three.js/examples/jsm/controls/OrbitControls.js

import {
	EventDispatcher,
	MOUSE,
	Quaternion,
	Spherical,
	TOUCH,
	Vector2,
	Vector3,
	Plane,
	Ray,
	MathUtils
} from 'three';

// OrbitControls performs orbiting, dollying (zooming), and panning.
// Unlike TrackballControls, it maintains the "up" direction object.up (+Y by default).
//
//    Orbit - left mouse / touch: one-finger move
//    Zoom - middle mouse, or mousewheel / touch: two-finger spread or squish
//    Pan - right mouse, or left mouse + ctrl/meta/shiftKey, or arrow keys / touch: two-finger move

const _changeEvent = { type: 'change' };
const _startEvent = { type: 'start' };
const _endEvent = { type: 'end' };
const _ray = new Ray();
const _plane = new Plane();
const TILT_LIMIT = Math.cos( 70 * MathUtils.DEG2RAD );

class OrbitControls extends EventDispatcher {

	constructor( object, domElement ) {

		super();

		this.object = object;
		this.domElement = domElement;
		this.domElement.style.touchAction = 'none'; // disable touch scroll

		// Set to false to disable this control
		this.enabled = true;

		// "target" sets the location of focus, where the object orbits around
		this.target = new Vector3();

		// Sets the 3D cursor (similar to Blender), from which the maxTargetRadius takes effect
		this.cursor = new Vector3();

		// How far you can dolly in and out ( PerspectiveCamera only )
		this.minDistance = 0;
		this.maxDistance = Infinity;

		// How far you can zoom in and out ( OrthographicCamera only )
		this.minZoom = 0;
		this.maxZoom = Infinity;

		// Limit camera target within a spherical area around the cursor
		this.minTargetRadius = 0;
		this.maxTargetRadius = Infinity;

		// How far you can orbit vertically, upper and lower limits.
		// Range is 0 to Math.PI radians.
		this.minPolarAngle = 0; // radians
		this.maxPolarAngle = Math.PI; // radians

		// How far you can orbit horizontally, upper and lower limits.
		// If set, the interval [ min, max ] must be a sub-interval of [ - 2 PI, 2 PI ], with ( max - min < 2 PI )
		this.minAzimuthAngle = - Infinity; // radians
		this.maxAzimuthAngle = Infinity; // radians

		// Set to true to enable damping (inertia)
		// If damping is enabled, you must call controls.update() in your animation loop
		this.enableDamping = false;
		this.dampingFactor = 0.05;

		// This option actually enables dollying in and out; left as "zoom" for backwards compatibility.
		// Set to false to disable zooming
		this.enableZoom = true;
		this.zoomSpeed = 1.0;

		// Set to false to disable rotating
		this.enableRotate = true;
		this.rotateSpeed = 1.0;

		// Set to false to disable panning
		this.enablePan = true;
		this.panSpeed = 1.0;
		this.screenSpacePanning = true; // if false, pan orthogonal to world-space direction camera.up
		this.keyPanSpeed = 7.0;	// pixels moved per arrow key push
		this.zoomToCursor = false;

		// Set to true to automatically rotate around the target
		// If auto-rotate is enabled, you must call controls.update() in your animation loop
		this.autoRotate = false;
		this.autoRotateSpeed = 2.0; // 30 seconds per orbit when fps is 60

		// The four arrow keys
		this.keys = { LEFT: 'ArrowLeft', UP: 'ArrowUp', RIGHT: 'ArrowRight', BOTTOM: 'ArrowDown' };

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

		// Touch fingers
		this.touches = { ONE: TOUCH.ROTATE, TWO: TOUCH.DOLLY_PAN };

		// for reset
		this.target0 = this.target.clone();
		this.position0 = this.object.position.clone();
		this.zoom0 = this.object.zoom;

		// the target DOM element for key events
		this._domElementKeyEvents = null;

		//
		// public methods
		//

		this.getPolarAngle = function () {

			return spherical.phi;

