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0002
0003 =========================================================
0004 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
0005 =========================================================
0006
0007 transforms
0008 ----------
0009
0010 This example illustrates various ways to place a volume.
0011 There are two G4PVPlacement constructors. One uses a direct rotation matrix,
0012 via G4Transform3D class. The other uses an inverse rotation matrix.
0013 The rotation matrices themselves, direct or inverse, can be explicitely computed
0014 by users, or built with various G4 build-in transformations methods,
0015 like axial rotations.
0016
0017 1- Geometry construction
0018 ---------------------
0019 Two G4Trd volumes (daughters) are placed within a G4Tubs (mother), in such a way
0020 that their z_axis are in the mother xy plane.
0021 To see the picture, run the example in interactive mode.
0022
0023 The various ways of placement are implemented in the DetectorConstruction class
0024 in the following private functions:
0025
0026 - PlaceWithDirectMatrix()
0027 This method is using G4PVPlacement with G4Transform3D, which is constructed from a rotation matrix (G4RotationMatrix) and a translation vector (G4ThreeVector). The rotation and translation in this case represent the active transformation: the solid itself is moved by rotating and translating it to bring it into the system of coordinates of the mother volume.
0028 The rotation matrix is defined via the daughter frame axes with respect to the mother frame.
0029
0030 - PlaceWithInverseMatrix()
0031 This method is using G4PVPlacement with a rotation matrix (G4RotationMatrix) and a translation vector (G4ThreeVector). The rotation Matrix represents the rotation of the reference frame of the considered volume relatively to its mother volume’s reference frame. The translation Vector represents the translation of the current volume in the reference frame of its mother volume.
0032 - If compared to the previous construct, the transformation in this case is generated by specifying the same translation with respect to its mother volume and the inverse of the rotation matrix.
0033 The rotation matrix is defined again via the daughter frame axes with respect to the mother frame.
0034
0035 - PlaceWithAxialRotations()
0036 This method is using G4PVPlacement with G4Transform3D again, but in difference from
0037 PlaceWithDirectMatrix(), the rotation matrix is defined via rotate[X,Y,Z]() member functions of G4RotationMatrix.
0038
0039 - PlaceWithEulerAngles()
0040 This method is using G4PVPlacement with G4Transform3D again, but with the rotation matrix is defined via Euler angles.
0041
0042 - PlaceWithReflections()
0043 In this method, in addition to two positions defined via "PlaceWithAxialRotations" method, two more positions including reflection symmetry are defined.
0044 When reflections are present in geometry, the placements have to be applied
0045 via G4ReflectionFactory::Place() method, where a G4Transform3D with reflection
0046 can be used.
0047
0048 These functions are then called from the Construct() function.
0049 All methods define exactly same geometry except for the placement
0050 with reflection where trapezoids are placed with their symmetry axis
0051 in parallel with z-axis in order to make easier to check reflection
0052 visually.
0053
0054 The method of placement can be selected interactively via the command
0055 (see DetectorMessenger):
0056 /placement/setMethod method (see transfoms.in)
0057
0058
0059 2- Physics list
0060 ------------
0061 PhysicsList.cc defines only geantino and transportation process.
0062
0063 3- Primary generator
0064 -----------------
0065 Default kinematic is a geantino at coordinate origin.
0066 Can be changed with particleGun commands.
0067
0068 4- Physics
0069 -------
0070 No physics; only transportation.
0071
0072 5- Visualisation
0073 -------------
0074 In interactive mode, visualization manager is set in the main().
0075 Initialisation of the drawing is done via the commands
0076 /vis/.. in the macro vis.mac : /control/execute vis.mac
0077
0078 6- How to start ?
0079 --------------
0080 - execute transforms in 'interactive mode' with visualization
0081 % transforms
0082 ....
0083 Idle> ---> type your commands. For example:
0084 Idle> /placement/setMethod WithInverseMatrix
0085 Idle> /control/execute vis.mac
0086 Idle> /tracking/verbose 1
0087 Idle> /run/beamOn 1
0088 Idle> exit
0089 or, simply
0090 Idle> /control/execute rotations.mac
0091 Idle> /control/execute reflections.mac
0092
0093 - execute transforms in 'batch' mode from macro files
0094 % transforms transforms.in
