Problem 388

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