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//
// class G4ErrorPropagationNavigator
//
// Class Description:
//
// Class for performing double navigation in the detector geometry and
// on the target surface for error propagation. It overloads ComputeStep()
// and ComputeSafety() methods.

// History:
// - Created. P. Arce, September 2004
// --------------------------------------------------------------------

#ifndef G4ErrorPropagationNavigator_hh
#define G4ErrorPropagationNavigator_hh

#include "G4Navigator.hh"
#include "G4ThreeVector.hh"

class G4ErrorPropagationNavigator : public G4Navigator
{
  public:  // with description

    G4ErrorPropagationNavigator();
   ~G4ErrorPropagationNavigator();
  
    G4double ComputeStep (const G4ThreeVector &pGlobalPoint,
                          const G4ThreeVector &pDirection,
                          const G4double pCurrentProposedStepLength,
                                G4double &pNewSafety);
      // Calls the navigation in the detector geometry and then checks
      // if the distance to surface is smaller than the proposed step

    G4double ComputeSafety(const G4ThreeVector &globalpoint,
                           const G4double pProposedMaxLength = DBL_MAX,
                           const G4bool keepState = true);
      // Calls the navigation in the detector geometry and then checks
      // if the distance to surface is smaller than the proposed safety
  
    G4ThreeVector GetGlobalExitNormal(const G4ThreeVector& point,
                                            G4bool* valid);
      // Return Exit Surface Normal and validity too. Can only be called if
      // the Navigator's last Step has crossed a volume geometrical boundary.
      // Normal points out of the volume exited and/or into the volume entered.

    G4double TargetSafetyFromPoint( const G4ThreeVector &pGlobalpoint );
      // Isotropic safety for 'Target' 
   
    //-- NOT implemented, as it is difficult to define the coordinate system:
    // G4ThreeVector GetLocalExitNormal(G4bool* valid);
    // G4ThreeVector GetLocalExitNormalAndCheck(const G4ThreeVector& point,
    //                                               G4bool* valid);
    // Convention:
    //   The *local* normal is in the coordinate system of the *final* volume.
};

#endif
