THREE.TrackballControls = function ( object, domElement ) {

	if ( domElement === undefined ) console.warn( 'THREE.TrackballControls: The second parameter "domElement" is now mandatory.' );
	if ( domElement === document ) console.error( 'THREE.TrackballControls: "document" should not be used as the target "domElement". Please use "renderer.domElement" instead.' );

	var scope = this;
	var STATE = { NONE: - 1, ROTATE: 0, ZOOM: 1, PAN: 2, TOUCH_ROTATE: 3, TOUCH_ZOOM_PAN: 4 };

	this.object = object;
	this.domElement = domElement;

	// API

	this.enabled = true;

	this.screen = { left: 0, top: 0, width: 0, height: 0 };

	this.rotateSpeed = 1.0;
	this.zoomSpeed = 1.2;
	this.panSpeed = 0.3;

	this.noRotate = false;
	this.noZoom = false;
	this.noPan = false;

	this.staticMoving = false;
	this.dynamicDampingFactor = 0.2;

	this.minDistance = 0;
	this.maxDistance = Infinity;

	this.keys = [ 'KeyA' /*A*/, 'KeyS' /*S*/, 'KeyD' /*D*/ ];

	this.mouseButtons = { LEFT: THREE.MOUSE.ROTATE, MIDDLE: THREE.MOUSE.DOLLY, RIGHT: THREE.MOUSE.PAN };

	// internals

	this.target = new THREE.Vector3();

	var EPS = 0.000001;

	var lastPosition = new THREE.Vector3();
	var lastZoom = 1;

	var _state = STATE.NONE,
		_keyState = STATE.NONE,

		_eye = new THREE.Vector3(),

		_movePrev = new THREE.Vector2(),
		_moveCurr = new THREE.Vector2(),

		_lastAxis = new THREE.Vector3(),
		_lastAngle = 0,

		_zoomStart = new THREE.Vector2(),
		_zoomEnd = new THREE.Vector2(),

		_touchZoomDistanceStart = 0,
		_touchZoomDistanceEnd = 0,

		_panStart = new THREE.Vector2(),
		_panEnd = new THREE.Vector2();

	// for reset

	this.target0 = this.target.clone();
	this.position0 = this.object.position.clone();
	this.up0 = this.object.up.clone();
	this.zoom0 = this.object.zoom;

	// events

	var changeEvent = { type: 'change' };
	var startEvent = { type: 'start' };
	var endEvent = { type: 'end' };


	// methods

	this.handleResize = function () {

		var box = scope.domElement.getBoundingClientRect();
		// adjustments come from similar code in the jquery offset() function
		var d = scope.domElement.ownerDocument.documentElement;
		scope.screen.left = box.left + window.pageXOffset - d.clientLeft;
		scope.screen.top = box.top + window.pageYOffset - d.clientTop;
		scope.screen.width = box.width;
		scope.screen.height = box.height;

	};

	var getMouseOnScreen = ( function () {

		var vector = new THREE.Vector2();

		return function getMouseOnScreen( pageX, pageY ) {

			vector.set(
				( pageX - scope.screen.left ) / scope.screen.width,
				( pageY - scope.screen.top ) / scope.screen.height
			);

			return vector;

		};

	}() );

	var getMouseOnCircle = ( function () {

		var vector = new THREE.Vector2();

		return function getMouseOnCircle( pageX, pageY ) {

			vector.set(
				( ( pageX - scope.screen.width * 0.5 - scope.screen.left ) / ( scope.screen.width * 0.5 ) ),
				( ( scope.screen.height + 2 * ( scope.screen.top - pageY ) ) / scope.screen.width ) // screen.width intentional
			);

			return vector;

		};

