Re: Optimising frame rate.

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Allan Schaffer (allan)
Fri, 30 May 1997 14:49:37 -0700


On May 29, 12:24pm, Simon Dimaio wrote:
> 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.

Each of the times above is how long the process takes before it
'returns'. But the DRAW process, for example, sends commands to the
graphics pipeline that could still take a long time to render, long
after the DRAW process is done sending them.

Put more simply the extra time is probably the time needed for the
graphics pipe to fill pixels.

I also wonder if the "total frame time" includes the time after
you're done drawing and waiting for the swapbuffers to occur?

> 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?

That would seem true. What do the performer stats 'lines' look
like? There's four parts of each [described in ch12 of the PFPG]

> 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().

VGXT does IRIS GL better than OpenGL; is this an OpenGL or IRIS GL
based Performer application? Texture in OpenGL on VGXT is especially
slow.

Allan

-- 
Allan Schaffer                                                allan++at++sgi.com
Silicon Graphics                               http://reality.sgi.com/allan
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