- Change from coordinates theta, phi to general coordinates Coor1 and Coor2.
[u/mrichter/AliRoot.git] / STEER / AliLegoGenerator.cxx
CommitLineData
8918e700 1/**************************************************************************
2 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
3 * *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
6 * *
7 * Permission to use, copy, modify and distribute this software and its *
8 * documentation strictly for non-commercial purposes is hereby granted *
9 * without fee, provided that the above copyright notice appears in all *
10 * copies and that both the copyright notice and this permission notice *
11 * appear in the supporting documentation. The authors make no claims *
12 * about the suitability of this software for any purpose. It is *
13 * provided "as is" without express or implied warranty. *
14 **************************************************************************/
15
16/*
17$Log$
ef42d733 18Revision 1.1 2000/07/12 08:56:25 fca
19Coding convention correction and warning removal
20
8918e700 21Revision 1.16 2000/05/26 08:35:03 fca
22Move the check on z after z has been retrieved
23
24Revision 1.15 2000/05/16 13:10:40 fca
25New method IsNewTrack and fix for a problem in Father-Daughter relations
26
27Revision 1.14 2000/04/27 10:38:21 fca
28Correct termination of Lego Run and introduce Lego getter in AliRun
29
30Revision 1.13 2000/04/26 10:17:31 fca
31Changes in Lego for G4 compatibility
32
33Revision 1.12 2000/04/07 11:12:33 fca
34G4 compatibility changes
35
36Revision 1.11 2000/03/22 13:42:26 fca
37SetGenerator does not replace an existing generator, ResetGenerator does
38
39Revision 1.10 2000/02/23 16:25:22 fca
40AliVMC and AliGeant3 classes introduced
41ReadEuclid moved from AliRun to AliModule
42
43Revision 1.9 1999/12/03 10:54:01 fca
44Fix lego summary
45
46Revision 1.8 1999/10/01 09:54:33 fca
47Correct logics for Lego StepManager
48
49Revision 1.7 1999/09/29 09:24:29 fca
50Introduction of the Copyright and cvs Log
51
52*/
53
54#include "AliLegoGenerator.h"
55#include "AliRun.h"
56
57ClassImp(AliLegoGenerator)
58
59//___________________________________________
60AliLegoGenerator::AliLegoGenerator(Int_t ntheta, Float_t themin,
61 Float_t themax, Int_t nphi,
62 Float_t phimin, Float_t phimax,
63 Float_t rmin, Float_t rmax, Float_t zmax) :
64 AliGenerator(0), fRadMin(rmin), fRadMax(rmax), fZMax(zmax), fNtheta(ntheta),
65 fNphi(nphi), fThetaBin(ntheta), fPhiBin(-1), fCurTheta(0), fCurPhi(0)
66
67{
ef42d733 68 //
69 // Standard generator for Lego rays
70 //
8918e700 71 SetPhiRange(phimin,phimax);
72 SetThetaRange(themin,themax);
73 SetName("Lego");
74}
75
76
77//___________________________________________
78void AliLegoGenerator::Generate()
79{
80// Create a geantino with kinematics corresponding to the current
81// bins in theta and phi.
82
83 //
84 // Rootinos are 0
85 const Int_t kMpart = 0;
86 Float_t orig[3], pmom[3];
87 Float_t t, cost, sint, cosp, sinp;
88
89 // Prepare for next step
90 if(fThetaBin>=fNtheta-1)
91 if(fPhiBin>=fNphi-1) {
92 Warning("Generate","End of Lego Generation");
93 return;
94 } else {
95 fPhiBin++;
96 printf("Generating rays in phi bin:%d\n",fPhiBin);
97 fThetaBin=0;
98 } else fThetaBin++;
99
100 fCurTheta = (fThetaMin+(fThetaBin+0.5)*(fThetaMax-fThetaMin)/fNtheta);
101 fCurPhi = (fPhiMin+(fPhiBin+0.5)*(fPhiMax-fPhiMin)/fNphi);
102 cost = TMath::Cos(fCurTheta);
103 sint = TMath::Sin(fCurTheta);
104 cosp = TMath::Cos(fCurPhi);
105 sinp = TMath::Sin(fCurPhi);
106
107 pmom[0] = cosp*sint;
108 pmom[1] = sinp*sint;
109 pmom[2] = cost;
110
111 // --- Where to start
112 orig[0] = orig[1] = orig[2] = 0;
113 Float_t dalicz = 3000;
114 if (fRadMin > 0) {
115 t = PropagateCylinder(orig,pmom,fRadMin,dalicz);
116 orig[0] = pmom[0]*t;
117 orig[1] = pmom[1]*t;
118 orig[2] = pmom[2]*t;
119 if (TMath::Abs(orig[2]) > fZMax) return;
120 }
121
122 Float_t polar[3]={0.,0.,0.};
123 Int_t ntr;
124 gAlice->SetTrack(1, 0, kMpart, pmom, orig, polar, 0, "LEGO ray", ntr);
125
126}
127
128//___________________________________________
129Float_t AliLegoGenerator::PropagateCylinder(Float_t *x, Float_t *v, Float_t r, Float_t z)
130{
131// Propagate to cylinder from inside
132
133 Double_t hnorm, sz, t, t1, t2, t3, sr;
134 Double_t d[3];
135 const Float_t kSmall = 1e-8;
136 const Float_t kSmall2 = kSmall*kSmall;
137
138// ---> Find intesection with Z planes
139 d[0] = v[0];
140 d[1] = v[1];
141 d[2] = v[2];
142 hnorm = TMath::Sqrt(1/(d[0]*d[0]+d[1]*d[1]+d[2]*d[2]));
143 d[0] *= hnorm;
144 d[1] *= hnorm;
145 d[2] *= hnorm;
146 if (d[2] > kSmall) sz = (z-x[2])/d[2];
147 else if (d[2] < -kSmall) sz = -(z+x[2])/d[2];
148 else sz = 1.e10; // ---> Direction parallel to X-Y, no intersection
149
150// ---> Intersection with cylinders
151// Intersection point (x,y,z)
152// (x,y,z) is on track : x=X(1)+t*D(1)
153// y=X(2)+t*D(2)
154// z=X(3)+t*D(3)
155// (x,y,z) is on cylinder : x**2 + y**2 = R**2
156//
157// (D(1)**2+D(2)**2)*t**2
158// +2.*(X(1)*D(1)+X(2)*D(2))*t
159// +X(1)**2+X(2)**2-R**2=0
160// ---> Solve second degree equation
161 t1 = d[0]*d[0] + d[1]*d[1];
162 if (t1 <= kSmall2) {
163 t = sz; // ---> Track parallel to the z-axis, take distance to planes
164 } else {
165 t2 = x[0]*d[0] + x[1]*d[1];
166 t3 = x[0]*x[0] + x[1]*x[1];
167 // ---> It should be positive, but there may be numerical problems
168 sr = (t2 +TMath::Sqrt(TMath::Max(t2*t2-(t3-r*r)*t1,0.)))/t1;
169 // ---> Find minimum distance between planes and cylinder
170 t = TMath::Min(sz,sr);
171 }
172 return t;
173}
174