-straight
  -helium bag
  -conical
It is possible to switch between them using switch in macro argument bpipe_type. This argument can be straight/bag/conical.
Macro is defined with 4 arguments. All of them have some default value:
create_bpipe_geometry_gen(char geoTag = "v24f", double beam_deflection_angle=0, enum bpipe_type = straight, double vacuum_presure = 1e-16)

beam_deflection angle is in DEG
vacuum presure is in Pa

The way of generating the geometry is following:
1) load the macro using .L create_bpipe_geometry_gen.C
2) call macro e.g. create_bpipe_geometry_gen(v24f, 0, straight, 1e-16)