Re: Scanline Smear...

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Angus Dorbie (dorbie++at++sgi.com)
Wed, 18 Mar 1998 15:45:43 -0800

Jan Barglowski wrote:
>
> Performers:
>
> I have a task to create scanline smear, that is, imagine a video camera
> panning so quickly that by the time the bottom scanline is imaged, the
> camera's heading is not close to when the top scanline was imaged. I
> am not interested in the scanline compression/expansion that also may
> happen, just the effect between scanlines.
>
> Solutions I've thought of:
> - create a channel for each scanline and run the app at 240X (yikes!)
> - create a slightly larger image, then shift the pixels manually with
> glReadPixels() et.al.
> - create a slightly larger image, and texture map it to a quad and
> stretch the quad along diagonally opposite corners in proportion to
> the speed of the pan.
>
> Has anyone done something like this before? I'd really like to have
> it run 60Hz on my iR, if possible. Convolutions are also possible,
> but I'm not that well versed to know if this is in their domain.
>
> Thanks in advance!
>

Some thermal sensors I've worked on exhibit this effect but the smearing
wasn't for every scanline, just every few scanlines.

You could overdraw to the framebuffer and copypixels the displacement
for
portions of the image.

I'd suggest a hybrid approach where you split the channel with
displacement
into some small number of divisions, overdraw enough for the
displacement
of lines within a sub-channel and copypixels some of these lines (some
will
be in the right place).

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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