1 /**************************************************************************
2 * Copyright(c) 1998-2003, ALICE Experiment at CERN, All rights reserved. *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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 ///////////////////////////////////////////////////////////////////
17 // A straight line is coded as a point (3 Double_t) and //
18 // 3 direction cosines //
20 ///////////////////////////////////////////////////////////////////
21 #include <Riostream.h>
23 #include "AliStrLine.h"
27 //________________________________________________________
28 AliStrLine::AliStrLine() {
29 // Default constructor
30 for(Int_t i=0;i<3;i++) {
38 //________________________________________________________
39 AliStrLine::AliStrLine(Double_t *point, Double_t *cd,Bool_t twopoints) {
40 // Standard constructor
41 // if twopoints is true: point and cd are the 3D coordinates of
42 // two points defininig the straight line
43 // if twopoint is false: point represents the 3D coordinates of a point
44 // belonging to the straight line and cd is the
47 InitTwoPoints(point,cd);
50 InitDirection(point,cd);
55 //________________________________________________________
56 void AliStrLine::InitDirection(Double_t *point, Double_t *cd){
57 // Initialization from a point and a direction
59 for(Int_t i=0;i<3;i++)norm+=cd[i]*cd[i];
61 norm = TMath::Sqrt(norm);
62 for(Int_t i=0;i<3;i++) cd[i]/=norm;
65 Error("AliStrLine","Null direction cosines!!!");
73 //________________________________________________________
74 void AliStrLine::InitTwoPoints(Double_t *pA, Double_t *pB){
75 // Initialization from the coordinates of two
76 // points in the space
78 for(Int_t i=0;i<3;i++)cd[i] = pB[i]-pA[i];
82 //________________________________________________________
83 AliStrLine::~AliStrLine() {
87 //________________________________________________________
88 void AliStrLine::PrintStatus() const {
89 // Print current status
90 cout <<"=======================================================\n";
91 cout <<"Direction cosines: ";
92 for(Int_t i=0;i<3;i++)cout <<fCd[i]<<"; ";
94 cout <<"Known point: ";
95 for(Int_t i=0;i<3;i++)cout <<fP0[i]<<"; ";
97 cout <<"Current value for the parameter: "<<fTpar<<endl;
98 cout <<" Debug flag: "<<fDebug<<endl;
101 //________________________________________________________
102 Int_t AliStrLine::IsParallelTo(AliStrLine *line) const {
103 // returns 1 if lines are parallel, 0 if not paralel
106 Double_t vecpx=fCd[1]*cd2[2]-fCd[2]*cd2[1];
107 if(vecpx!=0) return 0;
108 Double_t vecpy=-fCd[0]*cd2[2]+fCd[2]*cd2[0];
109 if(vecpy!=0) return 0;
110 Double_t vecpz=fCd[0]*cd2[1]-fCd[1]*cd2[0];
111 if(vecpz!=0) return 0;
114 //________________________________________________________
115 Int_t AliStrLine::Crossrphi(AliStrLine *line){
116 // Cross 2 lines in the X-Y plane
123 Double_t c=p2[0]-fP0[0];
126 Double_t f=p2[1]-fP0[1];
127 Double_t deno = a*e-b*d;
130 fTpar = (c*e-b*f)/deno;
138 //________________________________________________________
139 Int_t AliStrLine::CrossPoints(AliStrLine *line, Double_t *point1, Double_t *point2){
140 // Looks for the crossing point estimated starting from the
148 for(i=0;i<3;i++)k1+=(fP0[i]-p2[i])*fCd[i];
150 for(i=0;i<3;i++)k2+=(fP0[i]-p2[i])*cd2[i];
152 for(i=0;i<3;i++)a11+=fCd[i]*cd2[i];
155 for(i=0;i<3;i++)a21+=cd2[i]*cd2[i];
157 for(i=0;i<3;i++)a12-=fCd[i]*fCd[i];
158 Double_t deno = a11*a22-a21*a12;
159 if(deno == 0.) return -1;
160 fTpar = (a11*k2-a21*k1) / deno;
161 Double_t par2 = (k1*a22-k2*a12) / deno;
163 GetCurrentPoint(point1);
164 line->GetCurrentPoint(point2);
167 //________________________________________________________________
168 Int_t AliStrLine::Cross(AliStrLine *line, Double_t *point){
170 //Finds intersection between lines
173 Int_t retcod=CrossPoints(line,point1,point2);
175 for(Int_t i=0;i<3;i++)point[i]=(point1[i]+point2[i])/2.;
182 //___________________________________________________________
183 Double_t AliStrLine::GetDCA(AliStrLine *line){
184 //Returns the distance of closest approach between two lines
190 Int_t ispar=IsParallelTo(line);
192 Double_t dist1q=0,dist2=0,mod=0;
194 dist1q+=(fP0[i]-p2[i])*(fP0[i]-p2[i]);
195 dist2+=(fP0[i]-p2[i])*fCd[i];
200 return TMath::Sqrt(dist1q-dist2*dist2);
204 perp[0]=fCd[1]*cd2[2]-fCd[2]*cd2[1];
205 perp[1]=-fCd[0]*cd2[2]+fCd[2]*cd2[0];
206 perp[2]=fCd[0]*cd2[1]-fCd[1]*cd2[0];
207 Double_t mod=0,dist=0;
209 mod+=perp[i]*perp[i];
210 dist+=(fP0[i]-p2[i])*perp[i];
215 return TMath::Abs(dist);
219 //________________________________________________________
220 void AliStrLine::GetCurrentPoint(Double_t *point) const {
221 // Fills the array point with the current value on the line
222 for(Int_t i=0;i<3;i++)point[i]=fP0[i]+fCd[i]*fTpar;