three.js/examples/js/animation/MMDAnimationHelper.js

( function () {

	/**
 * MMDAnimationHelper handles animation of MMD assets loaded by MMDLoader
 * with MMD special features as IK, Grant, and Physics.
 *
 * Dependencies
 *  - ammo.js https://github.com/kripken/ammo.js
 *  - THREE.MMDPhysics
 *  - THREE.CCDIKSolver
 *
 * TODO
 *  - more precise grant skinning support.
 */

	class MMDAnimationHelper {

		/**
   * @param {Object} params - (optional)
   * @param {boolean} params.sync - Whether animation durations of added objects are synched. Default is true.
   * @param {Number} params.afterglow - Default is 0.0.
   * @param {boolean} params.resetPhysicsOnLoop - Default is true.
   */
		constructor( params = {} ) {

			this.meshes = [];
			this.camera = null;
			this.cameraTarget = new THREE.Object3D();
			this.cameraTarget.name = 'target';
			this.audio = null;
			this.audioManager = null;
			this.objects = new WeakMap();
			this.configuration = {
				sync: params.sync !== undefined ? params.sync : true,
				afterglow: params.afterglow !== undefined ? params.afterglow : 0.0,
				resetPhysicsOnLoop: params.resetPhysicsOnLoop !== undefined ? params.resetPhysicsOnLoop : true,
				pmxAnimation: params.pmxAnimation !== undefined ? params.pmxAnimation : false
			};
			this.enabled = {
				animation: true,
				ik: true,
				grant: true,
				physics: true,
				cameraAnimation: true
			};

			this.onBeforePhysics = function
			/* mesh */
			() {}; // experimental


			this.sharedPhysics = false;
			this.masterPhysics = null;

		}
		/**
   * Adds an Three.js Object to helper and setups animation.
   * The anmation durations of added objects are synched
   * if this.configuration.sync is true.
   *
   * @param {THREE.SkinnedMesh|THREE.Camera|THREE.Audio} object
   * @param {Object} params - (optional)
   * @param {THREE.AnimationClip|Array<THREE.AnimationClip>} params.animation - Only for THREE.SkinnedMesh and THREE.Camera. Default is undefined.
   * @param {boolean} params.physics - Only for THREE.SkinnedMesh. Default is true.
   * @param {Integer} params.warmup - Only for THREE.SkinnedMesh and physics is true. Default is 60.
   * @param {Number} params.unitStep - Only for THREE.SkinnedMesh and physics is true. Default is 1 / 65.
   * @param {Integer} params.maxStepNum - Only for THREE.SkinnedMesh and physics is true. Default is 3.
   * @param {Vector3} params.gravity - Only for THREE.SkinnedMesh and physics is true. Default ( 0, - 9.8 * 10, 0 ).
   * @param {Number} params.delayTime - Only for THREE.Audio. Default is 0.0.
   * @return {MMDAnimationHelper}
   */


		add( object, params = {} ) {

			if ( object.isSkinnedMesh ) {

				this._addMesh( object, params );

			} else if ( object.isCamera ) {

				this._setupCamera( object, params );

			} else if ( object.type === 'Audio' ) {

				this._setupAudio( object, params );

			} else {

				throw new Error( 'THREE.MMDAnimationHelper.add: ' + 'accepts only ' + 'THREE.SkinnedMesh or ' + 'THREE.Camera or ' + 'THREE.Audio instance.' );

			}

			if ( this.configuration.sync ) this._syncDuration();
			return this;

		}
		/**
   * Removes an Three.js Object from helper.
   *
   * @param {THREE.SkinnedMesh|THREE.Camera|THREE.Audio} object
   * @return {MMDAnimationHelper}
   */


		remove( object ) {

			if ( object.isSkinnedMesh ) {

				this._removeMesh( object );

			} else if ( object.isCamera ) {

				this._clearCamera( object );

			} else if ( object.type === 'Audio' ) {

				this._clearAudio( object );

