To reduce fill-limited drawing, use backface and frontface removal. For
example, if you are drawing a sphere, half of its polygons are backfacing at
any given time. Backface and frontface removal is done after transformation
calculations but before per-fragment operations. This means that backface
removal may make transform-limited polygons somewhat slower, but make
fill-limited polygons significantly faster. You can turn on backface removal when
you are drawing an object with many backfacing polygons, then turn it off
again when drawing is completed. Back face removal has the added advantage
of eliminating 
-fighting problems on objects with sharp edges.