		};

		this.getAzimuthalAngle = function () {

			return spherical.theta;

		};

		this.getDistance = function () {

			return this.object.position.distanceTo( this.target );

		};

		this.listenToKeyEvents = function ( domElement ) {

			domElement.addEventListener( 'keydown', onKeyDown );
			this._domElementKeyEvents = domElement;

		};

		this.stopListenToKeyEvents = function () {

			this._domElementKeyEvents.removeEventListener( 'keydown', onKeyDown );
			this._domElementKeyEvents = null;

		};

		this.saveState = function () {

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

		};

		this.reset = function () {

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

			scope.object.updateProjectionMatrix();
			scope.dispatchEvent( _changeEvent );

			scope.update();

			state = STATE.NONE;

		};

		// this method is exposed, but perhaps it would be better if we can make it private...
		this.update = function () {

			const offset = new Vector3();

			// so camera.up is the orbit axis
			const quat = new Quaternion().setFromUnitVectors( object.up, new Vector3( 0, 1, 0 ) );
			const quatInverse = quat.clone().invert();

			const lastPosition = new Vector3();
			const lastQuaternion = new Quaternion();
			const lastTargetPosition = new Vector3();

			const twoPI = 2 * Math.PI;

			return function update( deltaTime = null ) {

				const position = scope.object.position;

				offset.copy( position ).sub( scope.target );

				// rotate offset to "y-axis-is-up" space
				offset.applyQuaternion( quat );

				// angle from z-axis around y-axis
				spherical.setFromVector3( offset );

				if ( scope.autoRotate && state === STATE.NONE ) {

					rotateLeft( getAutoRotationAngle( deltaTime ) );

				}

				if ( scope.enableDamping ) {

					spherical.theta += sphericalDelta.theta * scope.dampingFactor;
					spherical.phi += sphericalDelta.phi * scope.dampingFactor;

				} else {

					spherical.theta += sphericalDelta.theta;
					spherical.phi += sphericalDelta.phi;

				}

				// restrict theta to be between desired limits

				let min = scope.minAzimuthAngle;
				let max = scope.maxAzimuthAngle;

				if ( isFinite( min ) && isFinite( max ) ) {

					if ( min < - Math.PI ) min += twoPI; else if ( min > Math.PI ) min -= twoPI;

					if ( max < - Math.PI ) max += twoPI; else if ( max > Math.PI ) max -= twoPI;

					if ( min <= max ) {

						spherical.theta = Math.max( min, Math.min( max, spherical.theta ) );

					} else {

						spherical.theta = ( spherical.theta > ( min + max ) / 2 ) ?
							Math.max( min, spherical.theta ) :
							Math.min( max, spherical.theta );

					}

				}

				// restrict phi to be between desired limits
				spherical.phi = Math.max( scope.minPolarAngle, Math.min( scope.maxPolarAngle, spherical.phi ) );

				spherical.makeSafe();


				// move target to panned location

				if ( scope.enableDamping === true ) {

					scope.target.addScaledVector( panOffset, scope.dampingFactor );

				} else {

					scope.target.add( panOffset );

				}

				// Limit the target distance from the cursor to create a sphere around the center of interest
				scope.target.sub( scope.cursor );
				scope.target.clampLength( scope.minTargetRadius, scope.maxTargetRadius );
				scope.target.add( scope.cursor );

				// adjust the camera position based on zoom only if we're not zooming to the cursor or if it's an ortho camera
				// we adjust zoom later in these cases
				if ( scope.zoomToCursor && performCursorZoom || scope.object.isOrthographicCamera ) {

					spherical.radius = clampDistance( spherical.radius );

				} else {

					spherical.radius = clampDistance( spherical.radius * scale );

				}

				offset.setFromSpherical( spherical );

