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// $Id: G4VPGeoDriver.hh,v 1.6 2002/10/14 12:36:01 dressel Exp $
// GEANT4 tag $Name: geant4-06-00 $
//
// ----------------------------------------------------------------------
// Class G4VPGeoDriver
//
// Class description:
//
// Used internally by importance sampling and scoring in a "parallel"
// geometry.
// It defines an interface to "drive" or "move" a particle in a 
// "parallel" geometry. 

// Author: Michael Dressel (Michael.Dressel@cern.ch)
// ----------------------------------------------------------------------
#ifndef G4VPGeoDriver_hh
#define G4VPGeoDriver_hh G4VPGeoDriver_hh

#include "globals.hh"
#include "G4ThreeVector.hh"
#include "G4GeometryCell.hh"

class G4VPhysicalVolume;

class G4VPGeoDriver
{

public:  // with description

  G4VPGeoDriver();
  virtual ~G4VPGeoDriver();
  
  virtual G4GeometryCell LocateOnBoundary(const G4ThreeVector &aPosition, 
					  const G4ThreeVector &aDirection) = 0;
    // The location of a track according to it's position
    // and direction in case the track crosses a boundary
    // of a "parallel" geometry.
    // Must be called in the PostDOIT of the ParallelTransportation.
    // (The track crosses the boundary if PostDOIT gets called.)
  
  virtual G4GeometryCell GetCurrentGeometryCell() const = 0;
    // get the current G4GeometryCell of the "parallel" geometry

  virtual G4double ComputeStepLengthInit(const G4ThreeVector &aPosition, 
                                         const G4ThreeVector &aDirection) = 0;
    // compute step length for a starting track. 

  virtual G4double ComputeStepLengthCrossBoundary(const G4ThreeVector &aPosition, 
				                  const G4ThreeVector &aDirection) = 0;
    // compute the step length after a track crossed a boundary
    // in a "parallel" geometry
 
  virtual G4double ComputeStepLengthInVolume(const G4ThreeVector &aPosition, 
                                             const G4ThreeVector &aDirection) = 0;
    // compute step length when track moves inside a volume.  

};

#endif