Re: RE:RE:Flickerkilling on RE2

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Rob Jenkins (robj++at++quid)
Mon, 2 Jun 1997 08:16:44 -0700

On Jun 2, 5:43am, Inge Henriksen wrote:
> Subject: RE:RE:Flickerkilling on RE2
> --
> Angus Dorbie wrote:
> >
> > You can make the polygon a subface of another which should prompt the
> > loader to use a pfLayer. Do this by adding a polygon to another polygon
> > instead of an object in the modelling tool.
> >
> > Cheers,Angus.
> >
> Hello Angus Dorbie
> ------------------
> Thank you for replying, sadly it is not the answer since we already have
> implemented subfaces in our DB. The thing is that not even the subfaces
> are respected when the size of the flight-DB increeces, they also for
> some reason starts to flicker, not just in our own programs, mind you,
> but in Perfly too. For some reason increesing the far clip or decreesing
> the near clip seems to worsen the unwanted flickering effect.
>
> Greetings.
>

It would do. The resolution of the zbuffer isn't linear ( for a perspective
view ), it's inversely proprtional to the distance from the eye. The *ratio* of
near/far clipping planes controls the spread of resolution so the best way to
optimise that ratio is *increasing* the near clip ( or decreasing the far clip,
although you need much bigger changes to effect the near/far ratio if you just
change far clip ). Some people have implemented dynamic values of near/far so
based on where you are and what you're looking at, set the values to optimise
the zbuffer, basically unless you really are looking at something very close,
push near clip out as far as possible.

Perfly will most likely set near/far based on the size of your scene, you might
need to override that.

Cheers
Rob

>
> > On May 31, 12:13am, Inge Henriksen wrote:
> > > Subject: Flickerkilling on RE2
> > > --
> > > Hello Performers
> > > ----------------
> > > We have a Onyx RE2 with:
> > > 4 150 MHZ IP19 Processors
> > > CPU: MIPS R4400 Processor Chip Revision: 5.0
> > > FPU: MIPS R4010 Floating Point Chip Revision: 0.0
> > > Data cache size: 16 Kbytes
> > > Instruction cache size: 16 Kbytes
> > > Secondary unified instruction/data cache size: 1 Mbyte
> > > Main memory size: 128 Mbytes, 2-way interleaved
> > > I/O board, Ebus slot 3: IO4 revision 1
> > > RealityEngineII Graphics Pipe 0 at IO Slot 3 Physical Adapter 2 (Fchip
> > > rev 2)
> > > VME bus: adapter 0 mapped to adapter 13
> > > VME bus: adapter 13
> > > Performer 2.0 + Patch 1414
> > > ...
> > >
> > > When our OpenFlight databases increeces in the number of polygons, the
> > > more inaccurate the the polygon calculations become, thus when two
> > > polygons (or a polygon with a subface) are close to oneanother they
> > > start to flicker because of this inaccuracy. How can we get rid of this
> > > problem? Other databases than our own also have this problem, like
> > > Multigens contribution to the IRIS PERFORMER 2.0 CD; the HunterLiggett95
> > > demo. We had the same flickering with V1.2 of Performer.
> > > When I asked this question at Info-Performer earlier, I got some answers
> > > back (thank you!), on of them saying to increece the near-clip, this
> > > reduces the flickering, but it sadly does not make it go away.
> > >
> > > Thank you for any help.
> ----------------------------
> 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

-- 
________________________________________________________________
Rob Jenkins mailto:robj++at++csd.sgi.com
Silicon Graphics, Mtn View, California, USA
=======================================================================
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