				// rotate offset back to "camera-up-vector-is-up" space
				offset.applyQuaternion( quatInverse );

				position.copy( scope.target ).add( offset );

				scope.object.lookAt( scope.target );

				if ( scope.enableDamping === true ) {

					sphericalDelta.theta *= ( 1 - scope.dampingFactor );
					sphericalDelta.phi *= ( 1 - scope.dampingFactor );

					panOffset.multiplyScalar( 1 - scope.dampingFactor );

				} else {

					sphericalDelta.set( 0, 0, 0 );

					panOffset.set( 0, 0, 0 );

				}

				// adjust camera position
				let zoomChanged = false;
				if ( scope.zoomToCursor && performCursorZoom ) {

					let newRadius = null;
					if ( scope.object.isPerspectiveCamera ) {

						// move the camera down the pointer ray
						// this method avoids floating point error
						const prevRadius = offset.length();
						newRadius = clampDistance( prevRadius * scale );

						const radiusDelta = prevRadius - newRadius;
						scope.object.position.addScaledVector( dollyDirection, radiusDelta );
						scope.object.updateMatrixWorld();

					} else if ( scope.object.isOrthographicCamera ) {

						// adjust the ortho camera position based on zoom changes
						const mouseBefore = new Vector3( mouse.x, mouse.y, 0 );
						mouseBefore.unproject( scope.object );

						scope.object.zoom = Math.max( scope.minZoom, Math.min( scope.maxZoom, scope.object.zoom / scale ) );
						scope.object.updateProjectionMatrix();
						zoomChanged = true;

						const mouseAfter = new Vector3( mouse.x, mouse.y, 0 );
						mouseAfter.unproject( scope.object );

						scope.object.position.sub( mouseAfter ).add( mouseBefore );
						scope.object.updateMatrixWorld();

						newRadius = offset.length();

					} else {

						console.warn( 'WARNING: OrbitControls.js encountered an unknown camera type - zoom to cursor disabled.' );
						scope.zoomToCursor = false;

					}

					// handle the placement of the target
					if ( newRadius !== null ) {

						if ( this.screenSpacePanning ) {

							// position the orbit target in front of the new camera position
							scope.target.set( 0, 0, - 1 )
								.transformDirection( scope.object.matrix )
								.multiplyScalar( newRadius )
								.add( scope.object.position );

						} else {

							// get the ray and translation plane to compute target
							_ray.origin.copy( scope.object.position );
							_ray.direction.set( 0, 0, - 1 ).transformDirection( scope.object.matrix );

							// if the camera is 20 degrees above the horizon then don't adjust the focus target to avoid
							// extremely large values
							if ( Math.abs( scope.object.up.dot( _ray.direction ) ) < TILT_LIMIT ) {

								object.lookAt( scope.target );

							} else {

								_plane.setFromNormalAndCoplanarPoint( scope.object.up, scope.target );
								_ray.intersectPlane( _plane, scope.target );

							}

						}

					}

				} else if ( scope.object.isOrthographicCamera ) {
					
					zoomChanged = scale !== 1;

					if ( zoomChanged ) {

						scope.object.zoom = Math.max( scope.minZoom, Math.min( scope.maxZoom, scope.object.zoom / scale ) );
						scope.object.updateProjectionMatrix();
						
					}

				}

				scale = 1;
				performCursorZoom = false;

				// update condition is:
				// min(camera displacement, camera rotation in radians)^2 > EPS
				// using small-angle approximation cos(x/2) = 1 - x^2 / 8

				if ( zoomChanged ||
					lastPosition.distanceToSquared( scope.object.position ) > EPS ||
					8 * ( 1 - lastQuaternion.dot( scope.object.quaternion ) ) > EPS ||
					lastTargetPosition.distanceToSquared( scope.target ) > 0 ) {

					scope.dispatchEvent( _changeEvent );

					lastPosition.copy( scope.object.position );
					lastQuaternion.copy( scope.object.quaternion );
					lastTargetPosition.copy( scope.target );

					return true;

				}

				return false;

			};

		}();

		this.dispose = function () {

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

			scope.domElement.removeEventListener( 'pointerdown', onPointerDown );
			scope.domElement.removeEventListener( 'pointercancel', onPointerUp );
			scope.domElement.removeEventListener( 'wheel', onMouseWheel );

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


			if ( scope._domElementKeyEvents !== null ) {

				scope._domElementKeyEvents.removeEventListener( 'keydown', onKeyDown );
				scope._domElementKeyEvents = null;

			}

			//scope.dispatchEvent( { type: 'dispose' } ); // should this be added here?