			} else {

				throw new Error( 'THREE.MMDAnimationHelper.remove: ' + 'accepts only ' + 'THREE.SkinnedMesh or ' + 'THREE.Camera or ' + 'THREE.Audio instance.' );

			}

			if ( this.configuration.sync ) this._syncDuration();
			return this;

		}
		/**
   * Updates the animation.
   *
   * @param {Number} delta
   * @return {MMDAnimationHelper}
   */


		update( delta ) {

			if ( this.audioManager !== null ) this.audioManager.control( delta );

			for ( let i = 0; i < this.meshes.length; i ++ ) {

				this._animateMesh( this.meshes[ i ], delta );

			}

			if ( this.sharedPhysics ) this._updateSharedPhysics( delta );
			if ( this.camera !== null ) this._animateCamera( this.camera, delta );
			return this;

		}
		/**
   * Changes the pose of SkinnedMesh as VPD specifies.
   *
   * @param {THREE.SkinnedMesh} mesh
   * @param {Object} vpd - VPD content parsed MMDParser
   * @param {Object} params - (optional)
   * @param {boolean} params.resetPose - Default is true.
   * @param {boolean} params.ik - Default is true.
   * @param {boolean} params.grant - Default is true.
   * @return {MMDAnimationHelper}
   */


		pose( mesh, vpd, params = {} ) {

			if ( params.resetPose !== false ) mesh.pose();
			const bones = mesh.skeleton.bones;
			const boneParams = vpd.bones;
			const boneNameDictionary = {};

			for ( let i = 0, il = bones.length; i < il; i ++ ) {

				boneNameDictionary[ bones[ i ].name ] = i;

			}

			const vector = new THREE.Vector3();
			const quaternion = new THREE.Quaternion();

			for ( let i = 0, il = boneParams.length; i < il; i ++ ) {

				const boneParam = boneParams[ i ];
				const boneIndex = boneNameDictionary[ boneParam.name ];
				if ( boneIndex === undefined ) continue;
				const bone = bones[ boneIndex ];
				bone.position.add( vector.fromArray( boneParam.translation ) );
				bone.quaternion.multiply( quaternion.fromArray( boneParam.quaternion ) );

			}

			mesh.updateMatrixWorld( true ); // PMX animation system special path

			if ( this.configuration.pmxAnimation && mesh.geometry.userData.MMD && mesh.geometry.userData.MMD.format === 'pmx' ) {

				const sortedBonesData = this._sortBoneDataArray( mesh.geometry.userData.MMD.bones.slice() );

				const ikSolver = params.ik !== false ? this._createCCDIKSolver( mesh ) : null;
				const grantSolver = params.grant !== false ? this.createGrantSolver( mesh ) : null;

				this._animatePMXMesh( mesh, sortedBonesData, ikSolver, grantSolver );

			} else {

				if ( params.ik !== false ) {

					this._createCCDIKSolver( mesh ).update();

				}

				if ( params.grant !== false ) {

					this.createGrantSolver( mesh ).update();

				}

			}

			return this;

		}
		/**
   * Enabes/Disables an animation feature.
   *
   * @param {string} key
   * @param {boolean} enabled
   * @return {MMDAnimationHelper}
   */


		enable( key, enabled ) {

			if ( this.enabled[ key ] === undefined ) {

				throw new Error( 'THREE.MMDAnimationHelper.enable: ' + 'unknown key ' + key );

			}

			this.enabled[ key ] = enabled;

			if ( key === 'physics' ) {

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

					this._optimizeIK( this.meshes[ i ], enabled );

				}

			}

			return this;

		}
		/**
   * Creates an GrantSolver instance.
   *
   * @param {THREE.SkinnedMesh} mesh
   * @return {GrantSolver}
   */


		createGrantSolver( mesh ) {

			return new GrantSolver( mesh, mesh.geometry.userData.MMD.grants );

