three.js/examples/js/animation/MMDPhysics.js

( function () {

	/**
 * Dependencies
 *  - Ammo.js https://github.com/kripken/ammo.js
 *
 * MMDPhysics calculates physics with Ammo(Bullet based JavaScript Physics engine)
 * for MMD model loaded by MMDLoader.
 *
 * TODO
 *  - Physics in Worker
 */

	/* global Ammo */

	class MMDPhysics {

		/**
   * @param {THREE.SkinnedMesh} mesh
   * @param {Array<Object>} rigidBodyParams
   * @param {Array<Object>} (optional) constraintParams
   * @param {Object} params - (optional)
   * @param {Number} params.unitStep - Default is 1 / 65.
   * @param {Integer} params.maxStepNum - Default is 3.
   * @param {Vector3} params.gravity - Default is ( 0, - 9.8 * 10, 0 )
   */
		constructor( mesh, rigidBodyParams, constraintParams = [], params = {} ) {

			if ( typeof Ammo === 'undefined' ) {

				throw new Error( 'THREE.MMDPhysics: Import ammo.js https://github.com/kripken/ammo.js' );

			}

			this.manager = new ResourceManager();
			this.mesh = mesh;
			/*
     * I don't know why but 1/60 unitStep easily breaks models
     * so I set it 1/65 so far.
     * Don't set too small unitStep because
     * the smaller unitStep can make the performance worse.
     */

			this.unitStep = params.unitStep !== undefined ? params.unitStep : 1 / 65;
			this.maxStepNum = params.maxStepNum !== undefined ? params.maxStepNum : 3;
			this.gravity = new THREE.Vector3( 0, - 9.8 * 10, 0 );
			if ( params.gravity !== undefined ) this.gravity.copy( params.gravity );
			this.world = params.world !== undefined ? params.world : null; // experimental

			this.bodies = [];
			this.constraints = [];

			this._init( mesh, rigidBodyParams, constraintParams );

		}
		/**
   * Advances Physics calculation and updates bones.
   *
   * @param {Number} delta - time in second
   * @return {MMDPhysics}
   */


		update( delta ) {

			const manager = this.manager;
			const mesh = this.mesh; // rigid bodies and constrains are for
			// mesh's world scale (1, 1, 1).
			// Convert to (1, 1, 1) if it isn't.

			let isNonDefaultScale = false;
			const position = manager.allocThreeVector3();
			const quaternion = manager.allocThreeQuaternion();
			const scale = manager.allocThreeVector3();
			mesh.matrixWorld.decompose( position, quaternion, scale );

			if ( scale.x !== 1 || scale.y !== 1 || scale.z !== 1 ) {

				isNonDefaultScale = true;

			}

			let parent;

			if ( isNonDefaultScale ) {

				parent = mesh.parent;
				if ( parent !== null ) mesh.parent = null;
				scale.copy( this.mesh.scale );
				mesh.scale.set( 1, 1, 1 );
				mesh.updateMatrixWorld( true );

			} // calculate physics and update bones


			this._updateRigidBodies();

			this._stepSimulation( delta );

			this._updateBones(); // restore mesh if converted above


			if ( isNonDefaultScale ) {

				if ( parent !== null ) mesh.parent = parent;
				mesh.scale.copy( scale );

			}

			manager.freeThreeVector3( scale );
			manager.freeThreeQuaternion( quaternion );
			manager.freeThreeVector3( position );
			return this;

		}
		/**
   * Resets rigid bodies transorm to current bone's.
   *
   * @return {MMDPhysics}
   */


		reset() {

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

				this.bodies[ i ].reset();

			}

			return this;

		}
		/**
   * Warm ups Rigid bodies. Calculates cycles steps.
   *
   * @param {Integer} cycles
   * @return {MMDPhysics}
   */


		warmup( cycles ) {

			for ( let i = 0; i < cycles; i ++ ) {

				this.update( 1 / 60 );

			}

			return this;

		}
		/**
   * Sets gravity.
   *
   * @param {Vector3} gravity
   * @return {MMDPhysicsHelper}
   */


		setGravity( gravity ) {

			this.world.setGravity( new Ammo.btVector3( gravity.x, gravity.y, gravity.z ) );
			this.gravity.copy( gravity );
			return this;

		}
		/**
   * Creates MMDPhysicsHelper
   *
   * @return {MMDPhysicsHelper}
   */


		createHelper() {

			return new MMDPhysicsHelper( this.mesh, this );

