GUI Quickstart
Add -gui to gemc to open the interactive Qt interface.
Using the Quickstart counter example:
gemc counter.yaml -gui
The window is divided into three zones:
- Top bar — run controls and event counters.
- Left button bar — four icon buttons that select the active page.
- Right content area — the page selected by the left bar.
Top bar
| Control | Description |
|---|---|
| N. Events | Number of events to process per run. Edit the field to change it. |
| Run | Execute one batch of N events, then update the event counter. |
| Cycle | Run one batch every 2 seconds continuously. |
| Stop | Stop a running cycle. |
| Event Number | Cumulative count of events processed since launch. |
| Exit | Quit GEMC. |
Pages
Display
The Geant4 3D visualization window.
The View tab exposes:
- Camera — theta/phi sliders and preset direction dropdowns to orbit the viewpoint.
- Light — theta/phi sliders to reposition the scene light source.
- View properties — projection mode (perspective / orthographic) and circle-segmentation precision.
- Slices — activate and position cutaway planes on X, Y, and Z; choose intersection or union mode for multiple planes.
- Toggles — one-click switches for hidden edges, anti-aliasing, auxiliary edges, field lines, coordinate axes, and scale bar.
Dialog
A searchable Geant4 command browser.
- A filterable tree of all available Geant4 UI commands.
- Contextual help and parameter descriptions for the selected command.
- A command prompt for typing and executing commands directly.
- History recall to repeat or modify previous commands.
Setup
The Setup page reads the geometry database and presents the available experiments and systems in a tree view.
Each system row shows:
| Column | Description |
|---|---|
| exp / system | Checkbox to enable or disable the system in the simulation. |
| volumes | Number of geometry entries for the current variation + run selection. |
| variation | Drop-down listing all variations stored for this system. |
| run | Drop-down listing all run numbers stored for this system. |
The green square (availability indicator) means the selected combination exists in the database.
To switch or add a system:
- Check the system(s) you want to include; uncheck the ones you want to exclude.
- Use the variation and run drop-downs to select the configuration you need.
- Click Reload to rebuild the geometry. The Display and Volumes pages update automatically.
Note
A single database can contain multiple experiments with different system sets. Only one experiment is active at a time; checking a row in a different experiment automatically unchecks the previous one.
Volumes
The Volumes page shows the complete detector geometry as a hierarchical tree, organized by system.
The tree has three columns:
| Column | Description |
|---|---|
| Visibility | Checkbox to show or hide the volume. Toggling a parent also toggles its direct children. |
| Color | Click to open a color picker and change the volume’s display color. |
| Name | Full volume name including the system prefix, shown as a hierarchy. |
The Properties panel on the right shows the selected volume’s opacity and system metadata.
All changes are applied to the Geant4 visualization immediately — no reload is required.
Example workflow — inspect a single volume:
- Navigate to the Volumes page.
- Uncheck the parent system row to hide all volumes.
- Expand the tree and check only the volume of interest.
- Click its color button and choose a highlight color.
- Adjust the opacity to make surrounding volumes semi-transparent instead of hidden.