text: import { MathUtils } from './MathUtils.js';
  
  class Quaternion {
  
  	constructor( x = 0, y = 0, z = 0, w = 1 ) {
  
  		Object.defineProperty( this, 'isQuaternion', { value: true } );
  
  		this._x = x;
  		this._y = y;
  		this._z = z;
  		this._w = w;
  
  	}
  
  	static slerp( qa, qb, qm, t ) {
  
  		return qm.copy( qa ).slerp( qb, t );
  
  	}
  
  	static slerpFlat( dst, dstOffset, src0, srcOffset0, src1, srcOffset1, t ) {
  
  		// fuzz-free, array-based Quaternion SLERP operation
  
  		let x0 = src0[ srcOffset0 + 0 ],
  			y0 = src0[ srcOffset0 + 1 ],
  			z0 = src0[ srcOffset0 + 2 ],
  			w0 = src0[ srcOffset0 + 3 ];
  
  		const x1 = src1[ srcOffset1 + 0 ],
  			y1 = src1[ srcOffset1 + 1 ],
  			z1 = src1[ srcOffset1 + 2 ],
  			w1 = src1[ srcOffset1 + 3 ];
  
  		if ( w0 !== w1 || x0 !== x1 || y0 !== y1 || z0 !== z1 ) {
  
  			let s = 1 - t;
  			const cos = x0 * x1 + y0 * y1 + z0 * z1 + w0 * w1,
  				dir = ( cos >= 0 ? 1 : - 1 ),
  				sqrSin = 1 - cos * cos;
  
  			// Skip the Slerp for tiny steps to avoid numeric problems:
  			if ( sqrSin > Number.EPSILON ) {
  
  				const sin = Math.sqrt( sqrSin ),
  					len = Math.atan2( sin, cos * dir );
  
  				s = Math.sin( s * len ) / sin;
  				t = Math.sin( t * len ) / sin;
  
  			}
  
  			const tDir = t * dir;
  
  			x0 = x0 * s + x1 * tDir;
  			y0 = y0 * s + y1 * tDir;
  			z0 = z0 * s + z1 * tDir;
  			w0 = w0 * s + w1 * tDir;
  
  			// Normalize in case we just did a lerp:
  			if ( s === 1 - t ) {
  
  				const f = 1 / Math.sqrt( x0 * x0 + y0 * y0 + z0 * z0 + w0 * w0 );
  
  				x0 *= f;
  				y0 *= f;
  				z0 *= f;
  				w0 *= f;
  
  			}
  
  		}
  
  		dst[ dstOffset ] = x0;
  		dst[ dstOffset + 1 ] = y0;
  		dst[ dstOffset + 2 ] = z0;
  		dst[ dstOffset + 3 ] = w0;
  
  	}
  
  	static multiplyQuaternionsFlat( dst, dstOffset, src0, srcOffset0, src1, srcOffset1 ) {
  
  		const x0 = src0[ srcOffset0 ];
  		const y0 = src0[ srcOffset0 + 1 ];
  		const z0 = src0[ srcOffset0 + 2 ];
  		const w0 = src0[ srcOffset0 + 3 ];
  
  		const x1 = src1[ srcOffset1 ];
  		const y1 = src1[ srcOffset1 + 1 ];
  		const z1 = src1[ srcOffset1 + 2 ];
  		const w1 = src1[ srcOffset1 + 3 ];
  
  		dst[ dstOffset ] = x0 * w1 + w0 * x1 + y0 * z1 - z0 * y1;
  		dst[ dstOffset + 1 ] = y0 * w1 + w0 * y1 + z0 * x1 - x0 * z1;
  		dst[ dstOffset + 2 ] = z0 * w1 + w0 * z1 + x0 * y1 - y0 * x1;
  		dst[ dstOffset + 3 ] = w0 * w1 - x0 * x1 - y0 * y1 - z0 * z1;
  
  		return dst;
  
  	}
  
  	get x() {
  
  		return this._x;
  
  	}
  
  	set x( value ) {
  
  		this._x = value;
  		this._onChangeCallback();
  
  	}
  
  	get y() {
  
  		return this._y;
  
  	}
  
  	set y( value ) {
  
  		this._y = value;
  		this._onChangeCallback();
  
  	}
  
  	get z() {
  
  		return this._z;
  
  	}
  
  	set z( value ) {
  
  		this._z = value;
  		this._onChangeCallback();
  
  	}
  
  	get w() {
  
  		return this._w;
  
  	}
  
  	set w( value ) {
  
  		this._w = value;
  		this._onChangeCallback();
  
  	}
  
  	set( x, y, z, w ) {
  
  		this._x = x;
  		this._y = y;
  		this._z = z;
  		this._w = w;
  
  		this._onChangeCallback();
  
  		return this;
  