		} // private methods


		_init( mesh, rigidBodyParams, constraintParams ) {

			const manager = this.manager; // rigid body/constraint parameters are for
			// mesh's default world transform as position(0, 0, 0),
			// quaternion(0, 0, 0, 1) and scale(0, 0, 0)

			let parent = mesh.parent;
			if ( parent !== null ) parent = null;
			const currentPosition = manager.allocThreeVector3();
			const currentQuaternion = manager.allocThreeQuaternion();
			const currentScale = manager.allocThreeVector3();
			currentPosition.copy( mesh.position );
			currentQuaternion.copy( mesh.quaternion );
			currentScale.copy( mesh.scale );
			mesh.position.set( 0, 0, 0 );
			mesh.quaternion.set( 0, 0, 0, 1 );
			mesh.scale.set( 1, 1, 1 );
			mesh.updateMatrixWorld( true );

			if ( this.world === null ) {

				this.world = this._createWorld();
				this.setGravity( this.gravity );

			}

			this._initRigidBodies( rigidBodyParams );

			this._initConstraints( constraintParams );

			if ( parent !== null ) mesh.parent = parent;
			mesh.position.copy( currentPosition );
			mesh.quaternion.copy( currentQuaternion );
			mesh.scale.copy( currentScale );
			mesh.updateMatrixWorld( true );
			this.reset();
			manager.freeThreeVector3( currentPosition );
			manager.freeThreeQuaternion( currentQuaternion );
			manager.freeThreeVector3( currentScale );

		}

		_createWorld() {

			const config = new Ammo.btDefaultCollisionConfiguration();
			const dispatcher = new Ammo.btCollisionDispatcher( config );
			const cache = new Ammo.btDbvtBroadphase();
			const solver = new Ammo.btSequentialImpulseConstraintSolver();
			const world = new Ammo.btDiscreteDynamicsWorld( dispatcher, cache, solver, config );
			return world;

		}

		_initRigidBodies( rigidBodies ) {

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

				this.bodies.push( new RigidBody( this.mesh, this.world, rigidBodies[ i ], this.manager ) );

			}

		}

		_initConstraints( constraints ) {

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

				const params = constraints[ i ];
				const bodyA = this.bodies[ params.rigidBodyIndex1 ];
				const bodyB = this.bodies[ params.rigidBodyIndex2 ];
				this.constraints.push( new Constraint( this.mesh, this.world, bodyA, bodyB, params, this.manager ) );

			}

		}

		_stepSimulation( delta ) {

			const unitStep = this.unitStep;
			let stepTime = delta;
			let maxStepNum = ( delta / unitStep | 0 ) + 1;

			if ( stepTime < unitStep ) {

				stepTime = unitStep;
				maxStepNum = 1;

			}

			if ( maxStepNum > this.maxStepNum ) {

				maxStepNum = this.maxStepNum;

			}

			this.world.stepSimulation( stepTime, maxStepNum, unitStep );

		}

		_updateRigidBodies() {

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

				this.bodies[ i ].updateFromBone();

			}

		}

		_updateBones() {

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

				this.bodies[ i ].updateBone();

			}

		}

	}
	/**
 * This manager's responsibilies are
 *
 * 1. manage Ammo.js and Three.js object resources and
 *    improve the performance and the memory consumption by
 *    reusing objects.
 *
 * 2. provide simple Ammo object operations.
 */


	class ResourceManager {

		constructor() {

			// for Three.js
			this.threeVector3s = [];
			this.threeMatrix4s = [];
			this.threeQuaternions = [];
			this.threeEulers = []; // for Ammo.js

			this.transforms = [];
			this.quaternions = [];
			this.vector3s = [];

		}

		allocThreeVector3() {

			return this.threeVector3s.length > 0 ? this.threeVector3s.pop() : new THREE.Vector3();

		}

		freeThreeVector3( v ) {

			this.threeVector3s.push( v );

		}

		allocThreeMatrix4() {

			return this.threeMatrix4s.length > 0 ? this.threeMatrix4s.pop() : new THREE.Matrix4();

		}

		freeThreeMatrix4( m ) {

			this.threeMatrix4s.push( m );

		}

		allocThreeQuaternion() {

			return this.threeQuaternions.length > 0 ? this.threeQuaternions.pop() : new THREE.Quaternion();

