute.getZ( j )
									);

								}

								target[ attributeName.toUpperCase() ] = processAccessor( relativeAttribute, geometry );

							}

							targets.push( target );

							weights.push( mesh.morphTargetInfluences[ i ] );
							if ( mesh.morphTargetDictionary !== undefined ) targetNames.push( reverseDictionary[ i ] );

						}

						gltfMesh.weights = weights;

						if ( targetNames.length > 0 ) {

							gltfMesh.extras = {};
							gltfMesh.extras.targetNames = targetNames;

						}

					}

					var extras = ( Object.keys( geometry.userData ).length > 0 ) ? serializeUserData( geometry ) : undefined;

					var forceIndices = options.forceIndices;
					var isMultiMaterial = Array.isArray( mesh.material );

					if ( isMultiMaterial && geometry.groups.length === 0 ) return null;

					if ( ! forceIndices && geometry.index === null && isMultiMaterial ) {

						// temporal workaround.
						console.warn( 'THREE.GLTFExporter: Creating index for non-indexed multi-material mesh.' );
						forceIndices = true;

					}

					var didForceIndices = false;

					if ( geometry.index === null && forceIndices ) {

						var indices = [];

						for ( var i = 0, il = geometry.attributes.position.count; i < il; i ++ ) {

							indices[ i ] = i;

						}

						geometry.setIndex( indices );

						didForceIndices = true;

					}

					var materials = isMultiMaterial ? mesh.material : [ mesh.material ];
					var groups = isMultiMaterial ? geometry.groups : [ { materialIndex: 0, start: undefined, count: undefined } ];

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

						var primitive = {
								mode: mode,
								attributes: attributes,
						};

						if ( extras ) primitive.extras = extras;

						if ( targets.length > 0 ) primitive.targets = targets;

						if ( geometry.index !== null ) {

							primitive.indices = processAccessor( geometry.index, geometry, groups[ i ].start, groups[ i ].count );

						}

						var material = processMaterial( materials[ groups[ i ].materialIndex ] );

						if ( material !== null ) {

							primitive.material = material;

						}

						primitives.push( primitive );

					}

					if ( didForceIndices ) {

						geometry.setIndex( null );

					}

					gltfMesh.primitives = primitives;

					if ( ! outputJSON.meshes ) {

						outputJSON.meshes = [];

					}

					outputJSON.meshes.push( gltfMesh );

					return outputJSON.meshes.length - 1;

				}

				/**
				 * Process camera
				 * 
				 * @param {THREE.Camera}
				 *            camera Camera to process
				 * @return {Integer} Index of the processed mesh in the "camera"
				 *         array
				 */
				function processCamera( camera ) {

					if ( ! outputJSON.cameras ) {

						outputJSON.cameras = [];

					}

					var isOrtho = camera.isOrthographicCamera;

					var gltfCamera = {

							type: isOrtho ? 'orthographic' : 'perspective'

					};

					if ( isOrtho ) {

						gltfCamera.orthographic = {

								xmag: camera.right * 2,
								ymag: camera.top * 2,
								zfar: camera.far <= 0 ? 0.001 : camera.far,
										znear: camera.near < 0 ? 0 : camera.near

						};

					} else {

						gltfCamera.perspective = {

								aspectRatio: camera.aspect,
								yfov: THREE.Math.degToRad( camera.fov ) / camera.aspect,
								zfar: camera.far <= 0 ? 0.001 : camera.far,
										znear: camera.near < 0 ? 0 : camera.near

						};

					}

					if ( camera.name !== '' ) {

						gltfCamera.name = camera.type;

					}

					outputJSON.cameras.push( gltfCamera );

					return outputJSON.cameras.length - 1;

