I have set G4VIS... environmental variables but visualization does not appear to be enabled.
This might be because you set the environment variables *after* already compiling. The environment variables control C-pre-processor macros of the same name and therefore influence what code gets compiled. It is suggested to proceed with the following manual procedure to correct the current installation:
While visualizing my geometry setup I often see the following error message printed out:
BooleanProcessor: boolean operation failed .
There is a known limitation for the visualization of Boolean solids in the so-called BooleanProcessor which is used to make polyhedra for visualisation. It does not affect the tracking which is done through such solids. So the error message you see does not affect the simulation in any way. The workaround is to move one of the affected solids by a small distance in order to avoid shared surfaces.