		}

		freeThreeQuaternion( q ) {

			this.threeQuaternions.push( q );

		}

		allocThreeEuler() {

			return this.threeEulers.length > 0 ? this.threeEulers.pop() : new THREE.Euler();

		}

		freeThreeEuler( e ) {

			this.threeEulers.push( e );

		}

		allocTransform() {

			return this.transforms.length > 0 ? this.transforms.pop() : new Ammo.btTransform();

		}

		freeTransform( t ) {

			this.transforms.push( t );

		}

		allocQuaternion() {

			return this.quaternions.length > 0 ? this.quaternions.pop() : new Ammo.btQuaternion();

		}

		freeQuaternion( q ) {

			this.quaternions.push( q );

		}

		allocVector3() {

			return this.vector3s.length > 0 ? this.vector3s.pop() : new Ammo.btVector3();

		}

		freeVector3( v ) {

			this.vector3s.push( v );

		}

		setIdentity( t ) {

			t.setIdentity();

		}

		getBasis( t ) {

			var q = this.allocQuaternion();
			t.getBasis().getRotation( q );
			return q;

		}

		getBasisAsMatrix3( t ) {

			var q = this.getBasis( t );
			var m = this.quaternionToMatrix3( q );
			this.freeQuaternion( q );
			return m;

		}

		getOrigin( t ) {

			return t.getOrigin();

		}

		setOrigin( t, v ) {

			t.getOrigin().setValue( v.x(), v.y(), v.z() );

		}

		copyOrigin( t1, t2 ) {

			var o = t2.getOrigin();
			this.setOrigin( t1, o );

		}

		setBasis( t, q ) {

			t.setRotation( q );

		}

		setBasisFromMatrix3( t, m ) {

			var q = this.matrix3ToQuaternion( m );
			this.setBasis( t, q );
			this.freeQuaternion( q );

		}

		setOriginFromArray3( t, a ) {

			t.getOrigin().setValue( a[ 0 ], a[ 1 ], a[ 2 ] );

		}

		setOriginFromThreeVector3( t, v ) {

			t.getOrigin().setValue( v.x, v.y, v.z );

		}

		setBasisFromArray3( t, a ) {

			var thQ = this.allocThreeQuaternion();
			var thE = this.allocThreeEuler();
			thE.set( a[ 0 ], a[ 1 ], a[ 2 ] );
			this.setBasisFromThreeQuaternion( t, thQ.setFromEuler( thE ) );
			this.freeThreeEuler( thE );
			this.freeThreeQuaternion( thQ );

		}

		setBasisFromThreeQuaternion( t, a ) {

			var q = this.allocQuaternion();
			q.setX( a.x );
			q.setY( a.y );
			q.setZ( a.z );
			q.setW( a.w );
			this.setBasis( t, q );
			this.freeQuaternion( q );

		}

		multiplyTransforms( t1, t2 ) {

			var t = this.allocTransform();
			this.setIdentity( t );
			var m1 = this.getBasisAsMatrix3( t1 );
			var m2 = this.getBasisAsMatrix3( t2 );
			var o1 = this.getOrigin( t1 );
			var o2 = this.getOrigin( t2 );
			var v1 = this.multiplyMatrix3ByVector3( m1, o2 );
			var v2 = this.addVector3( v1, o1 );
			this.setOrigin( t, v2 );
			var m3 = this.multiplyMatrices3( m1, m2 );
			this.setBasisFromMatrix3( t, m3 );
			this.freeVector3( v1 );
			this.freeVector3( v2 );
			return t;

		}

		inverseTransform( t ) {

			var t2 = this.allocTransform();
			var m1 = this.getBasisAsMatrix3( t );
			var o = this.getOrigin( t );
			var m2 = this.transposeMatrix3( m1 );
			var v1 = this.negativeVector3( o );
			var v2 = this.multiplyMatrix3ByVector3( m2, v1 );
			this.setOrigin( t2, v2 );
			this.setBasisFromMatrix3( t2, m2 );
			this.freeVector3( v1 );
			this.freeVector3( v2 );
			return t2;