				}

				/**
				 * Creates glTF animation entry from AnimationClip object.
				 * 
				 * Status: - Only properties listed in PATH_PROPERTIES may be
				 * animated.
				 * 
				 * @param {THREE.AnimationClip}
				 *            clip
				 * @param {THREE.Object3D}
				 *            root
				 * @return {number}
				 */
				function processAnimation( clip, root ) {

					if ( ! outputJSON.animations ) {

						outputJSON.animations = [];

					}

					var channels = [];
					var samplers = [];

					for ( var i = 0; i < clip.tracks.length; ++ i ) {

						var track = clip.tracks[ i ];
						var trackBinding = THREE.PropertyBinding.parseTrackName( track.name );
						var trackNode = THREE.PropertyBinding.findNode( root, trackBinding.nodeName );
						var trackProperty = PATH_PROPERTIES[ trackBinding.propertyName ];

						if ( trackBinding.objectName === 'bones' ) {

							if ( trackNode.isSkinnedMesh === true ) {

								trackNode = trackNode.skeleton.getBoneByName( trackBinding.objectIndex );

							} else {

								trackNode = undefined;

							}

						}

						if ( ! trackNode || ! trackProperty ) {

							console.warn( 'THREE.GLTFExporter: Could not export animation track "%s".', track.name );
							return null;

						}

						var inputItemSize = 1;
						var outputItemSize = track.values.length / track.times.length;

						if ( trackProperty === PATH_PROPERTIES.morphTargetInfluences ) {

							if ( trackNode.morphTargetInfluences.length !== 1 &&
									trackBinding.propertyIndex !== undefined ) {

								console.warn( 'THREE.GLTFExporter: Skipping animation track "%s". ' +
										'Morph target keyframe tracks must target all available morph targets ' +
										'for the given mesh.', track.name );
								continue;

							}

							outputItemSize /= trackNode.morphTargetInfluences.length;

						}

						var interpolation;

						// @TODO export CubicInterpolant(InterpolateSmooth) as
						// CUBICSPLINE

						// Detecting glTF cubic spline interpolant by checking
						// factory method's special property
						// GLTFCubicSplineInterpolant is a custom interpolant
						// and track doesn't return
						// valid value from .getInterpolation().
						if ( track.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline === true ) {

							interpolation = 'CUBICSPLINE';

							// itemSize of CUBICSPLINE keyframe is 9
							// (VEC3 * 3: inTangent, splineVertex, and
							// outTangent)
							// but needs to be stored as VEC3 so dividing by 3
							// here.
							outputItemSize /= 3;

						} else if ( track.getInterpolation() === THREE.InterpolateDiscrete ) {

							interpolation = 'STEP';

						} else {

							interpolation = 'LINEAR';

						}

						samplers.push( {

							input: processAccessor( new THREE.BufferAttribute( track.times, inputItemSize ) ),
							output: processAccessor( new THREE.BufferAttribute( track.values, outputItemSize ) ),
							interpolation: interpolation

						} );

						channels.push( {

							sampler: samplers.length - 1,
							target: {
								node: nodeMap.get( trackNode ),
								path: trackProperty
							}

						} );

					}

					outputJSON.animations.push( {

						name: clip.name || 'clip_' + outputJSON.animations.length,
						samplers: samplers,
						channels: channels

					} );

					return outputJSON.animations.length - 1;

				}

				function processSkin( object ) {

					var node = outputJSON.nodes[ nodeMap.get( object ) ];

					var skeleton = object.skeleton;
					var rootJoint = object.skeleton.bones[ 0 ];

					if ( rootJoint === undefined ) return null;

					var joints = [];
					var inverseBindMatrices = new Float32Array( skeleton.bones.length * 16 );

					for ( var i = 0; i < skeleton.bones.length; ++ i ) {

						joints.push( nodeMap.get( skeleton.bones[ i ] ) );

						skeleton.boneInverses[ i ].toArray( inverseBindMatrices, i * 16 );

					}

					if ( outputJSON.skins === undefined ) {

						outputJSON.skins = [];

