Coordinates on Geometry view with openGL

[whyaqm]

Hi all,
I have a geometry file named xxx.gdml, and use the following code to open a canvas, then go to menu view->view with->openGL.
In the new openGL window, I choose clipping->edit in Viewer, then the three
arrows(X,Y,Z) with different color appear.
The problem is sometimes these three arrows become three circles as shown in the attached plots. I would like to know how this happens and how to go back to the three arrows mode? I am using root v6-10-02 on Macbook. Thank you very much for any help.

{
   TGeoManager* geom = TGeoManager::Import("x.gdml");
   TBrowser*       b = new TBrowser();
   geom->GetVolume("VirtualDetector_STM_UpStr")->SetLineColor(kGreen);
   geom->GetTopVolume()->Draw();
}

[bellenot]

If you select Help->Help on GL Viewer on the top right menu, you will see:

MANIPULATORS

   A widget attached to the selected object - allowing direct manipulation
   of the object with respect to its local axes.

   There are three modes, toggled with keys while manipulator is active, that is,
   mouse pointer is above it (switches color to yellow):
   	Mode		Widget Component Style		Key
   	----		----------------------		---
   	Translation	Local axes with arrows		v
   	Scale		Local axes with boxes		x
   	Rotate		Local axes rings			c

   Each widget has three axis components - red (X), green (Y) and blue (Z).
   The component turns yellow, indicating an active state, when the mouse is moved
   over it. Left click and drag on the active component to adjust the objects
   translation, scale or rotation.
   Some objects do not support all manipulations (e.g. clipping planes cannot be 
   scaled). If a manipulation is not permitted the component it drawn in grey and 
   cannot be selected/dragged.

So place the mouse cursor on the manipulator and press the v key to get the translation one