Minor changes (R.Barbera)

[u/mrichter/AliRoot.git] / STEER / AliLegoGenerator.cxx

/**************************************************************************
 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
 *                                                                        *
 * Author: The ALICE Off-line Project.                                    *
 * Contributors are mentioned in the code where appropriate.              *
 *                                                                        *
 * Permission to use, copy, modify and distribute this software and its   *
 * documentation strictly for non-commercial purposes is hereby granted   *
 * without fee, provided that the above copyright notice appears in all   *
 * copies and that both the copyright notice and this permission notice   *
 * appear in the supporting documentation. The authors make no claims     *
 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/

/*
$Log$
Revision 1.3  2000/10/26 14:15:54  morsch
- Base class now
- Change from theta, phi to general coordinates Coor1, Coor2
- PropagateCylinder: bug in calculation of distance to limiting radius corrected.

Revision 1.2  2000/07/13 16:19:09  fca
Mainly coding conventions + some small bug fixes

Revision 1.1  2000/07/12 08:56:25  fca
Coding convention correction and warning removal

Revision 1.16  2000/05/26 08:35:03  fca
Move the check on z after z has been retrieved

Revision 1.15  2000/05/16 13:10:40  fca
New method IsNewTrack and fix for a problem in Father-Daughter relations

Revision 1.14  2000/04/27 10:38:21  fca
Correct termination of Lego Run and introduce Lego getter in AliRun

Revision 1.13  2000/04/26 10:17:31  fca
Changes in Lego for G4 compatibility

Revision 1.12  2000/04/07 11:12:33  fca
G4 compatibility changes

Revision 1.11  2000/03/22 13:42:26  fca
SetGenerator does not replace an existing generator, ResetGenerator does

Revision 1.10  2000/02/23 16:25:22  fca
AliVMC and AliGeant3 classes introduced
ReadEuclid moved from AliRun to AliModule

Revision 1.9  1999/12/03 10:54:01  fca
Fix lego summary

Revision 1.8  1999/10/01 09:54:33  fca
Correct logics for Lego StepManager

Revision 1.7  1999/09/29 09:24:29  fca
Introduction of the Copyright and cvs Log
*/

#include "AliLegoGenerator.h"
#include "AliRun.h"

ClassImp(AliLegoGenerator)

//___________________________________________

AliLegoGenerator::AliLegoGenerator()
{
  //
  // Default Constructor
  //
  SetName("Lego");

  fCoor1Bin  =  fCoor2Bin = -1;
  fCurCoor1  =  fCurCoor2 =  0;
}

AliLegoGenerator::AliLegoGenerator(Int_t nc1, Float_t c1min,
				   Float_t c1max, Int_t nc2, 
				   Float_t c2min, Float_t c2max,
				   Float_t rmin, Float_t rmax, Float_t zmax) :
  AliGenerator(0), fRadMin(rmin), fRadMax(rmax), fZMax(zmax), fNCoor1(nc1),
  fNCoor2(nc2), fCoor1Bin(nc1), fCoor2Bin(-1), fCurCoor1(0), fCurCoor2(0)
  
{
  //
  // Standard generator for Lego rays
  //
  SetCoor1Range(nc1, c1min, c1max);
  SetCoor2Range(nc2, c2min, c2max);
  SetName("Lego");
}

//___________________________________________
void AliLegoGenerator::Generate()
{
// Create a geantino with kinematics corresponding to the current bins
// Here: Coor1 =  theta 
//       Coor2 =  phi.
   
  //
  // Rootinos are 0
   const Int_t kMpart = 0;
   Float_t orig[3], pmom[3];
   Float_t t, cost, sint, cosp, sinp;
   if (fCoor1Bin==-1) fCoor1Bin=fNCoor1;
   // Prepare for next step
   if(fCoor1Bin>=fNCoor1-1)
     if(fCoor2Bin>=fNCoor2-1) {
       Warning("Generate","End of Lego Generation");
       return;
     } else { 
       fCoor2Bin++;
       printf("Generating rays in phi bin:%d\n",fCoor2Bin);
       fCoor1Bin=0;
     } else fCoor1Bin++;

   fCurCoor1 = (fCoor1Min+(fCoor1Bin+0.5)*(fCoor1Max-fCoor1Min)/fNCoor1);
   fCurCoor2 = (fCoor2Min+(fCoor2Bin+0.5)*(fCoor2Max-fCoor2Min)/fNCoor2);
   cost      = TMath::Cos(fCurCoor1 * TMath::Pi()/180.);
   sint      = TMath::Sin(fCurCoor1 * TMath::Pi()/180.);
   cosp      = TMath::Cos(fCurCoor2 * TMath::Pi()/180.);
   sinp      = TMath::Sin(fCurCoor2 * TMath::Pi()/180.);
   
   pmom[0] = cosp*sint;
   pmom[1] = sinp*sint;
   pmom[2] = cost;
   
   // --- Where to start
   orig[0] = orig[1] = orig[2] = 0;
   Float_t dalicz = 3000;
   if (fRadMin > 0) {
       t = PropagateCylinder(orig,pmom,fRadMin,dalicz);
       orig[0] = pmom[0]*t;
       orig[1] = pmom[1]*t;
       orig[2] = pmom[2]*t;
       if (TMath::Abs(orig[2]) > fZMax) return;
   }
   
   Float_t polar[3]={0.,0.,0.};
   Int_t ntr;
   gAlice->SetTrack(1, 0, kMpart, pmom, orig, polar, 0, kPPrimary, ntr);
   
}

//___________________________________________
Float_t AliLegoGenerator::PropagateCylinder(Float_t *x, Float_t *v, Float_t r, Float_t z)
{
// Propagate to cylinder from inside

   Double_t hnorm, sz, t, t1, t2, t3, sr;
   Double_t d[3];
   const Float_t kSmall  = 1e-8;
   const Float_t kSmall2 = kSmall*kSmall;

// ---> Find intesection with Z planes
   d[0]  = v[0];
   d[1]  = v[1];
   d[2]  = v[2];
   hnorm = TMath::Sqrt(1/(d[0]*d[0]+d[1]*d[1]+d[2]*d[2]));
   d[0] *= hnorm;
   d[1] *= hnorm;
   d[2] *= hnorm;
   if (d[2] > kSmall)       sz = (z-x[2])/d[2];
   else if (d[2] < -kSmall) sz = -(z+x[2])/d[2];
   else                     sz = 1.e10;  // ---> Direction parallel to X-Y, no intersection

// ---> Intersection with cylinders
//      Intersection point (x,y,z)
//      (x,y,z) is on track :    x=X(1)+t*D(1)
//                               y=X(2)+t*D(2)
//                               z=X(3)+t*D(3)
//      (x,y,z) is on cylinder : x**2 + y**2 = R**2
//
//      (D(1)**2+D(2)**2)*t**2
//      +2.*(X(1)*D(1)+X(2)*D(2))*t
//      +X(1)**2+X(2)**2-R**2=0
// ---> Solve second degree equation
   t1 = d[0]*d[0] + d[1]*d[1];
   if (t1 <= kSmall2) {
      t = sz;  // ---> Track parallel to the z-axis, take distance to planes
   } else {
      t2 = x[0]*d[0] + x[1]*d[1];
      t3 = x[0]*x[0] + x[1]*x[1];
      // ---> It should be positive, but there may be numerical problems
      sr = (-t2 +TMath::Sqrt(TMath::Max(t2*t2-(t3-r*r)*t1,0.)))/t1;
      // ---> Find minimum distance between planes and cylinder
      t  = TMath::Min(sz,sr);
   }
   return t;
}