No inline in the implementation file

[u/mrichter/AliRoot.git] / ITS / AliITSgeom.cxx

/**************************************************************************
 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
 *                                                                        *
 * Author: The ALICE Off-line Project.                                    *
 * Contributors are mentioned in the code where appropriate.              *
 *                                                                        *
 * Permission to use, copy, modify and distribute this software and its   *
 * documentation strictly for non-commercial purposes is hereby granted   *
 * without fee, provided that the above copyright notice appears in all   *
 * copies and that both the copyright notice and this permission notice   *
 * appear in the supporting documentation. The authors make no claims     *
 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/

/* $Id$ */

///////////////////////////////////////////////////////////////////////
// ITS geometry manipulation routines.                               //
// Created April 15 1999.                                            //
// version: 0.0.0                                                    //
// By: Bjorn S. Nilsen                                               //
// version: 0.0.1                                                    //
// Updated May 27 1999.                                              //
// Added Cylindrical random and global based changes.               //
// Added  function PrintComparison.                                  //
///////////////////////////////////////////////////////////////////////


////////////////////////////////////////////////////////////////////////
//     The local coordinate system by, default, is show in the following
// figures. Also shown are the ladder numbering scheme.
//Begin_Html
/*
<img src="picts/ITS/AliITSgeomMatrix_L1.gif">
</pre>
<br clear=left>
<font size=+2 color=blue>
<p>This shows the relative geometry differences between the ALICE Global
coordinate system and the local detector coordinate system.
</font>
<pre>

<pre>
<img src="picts/ITS/its1+2_convention_front_5.gif">
</pre>
<br clear=left>
<font size=+2 color=blue>
<p>This shows the front view of the SPDs and the orientation of the local
pixel coordinate system. Note that the inner pixel layer has its y coordinate
in the opposite direction from all of the other layers.
</font>
<pre>

<pre>
<img src="picts/ITS/its3+4_convention_front_5.gif">
</pre>
<br clear=left>
<font size=+2 color=blue>
<p>This shows the front view of the SDDs and the orientation of the local
pixel coordinate system.
</font>
<pre>

<pre>
<img src="picts/ITS/its5+6_convention_front_5.gif">
</pre>
<br clear=left>
<font size=+2 color=blue>
<p>This shows the front view of the SSDs and the orientation of the local
pixel coordinate system.
</font>
<pre>
*/
//End_Html
//
////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////
//
// version: 0
// Written by Bjorn S. Nilsen
//
// Data Members:
//
// Int_t fNlayers
//     The number of ITS layers for this geometry. By default this
//  is 6, but can be modified by the creator function if there are
// more layers defined.
//
// Int_t *fNlad
//     A pointer to an array fNlayers long containing the number of 
// ladders for each layer. This array is typically created and filled 
// by the AliITSgeom creator function.
//
// Int_t *fNdet
//     A pointer to an array fNlayers long containing the number of
// active detector volumes for each ladder. This array is typically
// created and filled by the AliITSgeom creator function.
//
// AliITSgeomMatrix *fGm
//     A pointer to an array of AliITSgeomMatrix classes. One element 
// per module (detector) in the ITS. AliITSgeomMatrix basicly contains
// all of the necessary information about the detector and it's coordinate
// transformations.
//
// TObjArray *fShape
//     A pointer to an array of TObjects containing the detailed shape
// information for each type of detector used in the ITS. For example
// I have created AliITSgeomSPD, AliITSgeomSDD, and AliITSgeomSSD as
// example structures, derived from TObjects, to hold the detector
// information. I would recommend that one element in each of these
// structures, that which describes the shape of the active volume,
// be one of the ROOT classes derived from TShape. In this way it would
// be easy to have the display program display the correct active
// ITS volumes. See the example classes AliITSgeomSPD, AliITSgeomSDD,
// and AliITSgeomSSD for a more detailed example.
////////////////////////////////////////////////////////////////////////
#include <Riostream.h>
//#include <stdlib.h>
//#include <stdio.h>
//#include <string.h>
//#include <ctype.h>

#include <TSystem.h>
#include <TRandom.h>

#include "AliITSgeom.h"
#include "AliITSgeomSPD.h"
#include "AliITSgeomSDD.h"
#include "AliITSgeomSSD.h"

ClassImp(AliITSgeom)

//______________________________________________________________________
AliITSgeom::AliITSgeom(){
    //     The default constructor for the AliITSgeom class. It, by default,
    // sets fNlayers to zero and zeros all pointers.
    // Do not allocate anything zero everything.

    fTrans   = 0; // standard GEANT global/local coordinate system.
    fNlayers = 0;
    fNlad    = 0;
    fNdet    = 0;
    fGm      = 0;
    fShape   = 0;
    strcpy(fVersion,"test");
    return;
}
//______________________________________________________________________
AliITSgeom::AliITSgeom(Int_t itype,Int_t nlayers,Int_t *nlads,Int_t *ndets,
		       Int_t mods){
    //     A simple constructor to set basic geometry class variables
    // Inputs:
    // Int_t itype   the type of transformation kept.
    //               bit 0 => Standard GEANT
    //               bit 1 => ITS tracking
    //               bit 2 => A change in the coordinate system has been made.
    //               others are still to be defined as needed.
    // Int_t nlayers The number of ITS layers also set the size of the arrays
    // Int_t *nlads  an array of the number of ladders for each layer. This
    //               array must be nlayers long.
    // Int_t *ndets  an array of the number of detectors per ladder for each
    //               layer. This array must be nlayers long.
    // Int_t mods    The number of modules. Typicaly the sum of all the 
    //               detectors on every layer and ladder.
    // Outputs:
    // none
    Int_t i;

    fTrans    = itype;
    fNlayers  = nlayers;
    fNlad     = new Int_t[nlayers];
    fNdet     = new Int_t[nlayers];
    for(i=0;i<nlayers;i++){fNlad[i] = nlads[i];fNdet[i] = ndets[i];}
    fNmodules = mods;
    fGm       = new TObjArray(mods,0);
    fShape    = new TObjArray(5); // default value
    for(i=0;i<5;i++) fShape->AddAt(0,i);
    strcpy(fVersion,"test");
    return;
}
//______________________________________________________________________
void AliITSgeom::CreatMatrix(Int_t mod,Int_t lay,Int_t lad,Int_t det,
			     AliITSDetector idet,const Double_t tran[3],
			     const Double_t rot[10]){
    // Given the translation vector tran[3] and the rotation matrix rot[1],
    // this function creates and adds to the TObject Array fGm the
    // AliITSgeomMatrix object.
    // Inputs are:
    // Int_t           mod     The module number. The location in TObjArray
    // Int_t           lay     The layer where this module is
    // Int_t           lad     On which ladder this module is
    // Int_t           det     Which detector on this ladder this module is
    // AliITSDetector idet     The type of detector see AliITSgeom.h
    // Double_t       tran[3]  The translation vector
    // Double_t       rot[10]  The rotation matrix.
    // Outputs are:
    //   none
    // The rot[10] matrix is set up like:
    /*   / rot[0]  rot[1]  rot[2] \
    //  |  rot[3]  rot[4]  rot[5]  |
    //   \ rot[6]  rot[7]  rot[8] /  if(rot[9]!=0) then the Identity matrix
    // is used regardless of the values in rot[0]-rot[8].
    */
    Int_t id[3];
    Double_t r[3][3] = {{1.0,0.0,0.0},{0.0,1.0,0.0},{0.0,0.0,1.0}};

