I can't run the demos for Ruby/GtkGLArea.  I get eg.:

/usr/local/src/ruby-gtkglarea-0.9.0/examples/gtkglarea_demo.rb:3:in `require': No such file to load -- opengl (LoadError)
        from /usr/local/src/ruby-gtkglarea-0.9.0/examples/gtkglarea_demo.rb:3

The offending line is "require opengl".  Obviously Ruby is failing to
find some library.  I thought maybe some search path was wrong, but
running "locate -i opengl" finds nothing of any use, so it looks like
I don't have the right file(s) anywhere on my system.  The
ruby-gtkglarea "examples/README" file simply says "some examples need
data files which are distributed with GtkGLArea.", but I can see
nothing in the GtkGLArea distro that looks like what I need (not that
I actually know what I need).  I'm stumped!

The RubyGTK and GtkGLArea demos all run OK.

Please help!  This was to be the basis of my first serious Ruby
project and I'm itching to get started.

TIA, 

Jeremy Henty 

PS.  Details: 

AMD K6
Linux 2.2.18
Red Hat Linux 6.2
GCC 2.95.2
Mesa 3.2
GTK 1.2.8
GtkGLArea 1.2.2
Ruby 1.6.3
Ruby/GTK 0.24
Ruby/GtkGLArea 0.9.0