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// $Id: G4ErrorMagFieldLimitProcess.cc,v 1.3 2009/11/11 17:10:33 arce Exp $
// GEANT4 tag $Name: geant4-09-03 $
//
// ------------------------------------------------------------
//      GEANT 4 class implementation file 
// ------------------------------------------------------------
//

#include "G4ErrorMagFieldLimitProcess.hh"
#include "G4ErrorMessenger.hh"
#include "G4TransportationManager.hh"
#include "G4FieldManager.hh"
#include "G4Field.hh"
#include "G4Track.hh"

#ifdef G4VERBOSE
#include "G4ErrorPropagatorData.hh"
#endif

//------------------------------------------------------------------------
G4ErrorMagFieldLimitProcess::
G4ErrorMagFieldLimitProcess(const G4String& processName)
  : G4VErrorLimitProcess(processName) 
{
  theStepLimit = kInfinity;
}


//------------------------------------------------------------------------
G4ErrorMagFieldLimitProcess::~G4ErrorMagFieldLimitProcess()
{ }


//------------------------------------------------------------------------
G4double G4ErrorMagFieldLimitProcess::
PostStepGetPhysicalInteractionLength( const G4Track& aTrack, G4double ,
                                            G4ForceCondition* condition )
{
  *condition = NotForced;
  const G4Field* field =
    G4TransportationManager::GetTransportationManager()->GetFieldManager()
    ->GetDetectorField();

  theStepLength = kInfinity;
  if( field != 0 ) {
    G4ThreeVector trkPosi = aTrack.GetPosition();
    G4double pos1[3];
       pos1[0] = trkPosi.x(); pos1[1] = trkPosi.y(); pos1[2] = trkPosi.z();

    G4double h1[3];
    field->GetFieldValue( pos1, h1 );

    G4ThreeVector BVec(h1[0],h1[1],h1[2]);
    G4double pmag = aTrack.GetMomentum().mag();
    G4double BPerpMom = BVec.cross( G4ThreeVector(pmag,0.,0.) ).mag() / pmag;

    theStepLength = theStepLimit * pmag / BPerpMom; 
#ifdef G4VERBOSE
  if(G4ErrorPropagatorData::verbose() >= 3 ) { 
    G4cout <<  "G4ErrorMagFieldLimitProcess:: stepLength "
           << theStepLength << " B " << BPerpMom << " BVec " << BVec
           << " pmag " << pmag << G4endl;
  }
#endif
  }

  return theStepLength;
}