    if(fGm->At(mod)!=0) delete fGm->At(mod);
    id[0] = lay; id[1] = lad; id[2] = det;
    if(rot[9]!=0.0) { // null rotation
	r[0][0] = rot[0]; r[0][1] = rot[1]; r[0][2] = rot[2];
	r[1][0] = rot[3]; r[1][1] = rot[4]; r[1][2] = rot[5];
	r[2][0] = rot[6]; r[2][1] = rot[7]; r[2][2] = rot[8];
    } // end if
    fGm->AddAt(new AliITSgeomMatrix(idet,id,r,tran),mod);
}
//______________________________________________________________________
AliITSgeom::~AliITSgeom(){
    //     The destructor for the AliITSgeom class. If the arrays fNlad,
    // fNdet, or fGm have had memory allocated to them, there pointer values
    // are non zero, then this memory space is freed and they are set
    // to zero. In addition, fNlayers is set to zero. The destruction of
    // TObjArray fShape is, by default, handled by the TObjArray destructor.

   if(fGm!=0){
     //for(Int_t i=0;i<fNlayers;i++) delete fGm->At(i);
      fGm->Delete();
      delete fGm;
   } // end if fGm!=0
   if(fNlad!=0) delete[] fNlad;
   if(fNdet!=0) delete[] fNdet;
   fNlayers = 0;
   fNlad    = 0;
   fNdet    = 0;
   fGm      = 0;
   return;
}
//______________________________________________________________________
void AliITSgeom::ReadNewFile(const char *filename){
    // It is generaly preferred to define the geometry in AliITSgeom
    // directly from the GEANT geometry, see AliITSvPPRasymm.cxx for
    // and example. Under some circumstances this may not be possible.
    // This function will read in a formatted file for all of the
    // information needed to define the geometry in AliITSgeom.
    // Unlike the older file format, this file may contain comments
    // and the order of the data does not need to be completely
    // respected. A file can be created using the function WriteNewFile
    // defined below.
    // Inputs are:
    // const char *filename The file name of the file to be read in.
    // Outputs are:
    //  none
    Int_t ncmd=9;
    const char *cmda[]={"Version"        ,"fTrans"  ,"fNmodules",
	                "fNlayers"       ,"fNladers","fNdetectors",
	                "fNDetectorTypes","fShape"  ,"Matrix"};
    Int_t i,j,lNdetTypes,ldet;
    char cmd[20],c;
    AliITSgeomSPD *spd=0;
    AliITSgeomSDD *sdd=0;
    AliITSgeomSSD *ssd=0;
    AliITSgeomMatrix *m=0;
    ifstream *fp=0;
    char *filtmp=0;

    filtmp = gSystem->ExpandPathName(filename);
    cout << "AliITSgeom, Reading New .det file " << filtmp << endl;
    fp = new ifstream(filtmp,ios::in);  // open file to write
    while(fp->get(c)!=NULL){ // for ever loop
	if(c==' ') continue; // remove blanks
	if(c=='\n') continue;
	if(c=='#' || c=='!'){for(;fp->get(c)!=NULL,c!='\n';); continue;}
	if(c=='/'){
	    fp->get(c);{
		if(c=='/'){for(;fp->get(c)!=NULL,c!='\n';);continue;}
		if(c=='*'){
		NotYet:
		    for(;fp->get(c)!=NULL,c!='*';);
		    fp->get(c);{
			if(c=='/') continue;
			goto NotYet;
		    } //
		} // end if c=='*'
	    } // end if second /
	} // end if first /
	fp->putback(c);
	*fp >> cmd;
	for(i=0;i<ncmd;i++) if(strcmp(cmd,cmda[i])==0) break;
	switch (i){
	case 0:   // Version
	    *fp >> fVersion;
	    break;
	case 1:  // fTrans
	    *fp >> fTrans;
	    break;
	case 2:  // fNModules
	    *fp >> fNmodules;
	    if(fGm!=0){
		for(j=0;j<fGm->GetEntriesFast();j++) delete fGm->At(j);
		delete fGm;
	    } // end if
	    fGm = new TObjArray(fNmodules,0);
	    break;
	case 3:  // fNlayers
	    *fp >> fNlayers;
	    if(fNlad!=0) delete fNlad;
	    if(fNdet!=0) delete fNdet;
	    fNlad = new Int_t[fNlayers];
	    fNdet = new Int_t[fNlayers];
	    break;
	case 4:  // fNladers
	    for(j=0;j<fNlayers;j++) *fp >> fNlad[j];
	    break;
	case 5:  // fNdetectors
	    for(j=0;j<fNlayers;j++) *fp >> fNdet[j];
	    break;
	case 6:  // fNDetectorTypes
	    *fp >> lNdetTypes;
	    if(fShape!=0){
		for(j=0;j<fShape->GetEntriesFast();j++) delete fShape->At(j);
		delete fShape;
	    } // end if
	    fShape = new TObjArray(lNdetTypes,0);
	    break;
	case 7:  // fShape
	    *fp >> ldet;
	    if(fShape==0) fShape = new TObjArray(5,0);
	    switch (ldet){
	    case kSPD :
		spd = new AliITSgeomSPD();
		*fp >> *spd;
		ReSetShape(ldet,spd);
		spd = 0;
		break;
	    case kSDD : case kSDDp:
		sdd = new AliITSgeomSDD();
		*fp >> *sdd;
		ReSetShape(ldet,sdd);
		sdd = 0;
		break;
	    case kSSD : case kSSDp :
		ssd = new AliITSgeomSSD();
		*fp >> *ssd;
		ReSetShape(ldet,ssd);
		ssd = 0;
		break;
	    default:
		Error("ReadNewFile","Unknown fShape type number=%d c=%c",ldet,c);
		for(;fp->get(c)==NULL,c!='\n';); // skip to end of line.
		break;
	    } // end switch
	    break;
	case 8:  // Matrix
	    *fp >> ldet;
	    if(fGm==0) fGm = new TObjArray(2270,0);
	    if(fGm->At(ldet)!=0) delete (fGm->At(ldet));
	    fGm->AddAt((TObject*)new AliITSgeomMatrix(),ldet);
	    m = (AliITSgeomMatrix*) fGm->At(ldet);
	    *fp >> *m;
	    m = 0;
	    break;
	default:
	    Error("ReadNewFile","Data line i=%d c=%c",i,c);
	    for(;fp->get(c)==NULL,c!='\n';); // skip this line
	    break;
	} // end switch i
    } // end while
    delete fp;

