// @(#)root/physics:$Name:  $:$Id: TVector3.cxx,v 1.8 2004/04/29 17:43:59 brun Exp $
// Author: Pasha Murat, Peter Malzacher   12/02/99
//    Aug 11 1999: added Pt == 0 guard to Eta()
//    Oct  8 1999: changed Warning to Error and
//                 return fX in Double_t & operator()
//    Oct 20 1999: Bug fix: sign in PseudoRapidity
//                 Warning-> Error in Double_t operator()
//______________________________________________________________________________
//*-*-*-*-*-*-*-*-*-*-*-*The Physics Vector package *-*-*-*-*-*-*-*-*-*-*-*
//*-*                    ==========================                       *
//*-* The Physics Vector package consists of five classes:                *
//*-*   - TVector2                                                        *
//*-*   - TVector3                                                        *
//*-*   - TRotation                                                       *
//*-*   - TLorentzVector                                                  *
//*-*   - TLorentzRotation                                                *
//*-* It is a combination of CLHEPs Vector package written by             *
//*-* Leif Lonnblad, Andreas Nilsson and Evgueni Tcherniaev               *
//*-* and a ROOT package written by Pasha Murat.                          *
//*-* for CLHEP see:  http://wwwinfo.cern.ch/asd/lhc++/clhep/             *
//*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
//

TVector3

TVector3 is a general three vector class, which can be used for the description of different vectors in 3D.

Declaration / Access to the components

TVector3 has been implemented as a vector of three Double_t variables, representing the cartesian coordinates. By default all components are initialized to zero:

  TVector3 v1;        // v1 = (0,0,0)
  TVector3 v2(1);     // v2 = (1,0,0)
  TVector3 v3(1,2,3); // v3 = (1,2,3)
  TVector3 v4(v2);    // v4 = v2

It is also possible (but not recommended) to initialize a TVector3 with a Double_t or Float_t C array.

You can get the basic components either by name or by index using operator():

  xx = v1.X();    or    xx = v1(0);
  yy = v1.Y();          yy = v1(1);
  zz = v1.Z();          zz = v1(2);

The memberfunctions SetX(), SetY(), SetZ() and SetXYZ() allow to set the components:

  v1.SetX(1.); v1.SetY(2.); v1.SetZ(3.);
  v1.SetXYZ(1.,2.,3.);
 

Noncartesian coordinates

To get information on the TVector3 in spherical (rho,phi,theta) or cylindrical (z,r,theta) coordinates, the
the member functions Mag() (=magnitude=rho in spherical coordinates), Mag2(), Theta(), CosTheta(), Phi(), Perp() (the transverse component=r in cylindrical coordinates), Perp2() can be used:

  Double_t m  = v.Mag();    // get magnitude (=rho=Sqrt(x*x+y*y+z*z)))
  Double_t m2 = v.Mag2();   // get magnitude squared
  Double_t t  = v.Theta();  // get polar angle
  Double_t ct = v.CosTheta();// get cos of theta
  Double_t p  = v.Phi();    // get azimuth angle
  Double_t pp = v.Perp();   // get transverse component
  Double_t pp2= v.Perp2();  // get transvers component squared

It is also possible to get the transverse component with respect to another vector:

  Double_t ppv1 = v.Perp(v1);
  Double_t pp2v1 = v.Perp2(v1);

The pseudorapiditiy ( eta=-ln (tan (phi/2)) ) can be get by Eta() or PseudoRapidity():
 
  Double_t eta = v.PseudoRapidity();

There are set functions to change one of the noncartesian coordinates:

  v.SetTheta(.5); // keeping rho and phi
  v.SetPhi(.8);   // keeping rho and theta
  v.SetMag(10.);  // keeping theta and phi
  v.SetPerp(3.);  // keeping z and phi
 

Arithmetic / Comparison

The TVector3 class provides the operators to add, subtract, scale and compare vectors:

  v3  = -v1;
  v1  = v2+v3;
  v1 += v3;
  v1  = v1 - v3
  v1 -= v3;
  v1 *= 10;
  v1  = 5*v2;

  if(v1==v2) {...}
  if(v1!=v2) {...}
 

Related Vectors

  v2 = v1.Unit();       // get unit vector parallel to v1
  v2 = v1.Orthogonal(); // get vector orthogonal to v1