		}

		multiplyMatrices3( m1, m2 ) {

			var m3 = [];
			var v10 = this.rowOfMatrix3( m1, 0 );
			var v11 = this.rowOfMatrix3( m1, 1 );
			var v12 = this.rowOfMatrix3( m1, 2 );
			var v20 = this.columnOfMatrix3( m2, 0 );
			var v21 = this.columnOfMatrix3( m2, 1 );
			var v22 = this.columnOfMatrix3( m2, 2 );
			m3[ 0 ] = this.dotVectors3( v10, v20 );
			m3[ 1 ] = this.dotVectors3( v10, v21 );
			m3[ 2 ] = this.dotVectors3( v10, v22 );
			m3[ 3 ] = this.dotVectors3( v11, v20 );
			m3[ 4 ] = this.dotVectors3( v11, v21 );
			m3[ 5 ] = this.dotVectors3( v11, v22 );
			m3[ 6 ] = this.dotVectors3( v12, v20 );
			m3[ 7 ] = this.dotVectors3( v12, v21 );
			m3[ 8 ] = this.dotVectors3( v12, v22 );
			this.freeVector3( v10 );
			this.freeVector3( v11 );
			this.freeVector3( v12 );
			this.freeVector3( v20 );
			this.freeVector3( v21 );
			this.freeVector3( v22 );
			return m3;

		}

		addVector3( v1, v2 ) {

			var v = this.allocVector3();
			v.setValue( v1.x() + v2.x(), v1.y() + v2.y(), v1.z() + v2.z() );
			return v;

		}

		dotVectors3( v1, v2 ) {

			return v1.x() * v2.x() + v1.y() * v2.y() + v1.z() * v2.z();

		}

		rowOfMatrix3( m, i ) {

			var v = this.allocVector3();
			v.setValue( m[ i * 3 + 0 ], m[ i * 3 + 1 ], m[ i * 3 + 2 ] );
			return v;

		}

		columnOfMatrix3( m, i ) {

			var v = this.allocVector3();
			v.setValue( m[ i + 0 ], m[ i + 3 ], m[ i + 6 ] );
			return v;

		}

		negativeVector3( v ) {

			var v2 = this.allocVector3();
			v2.setValue( - v.x(), - v.y(), - v.z() );
			return v2;

		}

		multiplyMatrix3ByVector3( m, v ) {

			var v4 = this.allocVector3();
			var v0 = this.rowOfMatrix3( m, 0 );
			var v1 = this.rowOfMatrix3( m, 1 );
			var v2 = this.rowOfMatrix3( m, 2 );
			var x = this.dotVectors3( v0, v );
			var y = this.dotVectors3( v1, v );
			var z = this.dotVectors3( v2, v );
			v4.setValue( x, y, z );
			this.freeVector3( v0 );
			this.freeVector3( v1 );
			this.freeVector3( v2 );
			return v4;

		}

		transposeMatrix3( m ) {

			var m2 = [];
			m2[ 0 ] = m[ 0 ];
			m2[ 1 ] = m[ 3 ];
			m2[ 2 ] = m[ 6 ];
			m2[ 3 ] = m[ 1 ];
			m2[ 4 ] = m[ 4 ];
			m2[ 5 ] = m[ 7 ];
			m2[ 6 ] = m[ 2 ];
			m2[ 7 ] = m[ 5 ];
			m2[ 8 ] = m[ 8 ];
			return m2;

		}

		quaternionToMatrix3( q ) {

			var m = [];
			var x = q.x();
			var y = q.y();
			var z = q.z();
			var w = q.w();
			var xx = x * x;
			var yy = y * y;
			var zz = z * z;
			var xy = x * y;
			var yz = y * z;
			var zx = z * x;
			var xw = x * w;
			var yw = y * w;
			var zw = z * w;
			m[ 0 ] = 1 - 2 * ( yy + zz );
			m[ 1 ] = 2 * ( xy - zw );
			m[ 2 ] = 2 * ( zx + yw );
			m[ 3 ] = 2 * ( xy + zw );
			m[ 4 ] = 1 - 2 * ( zz + xx );
			m[ 5 ] = 2 * ( yz - xw );
			m[ 6 ] = 2 * ( zx - yw );
			m[ 7 ] = 2 * ( yz + xw );
			m[ 8 ] = 1 - 2 * ( xx + yy );
			return m;

		}

		matrix3ToQuaternion( m ) {

			var t = m[ 0 ] + m[ 4 ] + m[ 8 ];
			var s, x, y, z, w;

			if ( t > 0 ) {

				s = Math.sqrt( t + 1.0 ) * 2;
				w = 0.25 * s;
				x = ( m[ 7 ] - m[ 5 ] ) / s;
				y = ( m[ 2 ] - m[ 6 ] ) / s;
				z = ( m[ 3 ] - m[ 1 ] ) / s;