					}

					outputJSON.skins.push( {

						inverseBindMatrices: processAccessor( new THREE.BufferAttribute( inverseBindMatrices, 16 ) ),
						joints: joints,
						skeleton: nodeMap.get( rootJoint )

					} );

					var skinIndex = node.skin = outputJSON.skins.length - 1;

					return skinIndex;

				}

				/**
				 * Process Object3D node
				 * 
				 * @param {THREE.Object3D}
				 *            node Object3D to processNode
				 * @return {Integer} Index of the node in the nodes list
				 */
				function processNode( object ) {

					if ( object.isLight ) {

						console.warn( 'GLTFExporter: Unsupported node type:', object.constructor.name );
						return null;

					}

					if ( ! outputJSON.nodes ) {

						outputJSON.nodes = [];

					}

					var gltfNode = {};

					if ( options.trs ) {

						var rotation = object.quaternion.toArray();
						var position = object.position.toArray();
						var scale = object.scale.toArray();

						if ( ! equalArray( rotation, [ 0, 0, 0, 1 ] ) ) {

							gltfNode.rotation = rotation;

						}

						if ( ! equalArray( position, [ 0, 0, 0 ] ) ) {

							gltfNode.translation = position;

						}

						if ( ! equalArray( scale, [ 1, 1, 1 ] ) ) {

							gltfNode.scale = scale;

						}

					} else {

						object.updateMatrix();
						if ( ! equalArray( object.matrix.elements, [ 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1 ] ) ) {

							gltfNode.matrix = object.matrix.elements;

						}

					}

					// We don't export empty strings name because it represents
					// no-name in Three.js.
					if ( object.name !== '' ) {

						gltfNode.name = String( object.name );

					}

					if ( object.userData && Object.keys( object.userData ).length > 0 ) {

						gltfNode.extras = serializeUserData( object );

					}

					if ( object.isMesh || object.isLine || object.isPoints ) {

						var mesh = processMesh( object );

						if ( mesh !== null ) {

							gltfNode.mesh = mesh;

						}

					} else if ( object.isCamera ) {

						gltfNode.camera = processCamera( object );

					}

					if ( object.isSkinnedMesh ) {

						skins.push( object );

					}

					if ( object.children.length > 0 ) {

						var children = [];

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

							var child = object.children[ i ];

							if ( child.visible || options.onlyVisible === false ) {

								var node = processNode( child );

								if ( node !== null ) {

									children.push( node );

								}

							}

						}

						if ( children.length > 0 ) {

							gltfNode.children = children;

						}


					}

					outputJSON.nodes.push( gltfNode );

					var nodeIndex = outputJSON.nodes.length - 1;
					nodeMap.set( object, nodeIndex );

					return nodeIndex;

				}

				/**
				 * Process Scene
				 * 
				 * @param {THREE.Scene}
				 *            node Scene to process
				 */
				function processScene( scene ) {

					if ( ! outputJSON.scenes ) {

						outputJSON.scenes = [];
						outputJSON.scene = 0;

					}

					var gltfScene = {

							nodes: []

					};

					if ( scene.name !== '' ) {

						gltfScene.name = scene.name;

					}

					outputJSON.scenes.push( gltfScene );

					var nodes = [];

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

						var child = scene.children[ i ];

						if ( child.visible || options.onlyVisible === false ) {

							var node = processNode( child );

							if ( node !== null ) {

								nodes.push( node );

							}

						}

					}

					if ( nodes.length > 0 ) {

						gltfScene.nodes = nodes;

					}

				}

				/**
				 * Creates a THREE.Scene to hold a list of objects and parse it
				 * 
				 * @param {Array}
				 *            objects List of objects to process
				 */
				function processObjects( objects ) {

					var scene = new THREE.Scene();
					scene.name = 'AuxScene';

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

						// We push directly to children instead of calling `add`
						// to prevent
						// modify the .parent and break its original scene and
						// hierarchy
						scene.children.push( objects[ i ] );

					}

					processScene( scene );

