Re: advice on using Performer (OpenGL Optimizer?)

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Angus Dorbie (dorbie++at++multipass.engr.sgi.com)
Fri, 12 Sep 1997 11:17:47 -0700

On Sep 12, 8:53am, David Weller wrote:
> Subject: Re: advice on using Performer (OpenGL Optimizer?)
> > > > > I am planning to write a walkthrough application on top of
Performer
> > > > > and would like some advice on the issues I am facing. I will be
using
> > > > > an SGI Octane with two R10000 processors.
> > > > > [deletia]
> > >
> > > The basic motivation of the application is to do occlusion culling in
> > > software.Hence, rather than rendering *all* triangles in the view
> > > frustum using the Z-buffer, I want to determine which are (partially)
> > > visible using the BSP and render only these.
> >
> > [deletia of some of Remi's comments]
> >
> > That is Occlusion culling, which BSP does not provide naturally, and that
> > would be a good win if this is the kind of database you are walking
through.
> >
>
> Perhaps slightly off-topic, but that was the primary focus of OpenGL
> Optimizer, was it not? Walkthru-type applications need occlusion
> culling, and that's exactly what OpenGL Optimizer does. Of course,
> the count of available database loaders, as far as I can tell, is
> currently at "2" :-) (Somebody correct me, PLEASE!)

Not sure what your point is.

Optimizer does more than just overlay, but there are performer features
which are still desirable. Optimizers occlusion culling is particularly
effective with very dense highly complex scenes. There are other
approaches which you might want to explore for Vis Sim applications.

>
> Which brings me to another small issue, which is that there doesn't
> appear to be very many good guidelines to help developers decide where
> the greatest advantage per application comes from (Performer v. OpenGL
> Optimizer). Certainly from my perspective, I'm going to get better
> performance using Performer for things like flight simulation. But if
> I have a customer that wants me to deliver an application of, say, a
> new selection of homes, I'm faced with a new set of decisions. SGI
> press releases say, "This is great for CAD/CAM/CAE stuff!" but many of
> us work in the fuzzy, gray areas (or in both domains :-).

These decisions are difficult. However things will become clearer when
we are further down the road with OpenGL++ and interoperable Optimizer,
Vis Sim, Imaging, Inventor other libraries.

>
> IMHO, this is a FAQ that belongs in both the Performer and OpenGL
> Optimizer FAQs.

Yep.

Cheers,Angus.
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