Re: Alias/Mipmap

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Rob Jenkins (robj++at++quid)
Thu, 16 Oct 1997 17:05:01 -0700

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On Oct 16, 2:28pm, Smith, James L. wrote:
> Subject: Alias/Mipmap
> SGI Info:
>
> I work with a group using SG's Onyx 2 /Reality Engine for real-time
> simulation at the Guided Weapons Evaluation Facility (GWEF) at Eglin AFB
> in Florida. Operating software uses IRIS Performer with IRIX.
> Questions arose when choosing the minification filter in Multigen for
> textured terrain. A bilinear, non-mipmapped scene showed considerable
> scintillation (alias) when moved. When they chose the "none" option, a
> scene without alias and quite good response time developed.
> The guys don't know what "none" is. They determine it selects
> Performer's default setting.
>
> Question: what is "default" regards filtering and mipmapping with the
> stated equipment. I feel default does mipmapping and at least point
> sampling. Your opinion?
> Lynn Smith
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> List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/
> Submissions: info-performer++at++sgi.com
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>-- End of excerpt from Smith, James L.

man pfTexture says ( around page 7 and 8 ):

     The default filter types are:
     magfilter = PFTEX_BILINEAR, minfilter = PFTEX_MIPMAP_TRILINEAR for both
     InfiniteReality and Reality Engine, and PFTEX_MIPMAP_LINEAR otherwise.

and ( around page 5 ):

         PFTEX_GEN_MIPMAP_FORMAT
                    Specifies whether or not MIPmap level should be
                    automatically created for a texture if a MIPmap
                    minification filter is in use. The default value is TRUE.

So by default it seems like you get mipmaps with trilinear min filter which
seems to agree with what you saw ( ie looked good ).

Cheers
Rob

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