| 1 | // -*- C++ -*-
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| 2 | // ---------------------------------------------------------------------------
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| 3 | //
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| 4 | // This file is a part of the CLHEP - a Class Library for High Energy Physics.
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| 5 | //
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| 6 | // This is the implementation of the subset of those methods of the Hep3Vector
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| 7 | // class which originated from the ZOOM SpaceVector class *and* which involve
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| 8 | // the esoteric concepts of polar/azimuthal angular decomposition.
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| 9 | //
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| 10 |
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| 11 | #ifdef GNUPRAGMA
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| 12 | #pragma implementation
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| 13 | #endif
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| 14 |
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| 15 | #include "CLHEP/Vector/defs.h"
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| 16 | #include "CLHEP/Vector/ThreeVector.h"
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| 17 | #include "CLHEP/Vector/ZMxpv.h"
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| 18 |
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| 19 | #include <cmath>
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| 20 |
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| 21 | namespace CLHEP {
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| 22 |
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| 23 | //-*********************************************
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| 24 | // - 6 -
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| 25 | // Decomposition of an angle between two vectors
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| 26 | //
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| 27 | //-*********************************************
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| 28 |
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| 29 |
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| 30 | double Hep3Vector::polarAngle (const Hep3Vector & v2) const {
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| 31 | return fabs(v2.getTheta() - getTheta());
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| 32 | } /* polarAngle */
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| 33 |
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| 34 | double Hep3Vector::polarAngle (const Hep3Vector & v2,
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| 35 | const Hep3Vector & ref) const {
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| 36 | return fabs( v2.angle(ref) - angle(ref) );
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| 37 | } /* polarAngle (v2, ref) */
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| 38 |
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| 39 | // double Hep3Vector::azimAngle (const Hep3Vector & v2) const
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| 40 | // is now in the .icc file as deltaPhi(v2)
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| 41 |
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| 42 | double Hep3Vector::azimAngle (const Hep3Vector & v2,
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| 43 | const Hep3Vector & ref) const {
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| 44 |
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| 45 | Hep3Vector vperp ( perpPart(ref) );
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| 46 | if ( vperp.mag2() == 0 ) {
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| 47 | ZMthrowC (ZMxpvAmbiguousAngle(
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| 48 | "Cannot find azimuthal angle with reference direction parallel to "
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| 49 | "vector 1 -- will return zero"));
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| 50 | return 0;
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| 51 | }
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| 52 |
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| 53 | Hep3Vector v2perp ( v2.perpPart(ref) );
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| 54 | if ( v2perp.mag2() == 0 ) {
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| 55 | ZMthrowC (ZMxpvAmbiguousAngle(
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| 56 | "Cannot find azimuthal angle with reference direction parallel to "
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| 57 | "vector 2 -- will return zero"));
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| 58 | return 0;
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| 59 | }
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| 60 |
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| 61 | double ang = vperp.angle(v2perp);
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| 62 |
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| 63 | // Now compute the sign of the answer: that of U*(VxV2) or
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| 64 | // the equivalent expression V*(V2xU).
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| 65 |
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| 66 | if ( dot(v2.cross(ref)) >= 0 ) {
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| 67 | return ang;
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| 68 | } else {
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| 69 | return -ang;
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| 70 | }
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| 71 |
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| 72 | //-| Note that if V*(V2xU) is zero, we want to return 0 or PI
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| 73 | //-| depending on whether vperp is aligned or antialigned with v2perp.
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| 74 | //-| The computed angle() expression does this properly.
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| 75 |
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| 76 | } /* azimAngle (v2, ref) */
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| 77 |
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| 78 | } // namespace CLHEP
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