Michael T. Jones (mtj++at++babar.asd.sgi.com)
Mon, 16 Sep 1996 18:07:15 -0700
Performer's immediate-mode rendering has always been as fast or
faster (usually faster) than IRIS GL or OpenGL display-list mode.
This is true on iR also, but there's more to the story...
...InfiniteReality has a 15+ megabyte cache on the geometry engine
board that is used to keep local copies of certain display lists.
Not all display lists can be kept locally (i.e., those that do
texture binds prevent lists from being cached). For those that are
in fact able to be cached, the difference between cached display
list and immediate mode over the Onyx-to-iR bus is significant and
will almost always result in better performance. This is due to
the cache's greater bandwidth than the bus interface.
For this reason, we made the perfly in Performer 2.1 default to the
display-list mode. To see the difference, use the "d" (for display
list) and "i" (for immediate mode) keys to toggle between the two
cases.
On other machines there is not the same advantage for display lists
that you'll see on iR. In the future, should bus speeds increase,
we'll see the advantage of display list mode decrease, perhaps to
the point where it won't be used.
Michael
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