		};

		//
		// internals
		//

		const scope = this;

		const STATE = {
			NONE: - 1,
			ROTATE: 0,
			DOLLY: 1,
			PAN: 2,
			TOUCH_ROTATE: 3,
			TOUCH_PAN: 4,
			TOUCH_DOLLY_PAN: 5,
			TOUCH_DOLLY_ROTATE: 6
		};

		let state = STATE.NONE;

		const EPS = 0.000001;

		// current position in spherical coordinates
		const spherical = new Spherical();
		const sphericalDelta = new Spherical();

		let scale = 1;
		const panOffset = new Vector3();

		const rotateStart = new Vector2();
		const rotateEnd = new Vector2();
		const rotateDelta = new Vector2();

		const panStart = new Vector2();
		const panEnd = new Vector2();
		const panDelta = new Vector2();

		const dollyStart = new Vector2();
		const dollyEnd = new Vector2();
		const dollyDelta = new Vector2();

		const dollyDirection = new Vector3();
		const mouse = new Vector2();
		let performCursorZoom = false;

		const pointers = [];
		const pointerPositions = {};

		function getAutoRotationAngle( deltaTime ) {

			if ( deltaTime !== null ) {

				return ( 2 * Math.PI / 60 * scope.autoRotateSpeed ) * deltaTime;

			} else {

				return 2 * Math.PI / 60 / 60 * scope.autoRotateSpeed;

			}

		}

		function getZoomScale( delta ) {

			const normalized_delta = Math.abs( delta ) / ( 100 * ( window.devicePixelRatio | 0 ) );
			return Math.pow( 0.95, scope.zoomSpeed * normalized_delta );

		}

		function rotateLeft( angle ) {

			sphericalDelta.theta -= angle;

		}

		function rotateUp( angle ) {

			sphericalDelta.phi -= angle;

		}

		const panLeft = function () {

			const v = new Vector3();

			return function panLeft( distance, objectMatrix ) {

				v.setFromMatrixColumn( objectMatrix, 0 ); // get X column of objectMatrix
				v.multiplyScalar( - distance );

				panOffset.add( v );

			};

		}();

		const panUp = function () {

			const v = new Vector3();

			return function panUp( distance, objectMatrix ) {

				if ( scope.screenSpacePanning === true ) {

					v.setFromMatrixColumn( objectMatrix, 1 );

				} else {

					v.setFromMatrixColumn( objectMatrix, 0 );
					v.crossVectors( scope.object.up, v );

				}

				v.multiplyScalar( distance );

				panOffset.add( v );

			};

		}();

		// deltaX and deltaY are in pixels; right and down are positive
		const pan = function () {

			const offset = new Vector3();

			return function pan( deltaX, deltaY ) {

				const element = scope.domElement;

				if ( scope.object.isPerspectiveCamera ) {

					// perspective
					const position = scope.object.position;
					offset.copy( position ).sub( scope.target );
					let targetDistance = offset.length();

					// half of the fov is center to top of screen
					targetDistance *= Math.tan( ( scope.object.fov / 2 ) * Math.PI / 180.0 );

					// we use only clientHeight here so aspect ratio does not distort speed
					panLeft( 2 * deltaX * targetDistance / element.clientHeight, scope.object.matrix );
					panUp( 2 * deltaY * targetDistance / element.clientHeight, scope.object.matrix );