			} else if ( m[ 0 ] > m[ 4 ] && m[ 0 ] > m[ 8 ] ) {

				s = Math.sqrt( 1.0 + m[ 0 ] - m[ 4 ] - m[ 8 ] ) * 2;
				w = ( m[ 7 ] - m[ 5 ] ) / s;
				x = 0.25 * s;
				y = ( m[ 1 ] + m[ 3 ] ) / s;
				z = ( m[ 2 ] + m[ 6 ] ) / s;

			} else if ( m[ 4 ] > m[ 8 ] ) {

				s = Math.sqrt( 1.0 + m[ 4 ] - m[ 0 ] - m[ 8 ] ) * 2;
				w = ( m[ 2 ] - m[ 6 ] ) / s;
				x = ( m[ 1 ] + m[ 3 ] ) / s;
				y = 0.25 * s;
				z = ( m[ 5 ] + m[ 7 ] ) / s;

			} else {

				s = Math.sqrt( 1.0 + m[ 8 ] - m[ 0 ] - m[ 4 ] ) * 2;
				w = ( m[ 3 ] - m[ 1 ] ) / s;
				x = ( m[ 2 ] + m[ 6 ] ) / s;
				y = ( m[ 5 ] + m[ 7 ] ) / s;
				z = 0.25 * s;

			}

			var q = this.allocQuaternion();
			q.setX( x );
			q.setY( y );
			q.setZ( z );
			q.setW( w );
			return q;

		}

	}
	/**
 * @param {THREE.SkinnedMesh} mesh
 * @param {Ammo.btDiscreteDynamicsWorld} world
 * @param {Object} params
 * @param {ResourceManager} manager
 */


	class RigidBody {

		constructor( mesh, world, params, manager ) {

			this.mesh = mesh;
			this.world = world;
			this.params = params;
			this.manager = manager;
			this.body = null;
			this.bone = null;
			this.boneOffsetForm = null;
			this.boneOffsetFormInverse = null;

			this._init();

		}
		/**
   * Resets rigid body transform to the current bone's.
   *
   * @return {RigidBody}
   */


		reset() {

			this._setTransformFromBone();

			return this;

		}
		/**
   * Updates rigid body's transform from the current bone.
   *
   * @return {RidigBody}
   */


		updateFromBone() {

			if ( this.params.boneIndex !== - 1 && this.params.type === 0 ) {

				this._setTransformFromBone();

			}

			return this;

		}
		/**
   * Updates bone from the current ridid body's transform.
   *
   * @return {RidigBody}
   */


		updateBone() {

			if ( this.params.type === 0 || this.params.boneIndex === - 1 ) {

				return this;

			}

			this._updateBoneRotation();

			if ( this.params.type === 1 ) {

				this._updateBonePosition();

			}

			this.bone.updateMatrixWorld( true );

			if ( this.params.type === 2 ) {

				this._setPositionFromBone();

			}

			return this;

		} // private methods


		_init() {

			function generateShape( p ) {

				switch ( p.shapeType ) {

					case 0:
						return new Ammo.btSphereShape( p.width );

					case 1:
						return new Ammo.btBoxShape( new Ammo.btVector3( p.width, p.height, p.depth ) );

					case 2:
						return new Ammo.btCapsuleShape( p.width, p.height );

					default:
						throw 'unknown shape type ' + p.shapeType;

				}

			}

			const manager = this.manager;
			const params = this.params;
			const bones = this.mesh.skeleton.bones;
			const bone = params.boneIndex === - 1 ? new THREE.Bone() : bones[ params.boneIndex ];
			const shape = generateShape( params );
			const weight = params.type === 0 ? 0 : params.weight;
			const localInertia = manager.allocVector3();
			localInertia.setValue( 0, 0, 0 );

			if ( weight !== 0 ) {

				shape.calculateLocalInertia( weight, localInertia );

