Geant4 Geometry ??(?)????????

1
Geant4 Geometry??(?)????????

• ?? ? (SLAC)

2
??

• Solid
• BREP solid
• Boolean solid
• Physical volume
• Parameterized volume
• Replica
• Assembly
• Voxelisation
• CAD interface

3
G4VSolid

• G4VSolid
• ??(????)
• G4VSolid ? abstract class
• ????????????

4
G4VSolid

• Geant4?????Solid
• CSG (Constructed Solid Geometry) solids
• G4Box, G4Tubs, G4Cons, G4Trd,
• Specific solids (CSG like)
• G4Polycone, G4Polyhedra, G4Hype,
• ????CSG??????BREP
• BREP (Boundary REPresented) solids
• G4BREPSolidPolycone, G4BSplineSurface,
• Any order surface
• Boolean solids
• G4UnionSolid, G4SubtractionSolid,
• STEP interface
• BREP solid models ? CAD file ??????
• STEP compliant solid modeler

5
G4Polycone
G4Polycone( const G4String name,
G4double phiStart,
G4double phiTotal, G4int
numZPlanes, const G4double
zPlane, const G4double
rInner, const G4double
rOuter )

• name
• Solid???
• phiStart, phiTotal
• ?????????????
• numZPlanes
• Z???????
• ???????4

• zPlane
• Z???????
• ???Z0
• rInner, rOuter
• ?????

6
G4Polyhedra
G4Polyhedra( const G4String name,
G4double phiStart,
G4double phiTotal, G4int
numSide, G4int numZPlanes,
const G4double zPlane,
const G4double rInner,
const G4double rOuter )

• name
• Solid???
• phiStart, phiTotal
• ?????????????
• numSide
• ????
• numZPlanes
• Z???????
• ???????4

• zPlane
• Z???????
• ???Z0
• rInner, rOuter
• ?????

7
BREP solid

• BREP Boundary REPresented Solid
• Solid?????????????
• ??????????6????
• BREP??????
• ???2?????????
• Splines, B-Splines,
• NURBS (Non-Uniform B-Splines)
• ???????BREP???????????
• box, cons, tubs, sphere, torus, polycone,
  polyhedra
• CAD file??????solid???BREP

8
Boolean solid

• 2??solid?boolean operation????????
• G4UnionSolid, G4IntersectionSolid,
  G4SubtractionSolid
• 1???solid????2???solid?????????
• Boolean operation????solid?????????operation???
• Tracking????boolean solid?????????primitive
  solid????????????????track????solid???????????????
  ?????????primitive solid????????????

G4SubtractionSolid
G4UnionSolid
G4IntersectionSolid
9
G4VPhysicalVolume

• G4VPhysicalVolume
• G4LogicalVolume ??????
• G4VPhysicalVolume ? abstract class
• ????????????

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G4VPhysicalVolume

• G4PVPlacement 1 Placement One
  Volume
• Logical volume?1???
• G4PVParameterized 1 Parameterized Many
  Volumes
• 1??physical volume?????volume???
• CopyNo?????????????????sensitivity???????
• ???????????????parameterised volume???volume?????
  ????
• G4PVReplica 1 Replica Many
  Volumes
• 1??physical volume?????volume???
• ????????volume??volume?????????
• ??tube,cone??R??
• ??????
• ?volume?placement volume?repeated
  volume????????????
• Repeated volume?CSG solid??

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G4PVParameterised
G4PVParameterised(const G4String pName,
G4LogicalVolume pLogical,
G4LogicalVolume pMotherLogical,
const EAxis pAxis, const G4int
nReplicas, G4VPVParameterisation
pParam)

• pName
• Physical volume?
• pLogical
• ???logical volume
• ??????????????????
• pMotherLogical
• ??logical volume
• ??physical volume???????????????

• pAxis
• ????????????????
• kXAxis,kYAxis,kZAxis
• nReplicas
• ?????
• ???CopyNo?0n-1
• ??CopyNo????????
• pParam
• G4VPVParameterisation

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G4VPVParameterisation

• ComputeTransformation
• CopyNo????physical volume????rotation
  matrix??????
• physVol-gtSetTranslation
• (G4ThreeVector(x,y,z))
• physVol-gtSetRotation(pRotM)
• Material, sensitivity, ???logical volume
  ?attribute??????
• physVol-gtGetLogicalVolume()-gtSet()
• ComputeSolid
• CopyNo????solid???
• ComputeMaterial
• CopyNo????material???
• ComputeDimensions
• ???parameterise?????????parameterise????????
• ?????????????????????CopyNo???????????????

class G4VPVParameterisation public virtual
void ComputeTransformation (const G4int,
G4VPhysicalVolume ) const 0 virtual
G4VSolid ComputeSolid (const G4int,
G4VPhysicalVolume ) virtual G4Material
ComputeMaterial (const G4int,
G4VPhysicalVolume ) virtual void
ComputeDimensions (G4Box , const G4int,
const G4VPhysicalVolume ) const
virtual void ComputeDimensions (G4Tubs ,
const G4int, const G4VPhysicalVolume )
const
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G4VPVParameterisation?????