	}() );

	this.rotateCamera = ( function () {

		var axis = new THREE.Vector3(),
			quaternion = new THREE.Quaternion(),
			eyeDirection = new THREE.Vector3(),
			objectUpDirection = new THREE.Vector3(),
			objectSidewaysDirection = new THREE.Vector3(),
			moveDirection = new THREE.Vector3(),
			angle;

		return function rotateCamera() {

			moveDirection.set( _moveCurr.x - _movePrev.x, _moveCurr.y - _movePrev.y, 0 );
			angle = moveDirection.length();

			if ( angle ) {

				_eye.copy( scope.object.position ).sub( scope.target );

				eyeDirection.copy( _eye ).normalize();
				objectUpDirection.copy( scope.object.up ).normalize();
				objectSidewaysDirection.crossVectors( objectUpDirection, eyeDirection ).normalize();

				objectUpDirection.setLength( _moveCurr.y - _movePrev.y );
				objectSidewaysDirection.setLength( _moveCurr.x - _movePrev.x );

				moveDirection.copy( objectUpDirection.add( objectSidewaysDirection ) );

				axis.crossVectors( moveDirection, _eye ).normalize();

				angle *= scope.rotateSpeed;
				quaternion.setFromAxisAngle( axis, angle );

				_eye.applyQuaternion( quaternion );
				scope.object.up.applyQuaternion( quaternion );

				_lastAxis.copy( axis );
				_lastAngle = angle;

			} else if ( ! scope.staticMoving && _lastAngle ) {

				_lastAngle *= Math.sqrt( 1.0 - scope.dynamicDampingFactor );
				_eye.copy( scope.object.position ).sub( scope.target );
				quaternion.setFromAxisAngle( _lastAxis, _lastAngle );
				_eye.applyQuaternion( quaternion );
				scope.object.up.applyQuaternion( quaternion );

			}

			_movePrev.copy( _moveCurr );

		};

	}() );


	this.zoomCamera = function () {

		var factor;

		if ( _state === STATE.TOUCH_ZOOM_PAN ) {

			factor = _touchZoomDistanceStart / _touchZoomDistanceEnd;
			_touchZoomDistanceStart = _touchZoomDistanceEnd;

			if ( scope.object.isPerspectiveCamera ) {

				_eye.multiplyScalar( factor );

			} else if ( scope.object.isOrthographicCamera ) {

				scope.object.zoom *= factor;
				scope.object.updateProjectionMatrix();

			} else {

				console.warn( 'THREE.TrackballControls: Unsupported camera type' );

			}

		} else {

			factor = 1.0 + ( _zoomEnd.y - _zoomStart.y ) * scope.zoomSpeed;

			if ( factor !== 1.0 && factor > 0.0 ) {

				if ( scope.object.isPerspectiveCamera ) {

					_eye.multiplyScalar( factor );

				} else if ( scope.object.isOrthographicCamera ) {

					scope.object.zoom /= factor;
					scope.object.updateProjectionMatrix();

				} else {

					console.warn( 'THREE.TrackballControls: Unsupported camera type' );

				}

			}

			if ( scope.staticMoving ) {

				_zoomStart.copy( _zoomEnd );

			} else {

				_zoomStart.y += ( _zoomEnd.y - _zoomStart.y ) * this.dynamicDampingFactor;

			}

		}

	};

	this.panCamera = ( function () {

		var mouseChange = new THREE.Vector2(),
			objectUp = new THREE.Vector3(),
			pan = new THREE.Vector3();

		return function panCamera() {

			mouseChange.copy( _panEnd ).sub( _panStart );

			if ( mouseChange.lengthSq() ) {

				if ( scope.object.isOrthographicCamera ) {

					var scale_x = ( scope.object.right - scope.object.left ) / scope.object.zoom / scope.domElement.clientWidth;
					var scale_y = ( scope.object.top - scope.object.bottom ) / scope.object.zoom / scope.domElement.clientWidth;

					mouseChange.x *= scale_x;
					mouseChange.y *= scale_y;