		} // private methods


		_addMesh( mesh, params ) {

			if ( this.meshes.indexOf( mesh ) >= 0 ) {

				throw new Error( 'THREE.MMDAnimationHelper._addMesh: ' + 'SkinnedMesh \'' + mesh.name + '\' has already been added.' );

			}

			this.meshes.push( mesh );
			this.objects.set( mesh, {
				looped: false
			} );

			this._setupMeshAnimation( mesh, params.animation );

			if ( params.physics !== false ) {

				this._setupMeshPhysics( mesh, params );

			}

			return this;

		}

		_setupCamera( camera, params ) {

			if ( this.camera === camera ) {

				throw new Error( 'THREE.MMDAnimationHelper._setupCamera: ' + 'Camera \'' + camera.name + '\' has already been set.' );

			}

			if ( this.camera ) this.clearCamera( this.camera );
			this.camera = camera;
			camera.add( this.cameraTarget );
			this.objects.set( camera, {} );

			if ( params.animation !== undefined ) {

				this._setupCameraAnimation( camera, params.animation );

			}

			return this;

		}

		_setupAudio( audio, params ) {

			if ( this.audio === audio ) {

				throw new Error( 'THREE.MMDAnimationHelper._setupAudio: ' + 'Audio \'' + audio.name + '\' has already been set.' );

			}

			if ( this.audio ) this.clearAudio( this.audio );
			this.audio = audio;
			this.audioManager = new AudioManager( audio, params );
			this.objects.set( this.audioManager, {
				duration: this.audioManager.duration
			} );
			return this;

		}

		_removeMesh( mesh ) {

			let found = false;
			let writeIndex = 0;

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

				if ( this.meshes[ i ] === mesh ) {

					this.objects.delete( mesh );
					found = true;
					continue;

				}

				this.meshes[ writeIndex ++ ] = this.meshes[ i ];

			}

			if ( ! found ) {

				throw new Error( 'THREE.MMDAnimationHelper._removeMesh: ' + 'SkinnedMesh \'' + mesh.name + '\' has not been added yet.' );

			}

			this.meshes.length = writeIndex;
			return this;

		}

		_clearCamera( camera ) {

			if ( camera !== this.camera ) {

				throw new Error( 'THREE.MMDAnimationHelper._clearCamera: ' + 'Camera \'' + camera.name + '\' has not been set yet.' );

			}

			this.camera.remove( this.cameraTarget );
			this.objects.delete( this.camera );
			this.camera = null;
			return this;

		}

		_clearAudio( audio ) {

			if ( audio !== this.audio ) {

				throw new Error( 'THREE.MMDAnimationHelper._clearAudio: ' + 'Audio \'' + audio.name + '\' has not been set yet.' );

			}

			this.objects.delete( this.audioManager );
			this.audio = null;
			this.audioManager = null;
			return this;

		}

		_setupMeshAnimation( mesh, animation ) {

			const objects = this.objects.get( mesh );

			if ( animation !== undefined ) {

				const animations = Array.isArray( animation ) ? animation : [ animation ];
				objects.mixer = new THREE.AnimationMixer( mesh );

				for ( let i = 0, il = animations.length; i < il; i ++ ) {

					objects.mixer.clipAction( animations[ i ] ).play();

				} // TODO: find a workaround not to access ._clip looking like a private property


				objects.mixer.addEventListener( 'loop', function ( event ) {

					const tracks = event.action._clip.tracks;
					if ( tracks.length > 0 && tracks[ 0 ].name.slice( 0, 6 ) !== '.bones' ) return;
					objects.looped = true;

				} );

			}

			objects.ikSolver = this._createCCDIKSolver( mesh );
			objects.grantSolver = this.createGrantSolver( mesh );
			return this;

		}

		_setupCameraAnimation( camera, animation ) {

			const animations = Array.isArray( animation ) ? animation : [ animation ];
			const objects = this.objects.get( camera );
			objects.mixer = new THREE.AnimationMixer( camera );

			for ( let i = 0, il = animations.length; i < il; i ++ ) {

				objects.mixer.clipAction( animations[ i ] ).play();