  	}
  
  	clone() {
  
  		return new this.constructor( this._x, this._y, this._z, this._w );
  
  	}
  
  	copy( quaternion ) {
  
  		this._x = quaternion.x;
  		this._y = quaternion.y;
  		this._z = quaternion.z;
  		this._w = quaternion.w;
  
  		this._onChangeCallback();
  
  		return this;
  
  	}
  
  	setFromEuler( euler, update ) {
  
  		if ( ! ( euler && euler.isEuler ) ) {
  
  			throw new Error( 'THREE.Quaternion: .setFromEuler() now expects an Euler rotation rather than a Vector3 and order.' );
  
  		}
  
  		const x = euler._x, y = euler._y, z = euler._z, order = euler._order;
  
  		// http://www.mathworks.com/matlabcentral/fileexchange/
  		// 	20696-function-to-convert-between-dcm-euler-angles-quaternions-and-euler-vectors/
  		//	content/SpinCalc.m
  
  		const cos = Math.cos;
  		const sin = Math.sin;
  
  		const c1 = cos( x / 2 );
  		const c2 = cos( y / 2 );
  		const c3 = cos( z / 2 );
  
  		const s1 = sin( x / 2 );
  		const s2 = sin( y / 2 );
  		const s3 = sin( z / 2 );
  
  		switch ( order ) {
  
  			case 'XYZ':
  				this._x = s1 * c2 * c3 + c1 * s2 * s3;
  				this._y = c1 * s2 * c3 - s1 * c2 * s3;
  				this._z = c1 * c2 * s3 + s1 * s2 * c3;
  				this._w = c1 * c2 * c3 - s1 * s2 * s3;
  				break;
  
  			case 'YXZ':
  				this._x = s1 * c2 * c3 + c1 * s2 * s3;
  				this._y = c1 * s2 * c3 - s1 * c2 * s3;
  				this._z = c1 * c2 * s3 - s1 * s2 * c3;
  				this._w = c1 * c2 * c3 + s1 * s2 * s3;
  				break;
  
  			case 'ZXY':
  				this._x = s1 * c2 * c3 - c1 * s2 * s3;
  				this._y = c1 * s2 * c3 + s1 * c2 * s3;
  				this._z = c1 * c2 * s3 + s1 * s2 * c3;
  				this._w = c1 * c2 * c3 - s1 * s2 * s3;
  				break;
  
  			case 'ZYX':
  				this._x = s1 * c2 * c3 - c1 * s2 * s3;
  				this._y = c1 * s2 * c3 + s1 * c2 * s3;
  				this._z = c1 * c2 * s3 - s1 * s2 * c3;
  				this._w = c1 * c2 * c3 + s1 * s2 * s3;
  				break;
  
  			case 'YZX':
  				this._x = s1 * c2 * c3 + c1 * s2 * s3;
  				this._y = c1 * s2 * c3 + s1 * c2 * s3;
  				this._z = c1 * c2 * s3 - s1 * s2 * c3;
  				this._w = c1 * c2 * c3 - s1 * s2 * s3;
  				break;
  
  			case 'XZY':
  				this._x = s1 * c2 * c3 - c1 * s2 * s3;
  				this._y = c1 * s2 * c3 - s1 * c2 * s3;
  				this._z = c1 * c2 * s3 + s1 * s2 * c3;
  				this._w = c1 * c2 * c3 + s1 * s2 * s3;
  				break;
  
  			default:
  				console.warn( 'THREE.Quaternion: .setFromEuler() encountered an unknown order: ' + order );
  
  		}
  
  		if ( update !== false ) this._onChangeCallback();
  
  		return this;
  
  	}
  
  	setFromAxisAngle( axis, angle ) {
  
  		// http://www.euclideanspace.com/maths/geometry/rotations/conversions/angleToQuaternion/index.htm
  
  		// assumes axis is normalized
  
  		const halfAngle = angle / 2, s = Math.sin( halfAngle );
  
  		this._x = axis.x * s;
  		this._y = axis.y * s;
  		this._z = axis.z * s;
  		this._w = Math.cos( halfAngle );
  
  		this._onChangeCallback();
  
  		return this;
  
  	}
  
  	setFromRotationMatrix( m ) {
  
  		// http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToQuaternion/index.htm
  