    return;
}
//______________________________________________________________________
void AliITSgeom::WriteNewFile(const char *filename){
    // Writes AliITSgeom, AliITSgeomMatrix, and the defined AliITSgeomS*D
    // classes to a file in a format that is more readable and commendable.
    // Inputs are:
    // const char *filename The file name of the file to be write to.
    // Outputs are:
    //  none
    ofstream *fp;
    Int_t i;
    char *filtmp;

    filtmp = gSystem->ExpandPathName(filename);
    cout << "AliITSgeom, Writing New .det file " << filtmp << endl;
    fp = new ofstream(filtmp,ios::out);  // open file to write
    *fp << "//Comment lines begin with two //, one #, or one !" << endl;
    *fp << "#Blank lines are skipped including /* and */ sections." << endl;
    *fp << "!and, in principle the order of the lines is not important" <<endl;
    *fp << "/* In AliITSgeom.h are defined an enumerated type called" << endl;
    *fp << " AliITSDetectors These are kSPD=" << (Int_t) kSPD ;
    *fp << ", kSDD=" << (Int_t) kSDD << ", kSSD=" << (Int_t) kSSD;
    *fp << ", kSSDp=" << (Int_t) kSSDp << ", and kSDDp=" << (Int_t) kSDDp;
    *fp << "*/" << endl;
    *fp << "Version " << fVersion << endl;//This should be consistent with the
                                           // geometry version.
    *fp << "fTrans " << fTrans << endl;
    *fp << "fNmodules " << fNmodules << endl;
    *fp << "fNlayers " << fNlayers << endl;
    *fp << "fNladers ";
    for(i=0;i<fNlayers;i++) *fp << fNlad[i] << " ";
    *fp << endl;
    *fp << "fNdetectors ";
    for(i=0;i<fNlayers;i++) *fp << fNdet[i] << " ";
    *fp << endl;
    *fp << "fNDetectorTypes " << fShape->GetEntriesFast() << endl;
    for(i=0;i<fShape->GetEntriesFast();i++){
	if(!IsShapeDefined(i)) continue; // only print out used shapes.
	switch (i){
	case kSPD :
	    *fp << "fShape " << (Int_t) kSPD << " ";
	    *fp << *((AliITSgeomSPD*)(fShape->At(i)));
	    break;
	case kSDD :
	    *fp << "fShape " << (Int_t) kSDD << " ";
	    *fp << *((AliITSgeomSDD*)(fShape->At(i)));
	    break;
	case kSSD : case kSSDp :
	    *fp << "fShape " << i << " ";
	    *fp << *((AliITSgeomSSD*)(fShape->At(i)));
	    break;
	default:
	    Error("AliITSgeom::WriteNewFile","Unknown Shape value");
	} // end switch (i)
    } // end for i
    for(i=0;i<fNmodules;i++){
	*fp << "Matrix " << i << " ";
	*fp << *GetGeomMatrix(i);
    } // end for i
    *fp << "//End of File" << endl;;

    delete fp;
    return;
}
//______________________________________________________________________
AliITSgeom::AliITSgeom(const char *filename){
    //     The constructor for the AliITSgeom class. All of the data to fill
    // this structure is read in from the file given my the input filename.
    // Inputs are:
    // const char *filename The file name of the file to be read in.
    // Outputs are:
    //  none
    FILE     *pf=0;
    Int_t    i,lm=0,id[3];
    Int_t    l,a,d;
    Float_t  x,y,z,o,p,q,r,s,t;
    Double_t rot6[6],tran[3];
    char     buf[200],*buff=0; // input character buffer;
    char *filtmp;

    filtmp = gSystem->ExpandPathName(filename);
    cout << "AliITSgeom reading old .det file " << filtmp << endl;
    fShape = 0;
    strcpy(fVersion,"DefauleV5");
    pf = fopen(filtmp,"r");

    fNlayers = 6; // set default number of ladders
 TryAgain:
    fNlad    = new Int_t[fNlayers];
    fNdet    = new Int_t[fNlayers];
    fNmodules = 0;
    // find the number of ladders and detectors in this geometry.
    for(i=0;i<fNlayers;i++){fNlad[i]=fNdet[i]=0;} // zero out arrays
    while(fgets(buf,200,pf)!=NULL){ // for ever loop
	for(i=0;i<200;i++)if(buf[i]!=' '){ // remove blank spaces.
	    buff = &(buf[i]);
	    break;
	} // end for i
	// remove blank lines and comments.
	if(buff[0]=='\n'||buff[0]=='#'||buff[0]=='!'||
	   (buff[0]=='/'&&buff[1]=='/')) continue;
	if(isalpha(buff[0])) { // must be the new file formated file.
            fclose(pf);
            delete[] fNlad;delete[] fNdet;
            ReadNewFile(filename);
            return;
	} // end if isalpha(buff[0])
	sscanf(buff,"%d %d %d %f %f %f %f %f %f %f %f %f",
	       &l,&a,&d,&x,&y,&z,&o,&p,&q,&r,&s,&t);
	if(l>lm) lm = l;
	if(l<1 || l>fNlayers) {
	    printf("error in file %s layer=%d min. is 1 max is %d\n",
		   filename,l,fNlayers);
	    continue;
	}// end if l
	fNmodules++;
	if(l<=fNlayers&&fNlad[l-1]<a) fNlad[l-1] = a;
	if(l<=fNlayers&&fNdet[l-1]<d) fNdet[l-1] = d;
    } // end while ever loop
    if(lm>fNlayers){
	delete[] fNlad;
	delete[] fNdet;
	fNlayers = lm;
	goto TryAgain;
    } // end if lm>fNlayers
    // counted the number of ladders and detectors now allocate space.
    fGm = new TObjArray(fNmodules,0);

