Getting started

• Get one of the GDML releases either by downloading the tarfile (see GDML page) or by checking it out from GDML2 CVS repository using the anonnymous access mode 'cvs -d :pserver:anonymous@simu.cvs.cern.ch:/cvs/simu co -r <version> -d <destination> GDML2' where <version> should be replaced by the GDML version number in the form GDML_X_Y_Z (for example GDML_2_8_0) and <destination> should be replaced by the destination directory (for example src)
• For the first-time users an installation script (GDMLSetup in CPPGDML directory) has been implemented to guide through the installation procedure. More advanced users can configure the build system by directly executing the 'configure' script in the CPPGDML directory with all the options properly set. The options should specify the platform (for instance Linux-g++), the location of the CLHEP, Geant4 and XercesC installations, the type of Geant4 libraries (global by default, or granular) as well as the kind of GDML libraries to be build (dynamic or static). The configure script can also extract all the necessary information from the environment variables if they have been set beforehead (for instance by executing the env.csh script from the Geant4 installation). Please have a look at the README file in CPPGDML directory for additional information on the GDML configuration system. An example of the configuration is given in CERNConfigure.(c)sh scripts which can be modified and used for the local user's system configuration. The full list of options can be obtained by issueing './configure -help'.
• Once the configuration is properly done, you can build the GDML libraries by issueing the 'make' (or 'gmake') command in CPPGDML directory. The built libraries can be found in CPPGDML/build/$PLATFORM/lib, where libgdml is the global library containing all the modules for both the Geant4 GDML reader as well as the writer. The last, optional step is to install the libraries, the binaries (the examples) as well as the includes in some specific place (following, for instance, some local software installation rules) using 'make install' command. The installation directories should be specified beforehead using --libdir=DIR --includedir=DIR and --bindir=DIR options of the configure script.

• Using GDML with Geant4
  In order to use the GDML file as geometry source for a Geant4 application one needs to instanciate and call the GDML processor. This can, for instance, be done within a special G4VUserDetectorConstruction class implementation. The g4gogdml example (in CPPGDML/g4gogdml directory) provides an implementation of such a detector construction class. Some more information can be found in the following section.
  In order to export the Geant4 geometry in the form of the GDML file, one needs to instanciate the G4GDMLWriter class and then call its DumpGeometryInfo method providing the pointer to the top volume of the geomety tree. This can be done anywhere in the user code provided only that the Geant4 geometry tree is already instanciated in the memory. The example code can be found in CPPGDML/Examples/g4N02gdml directory. For more information please refer to section.
• Using GDML with ROOT
  GDML reader and writer is fully integrated within the TGeoManager::Import and TGeoManager::Export methods which automatically call the appropriate GDML processing code whenever the file extension is .gdml.