G4EnclosingCylinder.cc

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//
// Implementation of G4EnclosingCylinder, a utility class
// for a quick check of geometry.
//
// Author: David C. Williams (davidw@scipp.ucsc.edu)
// --------------------------------------------------------------------

#include "G4EnclosingCylinder.hh"
#include "G4PhysicalConstants.hh"
#include "G4ReduciblePolygon.hh"
#include "G4GeometryTolerance.hh"

// Constructor
//
G4EnclosingCylinder::G4EnclosingCylinder( const G4ReduciblePolygon* rz,
                                                G4bool thePhiIsOpen, 
                                                G4double theStartPhi,
                                                G4double theTotalPhi )
  : startPhi(theStartPhi), totalPhi(theTotalPhi),
    concave(theTotalPhi > pi)
{
  //
  // Obtain largest r and smallest and largest z
  //
  radius = rz->Amax();
  zHi = rz->Bmax();
  zLo = rz->Bmin();

  G4double kCarTolerance = G4GeometryTolerance::GetInstance()
                           ->GetSurfaceTolerance();
  //
  // Save phi info
  //
  phiIsOpen = thePhiIsOpen;
  if ( phiIsOpen )
  {    
    rx1 = std::cos(startPhi);
    ry1 = std::sin(startPhi);
    dx1 = +ry1*10*kCarTolerance;
    dy1 = -rx1*10*kCarTolerance;
    
    rx2 = std::cos(startPhi+totalPhi);
    ry2 = std::sin(startPhi+totalPhi);
    dx2 = -ry2*10*kCarTolerance;
    dy2 = +rx2*10*kCarTolerance;
  }
  
  //
  // Add safety
  //
  radius += 10*kCarTolerance;
  zLo    -= 10*kCarTolerance;
  zHi    += 10*kCarTolerance;
}

// Fake default constructor - sets only member data and allocates memory
//                            for usage restricted to object persistency.
//
G4EnclosingCylinder::G4EnclosingCylinder( __void__& )
: radius(0.), zLo(0.), zHi(0.), phiIsOpen(0.), startPhi(0.), totalPhi(0.),
  concave(false)
{
}

// Destructor
//
G4EnclosingCylinder::~G4EnclosingCylinder()
{
}

// Outside
//
// Decide very rapidly if the point is outside the cylinder
//
// If one is not certain, return false
//
G4bool G4EnclosingCylinder::MustBeOutside( const G4ThreeVector& p ) const
{
  if (p.perp() > radius) return true;
  if (p.z() < zLo) return true;
  if (p.z() > zHi) return true;

  if (phiIsOpen)
  {
    if (concave)
    {
      if ( ((p.x()-dx1)*ry1 - (p.y()-dy1)*rx1) < 0) return false;
      if ( ((p.x()-dx2)*ry2 - (p.y()-dy2)*rx2) > 0) return false;
    }
    else
    {
      if ( ((p.x()-dx1)*ry1 - (p.y()-dy1)*rx1) > 0) return true;
      if ( ((p.x()-dx2)*ry2 - (p.y()-dy2)*rx2) < 0) return true;
    }
  }
  
  return false;
}

// Misses
//
// Decide very rapidly if the trajectory is going to miss the cylinder
//
// If one is not sure, return false
//
G4bool G4EnclosingCylinder::ShouldMiss( const G4ThreeVector& p,
                                        const G4ThreeVector& v ) const
{
  if (!MustBeOutside(p)) return false;
  
  G4double cross = p.x()*v.y() - p.y()*v.x();
  if (cross > radius) return true;
  
  if (p.perp() > radius)
  {
    G4double dot = p.x()*v.x() + p.y()*v.y();
    if (dot > 0) return true;
  }

  return false;
}