			}

		}

		_setupMeshPhysics( mesh, params ) {

			const objects = this.objects.get( mesh ); // shared physics is experimental

			if ( params.world === undefined && this.sharedPhysics ) {

				const masterPhysics = this._getMasterPhysics();

				if ( masterPhysics !== null ) world = masterPhysics.world; // eslint-disable-line no-undef

			}

			objects.physics = this._createMMDPhysics( mesh, params );

			if ( objects.mixer && params.animationWarmup !== false ) {

				this._animateMesh( mesh, 0 );

				objects.physics.reset();

			}

			objects.physics.warmup( params.warmup !== undefined ? params.warmup : 60 );

			this._optimizeIK( mesh, true );

		}

		_animateMesh( mesh, delta ) {

			const objects = this.objects.get( mesh );
			const mixer = objects.mixer;
			const ikSolver = objects.ikSolver;
			const grantSolver = objects.grantSolver;
			const physics = objects.physics;
			const looped = objects.looped;

			if ( mixer && this.enabled.animation ) {

				// alternate solution to save/restore bones but less performant?
				//mesh.pose();
				//this._updatePropertyMixersBuffer( mesh );
				this._restoreBones( mesh );

				mixer.update( delta );

				this._saveBones( mesh ); // PMX animation system special path


				if ( this.configuration.pmxAnimation && mesh.geometry.userData.MMD && mesh.geometry.userData.MMD.format === 'pmx' ) {

					if ( ! objects.sortedBonesData ) objects.sortedBonesData = this._sortBoneDataArray( mesh.geometry.userData.MMD.bones.slice() );

					this._animatePMXMesh( mesh, objects.sortedBonesData, ikSolver && this.enabled.ik ? ikSolver : null, grantSolver && this.enabled.grant ? grantSolver : null );

				} else {

					if ( ikSolver && this.enabled.ik ) {

						mesh.updateMatrixWorld( true );
						ikSolver.update();

					}

					if ( grantSolver && this.enabled.grant ) {

						grantSolver.update();

					}

				}

			}

			if ( looped === true && this.enabled.physics ) {

				if ( physics && this.configuration.resetPhysicsOnLoop ) physics.reset();
				objects.looped = false;

			}

			if ( physics && this.enabled.physics && ! this.sharedPhysics ) {

				this.onBeforePhysics( mesh );
				physics.update( delta );

			}

		} // Sort bones in order by 1. transformationClass and 2. bone index.
		// In PMX animation system, bone transformations should be processed
		// in this order.


		_sortBoneDataArray( boneDataArray ) {

			return boneDataArray.sort( function ( a, b ) {

				if ( a.transformationClass !== b.transformationClass ) {

					return a.transformationClass - b.transformationClass;

				} else {

					return a.index - b.index;

				}

			} );

		} // PMX Animation system is a bit too complex and doesn't great match to
		// Three.js Animation system. This method attempts to simulate it as much as
		// possible but doesn't perfectly simulate.
		// This method is more costly than the regular one so
		// you are recommended to set constructor parameter "pmxAnimation: true"
		// only if your PMX model animation doesn't work well.
		// If you need better method you would be required to write your own.


		_animatePMXMesh( mesh, sortedBonesData, ikSolver, grantSolver ) {

			_quaternionIndex = 0;

			_grantResultMap.clear();

			for ( let i = 0, il = sortedBonesData.length; i < il; i ++ ) {

				updateOne( mesh, sortedBonesData[ i ].index, ikSolver, grantSolver );

			}

			mesh.updateMatrixWorld( true );
			return this;

		}

		_animateCamera( camera, delta ) {

			const mixer = this.objects.get( camera ).mixer;

			if ( mixer && this.enabled.cameraAnimation ) {

				mixer.update( delta );
				camera.updateProjectionMatrix();
				camera.up.set( 0, 1, 0 );
				camera.up.applyQuaternion( camera.quaternion );
				camera.lookAt( this.cameraTarget.position );