Scalar and vector products

  s = v1.Dot(v2);   // scalar product
  s = v1 * v2;      // scalar product
  v = v1.Cross(v2); // vector product

 Angle between two vectors

  Double_t a = v1.Angle(v2);

Rotations

Rotation around axes
  v.RotateX(.5);
  v.RotateY(TMath::Pi());
  v.RotateZ(angle);
Rotation around a vector
  v1.Rotate(TMath::Pi()/4, v2); // rotation around v2
Rotation by TRotation
TVector3 objects can be rotated by objects of the TRotation class using the Transform() member functions,
the operator *= or the operator * of the TRotation class:

  TRotation m;
  ...
  v1.transform(m);
  v1 = m*v1;
  v1 *= m; // Attention v1 = m*v1

Transformation from rotated frame
  TVector3 direction = v.Unit()
  v1.RotateUz(direction); // direction must be TVector3 of unit length

transforms v1 from the rotated frame (z' parallel to direction, x' in the theta plane and y' in the xy plane as well as perpendicular to the theta plane) to the (x,y,z) frame. 


//

#include "TVector3.h"
#include "TRotation.h"
#include "TClass.h"

ClassImp(TVector3)

//______________________________________________________________________________
 TVector3::TVector3(const TVector3 & p) : TObject(p),
  fX(p.fX), fY(p.fY), fZ(p.fZ) {}

 TVector3::TVector3(Double_t x, Double_t y, Double_t z)
: fX(x), fY(y), fZ(z) {}

 TVector3::TVector3(const Double_t * x0)
: fX(x0[0]), fY(x0[1]), fZ(x0[2]) {}

 TVector3::TVector3(const Float_t * x0)
: fX(x0[0]), fY(x0[1]), fZ(x0[2]) {}

 TVector3::~TVector3() {}

//______________________________________________________________________________
Double_t TVector3::operator () (int i) const {
  switch(i) {
  case 0:
    return fX;
  case 1:
    return fY;
  case 2:
    return fZ;
  default:
    Error("operator()(i)", "bad index (%d) returning 0",i);
  }
  return 0.;
}

//______________________________________________________________________________
Double_t & TVector3::operator () (int i) {
  switch(i) {
  case 0:
    return fX;
  case 1:
    return fY;
  case 2:
    return fZ;
  default:
    Error("operator()(i)", "bad index (%d) returning &fX",i);
  }
  return fX;
}

//______________________________________________________________________________
TVector3 & TVector3::operator *= (const TRotation & m){
  return *this = m * (*this);
}

//______________________________________________________________________________
 TVector3 & TVector3::Transform(const TRotation & m) {
  return *this = m * (*this);
}

//______________________________________________________________________________
 void TVector3::RotateX(Double_t angle) {
  Double_t s = TMath::Sin(angle);
  Double_t c = TMath::Cos(angle);
  Double_t yy = fY;
  fY = c*yy - s*fZ;
  fZ = s*yy + c*fZ;
}

//______________________________________________________________________________
 void TVector3::RotateY(Double_t angle) {
  Double_t s = TMath::Sin(angle);
  Double_t c = TMath::Cos(angle);
  Double_t zz = fZ;
  fZ = c*zz - s*fX;
  fX = s*zz + c*fX;
}

//______________________________________________________________________________
 void TVector3::RotateZ(Double_t angle) {
  Double_t s = TMath::Sin(angle);
  Double_t c = TMath::Cos(angle);
  Double_t xx = fX;
  fX = c*xx - s*fY;
  fY = s*xx + c*fY;
}

//______________________________________________________________________________
 void TVector3::Rotate(Double_t angle, const TVector3 & axis){
  TRotation trans;
  trans.Rotate(angle, axis);
  operator*=(trans);
}

//______________________________________________________________________________
 void TVector3::RotateUz(const TVector3& NewUzVector) {
  // NewUzVector must be normalized !

