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() :
33 // Default constructor
34 for(Int_t i=0;i<3;i++) {
40 //________________________________________________________
41 AliStrLine::AliStrLine(Double_t *point, Double_t *cd,Bool_t twopoints) :
46 // Standard constructor
47 // if twopoints is true: point and cd are the 3D coordinates of
48 // two points defininig the straight line
49 // if twopoint is false: point represents the 3D coordinates of a point
50 // belonging to the straight line and cd is the
53 InitTwoPoints(point,cd);
56 InitDirection(point,cd);
61 //________________________________________________________
62 void AliStrLine::InitDirection(Double_t *point, Double_t *cd){
63 // Initialization from a point and a direction
65 for(Int_t i=0;i<3;i++)norm+=cd[i]*cd[i];
67 norm = TMath::Sqrt(norm);
68 for(Int_t i=0;i<3;i++) cd[i]/=norm;
71 Error("AliStrLine","Null direction cosines!!!");
79 //________________________________________________________
80 void AliStrLine::InitTwoPoints(Double_t *pA, Double_t *pB){
81 // Initialization from the coordinates of two
82 // points in the space
84 for(Int_t i=0;i<3;i++)cd[i] = pB[i]-pA[i];
88 //________________________________________________________
89 AliStrLine::~AliStrLine() {
93 //________________________________________________________
94 void AliStrLine::PrintStatus() const {
95 // Print current status
96 cout <<"=======================================================\n";
97 cout <<"Direction cosines: ";
98 for(Int_t i=0;i<3;i++)cout <<fCd[i]<<"; ";
100 cout <<"Known point: ";
101 for(Int_t i=0;i<3;i++)cout <<fP0[i]<<"; ";
103 cout <<"Current value for the parameter: "<<fTpar<<endl;
104 cout <<" Debug flag: "<<fDebug<<endl;
107 //________________________________________________________
108 Int_t AliStrLine::IsParallelTo(AliStrLine *line) const {
109 // returns 1 if lines are parallel, 0 if not paralel
112 Double_t vecpx=fCd[1]*cd2[2]-fCd[2]*cd2[1];
113 if(vecpx!=0) return 0;
114 Double_t vecpy=-fCd[0]*cd2[2]+fCd[2]*cd2[0];
115 if(vecpy!=0) return 0;
116 Double_t vecpz=fCd[0]*cd2[1]-fCd[1]*cd2[0];
117 if(vecpz!=0) return 0;
120 //________________________________________________________
121 Int_t AliStrLine::Crossrphi(AliStrLine *line){
122 // Cross 2 lines in the X-Y plane
129 Double_t c=p2[0]-fP0[0];
132 Double_t f=p2[1]-fP0[1];
133 Double_t deno = a*e-b*d;
136 fTpar = (c*e-b*f)/deno;
144 //________________________________________________________
145 Int_t AliStrLine::CrossPoints(AliStrLine *line, Double_t *point1, Double_t *point2){
146 // Looks for the crossing point estimated starting from the
154 for(i=0;i<3;i++)k1+=(fP0[i]-p2[i])*fCd[i];
156 for(i=0;i<3;i++)k2+=(fP0[i]-p2[i])*cd2[i];
158 for(i=0;i<3;i++)a11+=fCd[i]*cd2[i];
161 for(i=0;i<3;i++)a21+=cd2[i]*cd2[i];
163 for(i=0;i<3;i++)a12-=fCd[i]*fCd[i];
164 Double_t deno = a11*a22-a21*a12;
165 if(deno == 0.) return -1;
166 fTpar = (a11*k2-a21*k1) / deno;
167 Double_t par2 = (k1*a22-k2*a12) / deno;
169 GetCurrentPoint(point1);
170 line->GetCurrentPoint(point2);
173 //________________________________________________________________
174 Int_t AliStrLine::Cross(AliStrLine *line, Double_t *point){
176 //Finds intersection between lines
179 Int_t retcod=CrossPoints(line,point1,point2);
181 for(Int_t i=0;i<3;i++)point[i]=(point1[i]+point2[i])/2.;
188 //___________________________________________________________
189 Double_t AliStrLine::GetDCA(AliStrLine *line){
190 //Returns the distance of closest approach between two lines
196 Int_t ispar=IsParallelTo(line);
198 Double_t dist1q=0,dist2=0,mod=0;
200 dist1q+=(fP0[i]-p2[i])*(fP0[i]-p2[i]);
201 dist2+=(fP0[i]-p2[i])*fCd[i];
206 return TMath::Sqrt(dist1q-dist2*dist2);
210 perp[0]=fCd[1]*cd2[2]-fCd[2]*cd2[1];
211 perp[1]=-fCd[0]*cd2[2]+fCd[2]*cd2[0];
212 perp[2]=fCd[0]*cd2[1]-fCd[1]*cd2[0];
213 Double_t mod=0,dist=0;
215 mod+=perp[i]*perp[i];
216 dist+=(fP0[i]-p2[i])*perp[i];
221 return TMath::Abs(dist);
225 //________________________________________________________
226 void AliStrLine::GetCurrentPoint(Double_t *point) const {
227 // Fills the array point with the current value on the line
228 for(Int_t i=0;i<3;i++)point[i]=fP0[i]+fCd[i]*fTpar;