			}

		}

		_optimizeIK( mesh, physicsEnabled ) {

			const iks = mesh.geometry.userData.MMD.iks;
			const bones = mesh.geometry.userData.MMD.bones;

			for ( let i = 0, il = iks.length; i < il; i ++ ) {

				const ik = iks[ i ];
				const links = ik.links;

				for ( let j = 0, jl = links.length; j < jl; j ++ ) {

					const link = links[ j ];

					if ( physicsEnabled === true ) {

						// disable IK of the bone the corresponding rigidBody type of which is 1 or 2
						// because its rotation will be overriden by physics
						link.enabled = bones[ link.index ].rigidBodyType > 0 ? false : true;

					} else {

						link.enabled = true;

					}

				}

			}

		}

		_createCCDIKSolver( mesh ) {

			if ( THREE.CCDIKSolver === undefined ) {

				throw new Error( 'THREE.MMDAnimationHelper: Import THREE.CCDIKSolver.' );

			}

			return new THREE.CCDIKSolver( mesh, mesh.geometry.userData.MMD.iks );

		}

		_createMMDPhysics( mesh, params ) {

			if ( THREE.MMDPhysics === undefined ) {

				throw new Error( 'THREE.MMDPhysics: Import THREE.MMDPhysics.' );

			}

			return new THREE.MMDPhysics( mesh, mesh.geometry.userData.MMD.rigidBodies, mesh.geometry.userData.MMD.constraints, params );

		}
		/*
   * Detects the longest duration and then sets it to them to sync.
   * TODO: Not to access private properties ( ._actions and ._clip )
   */


		_syncDuration() {

			let max = 0.0;
			const objects = this.objects;
			const meshes = this.meshes;
			const camera = this.camera;
			const audioManager = this.audioManager; // get the longest duration

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

				const mixer = this.objects.get( meshes[ i ] ).mixer;
				if ( mixer === undefined ) continue;

				for ( let j = 0; j < mixer._actions.length; j ++ ) {

					const clip = mixer._actions[ j ]._clip;

					if ( ! objects.has( clip ) ) {

						objects.set( clip, {
							duration: clip.duration
						} );

					}

					max = Math.max( max, objects.get( clip ).duration );

				}

			}

			if ( camera !== null ) {

				const mixer = this.objects.get( camera ).mixer;

				if ( mixer !== undefined ) {

					for ( let i = 0, il = mixer._actions.length; i < il; i ++ ) {

						const clip = mixer._actions[ i ]._clip;

						if ( ! objects.has( clip ) ) {

							objects.set( clip, {
								duration: clip.duration
							} );

						}

						max = Math.max( max, objects.get( clip ).duration );

					}

				}

			}

			if ( audioManager !== null ) {

				max = Math.max( max, objects.get( audioManager ).duration );

			}

			max += this.configuration.afterglow; // update the duration

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

				const mixer = this.objects.get( this.meshes[ i ] ).mixer;
				if ( mixer === undefined ) continue;

				for ( let j = 0, jl = mixer._actions.length; j < jl; j ++ ) {

					mixer._actions[ j ]._clip.duration = max;

				}

			}

			if ( camera !== null ) {

				const mixer = this.objects.get( camera ).mixer;

				if ( mixer !== undefined ) {

					for ( let i = 0, il = mixer._actions.length; i < il; i ++ ) {

						mixer._actions[ i ]._clip.duration = max;

					}

				}

			}

			if ( audioManager !== null ) {

				audioManager.duration = max;

			}

		} // workaround


		_updatePropertyMixersBuffer( mesh ) {

			const mixer = this.objects.get( mesh ).mixer;
			const propertyMixers = mixer._bindings;
			const accuIndex = mixer._accuIndex;

			for ( let i = 0, il = propertyMixers.length; i < il; i ++ ) {

				const propertyMixer = propertyMixers[ i ];
				const buffer = propertyMixer.buffer;
				const stride = propertyMixer.valueSize;
				const offset = ( accuIndex + 1 ) * stride;
				propertyMixer.binding.getValue( buffer, offset );

