To add a graphics system:

1) implement 3 new classes:
 
     class G4XXX: public G4VGraphicsSystem
     class G4XXXSceneHandler: public G4VSceneHandler
     class G4XXXViewer: virtual public G4VViewer

   These should be placed in their own sub-directory under
   visualization, together with a GNUmakefile and a History file.
   Change the library name G4XXX in "name := G4XXX" in GNUmakefile.

2) Add to SUBDIRS and SUBLIBS in visualization/GNUmakefile.

3) Look at the XXX graphics system teamplate in visualization/XXX and
   use it to build your graphics system.

   You might also find it useful to look at ASCIITree (and VTree) as
   an example of a minimal graphics system.

   Look at FukuiRenderer as an example of a system which implements
   AddThis methods for some solids.

   Look at OpenGL as an example of a system which implements a graphical
   database (display lists) and the machinery to decide when to rebuild.
   (OpenGL is complicated by the proliferation of combinations of:

     immediate (no display lists) )   ( X-windows
     stored (uses display lists)  ) x ( X with motif - interactive
                                      ( Win32

   (6 combinations) and much use is made of inheritance to avoid code
   duplication.)

4) If it requires external libraries, introduce two new environment
   variables G4VIS_BUILD_XXX_DRIVER and G4VIS_USE_XXX and make the
   modifications to:

     source/visualization/management/include/MyVisManager.cc
     (similarly all examples vis managers)
     source/visualization/management/src/G4VisManager.cc
     config/G4VIS_BUILD.gmk
     config/G4VIS_USE.gmk

   In any case, augment the informational printing in G4VisManager.cc.