## 0.0 45.1 5.0 表示从0.0°开始，每间隔5.0°赋予一次数值，到小于45.1为止，和for循环很像

B5DetectorConstruction::B5DetectorConstruction(): G4VUserDetectorConstruction(),fMessenger(nullptr),fHodoscope1Logical(nullptr), fHodoscope2Logical(nullptr),fWirePlane1Logical(nullptr), fWirePlane2Logical(nullptr),fCellLogical(nullptr), fHadCalScintiLogical(nullptr),fMagneticLogical(nullptr),fVisAttributes(),fArmAngle(30.*deg), fArmRotation(nullptr),
fSecondArmPhys(nullptr)
// fArmAngle参数就是要改变的角度θ
{fArmRotation = new G4RotationMatrix();fArmRotation->rotateY(fArmAngle);
// fArmRotation为改变探测器角度的实际“参数”
//define commands for this class
DefineCommands();
// DefineCommands()这个函数放在初始化列表中就是为了通过UI命令直接定义初始化
//B5DetectorConstruction.cc，毫无疑问，DefineCommands()中一定是
//定义了有关fArmAngle怎样改变探测器角度的方法
}
//~~~~~~~~~~~~~~~~~~~~////second armauto secondArmSolid    =new G4Box("secondArmBox",2.*m,2.*m,3.5*m);auto secondArmLogical  =new G4LogicalVolume(secondArmSolid,air,"secondArmLogical");auto x = -5.*m * std::sin(fArmAngle);auto z = 5.*m * std::cos(fArmAngle);fSecondArmPhys  =new G4PVPlacement(fArmRotation,G4ThreeVector(x,0.,z),secondArmLogical,"fSecondArmPhys",worldLogical,false,0,checkOverlaps);
// fSecondArmPhys就是我们要放置的“探测器”，它的旋转角度以及三维位置都是由
//fArmAngle直接决定
//~~~~~~~~~~~~~~~~~~~~~~~~~//
void B5DetectorConstruction::SetArmAngle(G4double val)
{if(!fSecondArmPhys) {G4cerr << "Detector has not yet been constructed."<< G4endl;return;}fArmAngle = val;*fArmRotation = G4RotationMatrix(); // make it unit vector
fArmRotation->rotateY(fArmAngle);
//fArmRotation为探测器的角度设置auto x = -5.*m * std::sin(fArmAngle);auto z = 5.*m * std::cos(fArmAngle);fSecondArmPhys->SetTranslation(G4ThreeVector(x,0.,z));
//fSecondArmPhys->SetTranslation(…)为探测器的位置设置
//tell G4RunManager that we change the geometryG4RunManager::GetRunManager()->GeometryHasBeenModified();
}
//SetArmAngle()这个函数确实也应该包含在DefineCommands()中，借以实际改变探测角度及位置//~~~~~~~~~~~~~~~~~~~~~~~~~~~~//
void B5DetectorConstruction::DefineCommands()
{//Define /B5/detector command directory using generic messenger classfMessenger = new G4GenericMessenger(this,"/B5/detector/","Detector control");//armAngle commandauto& armAngleCmd=
fMessenger->DeclareMethodWithUnit("armAngle","deg",&B5DetectorConstruction::SetArmAngle,"Set rotation angle of the second arm.");armAngleCmd.SetParameterName("angle", true);armAngleCmd.SetRange("angle>=0. && angle<180.");armAngleCmd.SetDefaultValue("30.");
}
// DefineCommands()作为调整探测器角度位置的核心函数，定义了一个可以在*.mac中调用的命令，
// /B5/detector/armAngle 10 deg 表示将fArmAngle设置为10°，相应的探测角度和位置也与之对应改变

G4double edep = aStep->GetTotalEnergyDeposit();
theEvent->AddEdep(edep);

void EventAction::EndOfEventAction(const G4Event* aEvent)
{
if(fEdep>0.0) realcounts++;
G4long event_id = aEvent->GetEventID()+1;
fstream datafile;
if((event_id) % 100 == 0) {
G4cout<<"Event"<<event_id<<" is over"<<G4endl;
datafile.open("outputcounts.xls",ios::out|ios::app);
G4int outcounts=realcounts-tempcounts;
datafile <<outcounts<<G4endl;
tempcounts = realcounts;
datafile.close();
}
//关键部分，每跑100个粒子输出一次探测器计数

void MYPrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
const G4Run *nowrun=G4RunManager::GetRunManager()->GetCurrentRun();
G4int runid=nowrun->GetRunID();
//此时，runid就是一个反映当前第几个Run的变量，以每次Run100个粒子为例，也可通过设置int(eventID/100)来替代runid，二者等价
G4int posx,posy,posz;
posx=int(floor(runid/64));
posy=int(floor((runid%64)/8));
posz=int(floor((runid%64)%8));
particleGun->SetParticlePosition(G4ThreeVector((posx-3.5)*3.2*mm,(posy-3.5)*3.2*mm,(posz-3.5)*3.2*mm));
}