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Example GramsG4 macro files

If you want a formatted (or easier-to-read) version of this file, scroll to the bottom of GramsSim/README.md for instructions. If you're reading this on github, then it's already formatted.

To get you started, here are examples of how to set up event generation and the interactive display for GramsG4. To use one of these files, e.g., mac/test.mac:

./gramsg4 --macrofile mac/test.mac

See README.md in the parent directory for more information.

run.mac - shoots 20 1-MeV gammas along the z-axis, y-axis, and x-axis.

batch.mac - shoots 1000 1-MeV gamma along the z-axis.

sky.mac - shoots 1000 gammas from an imaginary sphere surrounding the detector (the 'sky') focused on the center of the TPC. The energy spectrum comes from a histogram (see scripts/Hist2Text.C).

crab.mac - a crude approximation of gammas from the Crab Nebula directed at the top of the GRAMS detector.

crab-45.mac - a crude approximation of gammas from the Crab Nebula directed at the top of the GRAMS detector at 45-degree angle.

debug-geom.mac - run Geant4's geometry validation (takes a long time!)

hepmc3.mac - how to run the simulation using an input file of generated events.

vis-hepmc3.mac - run the simulation with both an input events file and visualization.

Working with Geant4 visualization

To run an interactive or visualization job with, e.g., mac/vis.mac

./gramsg4 --ui --uimacrofile mac/vis.mac

Note that to use the interactive OGL visualizer, you use the combination --ui and --uimacrofile options (and/or edit the uimacrofile option in options.xml). This is to allow rapid switching between visualization and non-interactive running of the simulation.

Geant4 offers quite a few options for event visualization. Here's a description (PDF file) of the different options. As of Aug-2021, two example visualization methods are offered in these macro files.

OpenGL

With OpenGL, Geant4 offers an interactive display. Unfortunately, OpenGL is now considered obsolete by some OS manufacturers (Apple in particular) which means that support can be spotty. As noted in the GramsSim/README.md file, you'll need OpenGL libraries installed on the system that's running gramsg4. If you're using a local computer to view the display (e.g., you're running gramsg4 on a server by connecting from a laptop), you may also need to setup OpenGL on your local machine.

The sample OpenGL macro files:

vis.mac - setup for interactive display. Particles are aimed along the negative z-direction randomly across the top face of the inner detector.

vis-sphere.mac - another interactive display. The particles are generated on the surface of an imaginary sphere surrounding the detector (the 'sky') and are focused on the center of the TPC. The energy spectrum comes from a histogram (see scripts/Hist2Text.C).

outline.mac - just shows an outline of the detector, and is colored so that it's more suitable for inclusion in talks. Give this one some extra time to load, since it's turning off the visibility for a number of volumes.

vis-menus.mac - a fancy demonstration of how to switch commands via menus at the top of the G4 visualizer. This macro file invokes the draw-axes.mac, angle-view.mac, {x,y,z}-views.mac, energy-*.mac, and plane-*.mac sub-files from within its menus.

HepRep

HepRep is a non-interactive method of visualization, in the sense that you run a separate program to display events after you run gramsg4. It has the advantage that you can view the information for tracks on the display; e.g., instead of just seeing a track you can also view the PDG code and energy of the particle.

The disadvantages of HepRep compared to OpenGL:

  • It's harder to use. In particular, the user interface is more complex.

  • It can't be used to control Geant4 interactively.

  • It writes the event information in HepRep format, which uses XML, with each event in its own file. As a result HepRep outputs can take up a lot of disk space.

To use HepRep, run gramsg4 with appropriate macro commands; heprep.mac shows an example. For example:

./gramsg4 --macrofile mac/heprep.mac

To visualize a .heprep file, you must install both Java and the HepRApp visualizer. To run HepRApp:

java -jar HepRApp.jar

Once you've started HepRApp, select Open Data, navigate to the directory with your .heprep files, and open G4Data0.heprep. The Previous Event and Next Event buttons will move through the G4Data<N>.heprep files.

While running HepRApp, there are two key items in its Options menu:

  • Label Control - This affects which labels are included in the event display. Probably the two most useful are IMag (the track energy) and PDG; ID (G4 track ID) and PID (parent ID) may also be helpful.

  • Cut Control - This allows you to set cuts on which tracks are displayed. For example, in the IMag line, you can set the Min to 20 MeV to show only those tracks with more than 20 MeV. Note that you must include units in the cut.