Re: Q: pfLayerModes

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Angus Dorbie (dorbie++at++multipass.asd.sgi.com)
Thu, 12 Jun 1997 09:29:46 -0700

This 'poke throuch' is a classic symptom of the polygon offset method
for decals.

You need to use the STENCIL method which is fast on iR, I'd have
expected high quality to be equivalent to this but apparently not.

There's also a plane equation method in performer 2.2.

In summary, use PFDECAL_BASE_STENCIL,
don't use PFDECAL_BASE_DISPLACE or PFDECAL_LAYER_OFFSET

Cheers,Angus.

On Jun 11, 12:43pm, Mark Baranowski wrote:
> Subject: Q: pfLayerModes
>
> [ plain text
> Encoded with "quoted-printable" ] :
Hi all,
>
> Machine Details:
> Onyx iR, Irix 6.2 + Patch 1355, Vega 3.0 MP, Performer 2.1 (No
> specific Performer patches that I can see).
>
> I have recently been playing with the different pfLayer modes using
> the pfdConverterMode_flt function (I now see I could use
> pfdConverterMode instead) for our flt files.
>
> I want to use PFDECAL_BASE_HIGH_QUALITY as the particular application
> suffers from Z fighting when PFDECAL_BASE_FAST is used. I can't reduce
> the near/far clip ratio any further.
>
> PFDECAL_BASE_HIGH_QUALITY solves the Z fighting problem, but *some* of
> the subfaces tend to "poke through" when they should be hidden by
> other parts of the model/scene. Is this is the problem that occurs if
> the subfaces are not coplanar with, or bounded by, the parent face?
>
> The problems seem to occur mainly on building models which are
> provided with MultiGen's SmartScene tool, which I imagined would only
> have subfaces which were coplanar and contained within the parent
> face. I checked some of our own models which exhibit the problem and
> the subfaces *are* coplanar and entirely bounded by the parent
> polygon. Am I missing something?
>
> Any advice gratefully received.
>
> TIA.
>
> Mark.
> --
> Mark Baranowski at work (baranowski++at++marklynn.demon.co.uk)
> Pera, VR Division. Melton Mowbray, Leics. LE13 0PB. UK.
> Tel: +44 (0)1664 501501, Fax: +44 (0)1664 501553
> All opinions expressed are my own and should not be viewed
> as representing my employer unless stated otherwise.
> List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/
> Submissions: info-performer++at++sgi.com
> Admin. requests: info-performer-request++at++sgi.com
> SGI DevForum 97 info: http://www.sgi.com/Forum97/
>-- End of excerpt from Mark Baranowski

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