THelix


class description - source file - inheritance tree

class THelix : public TPolyLine3D


    protected:
Double_t FindClosestPhase(Double_t phi0, Double_t cosine) void SetRotMatrix() public:
THelix THelix() THelix THelix(Double_t x, Double_t y, Double_t z, Double_t vx, Double_t vy, Double_t vz, Double_t w) THelix THelix(Double_t* xyz, Double_t* v, Double_t w, Double_t* range = 0, EHelixRangeType rtype = kHelixZ, Double_t* axis = 0) THelix THelix(const THelix& helix) virtual void ~THelix() TClass* Class() virtual void Copy(TObject& helix) virtual void Draw(Option_t* option) virtual Option_t* GetOption() const virtual TClass* IsA() const virtual void Paint(Option_t* option) virtual void Print(Option_t* option) virtual void SavePrimitive(ofstream& out, Option_t* option) virtual void SetAxis(Double_t x, Double_t y, Double_t z) virtual void SetAxis(Double_t* axis) void SetHelix(Double_t* xyz, Double_t* v, Double_t w, Double_t* range = 0, EHelixRangeType type = kUnchanged, Double_t* axis = 0) virtual void SetOption(Option_t* option) virtual void SetRange(Double_t r1, Double_t r2, EHelixRangeType rtype = kHelixZ) virtual void SetRange(Double_t* range, EHelixRangeType rtype = kHelixZ) virtual void ShowMembers(TMemberInspector& insp, char* parent) virtual void Sizeof3D() const virtual void Streamer(TBuffer& b)

Data Members

protected:
Double_t fX0 Initial X position Double_t fY0 Initial Y position Double_t fZ0 Initial Z position Double_t fVt Transverse velocity (constant of motion) Double_t fPhi0 Initial phase, so vx0 = fVt*cos(fPhi0) Double_t fVz Z velocity (constant of motion) Double_t fW Angular frequency Double_t fAxis[3] Direction unit vector of the helix axis TRotMatrix* fRotMat Rotation matrix: axis // z --> axis // fAxis Double_t fRange[2] Range of helix parameter t static Int_t fgMinNSeg minimal number of segments in polyline

Class Description

 Helix is, hmmm, well, a helix.  It has 3 different constructors.

 Comments/suggestions/etc on this class should be sent to the author:
             pyeh@cdfsga.fnal.gov (Ping Yeh)

   If a particle with charge q passes through a point (x,y,z)
   with momentum (px,py,pz) with magnetic field B along an axis (nx,ny,nz),
   this helix can be constrcuted like

      THelix p(x0,y0,z0, px,py,pz, q*B, nx,ny,nz);

     (nx,ny,nz) defaults to (0,0,1).

   A helix in its own frame can be defined with initial position
   (x0,y0,z0) and "velocity" (vx0,vy0,vz0), both 3-vectors, and
   an angular frequency w.  The parametric equation of the helix is

    x = x0 - vt / w * sin(-w * t + phi0)
    y = y0 + vt / w * cos(-w * t + phi0)
    z = z0 + vz * t


   The 'normal constructor' has 6 parameters,

       Example:
                 THelix pl1(xyz0, v0, w, range, rtype, axis);

         where:
             xyz0  : array of initial position
             v0    : array of initial velocity
             w     : angular frequency
             range : helix range
             rtype : kHelixZ specifies allowed drawing range in helix Z direction, i.e., along B field.
                     kLabZ specifies drawing range in lab frame.
                     kHelixX, kHelixY, kLabX, kLabY, kUnchanged ... etc can also be specified
             axis  : helix axis



 A Third constructor uses several default values:

       Example:
   c1 = new TCanvas("c1");
   TView *view = new TView(1);
   view->SetRange(-1,-1,-1,1,1,1);
   THelix *helix = new THelix(0.0, 0.0, 0.0, 1.0, 0.0, 0.3, 10.0);
   helix->Draw();

 will initializes a helix with its axis in Z direction (rtype=kHelixZ).
 range[0] = 0 and range[1] = 1
______________________________________________________________________________

void SetHelix(Double_t *p, Double_t *v, Double_t w, Double_t *range, EHelixRangeType rType, Double_t *axis )
 Set all helix parameters.

THelix()
 Helix default constructor.

THelix(Double_t x, Double_t y, Double_t z, Double_t vx, Double_t vy, Double_t vz, Double_t w) : TPolyLine3D()
 Helix normal constructor.

THelix(Double_t * p, Double_t * v, Double_t w, Double_t * range, EHelixRangeType rType, Double_t * axis) : TPolyLine3D()
 Helix normal constructor.

THelix(const THelix &h) : TPolyLine3D()
 Helix copy constructor.

~THelix()
 Helix destructor.

THelix(const THelix &helix)

void Copy(TObject &obj)
 Copy this helix to obj.

void Draw(Option_t *option)
 Draw this helix with its current attributes.

void Print(Option_t *option)
 Dump this helix with its attributes.

void SavePrimitive(ofstream &out, Option_t *)
 Save primitive as a C++ statement(s) on output stream out.

void SetAxis(Double_t * axis)
 Set a new axis for the helix.  This will make a new rotation matrix.

void SetAxis(Double_t x, Double_t y, Double_t z)

void SetRange(Double_t * range, EHelixRangeType rType)
 set a new range for the helix.  This will remake the polyline.


void SetRange(Double_t r1, Double_t r2, EHelixRangeType rType)

void Sizeof3D() const
 Return total X3D size of this shape with its attributes.

void SetRotMatrix()
 set the rotational matrix according to the helix axis


Double_t FindClosestPhase(Double_t phi0, Double_t cosine)
 Finds the closest phase to phi0 that gives cos(phase) = cosine




Inline Functions


          Option_t* GetOption() const
               void Paint(Option_t* option)
               void SetOption(Option_t* option)
            TClass* Class()
            TClass* IsA() const
               void ShowMembers(TMemberInspector& insp, char* parent)
               void Streamer(TBuffer& b)


Author: Ping Yeh 19/12/97
Last update: 2.20/05 17/04/99 07.50.09 by Rene Brun
Copyright (c) 1995-1999, The ROOT System, All rights reserved. *


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