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// $Id: G4VMscModel.cc,v 1.18 2010/09/07 16:05:33 vnivanch Exp $
// GEANT4 tag $Name: emutils-V09-03-23 $
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name:     G4VMscModel
//
// Author:        Vladimir Ivanchenko
//
// Creation date: 07.03.2008
//
// Modifications:
//
//
// Class Description:
//
// General interface to msc models

// -------------------------------------------------------------------
//

#include "G4VMscModel.hh"
#include "G4ParticleChangeForMSC.hh"
#include "G4TransportationManager.hh"

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G4VMscModel::G4VMscModel(const G4String& nam):
  G4VEmModel(nam), 
  safetyHelper(0),
  facrange(0.04),
  facgeom(2.5),
  facsafety(0.3),
  skin(1.0),
  dtrl(0.05),
  lambdalimit(mm),
  geomMin(1.e-6*CLHEP::mm),
  geomMax(1.e50*CLHEP::mm),
  steppingAlgorithm(fUseSafety),
  samplez(false),
  latDisplasment(true)
{}

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G4VMscModel::~G4VMscModel()
{}

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G4ParticleChangeForMSC* G4VMscModel::GetParticleChangeForMSC()
{
  G4ParticleChangeForMSC* p = 0;
  if (pParticleChange) {
    p = static_cast<G4ParticleChangeForMSC*>(pParticleChange);
  } else {
    p = new G4ParticleChangeForMSC();
  }
  return p;
}

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void G4VMscModel::InitialiseSafetyHelper()
{
  if(!safetyHelper) {
    safetyHelper = G4TransportationManager::GetTransportationManager()
      ->GetSafetyHelper();
    safetyHelper->InitialiseHelper();
  }
}

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void G4VMscModel::ComputeDisplacement(G4ParticleChangeForMSC* fParticleChange,  
				      const G4ThreeVector& dir,
				      G4double displacement,
				      G4double postsafety)
{
  if(displacement <= geomMin) { return; }
  const G4ThreeVector* pos = fParticleChange->GetProposedPosition();

  // displaced point is definitely within the volume
  if(displacement < postsafety) {

    // compute new endpoint of the Step
    G4ThreeVector newPosition = *pos + displacement*dir;
    safetyHelper->ReLocateWithinVolume(newPosition);
    fParticleChange->ProposePosition(newPosition);
    return;
  }

  // displaced point may be outside the volume
  G4double newsafety = safetyHelper->ComputeSafety(*pos);

  // add a factor which ensure numerical stability
  G4double r = std::min(displacement, newsafety*0.99); 

  if(r > geomMin) {

    // compute new endpoint of the Step
    G4ThreeVector newPosition = *pos + r*dir;
    safetyHelper->ReLocateWithinVolume(newPosition);
    fParticleChange->ProposePosition(newPosition);
  }
}

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void G4VMscModel::SampleScattering(const G4DynamicParticle*, G4double)
{}

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G4double G4VMscModel::ComputeTruePathLengthLimit(const G4Track&, 
						 G4PhysicsTable*, 
						 G4double)
{
  return DBL_MAX;
}

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G4double G4VMscModel::ComputeGeomPathLength(G4double truePathLength)
{
  return truePathLength;
}

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G4double G4VMscModel::ComputeTrueStepLength(G4double geomPathLength)
{
  return geomPathLength;
}

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void G4VMscModel::SampleSecondaries(std::vector<G4DynamicParticle*>*,
				    const G4MaterialCutsCouple*,
				    const G4DynamicParticle*,
				    G4double, G4double)
{}

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