Re: magfilter strange problems

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Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Sat, 6 Jul 1996 10:08:46 +0100

TRILINEAR magnification & minification filters are for 3D textures only,
try a BILINEAR mag filter and a MIPMAP_TRILINEAR min filter.

Rgds,
Angus.

On Jul 5, 2:01pm, Nicolas Gauvin wrote:
> Subject: magfilter strange problems
>
> I ran into strange behevior of texture magnification filters lately.
> I have a 128x128 texture that I use as a cloud layer on a very large
> polygon covering the sky. This texture has alpha components.
>
> Texture mag filters are:
> tex->setFilter( PFTEX_MAGFILTER_ALPHA, PFTEX_TRILINEAR );
> tex->setFilter( PFTEX_MAGFILTER_COLOR, PFTEX_TRILINEAR );
>
> This give very good results on an Impact machine (compiled OpenGL)
> and on a RE2 (compiled IrisGL) with one RM4. The texture is magnified
> as expected.
>
> However, when the same program is run on a Infinite Reality or a RE2
> with 3 RM5, the same texture looks very bad. We see some very visible and
> discreet gradient of colors near the edge of the clouds. Much like contour
> lines.
>
> I suspect this is related to the fact that on those two machines,
> there is enough RMs to enable multisampling at the resolution I'm running
> where on the other RE2 and on the Impact, there was no multisampling.
>
> Is there something additionnal I should do to correct this sort of problem?
>
>
>
> Nicolas Gauvin CAE Electronics Ltd., 8585 Cote De
Liesse
> Software Developer Saint-Laurent, Quebec, Canada, H4L-4X4
> 3-D Graphics Applications tel: +1 514 341 2000 extension 2275
> nicolas++at++cae.ca fax: +1 514 340 5496
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>-- End of excerpt from Nicolas Gauvin

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