$Id: README,v 1.2 2010-09-17 11:21:45 maire Exp $
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     =========================================================
     Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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                            placement 
                            ---------
			    
 This example shows various ways of definition of 3D transformations for 
 placing volumes.
  	
 1- Geometry construction
    ---------------------
 Two G4Trd volumes (daughters) are placed within a G4Tubs (mother), as shown
 in picture rotm.jpg
 
 The various ways of placement are implemented in the DetectorConstruction class
 in the following private functions:
 
 - PlaceWithDirectMatrix()
 - PlaceWithInverseMatrix()
 - PlaceWithAxialRotations()
 - PlaceWithEulerAngles()
 - PlaceWithReflections()
 
 which are then called from the Construct() function.
 All methods define exactly same geometry except for the placement 
 with reflection where trapezoids are placed with their symmetry axis 
 in parallel with z-axis in order to make easier to check reflection 
 visually. 

 The method of placement can be selected interactively via the command
 (see DetectorMessenger):
 /placement/setMethod method

      
 2- Physics list
    ------------
 PhysicsList.cc defines only geantino and transportation process.
         	
 3- Primary generator
    ----------------- 
 Default kinematic is a geantino, at rest, at coordinate origin.
 Can be changed with particleGun commands.
         	
 4- Physics
    -------
 No physics; only transportation.
  	
 5- Visualisation
    ------------- 
 Visualization Manager is set in the main().
 Initialisation of the drawing is done via the commands
 /vis/.. in the macro vis.mac. This macro is automatically read from the main 
 in case of interactive running mode.
  
 6- How to start ?
    -------------- 
  - compile and link to generate an executable
 	% cd placement
 	% gmake
 		
  - execute rotations in 'interactive mode' with visualization
 	% placement
 	....
 	Idle>   ---> type your commands. For instance:
	Idle> /control/execute debug.mac 
	....
	Idle> /run/beamOn 1
	....				
 	Idle> exit
 		
  - execute placement in 'batch' mode from macro files
 	% placement   debug.mac