REveTrackPropagator.hxx

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// @(#)root/eve7:$Id$
// Authors: Matevz Tadel & Alja Mrak-Tadel: 2006, 2007
 
/*************************************************************************
 * Copyright (C) 1995-2019, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/
 
#ifndef ROOT7_REveTrackPropagator
#define ROOT7_REveTrackPropagator
 
#include <ROOT/REveVector.hxx>
#include <ROOT/REvePathMark.hxx>
#include <ROOT/REveUtil.hxx>
#include <ROOT/REveElement.hxx>
#include "TMarker.h"
 
#include <vector>
 
namespace ROOT {
namespace Experimental {
 
class REvePointSet;
 
////////////////////////////////////////////////////////////////////////////////
/// REveMagField
/// Abstract interface to magnetic field
////////////////////////////////////////////////////////////////////////////////
 
class REveMagField
{
protected:
   Bool_t fFieldConstant{kFALSE};
 
public:
   REveMagField() = default;
   virtual ~REveMagField() {}
 
   virtual Bool_t IsConst() const { return fFieldConstant; }
 
   virtual void PrintField(Double_t x, Double_t y, Double_t z) const
   {
      REveVector b = GetField(x, y, z);
      printf("v(%f, %f, %f) B(%f, %f, %f) \n", x, y, z, b.fX, b.fY, b.fZ);
   }
 
   virtual Double_t    GetMaxFieldMag() const = 0;
   virtual REveVectorD GetField(Double_t x, Double_t y, Double_t z) const = 0;
 
   REveVectorD GetField(const REveVectorD &v) const { return GetField(v.fX, v.fY, v.fZ); }
};
 
////////////////////////////////////////////////////////////////////////////////
/// REveMagFieldConst
/// Interface to constant magnetic field.
////////////////////////////////////////////////////////////////////////////////
 
class REveMagFieldConst : public REveMagField
{
protected:
   REveVectorD fB;
 
public:
   REveMagFieldConst(Double_t x, Double_t y, Double_t z) : REveMagField(), fB(x, y, z) { fFieldConstant = kTRUE; }
   ~REveMagFieldConst() override {}
 
   Double_t    GetMaxFieldMag() const override { return fB.Mag(); };
   REveVectorD GetField(Double_t /*x*/, Double_t /*y*/, Double_t /*z*/) const override { return fB; }
};
 
////////////////////////////////////////////////////////////////////////////////
/// REveMagFieldDuo
/// Interface to magnetic field with two different values depending on radius.
////////////////////////////////////////////////////////////////////////////////
 
class REveMagFieldDuo : public REveMagField
{
protected:
   REveVectorD fBIn;
   REveVectorD fBOut;
   Double_t fR2;
 
public:
   REveMagFieldDuo(Double_t r, Double_t bIn, Double_t bOut)
      : REveMagField(), fBIn(0, 0, bIn), fBOut(0, 0, bOut), fR2(r * r)
   {
      fFieldConstant = kFALSE;
   }
   ~REveMagFieldDuo() override {}
 
   Double_t GetMaxFieldMag() const override
   {
      Double_t b1 = fBIn.Mag(), b2 = fBOut.Mag();
      return b1 > b2 ? b1 : b2;
   }
 
   REveVectorD GetField(Double_t x, Double_t y, Double_t /*z*/) const override
   {
      return ((x * x + y * y) < fR2) ? fBIn : fBOut;
   }
};
 
////////////////////////////////////////////////////////////////////////////////
/// REveTrackPropagator
/// Calculates path of a particle taking into account special path-marks and imposed boundaries.
////////////////////////////////////////////////////////////////////////////////
 
class REveTrackPropagator : public REveElement,
                            public REveRefBackPtr
{
public:
   enum EStepper_e { kHelix, kRungeKutta };
 
   enum EProjTrackBreaking_e { kPTB_Break, kPTB_UseFirstPointPos, kPTB_UseLastPointPos };
 
protected:
   struct Helix_t {
      Int_t fCharge;     // Charge of tracked particle.
      Double_t fMaxAng;  // Maximum step angle.
      Double_t fMaxStep; // Maximum allowed step size.
      Double_t fDelta;   // Maximum error in the middle of the step.
 
