+//____________________________________________________________________
+Double_t AliTRDtrackerV1::FitKalman(AliTRDtrackV1 *track, AliTRDseedV1 *tracklets, Bool_t up, Int_t np, AliTrackPoint *points)
+{
+// Kalman filter implementation for the TRD.
+// It returns the positions of the fit in the array "points"
+//
+// Author : A.Bercuci@gsi.de
+
+ // printf("Start track @ x[%f]\n", track->GetX());
+
+ //prepare marker points along the track
+ Int_t ip = np ? 0 : 1;
+ while(ip<np){
+ if((up?-1:1) * (track->GetX() - points[ip].GetX()) > 0.) break;
+ //printf("AliTRDtrackerV1::FitKalman() : Skip track marker x[%d] = %7.3f. Before track start ( %7.3f ).\n", ip, points[ip].GetX(), track->GetX());
+ ip++;
+ }
+ //if(points) printf("First marker point @ x[%d] = %f\n", ip, points[ip].GetX());
+
+
+ AliTRDseedV1 tracklet, *ptrTracklet = 0x0;
+
+ //Loop through the TRD planes
+ for (Int_t jplane = 0; jplane < kNPlanes; jplane++) {
+ // GET TRACKLET OR BUILT IT
+ Int_t iplane = up ? jplane : kNPlanes - 1 - jplane;
+ if(tracklets){
+ if(!(ptrTracklet = &tracklets[iplane])) continue;
+ }else{
+ if(!(ptrTracklet = track->GetTracklet(iplane))){
+ /*AliTRDtrackerV1 *tracker = 0x0;
+ if(!(tracker = dynamic_cast<AliTRDtrackerV1*>( AliTRDReconstructor::Tracker()))) continue;
+ ptrTracklet = new(&tracklet) AliTRDseedV1(iplane);
+ if(!tracker->MakeTracklet(ptrTracklet, track)) */
+ continue;
+ }
+ }
+ if(!ptrTracklet->IsOK()) continue;
+
+ Double_t x = ptrTracklet->GetX0();
+
+ while(ip < np){
+ //don't do anything if next marker is after next update point.
+ if((up?-1:1) * (points[ip].GetX() - x) - fgkMaxStep < 0) break;
+ if(((up?-1:1) * (points[ip].GetX() - track->GetX()) < 0) && !PropagateToX(*track, points[ip].GetX(), fgkMaxStep)) return -1.;
+
+ Double_t xyz[3]; // should also get the covariance
+ track->GetXYZ(xyz);
+ track->Global2LocalPosition(xyz, track->GetAlpha());
+ points[ip].SetXYZ(xyz[0], xyz[1], xyz[2]);
+ ip++;
+ }
+ // printf("plane[%d] tracklet[%p] x[%f]\n", iplane, ptrTracklet, x);
+
+ // Propagate closer to the next update point
+ if(((up?-1:1) * (x - track->GetX()) + fgkMaxStep < 0) && !PropagateToX(*track, x + (up?-1:1)*fgkMaxStep, fgkMaxStep)) return -1.;
+
+ if(!AdjustSector(track)) return -1;
+ if(TMath::Abs(track->GetSnp()) > fgkMaxSnp) return -1;
+
+ //load tracklet to the tracker and the track
+/* Int_t index;
+ if((index = FindTracklet(ptrTracklet)) < 0){
+ ptrTracklet = SetTracklet(&tracklet);
+ index = fTracklets->GetEntriesFast()-1;
+ }
+ track->SetTracklet(ptrTracklet, index);*/
+
+
+ // register tracklet to track with tracklet creation !!
+ // PropagateBack : loaded tracklet to the tracker and update index
+ // RefitInward : update index
+ // MakeTrack : loaded tracklet to the tracker and update index
+ if(!tracklets) track->SetTracklet(ptrTracklet, -1);
+
+
+ //Calculate the mean material budget along the path inside the chamber
+ Double_t xyz0[3]; track->GetXYZ(xyz0);
+ Double_t alpha = track->GetAlpha();
+ Double_t xyz1[3], y, z;
+ if(!track->GetProlongation(x, y, z)) return -1;
+ xyz1[0] = x * TMath::Cos(alpha) - y * TMath::Sin(alpha);
+ xyz1[1] = +x * TMath::Sin(alpha) + y * TMath::Cos(alpha);
+ xyz1[2] = z;
+ if((xyz0[0] - xyz1[9] < 1e-3) && (xyz0[0] - xyz1[9] < 1e-3)) continue; // check wheter we are at the same global x position
+ Double_t param[7];
+ if(AliTracker::MeanMaterialBudget(xyz0, xyz1, param) <=0.) break;
+ Double_t xrho = param[0]*param[4]; // density*length
+ Double_t xx0 = param[1]; // radiation length
+
+ //Propagate the track
+ track->PropagateTo(x, xx0, xrho);
+ if (!AdjustSector(track)) break;
+
+ //Update track
+ Double_t chi2 = track->GetPredictedChi2(ptrTracklet);
+ if(chi2<1e+10) track->Update(ptrTracklet, chi2);
+ if(!up) continue;
+
+ //Reset material budget if 2 consecutive gold
+ if(iplane>0 && track->GetTracklet(iplane-1) && ptrTracklet->GetN() + track->GetTracklet(iplane-1)->GetN() > 20) track->SetBudget(2, 0.);
+ } // end planes loop
+
+ // extrapolation
+ while(ip < np){
+ if(((up?-1:1) * (points[ip].GetX() - track->GetX()) < 0) && !PropagateToX(*track, points[ip].GetX(), fgkMaxStep)) return -1.;
+
+ Double_t xyz[3]; // should also get the covariance
+ track->GetXYZ(xyz);
+ track->Global2LocalPosition(xyz, track->GetAlpha());
+ points[ip].SetXYZ(xyz[0], xyz[1], xyz[2]);
+ ip++;
+ }
+
+ return track->GetChi2();
+}