Geant 4中Run、Event、Step等数据提取（初学笔记）
Geant 4运行中涉及到Run、Event、Step、Track等过程，其ID、位置、时间、能量、几何体、材料、粒子类型、反应类型等各类数据均可被提取。数据提取方式较多，如SensitiveDetector，Hit和HitsCollection，以及RunAction， EventAction和SteppingAction等等。
相关知识的介绍可以参见官方手册（http://geant4-userdoc.web.cern.ch/geant4-userdoc/UsersGuides/ForApplicationDeveloper/html/index.html）或网络文章，如https://blog.csdn.net/Jack_chf/article/details/98631042和http://littlepascal.lofter.com/post/322764_ccda14b等。
Run、Event、Step、Track等过程的数据提取可参考官方网站FAQ（http://geant4-userdoc.web.cern.ch/geant4-userdoc/UsersGuides/FAQ/html/tracksAndSteps.html）。
Geant 4中各个类或例子的程序源码可参见：https://geant4.kek.jp/Reference/10.05/classG4BestUnit.html
本人在exampleB1例子的基础上，尝试在B1SteppingAction中提取并保存每个Step的部分数据，部分程序及输出结果如下所示：（output data 部分是本人添加的）
#include "G4RunManager.hh"
void B1SteppingAction::UserSteppingAction(const G4Step* step)
{
if (!fScoringVolume) {
const B1DetectorConstruction* detectorConstruction
= static_cast
(G4RunManager::GetRunManager()->GetUserDetectorConstruction());
fScoringVolume = detectorConstruction->GetScoringVolume();
}
// get volume of the current step
G4LogicalVolume* volume
= step->GetPreStepPoint()->GetTouchableHandle()
->GetVolume()->GetLogicalVolume();
// check if we are in scoring volume
if (volume != fScoringVolume) return;
// collect energy deposited in this step
G4double edepStep = step->GetTotalEnergyDeposit();
fEventAction->AddEdep(edepStep);
// output data
//
G4int eventID = G4RunManager::GetRunManager()->GetCurrentEvent()->GetEventID();
G4Track* track = step->GetTrack();
G4int trackID = track->GetTrackID();
G4int parentID = track->GetParentID();
G4int stepID = track->GetCurrentStepNumber();
G4double globalTime = track->GetGlobalTime();
G4String particalName = track->GetDefinition()->GetParticleName();// equal to GetDynamicParticle()
// G4String particalName2 = track->GetDynamicParticle()->GetDefinition()->GetParticleName();
G4ThreeVector xyzTrack = track->GetPosition();// equal to PostStepPoint()
G4ThreeVector xyzPost = step->GetPostStepPoint()->GetPosition();// string type
//
std::ofstream myData;
myData.open("MyData.data", std::ios::app);
if (energy.is_open()){
energy< 注：
1. xyzTrack输出的是string类型数据，xyzTrack[0/1/2]可以直接输出三维坐标。
2. EventID的提取还有一种复杂一些的方式，见文末。
3. 在RunAction.cc 中添加如下代码，确保每次程序运行前先清空前一次运行结果（不推荐）。
std::ofstream myData;
myData.open("MyData.data",std::ios::out);
myData.close();输出数据如下：
0 1 0 4 (-22.1688,22.4189,100) (-22.1688,22.4189,100) -22.1688 22.4189 100 gamma 0.83391
4 1 0 2 (-16.1019,68.5515,100) (-16.1019,68.5515,100) -16.1019 68.5515 100 gamma 0.83391
5 1 0 2 (45.9618,-22.952,100) (45.9618,-22.952,100) 45.9618 -22.952 100 gamma 0.83391
6 1 0 2 (32.5909,-42.5795,100) (32.5909,-42.5795,100) 32.5909 -42.5795 100 gamma 0.83391
7 1 0 2 (41.5544,-13.6419,66.3294) (41.5544,-13.6419,66.3294) 41.5544 -13.6419 66.3294 gamma 0.721597
7 1 0 3 (4.92261,-1.80317,70.8464) (4.92261,-1.80317,70.8464) 4.92261 -1.80317 70.8464 gamma 0.850891
7 1 0 4 (-20.7132,6.45138,64.4711) (-20.7132,6.45138,64.4711) -20.7132 6.45138 64.4711 gamma 0.943209
7 1 0 5 (-32.3885,-0.428879,53.6671) (-32.3885,-0.428879,53.6671) -32.3885 -0.428879 53.6671 gamma 1.00102
7 1 0 6 (-60,-61.2693,93.6792) (-60,-61.2693,93.6792) -60 -61.2693 93.6792 gamma 1.26079
7 1 0 9 (-49.8705,-83.0484,86.0968) (-49.8705,-83.0484,86.0968) -49.8705 -83.0484 86.0968 gamma 1.35398
7 5 1 1 (-32.4141,-0.422902,53.6124) (-32.4141,-0.422902,53.6124) -32.4141 -0.422902 53.6124 e- 1.00135
7 4 1 1 (-20.744,6.49458,64.4881) (-20.744,6.49458,64.4881) -20.744 6.49458 64.4881 e- 0.943521
7 3 1 1 (4.92159,-1.80282,70.8511) (4.92159,-1.80282,70.8511) 4.92159 -1.80282 70.8511 e- 0.850939
7 2 1 1 (42.9266,-12.9366,70.672) (42.9266,-12.9366,70.672) 42.9266 -12.9366 70.672 e- 0.7364
7 2 1 2 (45.6817,-11.3767,72.7819) (45.6817,-11.3767,72.7819) 45.6817 -11.3767 72.7819 e- 0.749168
7 2 1 3 (46.622,-10.0944,75.2173) (46.622,-10.0944,75.2173) 46.622 -10.0944 75.2173 e- 0.75897
7 2 1 4 (47.8083,-8.90427,76.5569) (47.8083,-8.90427,76.5569) 47.8083 -8.90427 76.5569 e- 0.766295
7 2 1 5 (47.4191,-9.00081,77.7972) (47.4191,-9.00081,77.7972) 47.4191 -9.00081 77.7972 e- 0.770881
7 2 1 6 (47.1056,-8.69988,77.9746) (47.1056,-8.69988,77.9746) 47.1056 -8.69988 77.9746 e- 0.772706
7 7 2 1 (43.0266,-12.8545,70.7928) (43.0266,-12.8545,70.7928) 43.0266 -12.8545 70.7928 gamma 0.73699
7 7 2 2 (42.917,-13.2873,70.172) (42.917,-13.2873,70.172) 42.917 -13.2873 70.172 gamma 0.739541
7 9 7 1 (42.9156,-13.2871,70.1727) (42.9156,-13.2871,70.1727) 42.9156 -13.2871 70.1727 e- 0.739562
9 1 0 4 (5.71433,4.95276,100) (5.71433,4.95276,100) 5.71433 4.95276 100 gamma 0.83391
7 8 7 1 (43.0266,-12.8545,70.7928) (43.0266,-12.8545,70.7928) 43.0266 -12.8545 70.7928 e- 0.736991附：EventID提取，参考程序（http://hurel.hanyang.ac.kr/Geant4/Doxygen/9.6.p02/html/_f04_event_action_8cc_source.html）
// G4UserEventAction.hh
//
protected:
G4EventManager* fpEventManager;
// F04EventAction.cc
//
#include "G4EventManager.hh"
G4int F04EventAction::GetEventNo()
{
G4int evno = fpEventManager->GetConstCurrentEvent()->GetEventID();
return evno ;
}
// SteppingAction.cc
//
G4int eventID = fEventAction->GetEventNo();