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 **************************************************************************/
18 ///////////////////////////////////////////////////////////////////
20 // A straight line is coded as a point (3 Double_t) and //
21 // 3 direction cosines //
23 ///////////////////////////////////////////////////////////////////
25 #include <Riostream.h>
29 #include "AliStrLine.h"
33 //________________________________________________________
34 AliStrLine::AliStrLine() :
39 // Default constructor
40 for(Int_t i=0;i<3;i++) {
46 //________________________________________________________
47 AliStrLine::AliStrLine(Double_t *point, Double_t *cd,Bool_t twopoints) :
52 // Standard constructor
53 // if twopoints is true: point and cd are the 3D coordinates of
54 // two points defininig the straight line
55 // if twopoint is false: point represents the 3D coordinates of a point
56 // belonging to the straight line and cd is the
59 InitTwoPoints(point,cd);
62 InitDirection(point,cd);
66 //________________________________________________________
67 AliStrLine::AliStrLine(Float_t *pointf, Float_t *cdf,Bool_t twopoints) :
72 // Standard constructor - with float arguments
73 // if twopoints is true: point and cd are the 3D coordinates of
74 // two points defininig the straight line
75 // if twopoint is false: point represents the 3D coordinates of a point
76 // belonging to the straight line and cd is the
80 for(Int_t i=0;i<3;i++){
85 InitTwoPoints(point,cd);
88 InitDirection(point,cd);
92 //________________________________________________________
93 void AliStrLine::InitDirection(Double_t *point, Double_t *cd){
94 // Initialization from a point and a direction
96 for(Int_t i=0;i<3;i++)norm+=cd[i]*cd[i];
98 norm = TMath::Sqrt(norm);
99 for(Int_t i=0;i<3;i++) cd[i]/=norm;
102 Error("AliStrLine","Null direction cosines!!!");
110 //________________________________________________________
111 void AliStrLine::InitTwoPoints(Double_t *pA, Double_t *pB){
112 // Initialization from the coordinates of two
113 // points in the space
115 for(Int_t i=0;i<3;i++)cd[i] = pB[i]-pA[i];
116 InitDirection(pA,cd);
119 //________________________________________________________
120 AliStrLine::~AliStrLine() {
124 //________________________________________________________
125 void AliStrLine::PrintStatus() const {
126 // Print current status
127 cout <<"=======================================================\n";
128 cout <<"Direction cosines: ";
129 for(Int_t i=0;i<3;i++)cout <<fCd[i]<<"; ";
131 cout <<"Known point: ";
132 for(Int_t i=0;i<3;i++)cout <<fP0[i]<<"; ";
134 cout <<"Current value for the parameter: "<<fTpar<<endl;
135 cout <<" Debug flag: "<<fDebug<<endl;
138 //________________________________________________________
139 Int_t AliStrLine::IsParallelTo(AliStrLine *line) const {
140 // returns 1 if lines are parallel, 0 if not paralel
143 Double_t vecpx=fCd[1]*cd2[2]-fCd[2]*cd2[1];
144 if(vecpx!=0) return 0;
145 Double_t vecpy=-fCd[0]*cd2[2]+fCd[2]*cd2[0];
146 if(vecpy!=0) return 0;
147 Double_t vecpz=fCd[0]*cd2[1]-fCd[1]*cd2[0];
148 if(vecpz!=0) return 0;
151 //________________________________________________________
152 Int_t AliStrLine::Crossrphi(AliStrLine *line){
153 // Cross 2 lines in the X-Y plane
160 Double_t c=p2[0]-fP0[0];
163 Double_t f=p2[1]-fP0[1];
164 Double_t deno = a*e-b*d;
167 fTpar = (c*e-b*f)/deno;
175 //________________________________________________________
176 Int_t AliStrLine::CrossPoints(AliStrLine *line, Double_t *point1, Double_t *point2){
177 // Looks for the crossing point estimated starting from the
185 for(i=0;i<3;i++)k1+=(fP0[i]-p2[i])*fCd[i];
187 for(i=0;i<3;i++)k2+=(fP0[i]-p2[i])*cd2[i];
189 for(i=0;i<3;i++)a11+=fCd[i]*cd2[i];
192 for(i=0;i<3;i++)a21+=cd2[i]*cd2[i];
194 for(i=0;i<3;i++)a12-=fCd[i]*fCd[i];
195 Double_t deno = a11*a22-a21*a12;
196 if(deno == 0.) return -1;
197 fTpar = (a11*k2-a21*k1) / deno;
198 Double_t par2 = (k1*a22-k2*a12) / deno;
200 GetCurrentPoint(point1);
201 line->GetCurrentPoint(point2);
204 //________________________________________________________________
205 Int_t AliStrLine::Cross(AliStrLine *line, Double_t *point){
207 //Finds intersection between lines
210 Int_t retcod=CrossPoints(line,point1,point2);
212 for(Int_t i=0;i<3;i++)point[i]=(point1[i]+point2[i])/2.;
219 //___________________________________________________________
220 Double_t AliStrLine::GetDCA(AliStrLine *line) const{
221 //Returns the distance of closest approach between two lines
227 Int_t ispar=IsParallelTo(line);
229 Double_t dist1q=0,dist2=0,mod=0;
231 dist1q+=(fP0[i]-p2[i])*(fP0[i]-p2[i]);
232 dist2+=(fP0[i]-p2[i])*fCd[i];
237 return TMath::Sqrt(dist1q-dist2*dist2);
241 perp[0]=fCd[1]*cd2[2]-fCd[2]*cd2[1];
242 perp[1]=-fCd[0]*cd2[2]+fCd[2]*cd2[0];
243 perp[2]=fCd[0]*cd2[1]-fCd[1]*cd2[0];
244 Double_t mod=0,dist=0;
246 mod+=perp[i]*perp[i];
247 dist+=(fP0[i]-p2[i])*perp[i];
252 return TMath::Abs(dist);
256 //________________________________________________________
257 void AliStrLine::GetCurrentPoint(Double_t *point) const {
258 // Fills the array point with the current value on the line
259 for(Int_t i=0;i<3;i++)point[i]=fP0[i]+fCd[i]*fTpar;
262 //________________________________________________________
263 Double_t AliStrLine::GetDistFromPoint(Double_t *point) const {
264 // computes distance from point
265 AliStrLine tmp(point,(Double_t *)fCd,kFALSE);
266 return this->GetDCA(&tmp);