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);
60 //________________________________________________________
61 AliStrLine::AliStrLine(Float_t *pointf, Float_t *cdf,Bool_t twopoints) :
66 // Standard constructor - with float arguments
67 // if twopoints is true: point and cd are the 3D coordinates of
68 // two points defininig the straight line
69 // if twopoint is false: point represents the 3D coordinates of a point
70 // belonging to the straight line and cd is the
74 for(Int_t i=0;i<3;i++){
79 InitTwoPoints(point,cd);
82 InitDirection(point,cd);
86 //________________________________________________________
87 void AliStrLine::InitDirection(Double_t *point, Double_t *cd){
88 // Initialization from a point and a direction
90 for(Int_t i=0;i<3;i++)norm+=cd[i]*cd[i];
92 norm = TMath::Sqrt(norm);
93 for(Int_t i=0;i<3;i++) cd[i]/=norm;
96 Error("AliStrLine","Null direction cosines!!!");
104 //________________________________________________________
105 void AliStrLine::InitTwoPoints(Double_t *pA, Double_t *pB){
106 // Initialization from the coordinates of two
107 // points in the space
109 for(Int_t i=0;i<3;i++)cd[i] = pB[i]-pA[i];
110 InitDirection(pA,cd);
113 //________________________________________________________
114 AliStrLine::~AliStrLine() {
118 //________________________________________________________
119 void AliStrLine::PrintStatus() const {
120 // Print current status
121 cout <<"=======================================================\n";
122 cout <<"Direction cosines: ";
123 for(Int_t i=0;i<3;i++)cout <<fCd[i]<<"; ";
125 cout <<"Known point: ";
126 for(Int_t i=0;i<3;i++)cout <<fP0[i]<<"; ";
128 cout <<"Current value for the parameter: "<<fTpar<<endl;
129 cout <<" Debug flag: "<<fDebug<<endl;
132 //________________________________________________________
133 Int_t AliStrLine::IsParallelTo(AliStrLine *line) const {
134 // returns 1 if lines are parallel, 0 if not paralel
137 Double_t vecpx=fCd[1]*cd2[2]-fCd[2]*cd2[1];
138 if(vecpx!=0) return 0;
139 Double_t vecpy=-fCd[0]*cd2[2]+fCd[2]*cd2[0];
140 if(vecpy!=0) return 0;
141 Double_t vecpz=fCd[0]*cd2[1]-fCd[1]*cd2[0];
142 if(vecpz!=0) return 0;
145 //________________________________________________________
146 Int_t AliStrLine::Crossrphi(AliStrLine *line){
147 // Cross 2 lines in the X-Y plane
154 Double_t c=p2[0]-fP0[0];
157 Double_t f=p2[1]-fP0[1];
158 Double_t deno = a*e-b*d;
161 fTpar = (c*e-b*f)/deno;
169 //________________________________________________________
170 Int_t AliStrLine::CrossPoints(AliStrLine *line, Double_t *point1, Double_t *point2){
171 // Looks for the crossing point estimated starting from the
179 for(i=0;i<3;i++)k1+=(fP0[i]-p2[i])*fCd[i];
181 for(i=0;i<3;i++)k2+=(fP0[i]-p2[i])*cd2[i];
183 for(i=0;i<3;i++)a11+=fCd[i]*cd2[i];
186 for(i=0;i<3;i++)a21+=cd2[i]*cd2[i];
188 for(i=0;i<3;i++)a12-=fCd[i]*fCd[i];
189 Double_t deno = a11*a22-a21*a12;
190 if(deno == 0.) return -1;
191 fTpar = (a11*k2-a21*k1) / deno;
192 Double_t par2 = (k1*a22-k2*a12) / deno;
194 GetCurrentPoint(point1);
195 line->GetCurrentPoint(point2);
198 //________________________________________________________________
199 Int_t AliStrLine::Cross(AliStrLine *line, Double_t *point){
201 //Finds intersection between lines
204 Int_t retcod=CrossPoints(line,point1,point2);
206 for(Int_t i=0;i<3;i++)point[i]=(point1[i]+point2[i])/2.;
213 //___________________________________________________________
214 Double_t AliStrLine::GetDCA(AliStrLine *line) const{
215 //Returns the distance of closest approach between two lines
221 Int_t ispar=IsParallelTo(line);
223 Double_t dist1q=0,dist2=0,mod=0;
225 dist1q+=(fP0[i]-p2[i])*(fP0[i]-p2[i]);
226 dist2+=(fP0[i]-p2[i])*fCd[i];
231 return TMath::Sqrt(dist1q-dist2*dist2);
235 perp[0]=fCd[1]*cd2[2]-fCd[2]*cd2[1];
236 perp[1]=-fCd[0]*cd2[2]+fCd[2]*cd2[0];
237 perp[2]=fCd[0]*cd2[1]-fCd[1]*cd2[0];
238 Double_t mod=0,dist=0;
240 mod+=perp[i]*perp[i];
241 dist+=(fP0[i]-p2[i])*perp[i];
246 return TMath::Abs(dist);
250 //________________________________________________________
251 void AliStrLine::GetCurrentPoint(Double_t *point) const {
252 // Fills the array point with the current value on the line
253 for(Int_t i=0;i<3;i++)point[i]=fP0[i]+fCd[i]*fTpar;
256 //________________________________________________________
257 Double_t AliStrLine::GetDistFromPoint(Double_t *point) const {
258 // computes distance from point
259 AliStrLine tmp(point,(Double_t *)fCd,kFALSE);
260 return this->GetDCA(&tmp);