			}

		}
		/*
   * Avoiding these two issues by restore/save bones before/after mixer animation.
   *
   * 1. PropertyMixer used by THREE.AnimationMixer holds cache value in .buffer.
   *    Calculating IK, Grant, and Physics after mixer animation can break
   *    the cache coherency.
   *
   * 2. Applying Grant two or more times without reset the posing breaks model.
   */


		_saveBones( mesh ) {

			const objects = this.objects.get( mesh );
			const bones = mesh.skeleton.bones;
			let backupBones = objects.backupBones;

			if ( backupBones === undefined ) {

				backupBones = new Float32Array( bones.length * 7 );
				objects.backupBones = backupBones;

			}

			for ( let i = 0, il = bones.length; i < il; i ++ ) {

				const bone = bones[ i ];
				bone.position.toArray( backupBones, i * 7 );
				bone.quaternion.toArray( backupBones, i * 7 + 3 );

			}

		}

		_restoreBones( mesh ) {

			const objects = this.objects.get( mesh );
			const backupBones = objects.backupBones;
			if ( backupBones === undefined ) return;
			const bones = mesh.skeleton.bones;

			for ( let i = 0, il = bones.length; i < il; i ++ ) {

				const bone = bones[ i ];
				bone.position.fromArray( backupBones, i * 7 );
				bone.quaternion.fromArray( backupBones, i * 7 + 3 );

			}

		} // experimental


		_getMasterPhysics() {

			if ( this.masterPhysics !== null ) return this.masterPhysics;

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

				const physics = this.meshes[ i ].physics;

				if ( physics !== undefined && physics !== null ) {

					this.masterPhysics = physics;
					return this.masterPhysics;

				}

			}

			return null;

		}

		_updateSharedPhysics( delta ) {

			if ( this.meshes.length === 0 || ! this.enabled.physics || ! this.sharedPhysics ) return;

			const physics = this._getMasterPhysics();

			if ( physics === null ) return;

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

				const p = this.meshes[ i ].physics;

				if ( p !== null && p !== undefined ) {

					p.updateRigidBodies();

				}

			}

			physics.stepSimulation( delta );

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

				const p = this.meshes[ i ].physics;

				if ( p !== null && p !== undefined ) {

					p.updateBones();

				}

			}

		}

	} // Keep working quaternions for less GC


	const _quaternions = [];
	let _quaternionIndex = 0;

	function getQuaternion() {

		if ( _quaternionIndex >= _quaternions.length ) {

			_quaternions.push( new THREE.Quaternion() );

		}

		return _quaternions[ _quaternionIndex ++ ];

	} // Save rotation whose grant and IK are already applied
	// used by grant children


	const _grantResultMap = new Map();

	function updateOne( mesh, boneIndex, ikSolver, grantSolver ) {

		const bones = mesh.skeleton.bones;
		const bonesData = mesh.geometry.userData.MMD.bones;
		const boneData = bonesData[ boneIndex ];
		const bone = bones[ boneIndex ]; // Return if already updated by being referred as a grant parent.

		if ( _grantResultMap.has( boneIndex ) ) return;
		const quaternion = getQuaternion(); // Initialize grant result here to prevent infinite loop.
		// If it's referred before updating with actual result later
		// result without applyting IK or grant is gotten
		// but better than composing of infinite loop.

