examples/extended/visualization/standalone

This example illustrates how one might use the Geant4 Visualization System as a "standalone" graphics library and viewer, i.e, without the overhead of the run manager and all the actions and physics.

It makes use of the "user action" feature of the Geant4 vis manager - for a simple example see examples/extended/visualization/userVisAction. You have to encapsulate your drawing in a vis action so that the vis manager can call it and re-call it as appropriate.

1) Define a G4VUserVisAction that implements a Draw method. Two examples are provided:

StandaloneVisAction:
- a simple box;
- a Boolean solid;
- an alternative way of drawing a solid by obtaining the polyhedral representation (included for interest, not as a recommendation).
DrawGeometryVisAction:
- Shows how to visualise your geometry alone, i.e., without the run manager and the physics stuff.

2) In the main program, the vis actions must be instantiated and registered with the visualization manager. You may (optionally) specify an extent to assist the viewers to locate the objects.

3) To visualise, you need:

/vis/scene/add/userAction

4) Use the usual Geant4 vis commands to create a scene and view (including the above command) - see standalone.mac.

Note: The system needs an "extent" in order to point the virtual camera and adjust its field of view, etc. This defines the "standard view". You may zoom, etc., from this standard view. The extent may be specified as suggested above or by using /vis/scene/add/extent.

John Allison 30th December 2022