				} else if ( scope.object.isOrthographicCamera ) {

					// orthographic
					panLeft( deltaX * ( scope.object.right - scope.object.left ) / scope.object.zoom / element.clientWidth, scope.object.matrix );
					panUp( deltaY * ( scope.object.top - scope.object.bottom ) / scope.object.zoom / element.clientHeight, scope.object.matrix );

				} else {

					// camera neither orthographic nor perspective
					console.warn( 'WARNING: OrbitControls.js encountered an unknown camera type - pan disabled.' );
					scope.enablePan = false;

				}

			};

		}();

		function dollyOut( dollyScale ) {

			if ( scope.object.isPerspectiveCamera || scope.object.isOrthographicCamera ) {

				scale /= dollyScale;

			} else {

				console.warn( 'WARNING: OrbitControls.js encountered an unknown camera type - dolly/zoom disabled.' );
				scope.enableZoom = false;

			}

		}

		function dollyIn( dollyScale ) {

			if ( scope.object.isPerspectiveCamera || scope.object.isOrthographicCamera ) {

				scale *= dollyScale;

			} else {

				console.warn( 'WARNING: OrbitControls.js encountered an unknown camera type - dolly/zoom disabled.' );
				scope.enableZoom = false;

			}

		}

		function updateZoomParameters( x, y ) {

			if ( ! scope.zoomToCursor ) {

				return;

			}

			performCursorZoom = true;

			const rect = scope.domElement.getBoundingClientRect();
			const dx = x - rect.left;
			const dy = y - rect.top;
			const w = rect.width;
			const h = rect.height;

			mouse.x = ( dx / w ) * 2 - 1;
			mouse.y = - ( dy / h ) * 2 + 1;

			dollyDirection.set( mouse.x, mouse.y, 1 ).unproject( scope.object ).sub( scope.object.position ).normalize();

		}

		function clampDistance( dist ) {

			return Math.max( scope.minDistance, Math.min( scope.maxDistance, dist ) );

		}

		//
		// event callbacks - update the object state
		//

		function handleMouseDownRotate( event ) {

			rotateStart.set( event.clientX, event.clientY );

		}

		function handleMouseDownDolly( event ) {

			updateZoomParameters( event.clientX, event.clientX );
			dollyStart.set( event.clientX, event.clientY );

		}

		function handleMouseDownPan( event ) {

			panStart.set( event.clientX, event.clientY );

		}

		function handleMouseMoveRotate( event ) {

			rotateEnd.set( event.clientX, event.clientY );

			rotateDelta.subVectors( rotateEnd, rotateStart ).multiplyScalar( scope.rotateSpeed );

			const element = scope.domElement;

			rotateLeft( 2 * Math.PI * rotateDelta.x / element.clientHeight ); // yes, height

			rotateUp( 2 * Math.PI * rotateDelta.y / element.clientHeight );

			rotateStart.copy( rotateEnd );

			scope.update();

		}

		function handleMouseMoveDolly( event ) {

			dollyEnd.set( event.clientX, event.clientY );

			dollyDelta.subVectors( dollyEnd, dollyStart );

			if ( dollyDelta.y > 0 ) {

				dollyOut( getZoomScale( dollyDelta.y ) );

			} else if ( dollyDelta.y < 0 ) {

				dollyIn( getZoomScale( dollyDelta.y ) );

			}

			dollyStart.copy( dollyEnd );

			scope.update();

		}

		function handleMouseMovePan( event ) {

			panEnd.set( event.clientX, event.clientY );

			panDelta.subVectors( panEnd, panStart ).multiplyScalar( scope.panSpeed );

			pan( panDelta.x, panDelta.y );

			panStart.copy( panEnd );

			scope.update();

		}

		function handleMouseWheel( event ) {

			updateZoomParameters( event.clientX, event.clientY );

			if ( event.deltaY < 0 ) {

				dollyIn( getZoomScale( event.deltaY ) );

			} else if ( event.deltaY > 0 ) {

				dollyOut( getZoomScale( event.deltaY ) );

