Using GDML with the SLAC Installation of the Geant4 Toolkit

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Introduction

A recipe for building and running a simulation executable using the Geant4 toolkit and the Geometry Description Markup Language is provided. Libraries for both of these packages are installed and maintained by the SLAC Geant4 group so that users need only link their applications to them. As a starting point for new users, a Geant4 extended example N03GDML has been provided.

Current Installation

Geant4 release - the GDML example uses Geant4 6.1 contained in the patch geant4-06-01-ref-00-patch-00. This is a local patch of the official March 2004 release.
Supported Platforms:
- Linux - noric
- Solaris - shire, tersk

GDML is a markup language which allows the definition of geometry data in XML format. Further information about GDML is available here. The Xerces-C++ libraries are needed for GDML. Information about Xerces-C++ is available here. Currently both GDML and Xerces-C++ libraries are installed only on noric.
Supported Platforms:
- Linux - noric

Accessing the SLAC installations

To compile and link a simulation executable using the current Geant4 toolkit and the GDML package, several environment variables must first be set. This can be done as follows:

choose a work directory, for example, mytestdir
copy to it the files

/afs/slac/package/geant4/vol3/G4Home/g4setup.env
and
/afs/slac/package/geant4/vol0/xerces/xerces.env
in g4setup.env modify the line in the file which sets the G4WORKDIR environment variable so that it reads:
setenv G4WORKDIR $HOME/mytestdir
source g4setup.env
source xerces.env

The essential variables set by g4setup.env file are:

G4WORKDIR - working directory which will contain your specific code and the binary application
G4INSTALL - location of the installed code and libraries
G4SYSTEM - G4 code for the system architecture
CLHEP_BASE_DIR - base directory of the CLHEP libraries against which the toolkit is linked and against which your code should be linked
CLHEP_LIB - location in the SLAC directory structure of CLHEP libraries built for a given platform

The essential variables set by xerces.env file are:

XERCESCROOT root directory of Xerces-C++
LD_LIBRARY_PATH - add Runtime Libraries Path to Xerces-C++

Building and Running the Executable

The following steps will lead you to a working executable of the extended example N03gdml :

go to your work directory: cd $G4WORKDIR
from the G4-SLAC installation copy the code for example N03gdml:
- cp -pr $G4INSTALL/examples/extended/gdml/N03gdml N03gdml
from the G4-SLAC installation copy the default namespace schema directory. This directory must be located just above the N03gdml directory.
- cp -pr $G4INSTALL/examples/extended/gdml/schema schema
cd to N03gdml
gmake clean
gmake
- gmake will create tmp and bin directories in your work directory. The executable, named N03gogdml, will be in /bin/$G4SYSTEM/
while in directory N03gdml, run the executable:
- ../bin/$G4SYSTEM/NO3gogdml
if all goes well, the same detector as novice example N03 will be constructed by GDML. If you use visualization, an OpenGL window will appear containing a side view of the detector.

At this point you are ready to add to and modify the code in your copy of N03gdml. To learn more about developing your own simulation code using Geant4, see the Application Developer's Guide .

Tatsumi Koi

Dennis Wright