Re: Texture minification filter PF_ vs GL_

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Angus Dorbie (dorbie++at++sgi.com)
Thu, 22 Oct 1998 11:15:12 -0700

Jean-Luc Dery wrote:
>
> On Oct 21, 2:29pm, Angus Dorbie wrote:
> Hi folks,
>
> Thank Angus for the very quick response on my previous mail.
>
> ... But I'm still having problems with texture filtering.
>
> Thanks to your reply, here's what I have which is behaving exactly the same way
> in both OGL and PF applications:
>
> PFTEX_POINT GL_NEAREST
> PFTEX_LINEAR GL_LINEAR
> PFTEX_MIPMAP_POINT GL_NEAREST_MIPMAP_NEAREST
> PFTEX_MIPMAP_LINEAR GL_NEAREST_MIPMAP_LINEAR
> PFTEX_MIPMAP_BILINEAR GL_LINEAR_MIPMAP_NEAREST
> PFTEX_MIPMAP_TRILINEAR GL_LINEAR_MIPMAP_LINEAR
>
> >
> > Derived from IrisGL tokens. Just use the OpenGL tokens if you are in any
> > doubt.
>
> I tried that and it didn't work; min filtering was always done with PFTEX_POINT
> no matter what GL_XXX token I used.

That's a surprise, I thought this worked. It certainly works for some
stuff like formats so you can use the new OpenGL token extensions. But I
would have bet it worked for the filter tokens also. I've just checked
this
and can confirm that it doesn't work for me either but I get a GL_LINEAR
default not a GL_NEAREST that you describe, but perhaps you have a
different
initial state.

It is highly desirable that these tokens get passed through, perhaps it
can be fixed in future, if the tokens have different enumeration.

>
> >
> > >
> > > And what exactly is PF_BILINEAR and PF_TRILINEAR ???
>
> If I rephrase my previous question the other way around, what would be the OGL
> equivalents of the following PF tokens ?
>
> PF minification filters:
> PFTEX_BILINEAR GL_???
> PFTEX_TRILINEAR GL_???

LINEAR.

man texdef

should give you the old IrisGL manual page and all will become clearer.
IrisGL used to specify the number of axes interpolated, so 1D was linear
2D
was bilinear 3D was trilinear 2D MIP map was trilinear 3D MIP map was
quadlinear. Performer tokens were born in those days.

OpenGL you just specify LINEAR and the number of axes is implied by
the circumstances. The MIP mapping tokens are now much clearer with
token naming reflecting the 1D level interpolation separately from
the bilinear image interpolation on each level.

>
> PF magnification filters:
> PFTEX_BILINEAR GL_???
> PFTEX_TRILINEAR GL_???

LINEAR again, read the manual and you'll see that the description of
a linear filter on magnification or minification is identical, it
actually does the same thing.

Cheers,Angus.

-- 
"Only the mediocre are always at their best." -- Jean Giraudoux 


For advanced 3D graphics Performer + OpenGL based examples and tutors:
http://www.dorbie.com/

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