Import Geant4 2.0.0 source tree

source/geometry/magneticfield/src/G4MagErrorStepper.cc

@@ -5,8 +5,8 @@
 // based on the Program) you indicate your acceptance of this statement,
 // and all its terms.
 //
-// $Id: G4MagErrorStepper.cc,v 1.6 1999/12/15 14:49:49 gunter Exp $
-// GEANT4 tag $Name: geant4-01-01 $
+// $Id: G4MagErrorStepper.cc,v 1.7 2000/05/09 11:41:00 japost Exp $
+// GEANT4 tag $Name: geant4-02-00 $
 //
 #include "G4MagErrorStepper.hh"
 #include "G4ThreeVector.hh"
@@ -61,11 +61,26 @@ G4MagErrorStepper::Stepper( const G4double yInput[],
 G4double
 G4MagErrorStepper::DistChord()   const 
 {
-  // Soon: must check whether h/R > 2 pi  !!
-  //  Method below is good only for < 2 pi
+  // Estimate the maximum distance from the curve to the chord
+  //
+  //  We estimate this using the distance of the midpoint to 
+  //  chord (the line between 
+  // 
+  //  Method below is good only for angle deviations < 2 pi, 
+  //   This restriction should not a problem for the Runge cutta methods, 
+  //   which generally cannot integrate accurately for large angle deviations.
+  G4double distLine, distChord; 
 
-  return G4LineSection::Distline( fMidPoint, fInitialPoint, fFinalPoint );
-  // This is a class method that gives distance of Mid 
-  //  from the Chord between the Initial and Final points.
+  if (fInitialPoint != fFinalPoint) {
+     distLine= G4LineSection::Distline( fMidPoint, fInitialPoint, fFinalPoint );
+     // This is a class method that gives distance of Mid 
+     //  from the Chord between the Initial and Final points.
+
+     distChord = distLine;
+  }else{
+     distChord = (fMidPoint-fInitialPoint).mag();
+  }
+
+  return distChord;
 }