    // Set up Shapes for a default configuration of 6 layers.
    fTrans   = 0; // standard GEANT global/local coordinate system.
    // prepare to read in transforms
    lm = 0; // reuse lm as counter of modules.
    rewind(pf); // start over reading file
    while(fgets(buf,200,pf)!=NULL){ // for ever loop
	for(i=0;i<200;i++)if(buf[i]!=' '){ // remove blank spaces.
	    buff = &(buf[i]);
	    break;
	} // end for i
	// remove blank lines and comments.
	if(buff[0]=='\n'||buff[0]=='#'||buff[0]=='!'||
	   (buff[0]=='/'&&buff[1]=='/')) continue;
	x = y = z = o = p = q = r = s = t = 0.0;
	sscanf(buff,"%d %d %d %f %f %f %f %f %f %f %f %f",
	       &l,&a,&d,&x,&y,&z,&o,&p,&q,&r,&s,&t);
	if(l<1 || l>fNlayers) {
	    printf("error in file %s layer=%d min. is 1 max is %d/n",
		   filename,l,fNlayers);
	    continue;
	}// end if l
	id[0] = l;id[1] = a;id[2] = d;
	tran[0] = tran[1] = tran[2]  = 0.0;
	tran[0] = (Double_t)x;tran[1] = (Double_t)y;tran[2] = (Double_t)z;
	rot6[0] = rot6[1] = rot6[2] = rot6[3] = rot6[4] = rot6[5] =0.0;
	rot6[0] = (Double_t)o;rot6[1] = (Double_t)p;rot6[2] = (Double_t)q;
	rot6[3] = (Double_t)r;rot6[4] = (Double_t)s;rot6[5] = (Double_t)t;
	switch (l){
	case 1: case 2: // layer 1 or2 SPD
	    fGm->AddAt(new AliITSgeomMatrix(rot6,kSPD,id,tran),lm++);
	    break;
	case 3: case 4: // layer 3 or 4 SDD
	    fGm->AddAt(new AliITSgeomMatrix(rot6,kSDD,id,tran),lm++);
	    break;
	case 5: case 6: // layer 5 or 6 SSD
	    fGm->AddAt(new AliITSgeomMatrix(rot6,kSSD,id,tran),lm++);
	    break;
	} // end switch
    } // end while ever loop
    fclose(pf);
}
//______________________________________________________________________
AliITSgeom::AliITSgeom(AliITSgeom &source) : TObject(source){
    //     The copy constructor for the AliITSgeom class. It calls the
    // = operator function. See the = operator function for more details.
    // Inputs are:
    // AliITSgeom &source  The AliITSgeom class with which to make this
    //                     a copy of.
    // Outputs are:
    // none.

    *this = source;  // Just use the = operator for now.
    return;
}
//______________________________________________________________________
AliITSgeom& AliITSgeom::operator=(AliITSgeom &source){
    //     The = operator function for the AliITSgeom class. It makes an
    // independent copy of the class in such a way that any changes made
    // to the copied class will not affect the source class in any way.
    // This is required for many ITS alignment studies where the copied
    // class is then modified by introducing some misalignment.
    // Inputs are:
    // AliITSgeom &source  The AliITSgeom class with which to make this
    //                     a copy of.
    // Outputs are:
    // return  *this       The a new copy of source.
   Int_t i;

   if(this == &source) return *this; // don't assign to ones self.

   // if there is an old structure allocated delete it first.
   if(this->fGm != 0){
      for(i=0;i<this->fNmodules;i++) delete this->fGm->At(i);
      delete this->fGm;
   } // end if fGm != 0 
   if(fNlad != 0) delete[] fNlad;
   if(fNdet != 0) delete[] fNdet;

   this->fTrans    = source.fTrans;
   this->fNmodules = source.fNmodules;
   this->fNlayers = source.fNlayers;
   this->fNlad = new Int_t[fNlayers];
   for(i=0;i<this->fNlayers;i++) this->fNlad[i] = source.fNlad[i];
   this->fNdet = new Int_t[fNlayers];
   for(i=0;i<this->fNlayers;i++) this->fNdet[i] = source.fNdet[i];
   this->fShape = new TObjArray(*(source.fShape));//This does not make a proper copy.
   this->fGm = new TObjArray(this->fNmodules,0);
   for(i=0;i<this->fNmodules;i++){
       this->fGm->AddAt(new AliITSgeomMatrix(*(
	   (AliITSgeomMatrix*)(source.fGm->At(i)))),i);
   } // end for i
   return *this;
}
//______________________________________________________________________
Int_t AliITSgeom::GetNdetectors(Int_t lay) const {
    // Return the number of detectors/ladder for the given layer
    // Inputs:
    //   Int_t lay   the layer number
    // Outputs:
    //   none.
    // Return:
    //   Int_t the number of detectors/ladders for the give layer
        Int_t ndet;

        ndet = fNdet[lay-1];
        return ndet;
}
//______________________________________________________________________
Int_t AliITSgeom::GetNladders(Int_t lay) const {
    // Return the number of ladders for the given layer
    // Inputs:
    //   Int_t lay   the layer number
    // Outputs:
    //   none.
    // Return:
    //   Int_t the number of ladders for the give layer
    Int_t nlad;

    nlad = fNlad[lay-1];
    return nlad;
}
//______________________________________________________________________
Int_t AliITSgeom::GetModuleIndex(Int_t lay,Int_t lad,Int_t det){
    //      This routine computes the module index number from the layer,
    // ladder, and detector numbers. The number of ladders and detectors
    // per layer is determined when this geometry package is constructed,
    // see AliITSgeom(const char *filename) for specifics.
    // Inputs are:
    // Int_t lay  The layer number. Starting from 1.
    // Int_t lad  The ladder number. Starting from 1.
    // Int_t det  The detector number. Starting from 1.
    // Outputs are:
    // return the module index number, starting from zero.
    Int_t i,j,k,id[3];

    i = fNdet[lay-1] * (lad-1) + det - 1;
    j = 0;
    for(k=0;k<lay-1;k++) j += fNdet[k]*fNlad[k];
    i = i+j;
    GetGeomMatrix(i)->GetIndex(id);
    if(id[0]==lay&&id[1]==lad&&id[2]==det) return i;
    // Array of modules fGm is not in expected order. Search for this index
    for(i=0;i<fNmodules;i++){
	GetGeomMatrix(i)->GetIndex(id);
	if(id[0]==lay&&id[1]==lad&&id[2]==det) return i;
    } // end for i
    // This layer ladder and detector combination does not exist return -1.
    return -1;
}
//______________________________________________________________________
void AliITSgeom::GetModuleId(Int_t index,Int_t &lay,Int_t &lad,Int_t &det){
    //      This routine computes the layer, ladder and detector number 
    // given the module index number. The number of ladders and detectors
    // per layer is determined when this geometry package is constructed,
    // see AliITSgeom(const char *filename) for specifics.
    // Inputs are:
    // Int_t index  The module index number, starting from zero.
    // Outputs are:
    // Int_t lay    The layer number. Starting from 1.
    // Int_t lad    The ladder number. Starting from 1.
    // Int_t det    The detector number. Starting from 1.
    Int_t id[3];
    AliITSgeomMatrix *g = GetGeomMatrix(index);
    if (g == 0x0)
     {
      Error("GetModuleId","Can not get GeoMatrix for index = %d",index);
      lay = -1; lad = -1; det = -1;
     }
    else
     {
      g->GetIndex(id);
      lay = id[0]; lad = id[1]; det = id[2];
     }
    return;