			}

			const boneOffsetForm = manager.allocTransform();
			manager.setIdentity( boneOffsetForm );
			manager.setOriginFromArray3( boneOffsetForm, params.position );
			manager.setBasisFromArray3( boneOffsetForm, params.rotation );
			const vector = manager.allocThreeVector3();
			const boneForm = manager.allocTransform();
			manager.setIdentity( boneForm );
			manager.setOriginFromThreeVector3( boneForm, bone.getWorldPosition( vector ) );
			const form = manager.multiplyTransforms( boneForm, boneOffsetForm );
			const state = new Ammo.btDefaultMotionState( form );
			const info = new Ammo.btRigidBodyConstructionInfo( weight, state, shape, localInertia );
			info.set_m_friction( params.friction );
			info.set_m_restitution( params.restitution );
			const body = new Ammo.btRigidBody( info );

			if ( params.type === 0 ) {

				body.setCollisionFlags( body.getCollisionFlags() | 2 );
				/*
       * It'd be better to comment out this line though in general I should call this method
       * because I'm not sure why but physics will be more like MMD's
       * if I comment out.
       */

				body.setActivationState( 4 );

			}

			body.setDamping( params.positionDamping, params.rotationDamping );
			body.setSleepingThresholds( 0, 0 );
			this.world.addRigidBody( body, 1 << params.groupIndex, params.groupTarget );
			this.body = body;
			this.bone = bone;
			this.boneOffsetForm = boneOffsetForm;
			this.boneOffsetFormInverse = manager.inverseTransform( boneOffsetForm );
			manager.freeVector3( localInertia );
			manager.freeTransform( form );
			manager.freeTransform( boneForm );
			manager.freeThreeVector3( vector );

		}

		_getBoneTransform() {

			const manager = this.manager;
			const p = manager.allocThreeVector3();
			const q = manager.allocThreeQuaternion();
			const s = manager.allocThreeVector3();
			this.bone.matrixWorld.decompose( p, q, s );
			const tr = manager.allocTransform();
			manager.setOriginFromThreeVector3( tr, p );
			manager.setBasisFromThreeQuaternion( tr, q );
			const form = manager.multiplyTransforms( tr, this.boneOffsetForm );
			manager.freeTransform( tr );
			manager.freeThreeVector3( s );
			manager.freeThreeQuaternion( q );
			manager.freeThreeVector3( p );
			return form;

		}

		_getWorldTransformForBone() {

			const manager = this.manager;
			const tr = this.body.getCenterOfMassTransform();
			return manager.multiplyTransforms( tr, this.boneOffsetFormInverse );

		}

		_setTransformFromBone() {

			const manager = this.manager;

			const form = this._getBoneTransform(); // TODO: check the most appropriate way to set
			//this.body.setWorldTransform( form );


			this.body.setCenterOfMassTransform( form );
			this.body.getMotionState().setWorldTransform( form );
			manager.freeTransform( form );

		}

		_setPositionFromBone() {

			const manager = this.manager;

			const form = this._getBoneTransform();

			const tr = manager.allocTransform();
			this.body.getMotionState().getWorldTransform( tr );
			manager.copyOrigin( tr, form ); // TODO: check the most appropriate way to set
			//this.body.setWorldTransform( tr );

			this.body.setCenterOfMassTransform( tr );
			this.body.getMotionState().setWorldTransform( tr );
			manager.freeTransform( tr );
			manager.freeTransform( form );

		}

		_updateBoneRotation() {

			const manager = this.manager;

			const tr = this._getWorldTransformForBone();

			const q = manager.getBasis( tr );
			const thQ = manager.allocThreeQuaternion();
			const thQ2 = manager.allocThreeQuaternion();
			const thQ3 = manager.allocThreeQuaternion();
			thQ.set( q.x(), q.y(), q.z(), q.w() );
			thQ2.setFromRotationMatrix( this.bone.matrixWorld );
			thQ2.conjugate();
			thQ2.multiply( thQ ); //this.bone.quaternion.multiply( thQ2 );

			thQ3.setFromRotationMatrix( this.bone.matrix ); // Renormalizing quaternion here because repeatedly transforming
			// quaternion continuously accumulates floating point error and
			// can end up being overflow. See #15335

			this.bone.quaternion.copy( thQ2.multiply( thQ3 ).normalize() );
			manager.freeThreeQuaternion( thQ );
			manager.freeThreeQuaternion( thQ2 );
			manager.freeThreeQuaternion( thQ3 );
			manager.freeQuaternion( q );
			manager.freeTransform( tr );

