three.js/examples/js/controls/DragControls.js

/*
 * @author zz85 / https://github.com/zz85
 * Running this will allow you to drag three.js objects around the screen.
 */
THREE.DragControls = function( _camera, _objects, _domElement ) {

	var _projector = new THREE.Projector();
	var _raycaster = new THREE.Raycaster();

	var _mouse = new THREE.Vector3(),
		_offset = new THREE.Vector3();
	var _selected, _hovered;

	var p3subp1 = new THREE.Vector3();
	var targetposition = new THREE.Vector3();
	var zerovector = new THREE.Vector3();

	this.enabled = false;

	 /* Custom Event Handling */
	var _listeners = {

	};

	var me = this;
	this.on = function( event, handler ) {
		
		if ( ! _listeners[ event ] ) _listeners[ event ] = [];

		_listeners[ event ].push( handler );
		return me;
	
	};

	this.off = function( event, handler ) {
		
		var l = _listeners[ event ];
		if ( ! l ) return me;

		if ( l.indexOf( handler ) > - 1 ) {
			
			l.splice( handler, 1 );
		
		}

		return me;

	};

	var notify = function( event, data, member ) {
			
		var l = _listeners[ event ];
		if ( ! l ) return;

		if ( ! member ) {
					
			for ( var i = 0; i < l.length; i ++ ) {
						
				l[ i ]( data );
					
			}
				
		}
		
	};

	this.setObjects = function( objects ) {
		
		if ( objects instanceof THREE.Scene ) {
			
			_objects = objects.children;
		
		} else {
			
			_objects = objects;
		
		}
	
	};

	this.setObjects( _objects );

	this.activate = function() {
		
		_domElement.addEventListener( 'mousemove', onDocumentMouseMove, false );
		_domElement.addEventListener( 'mousedown', onDocumentMouseDown, false );
		_domElement.addEventListener( 'mouseup', onDocumentMouseUp, false );
	
	};

	this.deactivate = function() {
		
		_domElement.removeEventListener( 'mousemove', onDocumentMouseMove, false );
		_domElement.removeEventListener( 'mousedown', onDocumentMouseDown, false );
		_domElement.removeEventListener( 'mouseup', onDocumentMouseUp, false );
	
	};

	this.dispose = function() {

		me.deactivate();

	};

	this.activate();

	function onDocumentMouseMove( event ) {

		event.preventDefault();

		_mouse.x = ( event.clientX / _domElement.width ) * 2 - 1;
		_mouse.y = - ( event.clientY / _domElement.height ) * 2 + 1;

		_raycaster.setFromCamera( _mouse, _camera );
		var ray = _raycaster.ray;


		if ( _selected && me.enabled ) {
			
			var normal = _selected.normal;

			// I found this article useful about plane-line intersections
			// http://paulbourke.net/geometry/planeline/

			var denom = normal.dot( ray.direction );
			if ( denom == 0 ) {

				// bail
				console.log( 'no or infinite solutions' );
				return;
			
			}

			var num = normal.dot( p3subp1.copy( _selected.point ).sub( ray.origin ) );
			var u = num / denom;

			targetposition.copy( ray.direction ).multiplyScalar( u ).add( ray.origin ).sub( _offset );
			// _selected.object.position.copy(targetposition);

			var xLock, yLock, zLock = false;

			var moveX, moveY, moveZ;
			

			if ( xLock ) {
				
				moveX = true;
				moveY = false;
				moveZ = false;
			
			} else if ( yLock ) {
							
				moveX = false;
				moveY = true;
				moveZ = false;
						
			} else {
							
				moveX = moveY = moveZ = true;
						
			}

			// Reverse Matrix?
			if ( moveX ) _selected.object.position.x = targetposition.x;
			if ( moveY ) _selected.object.position.y = targetposition.y;
			if ( moveZ ) _selected.object.position.z = targetposition.z;

			notify( 'drag', _selected );

			return;

		}

		_raycaster.setFromCamera( _mouse, _camera );
		var intersects = _raycaster.intersectObjects( _objects );

		if ( intersects.length > 0 ) {

			_domElement.style.cursor = 'pointer';
			_hovered = intersects[ 0 ];
			notify( 'hoveron', _hovered );

		} else {
			
			notify( 'hoveroff', _hovered );
			_hovered = null;
			_domElement.style.cursor = 'auto';

		}

	}

	function onDocumentMouseDown( event ) {

		event.preventDefault();

		_mouse.x = ( event.clientX / _domElement.width ) * 2 - 1;
		_mouse.y = - ( event.clientY / _domElement.height ) * 2 + 1;

		_raycaster.setFromCamera( _mouse, _camera );
		var intersects = _raycaster.intersectObjects( _objects );
		var ray = _raycaster.ray;

		var normal = ray.direction; // normal ray to the camera position
		if ( intersects.length > 0 ) {
			
			_selected = intersects[ 0 ];
			_selected.ray = ray;
			_selected.normal = normal ;
			_offset.copy( _selected.point ).sub( _selected.object.position );

			_domElement.style.cursor = 'move';

			notify( 'dragstart', _selected );

		}


	}

	function onDocumentMouseUp( event ) {

		event.preventDefault();

		if ( _selected ) {

			notify( 'dragend', _selected );
			_selected = null;
		
		}

		_domElement.style.cursor = 'auto';

	}

}