Fixed mousewheel zooming in TrackpadControls when staticMovig was set to true.

_zoomStart = _zoomEnd; <-- grrr

src/extras/controls/TrackballControls.js

@@ -142,7 +142,7 @@ THREE.TrackballControls = function ( object, domElement ) {
 
 			if ( _this.staticMoving ) {
 
-				_rotateStart = _rotateEnd;
+				_rotateStart.copy( _rotateEnd );
 
 			} else {
 
@@ -165,7 +165,7 @@ THREE.TrackballControls = function ( object, domElement ) {
 
 			if ( _this.staticMoving ) {
 
-				_zoomStart = _zoomEnd;
+				_zoomStart.copy( _zoomEnd );
 
 			} else {
 
@@ -392,16 +392,17 @@ THREE.TrackballControls = function ( object, domElement ) {
 
 		var delta = 0;
 
-		// WebKit / Opera / Explorer 9
-		if ( event.wheelDelta ) {
-			delta = event.wheelDelta/40;
-		// Firefox
-		} else if ( event.detail ) {
-			delta = -event.detail/3;
+		if ( event.wheelDelta ) { // WebKit / Opera / Explorer 9
+
+			delta = event.wheelDelta / 40;
+
+		} else if ( event.detail ) { // Firefox
+
+			delta = - event.detail / 3;
+
 		}
 
-		_zoomStart.y = delta*0.05;
-		_zoomEnd.y = 0;
+		_zoomStart.y += ( 1 / delta ) * 0.05;
 
 	}