      Double_t fPhi; // Accumulated angle to check fMaxOrbs by propagator.
      Bool_t fValid; // Corner case pT~0 or B~0, possible in variable mag field.
 
      // ----------------------------------------------------------------
 
      // helix parameters
      Double_t fLam;       // Momentum ratio pT/pZ.
      Double_t fR;         // Helix radius in cm.
      Double_t fPhiStep;   // Caluclated from fMinAng and fDelta.
      Double_t fSin, fCos; // Current sin/cos(phistep).
 
      // Runge-Kutta parameters
      Double_t fRKStep; // Step for Runge-Kutta.
 
      // cached
      REveVectorD fB;            // Current magnetic field, cached.
      REveVectorD fE1, fE2, fE3; // Base vectors: E1 -> B dir, E2->pT dir, E3 = E1xE2.
      REveVectorD fPt, fPl;      // Transverse and longitudinal momentum.
      Double_t fPtMag;           // Magnitude of pT.
      Double_t fPlMag;           // Momentum parallel to mag field.
      Double_t fLStep;           // Transverse step arc-length in cm.
 
      // ----------------------------------------------------------------
 
      Helix_t();
 
      void UpdateCommon(const REveVectorD &p, const REveVectorD &b);
      void UpdateHelix(const REveVectorD &p, const REveVectorD &b, Bool_t full_update, Bool_t enforce_max_step);
      void UpdateRK(const REveVectorD &p, const REveVectorD &b);
 
      void Step(const REveVector4D &v, const REveVectorD &p, REveVector4D &vOut, REveVectorD &pOut);
 
      Double_t GetStep() { return fLStep * TMath::Sqrt(1 + fLam * fLam); }
      Double_t GetStep2() { return fLStep * fLStep * (1 + fLam * fLam); }
   };
 
private:
   REveTrackPropagator(const REveTrackPropagator &) = delete;
   REveTrackPropagator &operator=(const REveTrackPropagator &) = delete;
 
   void DistributeOffset(const REveVectorD &off, Int_t first_point, Int_t np, REveVectorD &p);
 
protected:
   EStepper_e fStepper;
 
   REveMagField *fMagFieldObj{nullptr};
   Bool_t fOwnMagFiledObj{kFALSE};
 
   // Track extrapolation limits
   Double_t fMaxR; // Max radius for track extrapolation
   Double_t fMaxZ; // Max z-coordinate for track extrapolation.
   Int_t fNMax;    // Max steps
   // Helix limits
   Double_t fMaxOrbs; // Maximal angular path of tracks' orbits (1 ~ 2Pi).
 
   // Path-mark / first-vertex control
   Bool_t fEditPathMarks;   // Show widgets for path-mark control in GUI editor.
   Bool_t fFitDaughters;    // Pass through daughter creation points when extrapolating a track.
   Bool_t fFitReferences;   // Pass through given track-references when extrapolating a track.
   Bool_t fFitDecay;        // Pass through decay point when extrapolating a track.
   Bool_t fFitCluster2Ds;   // Pass through 2D-clusters when extrapolating a track.
   Bool_t fFitLineSegments; // Pass through line when extrapolating a track.
   Bool_t fRnrDaughters;    // Render daughter path-marks.
   Bool_t fRnrReferences;   // Render track-reference path-marks.
   Bool_t fRnrDecay;        // Render decay path-marks.
   Bool_t fRnrCluster2Ds;   // Render 2D-clusters.
   Bool_t fRnrFV;           // Render first vertex.
   TMarker fPMAtt;          // Marker attributes for rendering of path-marks.
   TMarker fFVAtt;          // Marker attributes for fits vertex.
 
   // Handling of discontinuities in projections
   UChar_t fProjTrackBreaking; // Handling of projected-track breaking.
   Bool_t fRnrPTBMarkers;      // Render break-points on tracks.
   TMarker fPTBAtt;            // Marker attributes for track break-points.
 