  		// assumes the upper 3x3 of m is a pure rotation matrix (i.e, unscaled)
  
  		const te = m.elements,
  
  			m11 = te[ 0 ], m12 = te[ 4 ], m13 = te[ 8 ],
  			m21 = te[ 1 ], m22 = te[ 5 ], m23 = te[ 9 ],
  			m31 = te[ 2 ], m32 = te[ 6 ], m33 = te[ 10 ],
  
  			trace = m11 + m22 + m33;
  
  		if ( trace > 0 ) {
  
  			const s = 0.5 / Math.sqrt( trace + 1.0 );
  
  			this._w = 0.25 / s;
  			this._x = ( m32 - m23 ) * s;
  			this._y = ( m13 - m31 ) * s;
  			this._z = ( m21 - m12 ) * s;
  
  		} else if ( m11 > m22 && m11 > m33 ) {
  
  			const s = 2.0 * Math.sqrt( 1.0 + m11 - m22 - m33 );
  
  			this._w = ( m32 - m23 ) / s;
  			this._x = 0.25 * s;
  			this._y = ( m12 + m21 ) / s;
  			this._z = ( m13 + m31 ) / s;
  
  		} else if ( m22 > m33 ) {
  
  			const s = 2.0 * Math.sqrt( 1.0 + m22 - m11 - m33 );
  
  			this._w = ( m13 - m31 ) / s;
  			this._x = ( m12 + m21 ) / s;
  			this._y = 0.25 * s;
  			this._z = ( m23 + m32 ) / s;
  
  		} else {
  
  			const s = 2.0 * Math.sqrt( 1.0 + m33 - m11 - m22 );
  
  			this._w = ( m21 - m12 ) / s;
  			this._x = ( m13 + m31 ) / s;
  			this._y = ( m23 + m32 ) / s;
  			this._z = 0.25 * s;
  
  		}
  
  		this._onChangeCallback();
  
  		return this;
  
  	}
  
  	setFromUnitVectors( vFrom, vTo ) {
  
  		// assumes direction vectors vFrom and vTo are normalized
  
  		const EPS = 0.000001;
  
  		let r = vFrom.dot( vTo ) + 1;
  
  		if ( r < EPS ) {
  
  			r = 0;
  
  			if ( Math.abs( vFrom.x ) > Math.abs( vFrom.z ) ) {
  
  				this._x = - vFrom.y;
  				this._y = vFrom.x;
  				this._z = 0;
  				this._w = r;
  
  			} else {
  
  				this._x = 0;
  				this._y = - vFrom.z;
  				this._z = vFrom.y;
  				this._w = r;
  
  			}
  
  		} else {
  
  			// crossVectors( vFrom, vTo ); // inlined to avoid cyclic dependency on Vector3
  
  			this._x = vFrom.y * vTo.z - vFrom.z * vTo.y;
  			this._y = vFrom.z * vTo.x - vFrom.x * vTo.z;
  			this._z = vFrom.x * vTo.y - vFrom.y * vTo.x;
  			this._w = r;
  
  		}
  
  		return this.normalize();
  
  	}
  
  	angleTo( q ) {
  
  		return 2 * Math.acos( Math.abs( MathUtils.clamp( this.dot( q ), - 1, 1 ) ) );
  
  	}
  
  	rotateTowards( q, step ) {
  
  		const angle = this.angleTo( q );
  
  		if ( angle === 0 ) return this;
  
  		const t = Math.min( 1, step / angle );
  
  		this.slerp( q, t );
  
  		return this;
  
  	}
  
  	identity() {
  
  		return this.set( 0, 0, 0, 1 );
  
  	}
  
  	inverse() {
  
  		// quaternion is assumed to have unit length
  
  		return this.conjugate();
  
  	}
  
  	conjugate() {
  
  		this._x *= - 1;
  		this._y *= - 1;
  		this._z *= - 1;
  
  		this._onChangeCallback();
  
  		return this;
  
  	}
  
  	dot( v ) {
  
  		return this._x * v._x + this._y * v._y + this._z * v._z + this._w * v._w;
  
  	}
  
  	lengthSq() {
  
  		return this._x * this._x + this._y * this._y + this._z * this._z + this._w * this._w;
  
  	}
  
  	length() {
  
  		return Math.sqrt( this._x * this._x + this._y * this._y + this._z * this._z + this._w * this._w );
  
  	}
  
  	normalize() {
  
  		let l = this.length();
  
  		if ( l === 0 ) {
  
  			this._x = 0;
  			this._y = 0;
  			this._z = 0;
  			this._w = 1;
  
  		} else {
  
  			l = 1 / l;
  
  			this._x = this._x * l;
  			this._y = this._y * l;
  			this._z = this._z * l;
  			this._w = this._w * l;
  
  		}
  
  		this._onChangeCallback();
  
  		return this;
  