				}

				mouseChange.multiplyScalar( _eye.length() * scope.panSpeed );

				pan.copy( _eye ).cross( scope.object.up ).setLength( mouseChange.x );
				pan.add( objectUp.copy( scope.object.up ).setLength( mouseChange.y ) );

				scope.object.position.add( pan );
				scope.target.add( pan );

				if ( scope.staticMoving ) {

					_panStart.copy( _panEnd );

				} else {

					_panStart.add( mouseChange.subVectors( _panEnd, _panStart ).multiplyScalar( scope.dynamicDampingFactor ) );

				}

			}

		};

	}() );

	this.checkDistances = function () {

		if ( ! scope.noZoom || ! scope.noPan ) {

			if ( _eye.lengthSq() > scope.maxDistance * scope.maxDistance ) {

				scope.object.position.addVectors( scope.target, _eye.setLength( scope.maxDistance ) );
				_zoomStart.copy( _zoomEnd );

			}

			if ( _eye.lengthSq() < scope.minDistance * scope.minDistance ) {

				scope.object.position.addVectors( scope.target, _eye.setLength( scope.minDistance ) );
				_zoomStart.copy( _zoomEnd );

			}

		}

	};

	this.update = function () {

		_eye.subVectors( scope.object.position, scope.target );

		if ( ! scope.noRotate ) {

			scope.rotateCamera();

		}

		if ( ! scope.noZoom ) {

			scope.zoomCamera();

		}

		if ( ! scope.noPan ) {

			scope.panCamera();

		}

		scope.object.position.addVectors( scope.target, _eye );

		if ( scope.object.isPerspectiveCamera ) {

			scope.checkDistances();

			scope.object.lookAt( scope.target );

			if ( lastPosition.distanceToSquared( scope.object.position ) > EPS ) {

				scope.dispatchEvent( changeEvent );

				lastPosition.copy( scope.object.position );

			}

		} else if ( scope.object.isOrthographicCamera ) {

			scope.object.lookAt( scope.target );

			if ( lastPosition.distanceToSquared( scope.object.position ) > EPS || lastZoom !== scope.object.zoom ) {

				scope.dispatchEvent( changeEvent );

				lastPosition.copy( scope.object.position );
				lastZoom = scope.object.zoom;

			}

		} else {

			console.warn( 'THREE.TrackballControls: Unsupported camera type' );

		}

	};

	this.reset = function () {

		_state = STATE.NONE;
		_keyState = STATE.NONE;

		scope.target.copy( scope.target0 );
		scope.object.position.copy( scope.position0 );
		scope.object.up.copy( scope.up0 );
		scope.object.zoom = scope.zoom0;

		scope.object.updateProjectionMatrix();

		_eye.subVectors( scope.object.position, scope.target );

		scope.object.lookAt( scope.target );

		scope.dispatchEvent( changeEvent );

		lastPosition.copy( scope.object.position );
		lastZoom = scope.object.zoom;

	};

	// listeners

	function onPointerDown( event ) {

		if ( scope.enabled === false ) return;

		switch ( event.pointerType ) {

			case 'mouse':
			case 'pen':
				onMouseDown( event );
				break;

			// TODO touch

		}

	}

	function onPointerMove( event ) {

		if ( scope.enabled === false ) return;

		switch ( event.pointerType ) {

			case 'mouse':
			case 'pen':
				onMouseMove( event );
				break;

			// TODO touch

		}

	}

	function onPointerUp( event ) {

		if ( scope.enabled === false ) return;

		switch ( event.pointerType ) {

			case 'mouse':
			case 'pen':
				onMouseUp( event );
				break;

			// TODO touch

		}

	}

	function keydown( event ) {

		if ( scope.enabled === false ) return;

		window.removeEventListener( 'keydown', keydown );

		if ( _keyState !== STATE.NONE ) {

			return;

		} else if ( event.code === scope.keys[ STATE.ROTATE ] && ! scope.noRotate ) {

			_keyState = STATE.ROTATE;

		} else if ( event.code === scope.keys[ STATE.ZOOM ] && ! scope.noZoom ) {

			_keyState = STATE.ZOOM;