   // ----------------------------------------------------------------
 
   // Propagation, state of current track
   std::vector<REveVector4D> fPoints;     // Calculated point.
   std::vector<REveVector4D> fLastPoints; // Copy of the latest calculated points.
   REveVectorD fV;                        // Start vertex.
   Helix_t fH;                            // Helix.
 
   void RebuildTracks();
   void Update(const REveVector4D &v, const REveVectorD &p, Bool_t full_update = kFALSE, Bool_t enforce_max_step = kFALSE);
   void Step(const REveVector4D &v, const REveVectorD &p, REveVector4D &vOut, REveVectorD &pOut);
 
   Bool_t LoopToVertex(REveVectorD &v, REveVectorD &p);
   Bool_t LoopToLineSegment(const REveVectorD &s, const REveVectorD &r, REveVectorD &p);
   void   LoopToBounds(REveVectorD &p);
 
   Bool_t LineToVertex(REveVectorD &v);
   void   LineToBounds(REveVectorD &p);
 
   void   StepRungeKutta(Double_t step, Double_t *vect, Double_t *vout);
 
   Bool_t HelixIntersectPlane(const REveVectorD &p, const REveVectorD &point, const REveVectorD &normal, REveVectorD &itsect);
   Bool_t LineIntersectPlane(const REveVectorD &p, const REveVectorD &point, const REveVectorD &normal, REveVectorD &itsect);
   Bool_t PointOverVertex(const REveVector4D &v0, const REveVector4D &v, Double_t *p = nullptr);
 
   void   ClosestPointFromVertexToLineSegment(const REveVectorD &v, const REveVectorD &s, const REveVectorD &r,
                                              Double_t rMagInv, REveVectorD &c);
   Bool_t ClosestPointBetweenLines(const REveVectorD &, const REveVectorD &, const REveVectorD &, const REveVectorD &,
                                   REveVectorD &out);
 
public:
   REveTrackPropagator(const std::string& n = "REveTrackPropagator", const std::string& t = "", REveMagField *field = nullptr,
                       Bool_t own_field = kTRUE);
   ~REveTrackPropagator() override;
 
   void OnZeroRefCount() override;
 
   void CheckReferenceCount(const std::string &from = "<unknown>") override;
 
   void StampAllTracks();
 
   // propagation
   void InitTrack(const REveVectorD &v, Int_t charge);
   void ResetTrack();
 
   Int_t    GetCurrentPoint() const;
   Double_t GetTrackLength(Int_t start_point = 0, Int_t end_point = -1) const;
 
   virtual void   GoToBounds(REveVectorD &p);
   virtual Bool_t GoToVertex(REveVectorD &v, REveVectorD &p);
   virtual Bool_t GoToLineSegment(const REveVectorD &s, const REveVectorD &r, REveVectorD &p);
 
   // REveVectorF wrappers
   void   InitTrack(const REveVectorF &v, Int_t charge);
   void   GoToBounds(REveVectorF &p);
   Bool_t GoToVertex(REveVectorF &v, REveVectorF &p);
   Bool_t GoToLineSegment(const REveVectorF &s, const REveVectorF &r, REveVectorF &p);
 
   Bool_t IntersectPlane(const REveVectorD &p, const REveVectorD &point, const REveVectorD &normal, REveVectorD &itsect);
 
   void FillPointSet(REvePointSet *ps) const;
 
   void SetStepper(EStepper_e s) { fStepper = s; }
 
   void SetMagField(Double_t bX, Double_t bY, Double_t bZ);
   void SetMagField(Double_t b) { SetMagField(0, 0, b); }
   void SetMagFieldObj(REveMagField *field, Bool_t own_field = kTRUE);
 
   void SetMaxR(Double_t x);
   void SetMaxZ(Double_t x);
   void SetMaxOrbs(Double_t x);
   void SetMinAng(Double_t x);
   void SetMaxAng(Double_t x);
   void SetMaxStep(Double_t x);
   void SetDelta(Double_t x);
 
   void SetEditPathMarks(Bool_t x) { fEditPathMarks = x; }
   void SetRnrDaughters(Bool_t x);
   void SetRnrReferences(Bool_t x);
   void SetRnrDecay(Bool_t x);
   void SetRnrCluster2Ds(Bool_t x);
   void SetFitDaughters(Bool_t x);
   void SetFitReferences(Bool_t x);
   void SetFitDecay(Bool_t x);
   void SetFitCluster2Ds(Bool_t x);
   void SetFitLineSegments(Bool_t x);
   void SetRnrFV(Bool_t x);
   void SetProjTrackBreaking(UChar_t x);
   void SetRnrPTBMarkers(Bool_t x);
 
