Again, Geant4 is NOT a program that can be double clicked and run. We can only run a Geant4 Application compiled into an executable locally or on the cloud.
We control a Geant4 application primarily through macro commands, which can be used in both graphic and command-line based user interfaces (UI). Their pro's and con's are summarized in the following YouTube video.
<iframe width="640" height="360" src="https://www.youtube.com/embed/3wJrE22P5Hk?si=6HhmxOg4D5JVxDQU" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>Every once in a while, we need to distribute a large Geant4 simulation on a computer cluster. There are at least two computer clusters in US that can be used for free if the simulation is done for research purpose. They are OSG and NRP. OSG relies on HTConder to submit jobs. NRP relies on Kubernetes.
It is the user's responsibility to provide a detector model for a Geant4 simulation. The Geant4 User Guide for Application Developers provides detailed instruction on how to program detector definition and response in C++. Again, end users are forced to become application developers if they choose to go that route.
Fortunately, Geant4 also allows end users to write their detector definition in plain text.
However, writing in a text file is not the most intuitive way to construct and debug 3D geometries. A graphic user interface (GUI) is better suited for this task. G4web is such a UI on the web. One can use the mouse to select, place, rotate basic shapes on a canvas, and export the constructed detector model to a plain text file called detector.tg, which can be read by a Geant4 application that is configured to accept detector definition in plain text.