		} else if ( event.code === scope.keys[ STATE.PAN ] && ! scope.noPan ) {

			_keyState = STATE.PAN;

		}

	}

	function keyup() {

		if ( scope.enabled === false ) return;

		_keyState = STATE.NONE;

		window.addEventListener( 'keydown', keydown );

	}

	function onMouseDown( event ) {

		event.preventDefault();

		if ( _state === STATE.NONE ) {

			switch ( event.button ) {

				case scope.mouseButtons.LEFT:
					_state = STATE.ROTATE;
					break;

				case scope.mouseButtons.MIDDLE:
					_state = STATE.ZOOM;
					break;

				case scope.mouseButtons.RIGHT:
					_state = STATE.PAN;
					break;

				default:
					_state = STATE.NONE;

			}

		}

		var state = ( _keyState !== STATE.NONE ) ? _keyState : _state;

		if ( state === STATE.ROTATE && ! scope.noRotate ) {

			_moveCurr.copy( getMouseOnCircle( event.pageX, event.pageY ) );
			_movePrev.copy( _moveCurr );

		} else if ( state === STATE.ZOOM && ! scope.noZoom ) {

			_zoomStart.copy( getMouseOnScreen( event.pageX, event.pageY ) );
			_zoomEnd.copy( _zoomStart );

		} else if ( state === STATE.PAN && ! scope.noPan ) {

			_panStart.copy( getMouseOnScreen( event.pageX, event.pageY ) );
			_panEnd.copy( _panStart );

		}

		scope.domElement.ownerDocument.addEventListener( 'pointermove', onPointerMove );
		scope.domElement.ownerDocument.addEventListener( 'pointerup', onPointerUp );

		scope.dispatchEvent( startEvent );

	}

	function onMouseMove( event ) {

		if ( scope.enabled === false ) return;

		event.preventDefault();

		var state = ( _keyState !== STATE.NONE ) ? _keyState : _state;

		if ( state === STATE.ROTATE && ! scope.noRotate ) {

			_movePrev.copy( _moveCurr );
			_moveCurr.copy( getMouseOnCircle( event.pageX, event.pageY ) );

		} else if ( state === STATE.ZOOM && ! scope.noZoom ) {

			_zoomEnd.copy( getMouseOnScreen( event.pageX, event.pageY ) );

		} else if ( state === STATE.PAN && ! scope.noPan ) {

			_panEnd.copy( getMouseOnScreen( event.pageX, event.pageY ) );

		}

	}

	function onMouseUp( event ) {

		if ( scope.enabled === false ) return;

		event.preventDefault();

		_state = STATE.NONE;

		scope.domElement.ownerDocument.removeEventListener( 'pointermove', onPointerMove );
		scope.domElement.ownerDocument.removeEventListener( 'pointerup', onPointerUp );

		scope.dispatchEvent( endEvent );

	}

	function mousewheel( event ) {

		if ( scope.enabled === false ) return;

		if ( scope.noZoom === true ) return;

		event.preventDefault();

		switch ( event.deltaMode ) {

			case 2:
				// Zoom in pages
				_zoomStart.y -= event.deltaY * 0.025;
				break;

			case 1:
				// Zoom in lines
				_zoomStart.y -= event.deltaY * 0.01;
				break;

			default:
				// undefined, 0, assume pixels
				_zoomStart.y -= event.deltaY * 0.00025;
				break;

		}

		scope.dispatchEvent( startEvent );
		scope.dispatchEvent( endEvent );