		_grantResultMap.set( boneIndex, quaternion.copy( bone.quaternion ) ); // @TODO: Support global grant and grant position


		if ( grantSolver && boneData.grant && ! boneData.grant.isLocal && boneData.grant.affectRotation ) {

			const parentIndex = boneData.grant.parentIndex;
			const ratio = boneData.grant.ratio;

			if ( ! _grantResultMap.has( parentIndex ) ) {

				updateOne( mesh, parentIndex, ikSolver, grantSolver );

			}

			grantSolver.addGrantRotation( bone, _grantResultMap.get( parentIndex ), ratio );

		}

		if ( ikSolver && boneData.ik ) {

			// @TODO: Updating world matrices every time solving an IK bone is
			// costly. Optimize if possible.
			mesh.updateMatrixWorld( true );
			ikSolver.updateOne( boneData.ik ); // No confident, but it seems the grant results with ik links should be updated?

			const links = boneData.ik.links;

			for ( let i = 0, il = links.length; i < il; i ++ ) {

				const link = links[ i ];
				if ( link.enabled === false ) continue;
				const linkIndex = link.index;

				if ( _grantResultMap.has( linkIndex ) ) {

					_grantResultMap.set( linkIndex, _grantResultMap.get( linkIndex ).copy( bones[ linkIndex ].quaternion ) );

				}

			}

		} // Update with the actual result here


		quaternion.copy( bone.quaternion );

	} //


	class AudioManager {

		/**
   * @param {THREE.Audio} audio
   * @param {Object} params - (optional)
   * @param {Nuumber} params.delayTime
   */
		constructor( audio, params = {} ) {

			this.audio = audio;
			this.elapsedTime = 0.0;
			this.currentTime = 0.0;
			this.delayTime = params.delayTime !== undefined ? params.delayTime : 0.0;
			this.audioDuration = this.audio.buffer.duration;
			this.duration = this.audioDuration + this.delayTime;

		}
		/**
   * @param {Number} delta
   * @return {AudioManager}
   */


		control( delta ) {

			this.elapsed += delta;
			this.currentTime += delta;
			if ( this._shouldStopAudio() ) this.audio.stop();
			if ( this._shouldStartAudio() ) this.audio.play();
			return this;

		} // private methods


		_shouldStartAudio() {

			if ( this.audio.isPlaying ) return false;

			while ( this.currentTime >= this.duration ) {

				this.currentTime -= this.duration;

			}

			if ( this.currentTime < this.delayTime ) return false; // 'duration' can be bigger than 'audioDuration + delayTime' because of sync configuration

			if ( this.currentTime - this.delayTime > this.audioDuration ) return false;
			return true;

		}

		_shouldStopAudio() {

			return this.audio.isPlaying && this.currentTime >= this.duration;

		}

	}

	const _q = new THREE.Quaternion();
	/**
 * Solver for Grant (Fuyo in Japanese. I just google translated because
 * Fuyo may be MMD specific term and may not be common word in 3D CG terms.)
 * Grant propagates a bone's transform to other bones transforms even if
 * they are not children.
 * @param {THREE.SkinnedMesh} mesh
 * @param {Array<Object>} grants
 */


	class GrantSolver {

		constructor( mesh, grants = [] ) {

			this.mesh = mesh;
			this.grants = grants;

		}
		/**
   * Solve all the grant bones
   * @return {GrantSolver}
   */


		update() {

			const grants = this.grants;

			for ( let i = 0, il = grants.length; i < il; i ++ ) {

				this.updateOne( grants[ i ] );

			}

			return this;

		}
		/**
   * Solve a grant bone
   * @param {Object} grant - grant parameter
   * @return {GrantSolver}
   */


		updateOne( grant ) {

			const bones = this.mesh.skeleton.bones;
			const bone = bones[ grant.index ];
			const parentBone = bones[ grant.parentIndex ];

			if ( grant.isLocal ) {

				// TODO: implement
				if ( grant.affectPosition ) {} // TODO: implement


				if ( grant.affectRotation ) {}

			} else {

				// TODO: implement
				if ( grant.affectPosition ) {}

				if ( grant.affectRotation ) {

					this.addGrantRotation( bone, parentBone.quaternion, grant.ratio );

				}

			}

			return this;

		}

		addGrantRotation( bone, q, ratio ) {

			_q.set( 0, 0, 0, 1 );

			_q.slerp( q, ratio );

			bone.quaternion.multiply( _q );
			return this;

		}

	}

	THREE.MMDAnimationHelper = MMDAnimationHelper;

} )();