   REveVectorD GetMagField(Double_t x, Double_t y, Double_t z) { return fMagFieldObj->GetField(x, y, z); }
   void        PrintMagField(Double_t x, Double_t y, Double_t z) const;
 
   EStepper_e GetStepper() const { return fStepper; }
 
   Double_t GetMaxR() const { return fMaxR; }
   Double_t GetMaxZ() const { return fMaxZ; }
   Double_t GetMaxOrbs() const { return fMaxOrbs; }
   Double_t GetMinAng() const;
   Double_t GetMaxAng() const { return fH.fMaxAng; }
   Double_t GetMaxStep() const { return fH.fMaxStep; }
   Double_t GetDelta() const { return fH.fDelta; }
 
   Bool_t GetEditPathMarks() const { return fEditPathMarks; }
   Bool_t GetRnrDaughters() const { return fRnrDaughters; }
   Bool_t GetRnrReferences() const { return fRnrReferences; }
   Bool_t GetRnrDecay() const { return fRnrDecay; }
   Bool_t GetRnrCluster2Ds() const { return fRnrCluster2Ds; }
   Bool_t GetFitDaughters() const { return fFitDaughters; }
   Bool_t GetFitReferences() const { return fFitReferences; }
   Bool_t GetFitDecay() const { return fFitDecay; }
   Bool_t GetFitCluster2Ds() const { return fFitCluster2Ds; }
   Bool_t GetFitLineSegments() const { return fFitLineSegments; }
   Bool_t GetRnrFV() const { return fRnrFV; }
   UChar_t GetProjTrackBreaking() const { return fProjTrackBreaking; }
   Bool_t GetRnrPTBMarkers() const { return fRnrPTBMarkers; }
 
   TMarker &RefPMAtt() { return fPMAtt; }
   TMarker &RefFVAtt() { return fFVAtt; }
   TMarker &RefPTBAtt() { return fPTBAtt; }
 
   const std::vector<REveVector4D> &GetLastPoints() const { return fLastPoints; }
 
   static Bool_t IsOutsideBounds(const REveVectorD &point, Double_t maxRsqr, Double_t maxZ);
 
   static Double_t fgDefMagField;        // Default value for constant solenoid magnetic field.
   static const Double_t fgkB2C;         // Constant for conversion of momentum to curvature.
   static REveTrackPropagator fgDefault; // Default track propagator.
};
 
//______________________________________________________________________________
inline Bool_t REveTrackPropagator::IsOutsideBounds(const REveVectorD &point, Double_t maxRsqr, Double_t maxZ)
{
   // Return true if point% is outside of cylindrical bounds detrmined by
   // square radius and z.
 
   return TMath::Abs(point.fZ) > maxZ || point.fX * point.fX + point.fY * point.fY > maxRsqr;
}
 
//______________________________________________________________________________
inline Bool_t REveTrackPropagator::PointOverVertex(const REveVector4D &v0, const REveVector4D &v, Double_t *p)
{
   static const Double_t kMinPl = 1e-5;
 
   REveVectorD dv;
   dv.Sub(v0, v);
 
   Double_t dotV;
 
   if (TMath::Abs(fH.fPlMag) > kMinPl) {
      // Use longitudinal momentum to determine crossing point.
      // Works ok for spiraling helices, also for loopers.
 
      dotV = fH.fE1.Dot(dv);
      if (fH.fPlMag < 0)
         dotV = -dotV;
   } else {
      // Use full momentum, which is pT, under this conditions.
 
      dotV = fH.fE2.Dot(dv);
   }
 
   if (p)
      *p = dotV;
 
   return dotV < 0;
}
 
} // namespace Experimental
} // namespace ROOT
 
#endif