    // The old way kept for posterity.
/*
    Int_t i,j,k;
    j = 0;
    for(k=0;k<fNlayers;k++){
	j += fNdet[k]*fNlad[k];
	if(j>index)break;
    } // end for k
    lay = k+1;
    i = index -j + fNdet[k]*fNlad[k];
    j = 0;
    for(k=0;k<fNlad[lay-1];k++){
	j += fNdet[lay-1];
	if(j>i)break;
    } // end for k
    lad = k+1;
    det = 1+i-fNdet[lay-1]*k;
    return;
*/
}
//______________________________________________________________________
Int_t AliITSgeom::GetStartDet(Int_t dtype){
    // returns the starting module index value for a give type of detector id.
    // This assumes that the detector types are different on different layers
    // and that they are not mixed up.
    // Inputs are:
    // Int_t dtype A detector type number. 0 for SPD, 1 for SDD, and 2 for SSD.
    // outputs:
    // return the module index for the first occurance of that detector type.

    switch(dtype){
    case 0:
	return GetModuleIndex(1,1,1);
	break;
    case 1:
	return GetModuleIndex(3,1,1);
	break;
    case 2:
	return GetModuleIndex(5,1,1);
	break;
    default:
	Warning("GetStartDet","undefined detector type %d",dtype);
	return 0;
    } // end switch

    Warning("GetStartDet","undefined detector type %d",dtype);
    return 0;
}
//______________________________________________________________________
Int_t AliITSgeom::GetLastDet(Int_t dtype){
    // returns the last module index value for a give type of detector id.
    // This assumes that the detector types are different on different layers
    // and that they are not mixed up.
    // Inputs are:
    // Int_t dtype A detector type number. 0 for SPD, 1 for SDD, and 2 for SSD.
    // outputs are:
    // return the module index for the last occurance of that detector type.

    switch(dtype){
    case 0:
	return GetLastSPD();
	break;
    case 1:
	return GetLastSDD();
	break;
    case 2:
	return GetLastSSD();
	break;
    default:
	Warning("GetLastDet","undefined detector type %d",dtype);
	return 0;
    } // end switch

    Warning("GetLastDet","undefined detector type %d",dtype);
    return 0;
}
//______________________________________________________________________
void AliITSgeom::GetCenterThetaPhi(Int_t lay,Int_t lad,Int_t det,
                                   TVector &x){
    //      This function returns the Cartesian translation [cm] and the
    // 6 GEANT rotation angles [degrees]for a given layer ladder and
    // detector number, in the TVector x (at least 9 elements large).
    // Inputs:
    //    Int_t lay    ITS Layer number
    //    Int_t lad    ITS Ladder number
    //    Int_t det    ITS Detector number
    // Outputs:
    //    TVector &x   The translation vector and the 6 rotaion angles
    // Return:
    //   none.
    Double_t t[3],ang[6];
    Int_t index=GetModuleIndex(lay,lad,det);

    GetTrans(index,t);
    GetGeantAngles(index,ang);
    x(0) =   t[0];x(1) =   t[1];x(2) =   t[2];
    x(3) = ang[0];x(4) = ang[1];x(5) = ang[2];
    x(6) = ang[3];x(7) = ang[4];x(8) = ang[5];
}
//______________________________________________________________________
void AliITSgeom::PrintComparison(FILE *fp,AliITSgeom *other){
    //     This function was primarily created for diagnostic reasons. It
    // print to a file pointed to by the file pointer fp the difference
    // between two AliITSgeom classes. The format of the file is basicly,
    // define d? to be the difference between the same element of the two
    // classes. For example dfrx = this->GetGeomMatrix(i)->frx 
    // - other->GetGeomMatrix(i)->frx.
    // if(at least one of dfx0, dfy0, dfz0,dfrx,dfry,dfrz are non zero) then
    // print layer ladder detector dfx0 dfy0 dfz0 dfrx dfry dfrz
    // if(at least one of the 9 elements of dfr[] are non zero) then print
    // layer ladder detector dfr[0] dfr[1] dfr[2]
    //                       dfr[3] dfr[4] dfr[5]
    //                       dfr[6] dfr[7] dfr[8]
    // Only non zero values are printed to save space. The differences are
    // typical written to a file because there are usually a lot of numbers
    // printed out and it is usually easier to read them in some nice editor
    // rather than zooming quickly past you on a screen. fprintf is used to
    // do the printing. The fShapeIndex difference is not printed at this time.
    // Inputs are:
    // FILE *fp           A file pointer to an opened file for writing in which
    //                    the results of the comparison will be written.
    // AliITSgeom *other  The other AliITSgeom class to which this one is
    //                    being compared.
    // outputs are:
    // none
    Int_t    i,j,idt[3],ido[3];
    Double_t tt[3],to[3];  // translation
    Double_t rt[3],ro[3];  // phi in radians
    Double_t mt[3][3],mo[3][3]; // matrixes
    AliITSgeomMatrix *gt,*go;
    Bool_t   t;