		}

		_updateBonePosition() {

			const manager = this.manager;

			const tr = this._getWorldTransformForBone();

			const thV = manager.allocThreeVector3();
			const o = manager.getOrigin( tr );
			thV.set( o.x(), o.y(), o.z() );

			if ( this.bone.parent ) {

				this.bone.parent.worldToLocal( thV );

			}

			this.bone.position.copy( thV );
			manager.freeThreeVector3( thV );
			manager.freeTransform( tr );

		}

	} //


	class Constraint {

		/**
   * @param {THREE.SkinnedMesh} mesh
   * @param {Ammo.btDiscreteDynamicsWorld} world
   * @param {RigidBody} bodyA
   * @param {RigidBody} bodyB
   * @param {Object} params
   * @param {ResourceManager} manager
   */
		constructor( mesh, world, bodyA, bodyB, params, manager ) {

			this.mesh = mesh;
			this.world = world;
			this.bodyA = bodyA;
			this.bodyB = bodyB;
			this.params = params;
			this.manager = manager;
			this.constraint = null;

			this._init();

		} // private method


		_init() {

			const manager = this.manager;
			const params = this.params;
			const bodyA = this.bodyA;
			const bodyB = this.bodyB;
			const form = manager.allocTransform();
			manager.setIdentity( form );
			manager.setOriginFromArray3( form, params.position );
			manager.setBasisFromArray3( form, params.rotation );
			const formA = manager.allocTransform();
			const formB = manager.allocTransform();
			bodyA.body.getMotionState().getWorldTransform( formA );
			bodyB.body.getMotionState().getWorldTransform( formB );
			const formInverseA = manager.inverseTransform( formA );
			const formInverseB = manager.inverseTransform( formB );
			const formA2 = manager.multiplyTransforms( formInverseA, form );
			const formB2 = manager.multiplyTransforms( formInverseB, form );
			const constraint = new Ammo.btGeneric6DofSpringConstraint( bodyA.body, bodyB.body, formA2, formB2, true );
			const lll = manager.allocVector3();
			const lul = manager.allocVector3();
			const all = manager.allocVector3();
			const aul = manager.allocVector3();
			lll.setValue( params.translationLimitation1[ 0 ], params.translationLimitation1[ 1 ], params.translationLimitation1[ 2 ] );
			lul.setValue( params.translationLimitation2[ 0 ], params.translationLimitation2[ 1 ], params.translationLimitation2[ 2 ] );
			all.setValue( params.rotationLimitation1[ 0 ], params.rotationLimitation1[ 1 ], params.rotationLimitation1[ 2 ] );
			aul.setValue( params.rotationLimitation2[ 0 ], params.rotationLimitation2[ 1 ], params.rotationLimitation2[ 2 ] );
			constraint.setLinearLowerLimit( lll );
			constraint.setLinearUpperLimit( lul );
			constraint.setAngularLowerLimit( all );
			constraint.setAngularUpperLimit( aul );

			for ( let i = 0; i < 3; i ++ ) {

				if ( params.springPosition[ i ] !== 0 ) {

					constraint.enableSpring( i, true );
					constraint.setStiffness( i, params.springPosition[ i ] );

				}

			}

			for ( let i = 0; i < 3; i ++ ) {

				if ( params.springRotation[ i ] !== 0 ) {

					constraint.enableSpring( i + 3, true );
					constraint.setStiffness( i + 3, params.springRotation[ i ] );

				}

			}
			/*
     * Currently(10/31/2016) official ammo.js doesn't support
     * btGeneric6DofSpringConstraint.setParam method.
     * You need custom ammo.js (add the method into idl) if you wanna use.
     * By setting this parameter, physics will be more like MMD's
     */


			if ( constraint.setParam !== undefined ) {

				for ( let i = 0; i < 6; i ++ ) {

					// this parameter is from http://www20.atpages.jp/katwat/three.js_r58/examples/mytest37/mmd.three.js
					constraint.setParam( 2, 0.475, i );

				}

			}

			this.world.addConstraint( constraint, true );
			this.constraint = constraint;
			manager.freeTransform( form );
			manager.freeTransform( formA );
			manager.freeTransform( formB );
			manager.freeTransform( formInverseA );
			manager.freeTransform( formInverseB );
			manager.freeTransform( formA2 );
			manager.freeTransform( formB2 );
			manager.freeVector3( lll );
			manager.freeVector3( lul );
			manager.freeVector3( all );
			manager.freeVector3( aul );

