Regenerates the drawing from within the current viewport. 
 
   REGEN regenerates the drawing with the following effects: 
  
 
  
- Recomputes the locations and visibility for all objects in the current viewport 
	 
 
- Reindexes the drawing database for optimum display and object selection performance 
	 
 
- Resets the overall area available for realtime panning and zooming in the current viewport