Re: Triangle Troubles

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Ran Yakir (rany++at++rtset.co.il)
Thu, 04 Jun 1998 21:40:08 +0300

This problem is an O2 bug (don't blame Uwe Pachler). I've had this problem a long
time ago where the O2 drops parts of polygons (mostly clipped polygons), when the
machine is stressed.
Yes, I've managed to write a test case. The way I could simulate the stress was by
causing many memory swaps and disk accesses while drawing one big polygon. The
answer from SGI was something along these lines : " If the user has dropped
polygons while the disk is swapping, then the user should avoid swapping when he
is drawing". This bug has a number (which I don't remember right now but I can
reproduce), and it was given a very low priority at SGI, which means it will never
be fixed.
I think this is quite surprising that a company that made its reputation on
drawing polygons should ignore a bug that causes polygons to be drawn incorrectly.

Ran

Rob Jenkins wrote:

> On Jun 3, 4:20pm, Uwe Pachler wrote:
> > Subject: Triangle Troubles
> > Hello!
> >
> > We run an O2 with CRM graphics and a R10000 with Performer 2.0 and IRIX
> > 6.3. We run a performer application that simulates an industry environment
> > where the user is able to put on helmets and gas masks.
> > The problem is that performer sometimes doesn't draw the whole area of a
> > triangle, if the triangle seems to be bigger than the screen (maybe a
> > clipping problem?)
> > For example, if the user wears a gasmask, the mask, consisting of
> > transparent polygons, covers the whole screen. The scene behind it is
> > visible of course because the mask is drawn transparently. Sometimes,
> > parts of the mask are not drawn. But not a whole triangle is missing, but
> > only triangular parts of a triangle, where one side of that missing
> > triangle is the screen's border (that's why I assume it is clipping bug in
> > the graphics library).
> > Has onybody heard before from this bug, or has even fixed it?
> >
> > Thanks in advance,
> > Uwe Pachler
> >
> > =======================================================================
> > 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 Uwe Pachler
>
> If Svend's suggestion doesn't help then there are a couple of ( mostly
> old/fixed ) bugs that might be related to this. It sounds to me like you're
> describing triangular sections dropping in/out rather than something where the
> problem is constant. Without a test case it would be hard to narrow down what
> problem you have, if it is a known thing so I suggest that you first make sure
> you have the latest O2 gfx patch ( actually, get the latest patchset from
> www.sgi.com/support ), any recent fixes will be in there and I also remember
> that there was an O2 gfx patch that was found to be bad and got yanked, some
> people might have it though. That was patch 1604. the latest O2 gfx patch is:
> 2943 although I'm not sure that is in a patchset yet, the latest in a patchset
> is probably patch 2862 and you should get at least that. If the patches and
> examination of your viewing frustum setup don't help then you ought to log a
> support call, ideally with some testcase they can use.
>
> Cheers
> Rob
>
> --
> ________________________________________________________________
> Rob Jenkins mailto:robj++at++sgi.com
> Silicon Graphics, Mtn View, California, USA
> =======================================================================
> List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/
> Submissions: info-performer++at++sgi.com
> Admin. requests: info-performer-request++at++sgi.com

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