KAHIBARO
2.3. Installing Visualization Libraries
Table of Contents
OpenGL
Geant4 uses visualization drivers to draw your geometry and particle tracks. OpenGL is the simplest and most commonly used driver for interactive 3D viewing.
Most Linux systems already include OpenGL libraries, but you need the development packages so that Geant4 can compile with OpenGL support. On Debian or Ubuntu, typical packages are libglu1-mesa-dev and freeglut3-dev. On Fedora or CentOS you might install mesa-libGLU-devel and freeglut-devel. Use your distribution’s package manager and search for OpenGL development packages if the exact names differ.
When you configure Geant4 with CMake, OpenGL support is enabled by setting the corresponding CMake option before you run the build. In your Geant4 build directory, you can do this either on the command line or in a CMake GUI. The important variable is the OpenGL X11 driver.
To enable OpenGL visualization when configuring Geant4, set
GEANT4_USE_OPENGL_X11=ON in CMake.
If you reconfigure an existing build directory, always run CMake again after changing this option, then rebuild Geant4. When configuration is successful, CMake prints lines indicating that the OpenGL driver has been found and enabled. After installation, you can verify OpenGL support by running one of the Geant4 example applications and using a macro that contains commands like /vis/open OGL 600x600 or /vis/open OGLIX.
If the build fails with messages about missing OpenGL headers or libraries, install the missing development packages, delete the CMake cache in your build directory, and reconfigure with CMake so that it can find the libraries on your system.
Qt
Qt can be used by Geant4 as a graphical user interface and as a visualization backend that integrates menus, command widgets, and a 3D viewer in one window. Qt support is optional but very convenient for beginners because it provides an interactive command console and menus for controlling visualization and runs.
To use Qt with Geant4, you need Qt development packages installed before configuring Geant4. On many systems, this means installing something like qtbase5-dev on Debian or Ubuntu, or qt5-qtbase-devel on Fedora or CentOS. If your distribution has multiple Qt versions, choose a recent Qt 5 package that matches your compiler.
Configuration is again controlled by CMake options. In your Geant4 build directory, enable the Qt driver before building.
To enable Qt visualization and GUI, set
GEANT4_USE_QT=ON in CMake.
CMake searches for Qt and fails if it cannot find the Qt development files. If that happens, check that the Qt development package is installed and that your CMake version is new enough to detect it. After successful configuration and compilation, Geant4 example applications that support Qt can be started with commands such as /vis/open OGLIQt or /vis/open Qt. This opens a window with menus, toolbars, and a text command console.
If you enable both OpenGL and Qt, the Qt visualization usually uses OpenGL internally to draw the 3D view. To avoid linking problems, make sure that both OpenGL and Qt development packages are available before running CMake, then rebuild Geant4 once after changing these options.
Optional visualization drivers
Besides OpenGL and Qt, Geant4 provides several other visualization drivers that you can optionally enable at CMake configuration time. These drivers provide alternative backends such as RayTracer or interfaces to external tools. You can enable or disable them depending on what you need and what libraries are available on your system.
Some common optional drivers are controlled by specific CMake options. The exact set can evolve between Geant4 versions, but typical examples include:
| Driver type | Example CMake option | Purpose |
|---|---|---|
| RayTracer | GEANT4_USE_RAYTRACER_X11 | Simple ray-traced images with X11 |
| VRML | GEANT4_USE_VRML | Export to VRML format for external viewers |
| HepRApp / DAWN | GEANT4_USE_HBOOK or similar | Interfaces to external HEP viewers |
Check the Geant4 installation documentation or the CMake cache in your build directory to see the exact option names in your version.
To enable an additional driver, set the corresponding CMake option to ON and rerun CMake in the Geant4 build directory, then rebuild and reinstall if necessary. You can enable several drivers at the same time. During a Geant4 session, each driver appears as a different option in the /vis/open command, for example /vis/open RayTracerX or /vis/open VRML1.
Visualization drivers are selected at CMake configuration time by setting their GEANT4_USE_... options to ON. Changes require reconfiguring and rebuilding Geant4 before they take effect.
If a driver fails to open at runtime, it usually means that the required external library or program is missing. Install the missing dependency if you really need that driver or simply use another driver that is already working, such as OpenGL or Qt, to continue with the course and examples.
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