    for(i=0;i<this->fNmodules;i++){
	gt  =  this->GetGeomMatrix(i);
	go  = other->GetGeomMatrix(i);
	gt->GetIndex(idt);
	go->GetIndex(ido);
	t = kFALSE;
	for(i=0;i<3;i++) t = t&&idt[i]!=ido[i];
	if(t) fprintf(fp,"%4.4d %1.1d %2.2d %2.2d %1.1d %2.2d %2.2d\n",i,
		      idt[0],idt[1],idt[2],ido[0],ido[1],ido[2]);
	gt->GetTranslation(tt);
	go->GetTranslation(to);
	gt->GetAngles(rt);
	go->GetAngles(ro);
	t = kFALSE;
	for(i=0;i<3;i++) t = t&&tt[i]!=to[i];
	if(t) fprintf(fp,"%1.1d %2.2d %2.2d dTrans=%f %f %f drot=%f %f %f\n",
		      idt[0],idt[1],idt[2],
		      tt[0]-to[0],tt[1]-to[1],tt[2]-to[2],
		      rt[0]-ro[0],rt[1]-ro[1],rt[2]-ro[2]);
	t = kFALSE;
	gt->GetMatrix(mt);
	go->GetMatrix(mo);
	for(i=0;i<3;i++)for(j=0;j<3;j++)  t = mt[i][j] != mo[i][j];
	if(t){
	    fprintf(fp,"%1.1d %2.2d %2.2d dfr= %e %e %e\n",
		    idt[0],idt[1],idt[2],
		    mt[0][0]-mo[0][0],mt[0][1]-mo[0][1],mt[0][2]-mo[0][2]);
	    fprintf(fp,"        dfr= %e %e %e\n",
		    mt[1][0]-mo[1][0],mt[1][1]-mo[1][1],mt[1][2]-mo[1][2]);
	    fprintf(fp,"        dfr= %e %e %e\n",
		    mt[2][0]-mo[2][0],mt[2][1]-mo[2][1],mt[2][2]-mo[2][2]);
	} // end if t
    } // end for i
    return;
}
//______________________________________________________________________
void AliITSgeom::PrintData(FILE *fp,Int_t lay,Int_t lad,Int_t det){
    //     This function prints out the coordinate transformations for
    // the particular detector defined by layer, ladder, and detector
    // to the file pointed to by the File pointer fp. fprintf statements
    // are used to print out the numbers. The format is
    // layer ladder detector Trans= fx0 fy0 fz0 rot= frx fry frz 
    // Shape=fShapeIndex
    //                         dfr= fr[0] fr[1] fr[2]
    //                         dfr= fr[3] fr[4] fr[5]
    //                         dfr= fr[6] fr[7] fr[8]
    // By indicating which detector, some control over the information 
    // is given to the user. The output it written to the file pointed
    // to by the file pointer fp. This can be set to stdout if you want.
    // Inputs are:
    // FILE *fp           A file pointer to an opened file for writing in which
    //                    the results of the comparison will be written.
    // Int_t lay          The layer number. Starting from 1.
    // Int_t lad          The ladder number. Starting from 1.
    // Int_t det          The detector number. Starting from 1.
    // outputs are:
    // none
    AliITSgeomMatrix *gt;
    Double_t t[3],r[3],m[3][3];

    gt = this->GetGeomMatrix(GetModuleIndex(lay,lad,det));
    gt->GetTranslation(t);
    gt->GetAngles(r);
    fprintf(fp,"%1.1d %2.2d %2.2d Trans=%f %f %f rot=%f %f %f Shape=%d\n",
	    lay,lad,det,t[0],t[1],t[2],r[0],r[1],r[2],
	    gt->GetDetectorIndex());
    gt->GetMatrix(m);
    fprintf(fp,"        dfr= %e %e %e\n",m[0][0],m[0][1],m[0][2]);
    fprintf(fp,"        dfr= %e %e %e\n",m[1][0],m[1][1],m[1][2]);
    fprintf(fp,"        dfr= %e %e %e\n",m[2][0],m[2][1],m[2][2]);
    return;
}
//______________________________________________________________________
ofstream & AliITSgeom::PrintGeom(ofstream &rb){
    //     Stream out an object of class AliITSgeom to standard output.
    // Intputs are:
    // ofstream &rb    The output streaming buffer.
    // Outputs are:
    // ofstream &rb    The output streaming buffer.
    Int_t i;

    rb.setf(ios::scientific);
    rb << fTrans << " ";
    rb << fNmodules << " ";
    rb << fNlayers << " ";
    for(i=0;i<fNlayers;i++) rb << fNlad[i] << " ";
    for(i=0;i<fNlayers;i++) rb << fNdet[i] << "\n";
    for(i=0;i<fNmodules;i++) {
	rb <<setprecision(16) << *(GetGeomMatrix(i)) << "\n";
    } // end for i
    rb << fShape->GetEntries()<<endl;
    for(i=0;i<fShape->GetEntries();i++) if(fShape->At(i)!=0) switch (i){
    case kSPD:
	rb << kSPD <<","<< (AliITSgeomSPD*)(fShape->At(kSPD));
	break;
    case kSDD:
	rb << kSDD <<","<< (AliITSgeomSDD*)(fShape->At(kSDD));
	break;
    case kSSD:
	rb << kSSD <<","<< (AliITSgeomSSD*)(fShape->At(kSSD));
	break;
    case kSSDp:
	rb << kSSDp <<","<< (AliITSgeomSSD*)(fShape->At(kSSDp));
	break;
    case kSDDp:
	rb << kSDDp <<","<< (AliITSgeomSDD*)(fShape->At(kSDDp));
	break;
    } // end for i / switch
    return rb;
}
//______________________________________________________________________
ifstream & AliITSgeom::ReadGeom(ifstream &rb){
    //     Stream in an object of class AliITSgeom from standard input.
    // Intputs are:
    // ifstream &rb    The input streaming buffer.
    // Outputs are:
    // ifstream &rb    The input streaming buffer.
    Int_t i,j;

    fNlad = new Int_t[fNlayers];
    fNdet = new Int_t[fNlayers];
    if(fGm!=0){
	for(i=0;i<fNmodules;i++) delete GetGeomMatrix(i);
	delete fGm;
    } // end if fGm!=0

