The visualization/HepRep component allows to create XML files (extension *.heprep) that are viewable using XML compatible software. The software recommended by geant4 Manual is Wired (http://www.slac.stanford.edu/BFROOT/www/Computing/Graphics/Wired/). The combination of Geant4 and Wired works just fine, with the one exception. The trajectories of particles are recorded into XML file with directive <heprep:attvalue showLabel="NONE" name="DrawAs" value="Line"/> (this is the actual two lines in a heprep file recorded by Geant4). After this directive, and a bunch of others, the coordinates of the particle's trajectory are recorded as a sequence of triplets (x, y, and z coordinates). Since the sequence of coordinates is called "Line," the XML reader looks only at the first two points in the sequence, and draws only the first leg of the trajectory. If we want to see the whole trajectory, and not just the first leg of it (the first straight line), the sequence of coordinates has to be recorded as "Polyline," and not as a "Line." I fix the problem in my version of Geant4 4.1 (and 4.0 before that) by changing two lines in the file G4HepRepFileScenneHandler.cc and recompiling the library. Specifically, line #250 has to be changed from AddHepRepInstance("Line",polyline); to AddHepRepInstance("Polyline",polyline); The line #413 has to be changed from if (strcmp("Line",primName)==0) to if (strcmp("Polyline",primName)==0) These two changes fixed the problem, and the resulting XML files have the trajectories of the particles recorded correctly. "Wired" software package shows them correctly. -- Elena Novikova, novikova@ssd5.nrl.navy.mil
Ms Novikova's analysis of the problem is entirely correct. It resulted from a mismatch between various early versions of HepRep and WIRED. For various reasons having to do with the intended evolution of HepRep, the right solution is to modify WIRED to have it handle Line and Polyline as synonymous, either of these being allowed to have 2 OR MORE points. A new WIRED release will be made tomorrow incorporating this fix. It will then work correctly with no change to G4 code.
A new version of WIRED, version 3.7, is now available that corrects this problem. No change is required to G4. The new WIRED version is available from the usual place, http://www.slac.stanford.edu/~wiredces/install.class
