Re: Hyperpipe mode

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Angus Dorbie (dorbie++at++multipass.asd.sgi.com)
Thu, 12 Jun 1997 09:12:57 -0700

There is no hardware in an iR to allow round robin rendering of
pipes to a single video, however it is possible to achieve this
using image readback from multiple pipes to host memory and
glDrawPixels on another pipe to get the same result.
For practical reasons performance only starts to scale
beyond 3 pipes, but is very linear beyond that (regardless of frame
rate), giving remarkable price performance for large configurations.
Scaling performance is possible with < 3 pipes at lower frame rates.

You may still be able to scale performance using other trans-pipe
image transfer methods within your application, but it does depend
on what you are rendering, resolution, frame rate, etc.

How many pipes were you thinking of using and specifically what
multipass rendering are you performing?

Here's a for instance:

If you have a scene with everything 2 pass and you have 2 pipes
you could draw different passes on each pipe, read back from one pipe and
perform a 2D blend of this image with the image on the other pipe,
(you wouldn't need z). For target framerates of 30Hz or less performance
would scale and you'd save on the expensive blend because you wouldn't
need to blend the whole second pass (depth complexity and all), that would
be done in the image composition. This would also leave you more options
as to what you could achieve with 2 passes.

Cheers,Angus.

On Jun 10, 11:05am, PHILIPPE.P.P.POUTIGNAT++at++TTS.thomson.fr wrote:
> Subject: Hyperpipe mode
> Hi Performers !
>
> I'm doing multipass rendering on an IR.
> Can anyone say to me if the hyperpipe mode is working
> on IR and Onyx2 and how to use it ?
> Thanx.
>
> ---Philippe Poutignat
>
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