			}

			scope.update();

		}

		function handleKeyDown( event ) {

			let needsUpdate = false;

			switch ( event.code ) {

				case scope.keys.UP:

					if ( event.ctrlKey || event.metaKey || event.shiftKey ) {

						rotateUp( 2 * Math.PI * scope.rotateSpeed / scope.domElement.clientHeight );

					} else {

						pan( 0, scope.keyPanSpeed );

					}

					needsUpdate = true;
					break;

				case scope.keys.BOTTOM:

					if ( event.ctrlKey || event.metaKey || event.shiftKey ) {

						rotateUp( - 2 * Math.PI * scope.rotateSpeed / scope.domElement.clientHeight );

					} else {

						pan( 0, - scope.keyPanSpeed );

					}

					needsUpdate = true;
					break;

				case scope.keys.LEFT:

					if ( event.ctrlKey || event.metaKey || event.shiftKey ) {

						rotateLeft( 2 * Math.PI * scope.rotateSpeed / scope.domElement.clientHeight );

					} else {

						pan( scope.keyPanSpeed, 0 );

					}

					needsUpdate = true;
					break;

				case scope.keys.RIGHT:

					if ( event.ctrlKey || event.metaKey || event.shiftKey ) {

						rotateLeft( - 2 * Math.PI * scope.rotateSpeed / scope.domElement.clientHeight );

					} else {

						pan( - scope.keyPanSpeed, 0 );

					}

					needsUpdate = true;
					break;

			}

			if ( needsUpdate ) {

				// prevent the browser from scrolling on cursor keys
				event.preventDefault();

				scope.update();

			}


		}

		function handleTouchStartRotate( event ) {

			if ( pointers.length === 1 ) {

				rotateStart.set( event.pageX, event.pageY );

			} else {

				const position = getSecondPointerPosition( event );

				const x = 0.5 * ( event.pageX + position.x );
				const y = 0.5 * ( event.pageY + position.y );

				rotateStart.set( x, y );

			}

		}

		function handleTouchStartPan( event ) {

			if ( pointers.length === 1 ) {

				panStart.set( event.pageX, event.pageY );

			} else {

				const position = getSecondPointerPosition( event );

				const x = 0.5 * ( event.pageX + position.x );
				const y = 0.5 * ( event.pageY + position.y );

				panStart.set( x, y );

			}

		}

		function handleTouchStartDolly( event ) {

			const position = getSecondPointerPosition( event );

			const dx = event.pageX - position.x;
			const dy = event.pageY - position.y;

			const distance = Math.sqrt( dx * dx + dy * dy );

			dollyStart.set( 0, distance );

		}

		function handleTouchStartDollyPan( event ) {

			if ( scope.enableZoom ) handleTouchStartDolly( event );

			if ( scope.enablePan ) handleTouchStartPan( event );

		}

		function handleTouchStartDollyRotate( event ) {

			if ( scope.enableZoom ) handleTouchStartDolly( event );

			if ( scope.enableRotate ) handleTouchStartRotate( event );

		}

		function handleTouchMoveRotate( event ) {

			if ( pointers.length == 1 ) {

				rotateEnd.set( event.pageX, event.pageY );

			} else {

				const position = getSecondPointerPosition( event );

				const x = 0.5 * ( event.pageX + position.x );
				const y = 0.5 * ( event.pageY + position.y );

				rotateEnd.set( x, y );

			}

			rotateDelta.subVectors( rotateEnd, rotateStart ).multiplyScalar( scope.rotateSpeed );

			const element = scope.domElement;

			rotateLeft( 2 * Math.PI * rotateDelta.x / element.clientHeight ); // yes, height

			rotateUp( 2 * Math.PI * rotateDelta.y / element.clientHeight );

			rotateStart.copy( rotateEnd );

		}

		function handleTouchMovePan( event ) {

			if ( pointers.length === 1 ) {

				panEnd.set( event.pageX, event.pageY );