  Double_t u1 = NewUzVector.fX;
  Double_t u2 = NewUzVector.fY;
  Double_t u3 = NewUzVector.fZ;
  Double_t up = u1*u1 + u2*u2;

  if (up) {
      up = TMath::Sqrt(up);
      Double_t px = fX,  py = fY,  pz = fZ;
      fX = (u1*u3*px - u2*py + u1*up*pz)/up;
      fY = (u2*u3*px + u1*py + u2*up*pz)/up;
      fZ = (u3*u3*px -    px + u3*up*pz)/up;
    }
  else if (u3 < 0.) { fX = -fX; fZ = -fZ; }      // phi=0  teta=pi
  else {};
}

//______________________________________________________________________________
 Double_t TVector3::PseudoRapidity() const {
  //Double_t m = Mag();
  //return 0.5*log( (m+fZ)/(m-fZ) );
  // guard against Pt=0
  double cosTheta = CosTheta();
  if (cosTheta*cosTheta < 1) return -0.5* TMath::Log( (1.0-cosTheta)/(1.0+cosTheta) );
  Warning("PseudoRapidity","transvers momentum = 0! return +/- 10e10");
  if (fZ > 0) return 10e10;
  else        return -10e10;
}

//______________________________________________________________________________
 void TVector3::SetPtEtaPhi(Double_t pt, Double_t eta, Double_t phi) {
  Double_t apt = TMath::Abs(pt);
  SetXYZ(apt*TMath::Cos(phi), apt*TMath::Sin(phi), apt/TMath::Tan(2.0*TMath::ATan(TMath::Exp(-eta))) );
}

//______________________________________________________________________________
 void TVector3::SetPtThetaPhi(Double_t pt, Double_t theta, Double_t phi) {
  fX = pt * TMath::Cos(phi);
  fY = pt * TMath::Sin(phi); 
  Double_t tanTheta = TMath::Tan(theta);
  fZ = tanTheta ? pt / tanTheta : 0;
}

//______________________________________________________________________________
 void TVector3::Streamer(TBuffer &R__b)
{
   // Stream an object of class TVector3.

   if (R__b.IsReading()) {
      UInt_t R__s, R__c;
      Version_t R__v = R__b.ReadVersion(&R__s, &R__c);
      if (R__v > 2) {
         TVector3::Class()->ReadBuffer(R__b, this, R__v, R__s, R__c);
         return;
      }
      //====process old versions before automatic schema evolution
      if (R__v < 2) TObject::Streamer(R__b);
      R__b >> fX;
      R__b >> fY;
      R__b >> fZ;
      R__b.CheckByteCount(R__s, R__c, TVector3::IsA());
      //====end of old versions
      
   } else {
      TVector3::Class()->WriteBuffer(R__b,this);
   }
}

TVector3 operator + (const TVector3 & a, const TVector3 & b) {
  return TVector3(a.X() + b.X(), a.Y() + b.Y(), a.Z() + b.Z());
}

TVector3 operator - (const TVector3 & a, const TVector3 & b) {
  return TVector3(a.X() - b.X(), a.Y() - b.Y(), a.Z() - b.Z());
}

TVector3 operator * (const TVector3 & p, Double_t a) {
  return TVector3(a*p.X(), a*p.Y(), a*p.Z());
}

TVector3 operator * (Double_t a, const TVector3 & p) {
  return TVector3(a*p.X(), a*p.Y(), a*p.Z());
}

Double_t operator * (const TVector3 & a, const TVector3 & b) {
  return a.Dot(b);
}

TVector3 operator * (const TMatrix & m, const TVector3 & v ) {
  return TVector3( m(0,0)*v.X()+m(0,1)*v.Y()+m(0,2)*v.Z(),
                   m(1,0)*v.X()+m(1,1)*v.Y()+m(1,2)*v.Z(),
                   m(2,0)*v.X()+m(2,1)*v.Y()+m(2,2)*v.Z());
}


//const TVector3 kXHat(1.0, 0.0, 0.0);
//const TVector3 kYHat(0.0, 1.0, 0.0);
//const TVector3 kZHat(0.0, 0.0, 1.0);

 void TVector3::Print(Option_t*)const
{
  Printf("%s %s (x,y,z)=(%f,%f,%f) (rho,theta,phi)=(%f,%f,%f)",GetName(),GetTitle(),X(),Y(),Z(),
                                          Mag(),Theta()*TMath::RadToDeg(),Phi()*TMath::RadToDeg());
}

ROOT page - Class index - Class Hierarchy - Top of the page
This page has been automatically generated. If you have any comments or suggestions about the page layout send a mail to ROOT support, or contact the developers with any questions or problems regarding ROOT.