		}

	} //


	const _position = new THREE.Vector3();

	const _quaternion = new THREE.Quaternion();

	const _scale = new THREE.Vector3();

	const _matrixWorldInv = new THREE.Matrix4();

	class MMDPhysicsHelper extends THREE.Object3D {

		/**
   * Visualize Rigid bodies
   *
   * @param {THREE.SkinnedMesh} mesh
   * @param {Physics} physics
   */
		constructor( mesh, physics ) {

			super();
			this.root = mesh;
			this.physics = physics;
			this.matrix.copy( mesh.matrixWorld );
			this.matrixAutoUpdate = false;
			this.materials = [];
			this.materials.push( new THREE.MeshBasicMaterial( {
				color: new THREE.Color( 0xff8888 ),
				wireframe: true,
				depthTest: false,
				depthWrite: false,
				opacity: 0.25,
				transparent: true
			} ) );
			this.materials.push( new THREE.MeshBasicMaterial( {
				color: new THREE.Color( 0x88ff88 ),
				wireframe: true,
				depthTest: false,
				depthWrite: false,
				opacity: 0.25,
				transparent: true
			} ) );
			this.materials.push( new THREE.MeshBasicMaterial( {
				color: new THREE.Color( 0x8888ff ),
				wireframe: true,
				depthTest: false,
				depthWrite: false,
				opacity: 0.25,
				transparent: true
			} ) );

			this._init();

		}
		/**
   * Updates Rigid Bodies visualization.
   */


		updateMatrixWorld( force ) {

			var mesh = this.root;

			if ( this.visible ) {

				var bodies = this.physics.bodies;

				_matrixWorldInv.copy( mesh.matrixWorld ).decompose( _position, _quaternion, _scale ).compose( _position, _quaternion, _scale.set( 1, 1, 1 ) ).invert();

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

					var body = bodies[ i ].body;
					var child = this.children[ i ];
					var tr = body.getCenterOfMassTransform();
					var origin = tr.getOrigin();
					var rotation = tr.getRotation();
					child.position.set( origin.x(), origin.y(), origin.z() ).applyMatrix4( _matrixWorldInv );
					child.quaternion.setFromRotationMatrix( _matrixWorldInv ).multiply( _quaternion.set( rotation.x(), rotation.y(), rotation.z(), rotation.w() ) );

				}

			}

			this.matrix.copy( mesh.matrixWorld ).decompose( _position, _quaternion, _scale ).compose( _position, _quaternion, _scale.set( 1, 1, 1 ) );
			super.updateMatrixWorld( force );

		} // private method


		_init() {

			var bodies = this.physics.bodies;

			function createGeometry( param ) {

				switch ( param.shapeType ) {

					case 0:
						return new THREE.SphereGeometry( param.width, 16, 8 );

					case 1:
						return new THREE.BoxGeometry( param.width * 2, param.height * 2, param.depth * 2, 8, 8, 8 );

					case 2:
						return new createCapsuleGeometry( param.width, param.height, 16, 8 );

					default:
						return null;

				}

			}

			function createCapsuleGeometry( radius, cylinderHeight, segmentsRadius, segmentsHeight ) {

				var geometry = new THREE.CylinderGeometry( radius, radius, cylinderHeight, segmentsRadius, segmentsHeight, true );
				var upperSphere = new THREE.Mesh( new THREE.SphereGeometry( radius, segmentsRadius, segmentsHeight, 0, Math.PI * 2, 0, Math.PI / 2 ) );
				var lowerSphere = new THREE.Mesh( new THREE.SphereGeometry( radius, segmentsRadius, segmentsHeight, 0, Math.PI * 2, Math.PI / 2, Math.PI / 2 ) );
				upperSphere.position.set( 0, cylinderHeight / 2, 0 );
				lowerSphere.position.set( 0, - cylinderHeight / 2, 0 );
				upperSphere.updateMatrix();
				lowerSphere.updateMatrix();
				geometry.merge( upperSphere.geometry, upperSphere.matrix );
				geometry.merge( lowerSphere.geometry, lowerSphere.matrix );
				return geometry;

			}

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

				var param = bodies[ i ].params;
				this.add( new THREE.Mesh( createGeometry( param ), this.materials[ param.type ] ) );

			}

		}

	}

	THREE.MMDPhysics = MMDPhysics;

} )();