  	}
  
  	multiply( q, p ) {
  
  		if ( p !== undefined ) {
  
  			console.warn( 'THREE.Quaternion: .multiply() now only accepts one argument. Use .multiplyQuaternions( a, b ) instead.' );
  			return this.multiplyQuaternions( q, p );
  
  		}
  
  		return this.multiplyQuaternions( this, q );
  
  	}
  
  	premultiply( q ) {
  
  		return this.multiplyQuaternions( q, this );
  
  	}
  
  	multiplyQuaternions( a, b ) {
  
  		// from http://www.euclideanspace.com/maths/algebra/realNormedAlgebra/quaternions/code/index.htm
  
  		const qax = a._x, qay = a._y, qaz = a._z, qaw = a._w;
  		const qbx = b._x, qby = b._y, qbz = b._z, qbw = b._w;
  
  		this._x = qax * qbw + qaw * qbx + qay * qbz - qaz * qby;
  		this._y = qay * qbw + qaw * qby + qaz * qbx - qax * qbz;
  		this._z = qaz * qbw + qaw * qbz + qax * qby - qay * qbx;
  		this._w = qaw * qbw - qax * qbx - qay * qby - qaz * qbz;
  
  		this._onChangeCallback();
  
  		return this;
  
  	}
  
  	slerp( qb, t ) {
  
  		if ( t === 0 ) return this;
  		if ( t === 1 ) return this.copy( qb );
  
  		const x = this._x, y = this._y, z = this._z, w = this._w;
  
  		// http://www.euclideanspace.com/maths/algebra/realNormedAlgebra/quaternions/slerp/
  
  		let cosHalfTheta = w * qb._w + x * qb._x + y * qb._y + z * qb._z;
  
  		if ( cosHalfTheta < 0 ) {
  
  			this._w = - qb._w;
  			this._x = - qb._x;
  			this._y = - qb._y;
  			this._z = - qb._z;
  
  			cosHalfTheta = - cosHalfTheta;
  
  		} else {
  
  			this.copy( qb );
  
  		}
  
  		if ( cosHalfTheta >= 1.0 ) {
  
  			this._w = w;
  			this._x = x;
  			this._y = y;
  			this._z = z;
  
  			return this;
  
  		}
  
  		const sqrSinHalfTheta = 1.0 - cosHalfTheta * cosHalfTheta;
  
  		if ( sqrSinHalfTheta <= Number.EPSILON ) {
  
  			const s = 1 - t;
  			this._w = s * w + t * this._w;
  			this._x = s * x + t * this._x;
  			this._y = s * y + t * this._y;
  			this._z = s * z + t * this._z;
  
  			this.normalize();
  			this._onChangeCallback();
  
  			return this;
  
  		}
  
  		const sinHalfTheta = Math.sqrt( sqrSinHalfTheta );
  		const halfTheta = Math.atan2( sinHalfTheta, cosHalfTheta );
  		const ratioA = Math.sin( ( 1 - t ) * halfTheta ) / sinHalfTheta,
  			ratioB = Math.sin( t * halfTheta ) / sinHalfTheta;
  
  		this._w = ( w * ratioA + this._w * ratioB );
  		this._x = ( x * ratioA + this._x * ratioB );
  		this._y = ( y * ratioA + this._y * ratioB );
  		this._z = ( z * ratioA + this._z * ratioB );
  
  		this._onChangeCallback();
  
  		return this;
  
  	}
  
  	equals( quaternion ) {
  
  		return ( quaternion._x === this._x ) && ( quaternion._y === this._y ) && ( quaternion._z === this._z ) && ( quaternion._w === this._w );
  
  	}
  
  	fromArray( array, offset ) {
  
  		if ( offset === undefined ) offset = 0;
  
  		this._x = array[ offset ];
  		this._y = array[ offset + 1 ];
  		this._z = array[ offset + 2 ];
  		this._w = array[ offset + 3 ];
  
  		this._onChangeCallback();
  
  		return this;
  
  	}
  
  	toArray( array, offset ) {
  
  		if ( array === undefined ) array = [];
  		if ( offset === undefined ) offset = 0;
  
  		array[ offset ] = this._x;
  		array[ offset + 1 ] = this._y;
  		array[ offset + 2 ] = this._z;
  		array[ offset + 3 ] = this._w;
  
  		return array;
  
  	}
  
  	fromBufferAttribute( attribute, index ) {
  
  		this._x = attribute.getX( index );
  		this._y = attribute.getY( index );
  		this._z = attribute.getZ( index );
  		this._w = attribute.getW( index );
  
  		return this;
  
  	}
  
  	_onChange( callback ) {
  
  		this._onChangeCallback = callback;
  
  		return this;
  
  	}
  
  	_onChangeCallback() {}
  
  }
  
  
  export { Quaternion };
  