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<!--    1st version created:  Katsuya Amako, Dec-2006         -->
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<!-- ********************* QandA Section ******************** -->
<section id="qanda.Vis">
<title>
Visualization
</title>

<qandaset defaultlabel="qanda">


<!-- ******* QandA Entry ******** -->
<qandaentry  id="qanda.Vis.NoVisAppr">

<question><para>
  I have set G4VIS... environmental variables but visualization does not 
  appear to be enabled. 
</para></question>

<answer><para>
  This might be because you set the environment variables *after* already 
  compiling. The environment variables control C-pre-processor macros of 
  the same name and therefore influence what code gets compiled. It is 
  suggested to proceed with the following manual procedure to correct the 
  current installation:

  <itemizedlist spacing="compact">
    <listitem><para>
      Configure the environment according to the installation making sure 
      to -unset- the <literal>G4WORKDIR</literal> environment variable, 
      if set.
    </para></listitem>
    <listitem><para>
      Verify and eventually set the environment variables of the 
      visualization module [name] concerned (setenv or export both 
      <literal>G4VIS_BUILD_[name]_DRIVER</literal> and 
      <literal>G4VIS_USE_[name]</literal> variables according to the UNIX 
      shell used), and then proceed as follows:

      <informalexample><programlisting>
      cd $G4INSTALL/source/visualization
      gmake clean
      gmake
      cd $G4INSTALL/source/interfaces
      gmake clean
      gmake
      cd $G4INSTALL/source
      gmake libmap
      setenv G4WORKDIR [your working directory]   (or export)
      cd [your application directory]
      gmake clean
      gmake
      </programlisting></informalexample>
    </para></listitem>
  </itemizedlist>

</para></answer>

</qandaentry>


<!-- ******* QandA Entry ******** -->
<qandaentry  id="qanda.Vis.BooleanProc">

<question><para>
  While visualizing my geometry setup I often see the following error 
  message printed out:

  <informalexample><programlisting>
  BooleanProcessor: boolean operation failed . 
  </programlisting></informalexample>
</para></question>

<answer><para>
  There is a known limitation for the visualization of Boolean solids 
  in the so-called BooleanProcessor which is used to make polyhedra 
  for visualisation. It does not affect the tracking which is done 
  through such solids. So the error message you see does not affect 
  the simulation in any way. The workaround is to move one of the 
  affected solids by a small distance in order to avoid shared surfaces.
</para></answer>

</qandaentry>


</qandaset>
</section>
