Geant4  10.03.p03
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G4LineSection.cc
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27 // $Id: G4LineSection.cc 85845 2014-11-05 15:43:58Z gcosmo $
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29 // --------------------------------------------------------------------
30 
31 #include "G4LineSection.hh"
32 
34 {
35  G4double dist_sq;
36  G4ThreeVector VecAZ;
37  G4double sq_VecAZ, inner_prod, unit_projection ;
38 
39  VecAZ= OtherPnt - EndpointA;
40  sq_VecAZ = VecAZ.mag2();
41 
42  inner_prod= VecAtoB.dot( VecAZ );
43 
44  // Determine Projection(AZ on AB) / Length(AB)
45  //
46  if( fABdistanceSq != 0.0 )
47  {
48  // unit_projection= inner_prod * InvsqDistAB();
49  unit_projection = inner_prod/fABdistanceSq;
50 
51  if( (0. <= unit_projection ) && (unit_projection <= 1.0 ) )
52  {
53  dist_sq= sq_VecAZ - unit_projection * inner_prod ;
54  }
55  else
56  {
57  // The perpendicular from the point to the line AB meets the line
58  // in a point outside the line segment!
59 
60  if( unit_projection < 0. ) // A is the closest point
61  {
62  dist_sq= sq_VecAZ;
63  }
64  else // B is the closest point
65  {
66  G4ThreeVector EndpointB = EndpointA + VecAtoB;
67  G4ThreeVector VecBZ = OtherPnt - EndpointB;
68  dist_sq = VecBZ.mag2();
69  }
70  }
71  }
72  else
73  {
74  dist_sq = (OtherPnt - EndpointA).mag2() ;
75  }
76  if( dist_sq < 0.0 ) dist_sq = 0.0 ;
77 
78  return std::sqrt(dist_sq) ;
79 }
G4double Dist(G4ThreeVector OtherPnt) const
double dot(const Hep3Vector &) const
double mag2() const
double G4double
Definition: G4Types.hh:76