Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Fri, 20 Sep 1996 10:05:20 +0100
My 2p.
Angus.
On Sep 19, 3:57pm, Guy Russell wrote:
> Subject: Re: Benefits of Display listing of geosets
> On Sep 16, 6:07pm, Michael T. Jones wrote:
> > Subject: Re: Benefits of Display listing of geosets
> > On Sep 16, 12:43pm, Ken Sakai wrote:
> > > Subject: Benefits of Display listing of geosets
> > >
> > > Perfomers,
> > >
> > > Does anyone have an idea of how much of a performance increase
> > > pfGSetDrawMode(geoset, PFGS_COMPILE_GL, val) will tend to buy you
> > > on the various platforms? I know that objects drawn using OpenGL
> > > display lists display MUCH faster than those drawn in immediate mode
> > > in iR's. Will OpenGL display lists buy you much on Impact graphics,
> > > RE graphics, and on Extreme graphics systems? I was told that
> > > OpenGL display lists should also run faster on Impact machines but I do
not
> > > seem to be getting any speed increase with
> > > pfGSetDrawMode(geoset, PFGS_COMPILE_GL, val) on Impacts.
> >
> > 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.
>
> It is true that other machines do not have display list memory in hardware,
> however display lists are still a potential performance win on the Impact.
If
> a display list is pullable, the graphics will initiate the DMA for the
display
> list from main memory. Pullability keeps the processor from getting involved
> in the I/O for the display list. On a single processor system this can be a
> big win if you are CPU limited. Most vis sim oriented display lists will be
> pullable. The one major exception to date is anytime a display list binds a
> texture. This limitation will be removed in upcoming releases, but for now
you
> must keep bind texture calls out of pullable display lists.
>
> >
> > Michael
> > =======================================================================
> > List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/
> > Submissions: info-performer++at++sgi.com
> > Admin. requests: info-performer-request++at++sgi.com
> >-- End of excerpt from Michael T. Jones
>
>
> Guy
>
> --
> Guy Russell
> Vis Sim Applied Engineering Silicon Graphics Inc.
> Email:guyr++at++engr.sgi.com 2011 N. Shoreline Blvd. M/S 3L-916
> Phone:(415)933-6113 Mountain View CA 94043
> =======================================================================
> List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/
> Submissions: info-performer++at++sgi.com
> Admin. requests: info-performer-request++at++sgi.com
>-- End of excerpt from Guy Russell
=======================================================================
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