Brian Furtaw (brian++at++dingbat.clubfed.sgi.com)
Fri, 30 May 1997 14:22:16 -0400
"IRIS Performer is designed to run at a fixed frame rate. The rate
argument to pfFrameRate specifies the desired rate in units of frames per
second. The actual rate used is based on the video timing of the display
hardware. rate is rounded to the nearest frame rate which corresponds to
an integral multiple of video fields.
For a 60Hz video rate, possible frame rates are (in Hz) 60.0, 30.0, 20.0,
15.0, 12.0, 10.0, 8.57, 7.5, 6.67, and 6.0. These rates would mean that
the number of fields per frame would range from 1 (for 60Hz) to 10 (for
6Hz)."
Your total time is till the next vertical retrace as specified by the video
display hardware. The difference between total time and the sums of the
APP+CULL+DRAW is taken up by pfSync(). The O2 can't render your scene as fast
as your Powerseries machine could that is why you see the sluggishness. Locking
the framerate at 60Hz simply means you will not go faster then 60Hz it may draw
slower then 60Hz if it can't keep up.
Brian
On May 30, 3:08pm, Inge Henriksen wrote:
> Subject: Re: Optimising frame rate.
> Simon Dimaio wrote:
> >
> > Hi
> >
> > This is a question regarding graphics performance. I have written a
> > relatively small visual simulation on an old PowerSeries system with 2
> > processors (R2000A/R3000) and VGX graphics, which is to be ported to an O2
> > with an R5000.
> >
> > Channel statistics (Powerseries) show the following process times:
> >
> > Application = 4.6ms
> > Cull = 4ms
> > Draw = 40ms
> >
> > Yet the total frame time is reported as 75ms.
> >
> > After the addition of some "on the fly" geometry (Geode), the process
> > times become.
> >
> > Application = 4.6ms
> > Cull = 11ms
> > Draw = 60ms
> >
> > Total frame time = 120ms!
> >
> > On the Powerseries, locked at 60Hz, the graphics looks reasonable. The O2
> > is not capable of locking the frame rate and the simulation becomes
> > extremely sluggish.
> >
> > Why is the frame time so much longer than the sum of APP+CULL+DRAW?
> > Surely, in APPCULL_DRAW multiprocess mode, my frame time should be more
> > like 70ms?
> >
> > I know that this is a tricky question to answer without seeing the code,
> > but how can I optimise my simulation? I have used backface culling
> > wherever possible, have flattened the scene tree and have put all the
> > non-latency critical simulation updates after pfFrame().
>
>
>
> For optimization of your app. you could look at chapter 13;Performance
> tuning and Debugging, in the IRIS Performer programming guide. What also
> about using LOD's ???
>
>
>
>
> >
> > Thanks for your time.
> >
> > Regards
> > Simon Dimaio
> >
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> --
>
> Greetings
>
> ----------------------------
> Inge Eivind Henriksen
> Autosim A.S
> Postboks 2303
> N-9002 Tromsoe
> Norway
> Tlf.nr.: +(47) 77 67 50 75
> Fax.nr.: +(47) 77 67 67 01
> E-mail: <inge++at++autosim.no>
> ----------------------------
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>
>-- End of excerpt from Inge Henriksen
--
----oOOo---- ----oOOo---- ----oOOo---- ----oOOo----
Brian Furtaw (brian++at++sgi.com)
VisSim Technical Consultant
12200-G Plum Orchard Drive Office:(410)796-0394 Fax: (301)872-3293
Silver Spring, Maryland 20904 OpenGL/ImageVision/OpenInventor/Performer
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