Merge pull request #9239 from sebavan/master

Add drag behavior on drag

src/Behaviors/Meshes/sixDofDragBehavior.ts

@@ -53,6 +53,10 @@ export class SixDofDragBehavior implements Behavior<Mesh> {
      */
     public onDragStartObservable = new Observable<{}>();
     /**
+     * Fires each time a drag happens
+     */
+    public onDragObservable = new Observable<void>();
+    /**
      *  Fires each time a drag ends (eg. mouse release after drag)
      */
     public onDragEndObservable = new Observable<{}>();
@@ -239,6 +243,8 @@ export class SixDofDragBehavior implements Behavior<Mesh> {
                     }
                 }
                 PivotTools._RestorePivotPoint(pickedMesh);
+
+                this.onDragObservable.notifyObservers();
             }
         });
     }
@@ -263,6 +269,7 @@ export class SixDofDragBehavior implements Behavior<Mesh> {
             this._virtualDragMesh.dispose();
         }
         this.onDragEndObservable.clear();
+        this.onDragObservable.clear();
         this.onDragStartObservable.clear();
     }
 }