    rb >> fTrans >> fNmodules >> fNlayers;
    fNlad = new Int_t[fNlayers];
    fNdet = new Int_t[fNlayers];
    for(i=0;i<fNlayers;i++) rb >> fNlad[i];
    for(i=0;i<fNlayers;i++) rb >> fNdet[i];
    fGm = new TObjArray(fNmodules,0);
    for(i=0;i<fNmodules;i++){
	fGm->AddAt(new AliITSgeomMatrix,i);
	rb >> *(GetGeomMatrix(i));
    } // end for i
    rb >> i;
    fShape = new TObjArray(i);
    for(i=0;i<fShape->GetEntries();i++) {
	rb >> j;
	switch (j){
	case kSPD:{
	    AliITSgeomSPD *s = new AliITSgeomSPD();
	    rb >> *s;
	    fShape->AddAt(s,kSPD);}
	    break;
	case kSDD:{
	    AliITSgeomSDD *s = new AliITSgeomSDD();
	    rb >> *s;
	    fShape->AddAt(s,kSDD);}
	    break;
	case kSSD:{
	    AliITSgeomSSD *s = new AliITSgeomSSD();
	    rb >> *s;
	    fShape->AddAt(s,kSSD);}
	    break;
	case kSSDp:{
	    AliITSgeomSSD *s = new AliITSgeomSSD();
	    rb >> *s;
	    fShape->AddAt(s,kSSDp);}
	    break;
	case kSDDp:{
	    AliITSgeomSDD *s = new AliITSgeomSDD();
	    rb >> *s;
	    fShape->AddAt(s,kSDDp);}
	    break;
	} // end  switch
    } //  end for i
    return rb;
}
//______________________________________________________________________
//     The following routines modify the transformation of "this"
// geometry transformations in a number of different ways.
//______________________________________________________________________
void AliITSgeom::GlobalChange(const Float_t *tran,const Float_t *rot){
    //     This function performs a Cartesian translation and rotation of
    // the full ITS from its default position by an amount determined by
    // the three element arrays tran and rot. If every element
    // of tran and rot are zero then there is no change made
    // the geometry. The change is global in that the exact same translation
    // and rotation is done to every detector element in the exact same way.
    // The units of the translation are those of the Monte Carlo, usually cm,
    // and those of the rotation are in radians. The elements of tran
    // are tran[0] = x, tran[1] = y, and tran[2] = z.
    // The elements of rot are rot[0] = rx, rot[1] = ry, and
    // rot[2] = rz. A change in x will move the hole ITS in the ALICE
    // global x direction, the same for a change in y. A change in z will
    // result in a translation of the ITS as a hole up or down the beam line.
    // A change in the angles will result in the inclination of the ITS with
    // respect to the beam line, except for an effective rotation about the
    // beam axis which will just rotate the ITS as a hole about the beam axis.
    // Intputs are:
    // Float_t *tran   A 3 element array representing the global translations.
    //                 the elements are x,y,z in cm.
    // Float_t *rot    A 3 element array representing the global rotation
    //                 angles about the three axis x,y,z in radians
    // Outputs are:
    // none.
    Int_t    i,j;
    Double_t t[3],r[3];
    AliITSgeomMatrix *g;

    fTrans = (fTrans && 0xfffd) + 2;  // set bit 1 true.
    for(i=0;i<fNmodules;i++){
	g = this->GetGeomMatrix(i);
	g->GetTranslation(t);
	g->GetAngles(r);
	for(j=0;j<3;j++){
	    t[j] += tran[j];
	    r[j] += rot[j];
	} // end for j
	g->SetTranslation(t);
	g->SetAngles(r);
    } // end for i
    return;
}
//______________________________________________________________________
void AliITSgeom::GlobalCylindericalChange(const Float_t *tran,
					  const Float_t *rot){
    //     This function performs a cylindrical translation and rotation of
    // each ITS element by a fixed about in radius, rphi, and z from its
    // default position by an amount determined by the three element arrays
    // tran and rot. If every element of tran and
    // rot are zero then there is no change made the geometry. The
    // change is global in that the exact same distance change in translation
    // and rotation is done to every detector element in the exact same way.
    // The units of the translation are those of the Monte Carlo, usually cm,
    // and those of the rotation are in radians. The elements of tran
    // are tran[0] = r, tran[1] = rphi, and tran[2] = z.
    // The elements of rot are rot[0] = rx, rot[1] = ry, and
    // rot[2] = rz. A change in r will results in the increase of the
    // radius of each layer by the same about. A change in rphi will results in
    // the rotation of each layer by a different angle but by the same
    // circumferential distance. A change in z will result in a translation
    // of the ITS as a hole up or down the beam line. A change in the angles
    // will result in the inclination of the ITS with respect to the beam
    // line, except for an effective rotation about the beam axis which will
    // just rotate the ITS as a hole about the beam axis.
    // Intputs are:
    // Float_t *tran   A 3 element array representing the global translations.
    //                 the elements are r,theta,z in cm/radians.
    // Float_t *rot    A 3 element array representing the global rotation
    //                 angles about the three axis x,y,z in radians
    // Outputs are:
    // none.
    Int_t    i,j;
    Double_t t[3],ro[3],r,r0,phi,rphi;
    AliITSgeomMatrix *g;

    fTrans = (fTrans && 0xfffd) + 2;  // set bit 1 true.
    for(i=0;i<fNmodules;i++){
	g = this->GetGeomMatrix(i);
	g->GetTranslation(t);
	g->GetAngles(ro);
	r = r0= TMath::Hypot(t[1],t[0]);
	phi   = TMath::ATan2(t[1],t[0]);
	rphi  = r0*phi;
	r    += tran[0];
	rphi += tran[1];
	phi   = rphi/r0;
	t[0]  = r*TMath::Cos(phi);
	t[1]  = r*TMath::Sin(phi);
	t[2] += tran[2];
	for(j=0;j<3;j++){
	    ro[j] += rot[j];
	} // end for j
	g->SetTranslation(t);
	g->SetAngles(ro);
    } // end for i
    return;
}
//______________________________________________________________________
void AliITSgeom::RandomChange(const Float_t *stran,const Float_t *srot){
    //     This function performs a Gaussian random displacement and/or
    // rotation about the present global position of each active
    // volume/detector of the ITS. The sigma of the random displacement
    // is determined by the three element array stran, for the
    // x y and z translations, and the three element array srot,
    // for the three rotation about the axis x y and z.
    // Intputs are:
    // Float_t *stran  A 3 element array representing the global translations
    //                 variances. The elements are x,y,z in cm.
    // Float_t *srot   A 3 element array representing the global rotation
    //                 angles variances about the three axis x,y,z in radians.
    // Outputs are:
    // none.
    Int_t    i,j;
    Double_t t[3],r[3];
    AliITSgeomMatrix *g;

    fTrans = (fTrans && 0xfffd) + 2;  // set bit 1 true.
    for(i=0;i<fNmodules;i++){
	g = this->GetGeomMatrix(i);
	g->GetTranslation(t);
	g->GetAngles(r);
	for(j=0;j<3;j++){
	    t[j] += gRandom->Gaus(0.0,stran[j]);
	    r[j] += gRandom->Gaus(0.0, srot[j]);
	} // end for j
	g->SetTranslation(t);
	g->SetAngles(r);
    } // end for i
    return;
}
//______________________________________________________________________
void AliITSgeom::RandomCylindericalChange(const Float_t *stran,
					  const Float_t *srot){
    //     This function performs a Gaussian random displacement and/or
    // rotation about the present global position of each active
    // volume/detector of the ITS. The sigma of the random displacement
    // is determined by the three element array stran, for the
    // r rphi and z translations, and the three element array srot,
    // for the three rotation about the axis x y and z. This random change
    // in detector position allow for the simulation of a random uncertainty
    // in the detector positions of the ITS.
    // Intputs are:
    // Float_t *stran  A 3 element array representing the global translations
    //                 variances. The elements are r,theta,z in cm/readians.
    // Float_t *srot   A 3 element array representing the global rotation
    //                 angles variances about the three axis x,y,z in radians.
    // Outputs are:
    // none.
    Int_t    i,j;
    Double_t t[3],ro[3],r,r0,phi,rphi;
    TRandom ran;
    AliITSgeomMatrix *g;

