void setVisibilityFlags(BitSet bs) {
    /*
     * set all fixed objects visible; others based on model being displayed
     * 
     */
    for (int i = dipoleCount; --i >= 0;) {
      Dipole dipole = dipoles[i];
      dipole.visibilityFlags = ((dipole.modelIndex < 0 || bs
          .get(dipole.modelIndex))
          && dipole.mad != 0
          && dipole.visible
          && dipole.origin != null
          && dipole.vector != null
          && dipole.vector.length() != 0
          && dipole.dipoleValue != 0 ? myVisibilityFlag : 0);
    }
    //dumpDipoles("setVis");
  }