				}

				function processInput( input ) {

					input = input instanceof Array ? input : [ input ];

					var objectsWithoutScene = [];

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

						if ( input[ i ] instanceof THREE.Scene ) {

							processScene( input[ i ] );

						} else {

							objectsWithoutScene.push( input[ i ] );

						}

					}

					if ( objectsWithoutScene.length > 0 ) {

						processObjects( objectsWithoutScene );

					}

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

						processSkin( skins[ i ] );

					}

					for ( var i = 0; i < options.animations.length; ++ i ) {

						processAnimation( options.animations[ i ], input[ 0 ] );

					}

				}

				processInput( input );

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

					// Merge buffers.
					var blob = new Blob( buffers, { type: 'application/octet-stream' } );

					// Declare extensions.
					var extensionsUsedList = Object.keys( extensionsUsed );
					if ( extensionsUsedList.length > 0 ) outputJSON.extensionsUsed = extensionsUsedList;

					if ( outputJSON.buffers && outputJSON.buffers.length > 0 ) {

						// Update bytelength of the single buffer.
						outputJSON.buffers[ 0 ].byteLength = blob.size;

						var reader = new window.FileReader();

						if ( options.binary === true ) {

							// https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#glb-file-format-specification

							var GLB_HEADER_BYTES = 12;
							var GLB_HEADER_MAGIC = 0x46546C67;
							var GLB_VERSION = 2;

							var GLB_CHUNK_PREFIX_BYTES = 8;
							var GLB_CHUNK_TYPE_JSON = 0x4E4F534A;
							var GLB_CHUNK_TYPE_BIN = 0x004E4942;

							reader.readAsArrayBuffer( blob );
							reader.onloadend = function () {

								// Binary chunk.
								var binaryChunk = getPaddedArrayBuffer( reader.result );
								var binaryChunkPrefix = new DataView( new ArrayBuffer( GLB_CHUNK_PREFIX_BYTES ) );
								binaryChunkPrefix.setUint32( 0, binaryChunk.byteLength, true );
								binaryChunkPrefix.setUint32( 4, GLB_CHUNK_TYPE_BIN, true );

								// JSON chunk.
								var jsonChunk = getPaddedArrayBuffer( stringToArrayBuffer( JSON.stringify( outputJSON ) ), 0x20 );
								var jsonChunkPrefix = new DataView( new ArrayBuffer( GLB_CHUNK_PREFIX_BYTES ) );
								jsonChunkPrefix.setUint32( 0, jsonChunk.byteLength, true );
								jsonChunkPrefix.setUint32( 4, GLB_CHUNK_TYPE_JSON, true );

								// GLB header.
								var header = new ArrayBuffer( GLB_HEADER_BYTES );
								var headerView = new DataView( header );
								headerView.setUint32( 0, GLB_HEADER_MAGIC, true );
								headerView.setUint32( 4, GLB_VERSION, true );
								var totalByteLength = GLB_HEADER_BYTES
								+ jsonChunkPrefix.byteLength + jsonChunk.byteLength
								+ binaryChunkPrefix.byteLength + binaryChunk.byteLength;
								headerView.setUint32( 8, totalByteLength, true );

								var glbBlob = new Blob( [
									header,
									jsonChunkPrefix,
									jsonChunk,
									binaryChunkPrefix,
									binaryChunk
									], { type: 'application/octet-stream' } );

								var glbReader = new window.FileReader();
								glbReader.readAsArrayBuffer( glbBlob );
								glbReader.onloadend = function () {

									onDone( glbReader.result );

								};

							};

						} else {

							reader.readAsDataURL( blob );
							reader.onloadend = function () {

								var base64data = reader.result;
								outputJSON.buffers[ 0 ].uri = base64data;
								onDone( outputJSON );

							};

						}

					} else {

						onDone( outputJSON );

					}

				} );
			}
	};
	return GLTFExporter;
})();
module.exports = _GLTFExporter;