Re: fbsubtexload() problem

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Hansong Zhang (zhangh++at++cs.unc.edu)
Thu, 30 May 1996 11:04:31 -0400 (EDT)

Simon, I didn't have viewing/projection calls at all, which I
guess is equiverlent to
ortho2(0, win_width-1, 0, win_height-1);

I have found the reason for the unexpected animation of the texture:
If I offset the texture coordinates of the square I draw by half the
size of a texel, the window image stays the same - as expected.
I wonder if I should do the same in Opengl (haven't tried the opengl
version yet).

(As a reminder this is what my program does...
I draw a square that covers the entire 256x256 window (i.e. the square
is (0,0)-(255,255)) with a 256x256 texture map. then I fbsubtexload
the window image into the texture and draw the textured square (now
the texture is the windows image -- should be the same as the original
texture map), and so on...)

hansong

>
>
> > From: Hansong Zhang <zhangh++at++cs.unc.edu>
> > Subject: Re: fbsubtexload() problem
> >
> > I have another question on interpolation of texels.
> >
> > I expected a static image of the texture map loaded from a file; and
> > such I got when TX_MINFILTER is TX_POINT, TX_TRILINEAR etc.
>
> TX_TRILINEAR is for 3D textures only; if you want mipmapped 2D textures,
> use TX_MIPMAP_TRILINEAR. If you really set the min filter to TX_TRILINEAR,
> that's an error, and the GL probably ignored it.
>
> What is your projection matrix and viewport? Can you email the code
> fragments that set them?
>
> thanks
>
> simon w. hui iris performer
> shui++at++sgi.com advanced systems div
> 415.933.3244 silicon graphics inc
>
>

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