library: libPhysics #include "TVector3.h"

# TVector3

class description - source file - inheritance tree (.pdf)

## class TVector3 : public TObject

| Inheritance Chart:

`TObject`

<-

`TVector3`

        public:

                          TVector3(Double_t x = 0.0, Double_t y = 0.0, Double_t z = 0.0)
                          TVector3(const Double_t*)
                          TVector3(const Float_t*)
                          TVector3(const TVector3&)
                 TVector3 operator-() const
                 TVector3 Unit() const
                 TVector3 Orthogonal() const
                 TVector3 Cross(const TVector3& p) const
                  virtual ~TVector3()
                 Double_t Angle(const TVector3& q) const
           static TClass* Class()
                 Double_t CosTheta() const
                 Double_t DeltaPhi(const TVector3& v) const
                 Double_t DeltaR(const TVector3& v) const
                 Double_t Dot(const TVector3& p) const
                 Double_t DrEtaPhi(const TVector3& v) const
                 Double_t Eta() const
                 TVector2 EtaPhiVector() const
                     void GetXYZ(Double_t* carray) const
                     void GetXYZ(Float_t* carray) const
          virtual TClass* IsA() const
                 Double_t Mag() const
                 Double_t Mag2() const
                   Bool_t operator!=(const TVector3& v) const
                 Double_t operator()(int) const
                Double_t& operator()(int)
                TVector3& operator*=(Double_t a)
                TVector3& operator*=(const TRotation&)
                TVector3& operator+=(const TVector3& p)
                TVector3& operator-=(const TVector3& p)
                TVector3& operator=(const TVector3& p)
                   Bool_t operator==(const TVector3& v) const
                 Double_t operator[](int i) const
                Double_t& operator[](int i)
                 Double_t Perp() const
                 Double_t Perp(const TVector3& p) const
                 Double_t Perp2() const
                 Double_t Perp2(const TVector3& p) const
                 Double_t Phi() const
             virtual void Print(Option_t* option = "") const
                 Double_t PseudoRapidity() const
                 Double_t Pt() const
                 Double_t Pt(const TVector3& p) const
                 Double_t Px() const
                 Double_t Py() const
                 Double_t Pz() const
                     void Rotate(Double_t, const TVector3&)
                     void RotateUz(const TVector3&)
                     void RotateX(Double_t)
                     void RotateY(Double_t)
                     void RotateZ(Double_t)
                     void SetMag(Double_t ma)
                     void SetMagThetaPhi(Double_t mag, Double_t theta, Double_t phi)
                     void SetPerp(Double_t r)
                     void SetPhi(Double_t ph)
                     void SetPtEtaPhi(Double_t pt, Double_t eta, Double_t phi)
                     void SetPtThetaPhi(Double_t pt, Double_t theta, Double_t phi)
                     void SetTheta(Double_t th)
                     void SetX(Double_t x)
                     void SetXYZ(Double_t x, Double_t y, Double_t z)
                     void SetY(Double_t y)
                     void SetZ(Double_t z)
             virtual void ShowMembers(TMemberInspector& insp, char* parent)
             virtual void Streamer(TBuffer& b)
                     void StreamerNVirtual(TBuffer& b)
                 Double_t Theta() const
                TVector3& Transform(const TRotation&)
                 Double_t x() const
                 Double_t X() const
                 TVector2 XYvector() const
                 Double_t y() const
                 Double_t Y() const
                 Double_t z() const
                 Double_t Z() const

### Data Members

        private:

          Double_t fX
          Double_t fY
          Double_t fZ

## Class Description

    *-*-*-*-*-*-*-*-*-*-*-*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.

TVector3(const TVector3 & p) : TObject(p), fX(p.fX), fY(p.fY), fZ(p.fZ)

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

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

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

~TVector3()

TVector3& Transform(const TRotation & m)

void RotateX(Double_t angle)

void RotateY(Double_t angle)

void RotateZ(Double_t angle)

void Rotate(Double_t angle, const TVector3 & axis)

void RotateUz(const TVector3& NewUzVector)

     NewUzVector must be normalized !

Double_t PseudoRapidity() const

    Double_t m = Mag();
    return 0.5*log( (m+fZ)/(m-fZ) );
     guard against Pt=0

void SetPtEtaPhi(Double_t pt, Double_t eta, Double_t phi)

void SetPtThetaPhi(Double_t pt, Double_t theta, Double_t phi)

void Streamer(TBuffer &R__b)

     Stream an object of class TVector3.

void Print(Option_t*)const

### Inline Functions

               Double_t operator()(int) const
               Double_t operator[](int i) const
              Double_t& operator()(int)
              Double_t& operator[](int i)
               Double_t x() const
               Double_t y() const
               Double_t z() const
               Double_t X() const
               Double_t Y() const
               Double_t Z() const
               Double_t Px() const
               Double_t Py() const
               Double_t Pz() const
                   void SetX(Double_t x)
                   void SetY(Double_t y)
                   void SetZ(Double_t z)
                   void SetXYZ(Double_t x, Double_t y, Double_t z)
                   void GetXYZ(Double_t* carray) const
                   void GetXYZ(Float_t* carray) const
               Double_t Phi() const
               Double_t Theta() const
               Double_t CosTheta() const
               Double_t Mag2() const
               Double_t Mag() const
                   void SetPhi(Double_t ph)
                   void SetTheta(Double_t th)
                   void SetMag(Double_t ma)
               Double_t Perp2() const
               Double_t Pt() const
               Double_t Perp() const
                   void SetPerp(Double_t r)
               Double_t Perp2(const TVector3& p) const
               Double_t Pt(const TVector3& p) const
               Double_t Perp(const TVector3& p) const
               Double_t DeltaPhi(const TVector3& v) const
               Double_t DeltaR(const TVector3& v) const
               Double_t DrEtaPhi(const TVector3& v) const
               TVector2 EtaPhiVector() const
                   void SetMagThetaPhi(Double_t mag, Double_t theta, Double_t phi)
              TVector3& operator=(const TVector3& p)
                 Bool_t operator==(const TVector3& v) const
                 Bool_t operator!=(const TVector3& v) const
              TVector3& operator+=(const TVector3& p)
              TVector3& operator-=(const TVector3& p)
               TVector3 operator-() const
              TVector3& operator*=(Double_t a)
               TVector3 Unit() const
               TVector3 Orthogonal() const
               Double_t Dot(const TVector3& p) const
               TVector3 Cross(const TVector3& p) const
               Double_t Angle(const TVector3& q) const
               Double_t Eta() const
              TVector3& operator*=(const TRotation&)
               TVector2 XYvector() const
                TClass* Class()
                TClass* IsA() const
                   void ShowMembers(TMemberInspector& insp, char* parent)
                   void StreamerNVirtual(TBuffer& b)

Author: Pasha Murat, Peter Malzacher 12/02/99
Last update: root/physics:$Name: $:$Id: TVector3.cxx,v 1.8 2004/04/29 17:43:59 brun Exp $