    fTrans = (fTrans && 0xfffd) + 2;  // set bit 1 true.
    for(i=0;i<fNmodules;i++){
	g = this->GetGeomMatrix(i);
	g->GetTranslation(t);
	g->GetAngles(ro);
	r = r0= TMath::Hypot(t[1],t[0]);
	phi   = TMath::ATan2(t[1],t[0]);
	rphi  = r0*phi;
	r    += ran.Gaus(0.0,stran[0]);
	rphi += ran.Gaus(0.0,stran[1]);
	phi   = rphi/r0;
	t[0]  = r*TMath::Cos(phi);
	t[1]  = r*TMath::Sin(phi);
	t[2] += ran.Gaus(0.0,stran[2]);
	for(j=0;j<3;j++){
	    ro[j] += ran.Gaus(0.0, srot[j]);
	} // end for j
	g->SetTranslation(t);
	g->SetAngles(ro);
    } // end for i
    return;
}
//______________________________________________________________________
void AliITSgeom::GeantToTracking(AliITSgeom &source){
    //     Copy the geometry data but change it to go between the ALICE
    // Global coordinate system to that used by the ITS tracking. A slightly
    // different coordinate system is used when tracking. This coordinate 
    // system is only relevant when the geometry represents the cylindrical
    // ALICE ITS geometry. For tracking the Z axis is left alone but X-> -Y
    // and Y-> X such that X always points out of the ITS cylinder for every
    // layer including layer 1 (where the detectors are mounted upside down).
    // Inputs are:
    // AliITSgeom &source  The AliITSgeom class with which to make this
    //                     a copy of.
    // Outputs are:
    // return  *this       The a new copy of source.
    //Begin_Html
    /*
      <img src="picts/ITS/AliITSgeomMatrix_T1.gif">
    */
    //End_Html
    Int_t    i,j,k,l,id[3];
    Double_t r0[3][3],r1[3][3];
    Double_t a0[3][3] = {{0.,+1.,0.},{-1.,0.,0.},{0.,0.,+1.}};
    Double_t a1[3][3] = {{0.,-1.,0.},{+1.,0.,0.},{0.,0.,+1.}};

    *this = source;  // copy everything
    for(i=0;i<GetIndexMax();i++){
	GetGeomMatrix(i)->GetIndex(id);
	GetGeomMatrix(i)->GetMatrix(r0);
	if(id[0]==1){ // Layer 1 is treated different from the others.
	    for(j=0;j<3;j++) for(k=0;k<3;k++){
		r1[j][k] = 0.;
		for(l=0;l<3;l++) r1[j][k] += a0[j][l]*r0[l][k];
	    } // end for j,k
	}else{
	    for(j=0;j<3;j++) for(k=0;k<3;k++){
		r1[j][k] = 0.;
		for(l=0;l<3;l++) r1[j][k] += a1[j][l]*r0[l][k];
	    } // end for j,k
	} // end if
	GetGeomMatrix(i)->SetMatrix(r1);
    } // end for i
    this->fTrans = (this->fTrans && 0xfffe) + 1;  // set bit 0 true.
    return;
}
//______________________________________________________________________
Int_t AliITSgeom::GetNearest(const Double_t g[3],Int_t lay){
    //      Finds the Detector (Module) that is nearest the point g [cm] in
    // ALICE Global coordinates. If layer !=0 then the search is restricted
    // to Detectors (Modules) in that particular layer.
    // Inputs are:
    // Double_t g[3]  The ALICE Cartesean global coordinate from which the
    //                distance is to be calculated with.
    // Int_t lay      The layer to restrict the search to. If layer=0 then
    //                all layers are searched. Default is lay=0.
    // Outputs are:
    // return         The module number representing the nearest module.
    Int_t    i,l,a,e,in=0;
    Double_t d,dn=1.0e10;
    Bool_t   t=lay!=0; // skip if lay = 0 default value check all layers.

    for(i=0;i<fNmodules;i++){
	if(t){GetModuleId(i,l,a,e);if(l!=lay) continue;}
	if((d=GetGeomMatrix(i)->Distance2(g))<dn){
	    dn = d;
	    in = i;
	} // end if
    } // end for i
    return in;
}
//______________________________________________________________________
void AliITSgeom::GetNearest27(const Double_t g[3],Int_t n[27],Int_t lay){
    //      Finds 27 Detectors (Modules) that are nearest the point g [cm] in
    // ALICE Global coordinates. If layer !=0 then the search is restricted
    // to Detectors (Modules) in that particular layer. The number 27 comes 
    // from including the nearest detector and all those around it (up, down,
    // left, right, forwards, backwards, and the corners).
    // Inputs are:
    // Double_t g[3]  The ALICE Cartesean global coordinate from which the
    //                distance is to be calculated with.
    // Int_t lay      The layer to restrict the search to. If layer=0 then
    //                all layers are searched. Default is lay=0.
    // Outputs are:
    // Int_t n[27]    The module number representing the nearest 27 modules
    //                in order.
    Int_t    i,l,a,e,in[27]={0,0,0,0,0,0,0,0,0,
			     0,0,0,0,0,0,0,0,0,
			     0,0,0,0,0,0,0,0,0,};
    Double_t d,dn[27]={1.0e10,1.0e10,1.0e10,1.0e10,1.0e10,1.0e10,
		       1.0e10,1.0e10,1.0e10,1.0e10,1.0e10,1.0e10,
		       1.0e10,1.0e10,1.0e10,1.0e10,1.0e10,1.0e10,
		       1.0e10,1.0e10,1.0e10,1.0e10,1.0e10,1.0e10,
		       1.0e10,1.0e10,1.0e10};
    Bool_t   t=(lay!=0); // skip if lay = 0 default value check all layers.

    for(i=0;i<fNmodules;i++){
	if(t){GetModuleId(i,l,a,e);if(l!=lay) continue;}
	for(a=0;a<27;a++){
	    d = GetGeomMatrix(i)->Distance2(g);
	    if(d<dn[a]){
		for(e=26;e>a;e--){dn[e] = dn[e-1];in[e] = in[e-1];}
		dn[a] = d; in[a] = i;
	    } // end if d<dn[i]
	} // end for a
    } // end for i
    for(i=0;i<27;i++) n[i] = in[i];
}
//----------------------------------------------------------------------