			} else {

				const position = getSecondPointerPosition( event );

				const x = 0.5 * ( event.pageX + position.x );
				const y = 0.5 * ( event.pageY + position.y );

				panEnd.set( x, y );

			}

			panDelta.subVectors( panEnd, panStart ).multiplyScalar( scope.panSpeed );

			pan( panDelta.x, panDelta.y );

			panStart.copy( panEnd );

		}

		function handleTouchMoveDolly( event ) {

			const position = getSecondPointerPosition( event );

			const dx = event.pageX - position.x;
			const dy = event.pageY - position.y;

			const distance = Math.sqrt( dx * dx + dy * dy );

			dollyEnd.set( 0, distance );

			dollyDelta.set( 0, Math.pow( dollyEnd.y / dollyStart.y, scope.zoomSpeed ) );

			dollyOut( dollyDelta.y );

			dollyStart.copy( dollyEnd );

			const centerX = ( event.pageX + position.x ) * 0.5;
			const centerY = ( event.pageY + position.y ) * 0.5;

			updateZoomParameters( centerX, centerY );

		}

		function handleTouchMoveDollyPan( event ) {

			if ( scope.enableZoom ) handleTouchMoveDolly( event );

			if ( scope.enablePan ) handleTouchMovePan( event );

		}

		function handleTouchMoveDollyRotate( event ) {

			if ( scope.enableZoom ) handleTouchMoveDolly( event );

			if ( scope.enableRotate ) handleTouchMoveRotate( event );

		}

		//
		// event handlers - FSM: listen for events and reset state
		//

		function onPointerDown( event ) {

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

			if ( pointers.length === 0 ) {

				scope.domElement.setPointerCapture( event.pointerId );

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

			}

			//

			addPointer( event );

			if ( event.pointerType === 'touch' ) {

				onTouchStart( event );

			} else {

				onMouseDown( event );

			}

		}

		function onPointerMove( event ) {

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

			if ( event.pointerType === 'touch' ) {

				onTouchMove( event );

			} else {

				onMouseMove( event );

			}

		}

		function onPointerUp( event ) {

			removePointer( event );

			if ( pointers.length === 0 ) {

				scope.domElement.releasePointerCapture( event.pointerId );

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

			}

			scope.dispatchEvent( _endEvent );

			state = STATE.NONE;

			if ( pointers.length == 1 ) {

				const pointerId = pointers[ 0 ];
				const position = pointerPositions[ pointerId ];

				// minimal placeholder event - allows state correction on pointer-up
				onTouchStart( { pointerId: pointerId, pageX: position.x, pageY: position.y } );

			}

		}

		function onMouseDown( event ) {

			let mouseAction;

			switch ( event.button ) {

				case 0:

					mouseAction = scope.mouseButtons.LEFT;
					break;

				case 1:

					mouseAction = scope.mouseButtons.MIDDLE;
					break;

				case 2:

					mouseAction = scope.mouseButtons.RIGHT;
					break;

				default:

					mouseAction = - 1;

			}

			switch ( mouseAction ) {

				case MOUSE.DOLLY:

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

					handleMouseDownDolly( event );

					state = STATE.DOLLY;

					break;

				case MOUSE.ROTATE:

					if ( event.ctrlKey || event.metaKey || event.shiftKey ) {

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

						handleMouseDownPan( event );

						state = STATE.PAN;

					} else {

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

						handleMouseDownRotate( event );

						state = STATE.ROTATE;

					}

					break;

				case MOUSE.PAN:

					if ( event.ctrlKey || event.metaKey || event.shiftKey ) {

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

						handleMouseDownRotate( event );

						state = STATE.ROTATE;

					} else {

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

						handleMouseDownPan( event );

						state = STATE.PAN;

					}

					break;

				default:

					state = STATE.NONE;

			}

			if ( state !== STATE.NONE ) {

				scope.dispatchEvent( _startEvent );

			}

		}

		function onMouseMove( event ) {

			switch ( state ) {

				case STATE.ROTATE:

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

					handleMouseMoveRotate( event );

					break;

				case STATE.DOLLY:

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

					handleMouseMoveDolly( event );

					break;

				case STATE.PAN:

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

					handleMouseMovePan( event );

					break;

			}

		}

		function onMouseWheel( event ) {

			if ( scope.enabled === false || scope.enableZoom === false || state !== STATE.NONE ) return;

			event.preventDefault();

			scope.dispatchEvent( _startEvent );

			handleMouseWheel( event );

			scope.dispatchEvent( _endEvent );

		}

		function onKeyDown( event ) {

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

			handleKeyDown( event );

		}

		function onTouchStart( event ) {

			trackPointer( event );

			switch ( pointers.length ) {

				case 1:

					switch ( scope.touches.ONE ) {

						case TOUCH.ROTATE:

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

							handleTouchStartRotate( event );

							state = STATE.TOUCH_ROTATE;

							break;

						case TOUCH.PAN:

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

							handleTouchStartPan( event );

							state = STATE.TOUCH_PAN;

							break;

						default:

							state = STATE.NONE;

					}

					break;

				case 2:

					switch ( scope.touches.TWO ) {

						case TOUCH.DOLLY_PAN:

							if ( scope.enableZoom === false && scope.enablePan === false ) return;

							handleTouchStartDollyPan( event );

							state = STATE.TOUCH_DOLLY_PAN;

							break;

						case TOUCH.DOLLY_ROTATE:

							if ( scope.enableZoom === false && scope.enableRotate === false ) return;

							handleTouchStartDollyRotate( event );

							state = STATE.TOUCH_DOLLY_ROTATE;

							break;

						default:

							state = STATE.NONE;

					}

					break;

				default:

					state = STATE.NONE;

			}

			if ( state !== STATE.NONE ) {

				scope.dispatchEvent( _startEvent );

			}

		}

		function onTouchMove( event ) {

			trackPointer( event );

			switch ( state ) {

				case STATE.TOUCH_ROTATE:

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

					handleTouchMoveRotate( event );

					scope.update();

					break;

				case STATE.TOUCH_PAN:

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

					handleTouchMovePan( event );

					scope.update();

					break;

				case STATE.TOUCH_DOLLY_PAN:

					if ( scope.enableZoom === false && scope.enablePan === false ) return;

					handleTouchMoveDollyPan( event );

					scope.update();

					break;

				case STATE.TOUCH_DOLLY_ROTATE:

					if ( scope.enableZoom === false && scope.enableRotate === false ) return;

					handleTouchMoveDollyRotate( event );

					scope.update();

					break;

				default:

					state = STATE.NONE;

			}

		}

		function onContextMenu( event ) {

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

			event.preventDefault();

		}

		function addPointer( event ) {

			pointers.push( event.pointerId );

		}

		function removePointer( event ) {

			delete pointerPositions[ event.pointerId ];

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

				if ( pointers[ i ] == event.pointerId ) {

					pointers.splice( i, 1 );
					return;

				}

			}

		}

		function trackPointer( event ) {

			let position = pointerPositions[ event.pointerId ];

			if ( position === undefined ) {

				position = new Vector2();
				pointerPositions[ event.pointerId ] = position;

			}

			position.set( event.pageX, event.pageY );

		}

		function getSecondPointerPosition( event ) {

			const pointerId = ( event.pointerId === pointers[ 0 ] ) ? pointers[ 1 ] : pointers[ 0 ];

			return pointerPositions[ pointerId ];

		}

		//

		scope.domElement.addEventListener( 'contextmenu', onContextMenu );

		scope.domElement.addEventListener( 'pointerdown', onPointerDown );
		scope.domElement.addEventListener( 'pointercancel', onPointerUp );
		scope.domElement.addEventListener( 'wheel', onMouseWheel, { passive: false } );

		// force an update at start

		this.update();

	}

}

export { OrbitControls };