Is the tag currently supported in the ROOT GDML parser?
If not, is support for it planned for sometime in the future?
There is an existing parser implementation in Geant4 that could be used for reference about how to do this.
No, loops are not supported and there is no plan yet to do that, as GDML in ROOT was intended more like an exchange format than a definition language. However, many new features were contributed lately in the parser, so this feature may come as contribution as well, specially if there is an example in Geant4.
Thanks for the reply.
If I have an existing GDML geometry with loops and I want to load this into ROOT, should I load it into the Geant4 runtime and then export to GDML in order to write out a compatible file?
Right, this looks like the path to follow, as the G4 GDML writer will likely unfold the loop while going through the geometry structure.