	}

	function touchstart( event ) {

		if ( scope.enabled === false ) return;

		event.preventDefault();

		switch ( event.touches.length ) {

			case 1:
				_state = STATE.TOUCH_ROTATE;
				_moveCurr.copy( getMouseOnCircle( event.touches[ 0 ].pageX, event.touches[ 0 ].pageY ) );
				_movePrev.copy( _moveCurr );
				break;

			default: // 2 or more
				_state = STATE.TOUCH_ZOOM_PAN;
				var dx = event.touches[ 0 ].pageX - event.touches[ 1 ].pageX;
				var dy = event.touches[ 0 ].pageY - event.touches[ 1 ].pageY;
				_touchZoomDistanceEnd = _touchZoomDistanceStart = Math.sqrt( dx * dx + dy * dy );

				var x = ( event.touches[ 0 ].pageX + event.touches[ 1 ].pageX ) / 2;
				var y = ( event.touches[ 0 ].pageY + event.touches[ 1 ].pageY ) / 2;
				_panStart.copy( getMouseOnScreen( x, y ) );
				_panEnd.copy( _panStart );
				break;

		}

		scope.dispatchEvent( startEvent );

	}

	function touchmove( event ) {

		if ( scope.enabled === false ) return;

		event.preventDefault();

		switch ( event.touches.length ) {

			case 1:
				_movePrev.copy( _moveCurr );
				_moveCurr.copy( getMouseOnCircle( event.touches[ 0 ].pageX, event.touches[ 0 ].pageY ) );
				break;

			default: // 2 or more
				var dx = event.touches[ 0 ].pageX - event.touches[ 1 ].pageX;
				var dy = event.touches[ 0 ].pageY - event.touches[ 1 ].pageY;
				_touchZoomDistanceEnd = Math.sqrt( dx * dx + dy * dy );

				var x = ( event.touches[ 0 ].pageX + event.touches[ 1 ].pageX ) / 2;
				var y = ( event.touches[ 0 ].pageY + event.touches[ 1 ].pageY ) / 2;
				_panEnd.copy( getMouseOnScreen( x, y ) );
				break;

		}

	}

	function touchend( event ) {

		if ( scope.enabled === false ) return;

		switch ( event.touches.length ) {

			case 0:
				_state = STATE.NONE;
				break;

			case 1:
				_state = STATE.TOUCH_ROTATE;
				_moveCurr.copy( getMouseOnCircle( event.touches[ 0 ].pageX, event.touches[ 0 ].pageY ) );
				_movePrev.copy( _moveCurr );
				break;

		}

		scope.dispatchEvent( endEvent );

	}

	function contextmenu( event ) {

		if ( scope.enabled === false ) return;

		event.preventDefault();

	}

	this.dispose = function () {

		scope.domElement.removeEventListener( 'contextmenu', contextmenu );

		scope.domElement.removeEventListener( 'pointerdown', onPointerDown );
		scope.domElement.removeEventListener( 'wheel', mousewheel );

		scope.domElement.removeEventListener( 'touchstart', touchstart );
		scope.domElement.removeEventListener( 'touchend', touchend );
		scope.domElement.removeEventListener( 'touchmove', touchmove );

		scope.domElement.ownerDocument.removeEventListener( 'pointermove', onPointerMove );
		scope.domElement.ownerDocument.removeEventListener( 'pointerup', onPointerUp );

		window.removeEventListener( 'keydown', keydown );
		window.removeEventListener( 'keyup', keyup );

	};

	this.domElement.addEventListener( 'contextmenu', contextmenu );

	this.domElement.addEventListener( 'pointerdown', onPointerDown );
	this.domElement.addEventListener( 'wheel', mousewheel );

	this.domElement.addEventListener( 'touchstart', touchstart );
	this.domElement.addEventListener( 'touchend', touchend );
	this.domElement.addEventListener( 'touchmove', touchmove );

	this.domElement.ownerDocument.addEventListener( 'pointermove', onPointerMove );
	this.domElement.ownerDocument.addEventListener( 'pointerup', onPointerUp );

	window.addEventListener( 'keydown', keydown );
	window.addEventListener( 'keyup', keyup );

	this.handleResize();

	// force an update at start
	this.update();

};

THREE.TrackballControls.prototype = Object.create( THREE.EventDispatcher.prototype );
THREE.TrackballControls.prototype.constructor = THREE.TrackballControls;
