Analysing Geometry

Finding volumes

Before editing geometry it is useful to find a logical volume. The registry contains all the logical volumes using the GDML in pyg4ometry/test/gdmlG4examples/ChargeExchangeMC/

import pyg4ometry
r = pyg4ometry.gdml.Reader("lht.gdml")
reg = r.getRegistry()

The registry instance reg has a member variable called logicalVolumeDict so calling

reg.logicalVolumeDict.keys()

should print

In [4]: reg.logicalVolumeDict.keys()
Out[4]: odict_keys(['vMonitor', 'vMonitorBack', 'vTarget', 'vTargetInnerCover', 'vTargetColumn', 'vTargetInnerColumn',
                    'vTargetVacuumSpace', 'vTargetOuterCover', 'vCrystal', 'vCrystalRow', 'vCalorimeter', 'vVetoCounter',
                    'vOuterFerrumRing', 'vInnerFerrumRing', 'vInnerCuprumRing', 'vTargetWindow', 'vTargetWindowCap',
                    'vTargetWindowMylarCover', 'vTargetWindowAluminiumCover', 'vWorldVisible', 'World'])

then the LogicalVolume can be obtained simply from the dictionary

lv = reg.logicalVolumeDict['vTargetInnerColumn']

This lv can be used for manipulating geometry, passing to visualisers etc.

Navigating the LV-PV hierarchy

There is a hierarchy of LV-PVs to describe a GDML/Geant4 geometry. An LV in terms of geometry consists of an outer solid lv.solid and lv.daughterVolumes. lv.solid is one of the pyg4ometry.geant4.solid types which match the GDML/Geant4 solids. lv.daughterVolumes is a list of pyg4ometry.geant4.PhysicalVolumes.

The best way to explore the methods and data members of pyg4ometry.geant4.LogicalVolume and pyg4ometry.geant4.PhysicalVolume is to explore in iPython. See cute video based on the lht.gdml example above.

Geometry Complexity Analysis

For a given logical volume we can get some statistics on the complexity of the geometry. A simple class called GeometryComplexityInformation is returned that has a serious of dictionaries with information.

cd pyg4ometry/test/gdmlCompoundExamples/bdsim_2
ipython
>>> import pyg4ometry
>>> r = pyg4ometry.gdml.Reader("22-size-variation-facetcrop-quad.gdml")
>>> info = pyg4ometry.geant4.AnalyseGeometryComplexity(r.getRegistry().getWorldVolume())
>>> info.printSummary()
Types of solids
ExtrudedSolid        : 96
Tubs                 : 51
Intersection         : 24
Polyhedra            : 12
Subtraction          : 6
Box                  : 1

# of daughters       count
0                    : 152
2                    : 19
4                    : 12
13                   : 6
25                   : 1

Depth of booleans    count
1                    : 30

Booleans width depth over  3
Solid name                               : n Booleans

>>> info. <tab>
comp.booleanDepth      comp.nDaughtersPerLV
comp.booleanDepthCount comp.printSummary
comp.nDaughters        comp.solids