use OverlayObject in OverlayTextDisplay
use OverlayObject in OverlayCameraDisplay
use OverlayObject on OverlayImageDisplay
fix the timing to initialize OverlayObject in OverlayCameraDisplay
use OverlayObject in OverlayDiagnosticDisplay
use OverlayObject in OverlayMenuDisplay
dispose material when deleting OverlayObject