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//
// Implementation of inline methods of G4TwistBoxSide
// --------------------------------------------------------------------

inline
G4double G4TwistBoxSide::GetValueA(G4double phi)
{
  return ( fDx4plus2 + fDx4minus2 * ( 2 * phi ) / fPhiTwist  ) ;
}


inline 
G4double G4TwistBoxSide::GetValueB(G4double phi) 
{
  return ( fDy2plus1 + fDy2minus1 * ( 2 * phi ) / fPhiTwist ) ;
}

inline
G4double G4TwistBoxSide::Xcoef(G4double u, G4double phi)
{
  
  return GetValueA(phi)/2. + u*fTAlph    ;

}

inline G4ThreeVector
G4TwistBoxSide::SurfacePoint( G4double phi, G4double u, G4bool isGlobal ) 
{
  // function to calculate a point on the surface, given by parameters phi,u

  G4ThreeVector SurfPoint ( Xcoef(u,phi) * std::cos(phi)
                          - u * std::sin(phi) + fdeltaX*phi/fPhiTwist,
                            Xcoef(u,phi) * std::sin(phi)
                          + u * std::cos(phi) + fdeltaY*phi/fPhiTwist,
                            2*fDz*phi/fPhiTwist  );

  if (isGlobal) { return (fRot * SurfPoint + fTrans); }
  return SurfPoint;
}

inline
G4double G4TwistBoxSide::GetBoundaryMin(G4double phi)
{
  return -0.5*GetValueB(phi) ;
}

inline
G4double G4TwistBoxSide::GetBoundaryMax(G4double phi)
{
  return 0.5*GetValueB(phi) ;
}

inline
G4double G4TwistBoxSide::GetSurfaceArea()
{
  return (fDz*(std::sqrt(16*fDy1*fDy1
         + (fa1md1 + 4*fDy1*fTAlph)*(fa1md1 + 4*fDy1*fTAlph))
         + std::sqrt(16*fDy1*fDy1 + (fa2md2 + 4*fDy1*fTAlph)
         * (fa2md2 + 4*fDy1*fTAlph))))/2. ;
}

inline
G4ThreeVector G4TwistBoxSide::NormAng( G4double phi, G4double u ) 
{
  // function to calculate the norm at a given point on the surface
  // replace a1-d1

  G4ThreeVector nvec( 4*fDz*(std::cos(phi) + fTAlph*std::sin(phi)) ,
                      4*fDz*(-(fTAlph*std::cos(phi)) + std::sin(phi)),
                      (fDx2 + fDx4)*fPhiTwist*fTAlph
                                   + 2*fDx4minus2*(-1 + fTAlph*phi)
                                   + 2*fPhiTwist*(1 + fTAlph*fTAlph)*u
                                - 2*(fdeltaX - fdeltaY*fTAlph)*std::cos(phi)
                                - 2*(fdeltaY + fdeltaX*fTAlph)*std::sin(phi) );
  return nvec.unit();
}