• Rotation matrix, solid????????????????????????????
  ?????????????????Navigator??????????local
  scope?????????????????????????????????????????
• ???????????????????????????sin,
  cos????????????????????performance?????????
• ??????????????????????????????????????????????????
  ?????
• ???????ComputeDimensions??????base class
  virtual?????????warning message?????????????????

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G4PVReplica

• 1?????????????1??G4PVReplica????
• ????volume????????????????????????solid?logical
  volume??????
• ???parameterise??????????????????

• pName
• Physical volume?
• pLogical
• ???logical volume
• pMotherLogical
• ??logical volume
• ??physical volume???????????????
• nReplicas
• ?????
• ???CopyNo?0n-1

G4PVReplica( const G4String pName,
G4LogicalVolume pLogical, G4LogicalVolume
pMother, const EAxis pAxis, const G4int
nReplicas, const G4double width, const
G4double offset0 )
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G4PVReplica pAxis, width, offset

• pAxis?????????
• kXAxis, kYAxis, kZAxis
• n??????????????
• -width(nReplicas-1)0.5nwidth
• ??????
• Offset??????
• pAxis????????
• kRho
• n??????widthnoffset??
• width(n1)offset???????
• pAxis?phi?????
• kPhi
• n??????widthnoffset??
• width(n1)offset???????

G4PVReplica( const G4String pName,
G4LogicalVolume pLogical, G4LogicalVolume
pMother, const EAxis pAxis, const G4int
nReplicas, const G4double width, const
G4double offset0 )
width
offset
width
offset
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G4AssemblyVolume

• ?????geometry??????????volume??????????????????

• G4AssemblyVolume??????????
• G4AssemblyVolume???physical volume????
• ???????logical volume????????logical
  volume?????????????????
• ???????volume?placement?????????????????????????
• ????geometry?????parameterised volume?????

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G4AssemblyVolume

• G4AssemblyVolume
• ???????
• AddPlacedVolume
• G4AssemblyVolume??volume???????????????logical
  volume???
• MakeImprint
• G4AssemblyVolume????logical volume????????????????
  
• ?????(G4Transform3D)?????transform
  G4ThreeVector?rotation matrix??????????????????

class G4AssemblyVolume public
G4AssemblyVolume() void AddPlacedVolume (
G4LogicalVolume pPlacedVolume,
G4Transform3D transformation) void
MakeImprint ( G4LogicalVolume pMotherLV,
G4Transform3D transformation)
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Voxelisation

• Run????navigation?????????smart voxel???
• ??????tracking????????????????????????????
• Binary search
• ?????1??????voxel???
• ?????voxel???volume??????????merge???
• ??????2???3????????voxelise??
• ???logical volume????voxelisation????
• Voxelisation????????????????????????????
• ????????????????????

19
CAD interface

• CAD file (STEP AP203 compliant)?solid?????????????
  
• ???sensitivity?????????????DetectorConstruction???
  ?????
• ???solid?1???????????
• ??placement volume???
• ?????detector component??CAD file??????????volume?
  ???
• G4PlacedSolid
• 1??STEP solid?????Geant4 solid???
• G4Assembly
• G4PlacedSolid???
• G4AssemblyCreator
• STEP file????G4Assembly?G4PlacedSolid?????????????

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CAD interface

• G4AssemblyCreator MyAC("tracker.stp")
• MyAC.ReadStepFile()
• STEPentity ent0
• MyAC.CreateG4Geometry(ent)
• void pl MyAC.GetCreatedObject()
• G4Assembly assembly new G4Assembly()
• assembly-gtSetPlacedVector((G4PlacedVector)pl)
• G4int solids assembly-gtGetNumberOfSolids()
• for(G4int c0 cltsolids c)
• G4PlacedSolid ps assembly-gtGetPlacedSolid(c)
  
• G4LogicalVolume lv
• new G4LogicalVolume(ps-gtGetSolid(), Lead,
  "STEPlog")
• G4RotationMatrix hr ps-gtGetRotation()
• G4ThreeVector tr ps-gtGetTranslation()
• G4VPhysicalVolume pv
• new G4PVPlacement(hr, tr,
  ps-gtGetSolid()-gtGetName(),
• lv, experimentalHall_phys,
  false, c)