Steve Baker (sbaker++at++link.com)
Thu, 19 Mar 1998 07:19:47 -0600 (CST)
> 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.
On iR, the last one will work faster than any of the others. Whether you
make 60Hz depends on a lot of factors. Also, don't deform the quad, just
change the texture coordinates at its vertices.
> Has anyone done something like this before?
Not for shearing the image - but I do use it to zoom an image (to make
it deliberately 'pixellated'.
In my case, it was a very small monochrome image - but some of the
SGI demo's I've seen use this technique for non-linear image
pre-distortion for dome displays and such. At least one of those
demos ran at 60Hz IIRC (although the resolution was not really huge).
Steve Baker 817-619-8776 (Vox/Vox-Mail)
Raytheon Systems Inc. 817-619-4028 (Fax)
2200 Arlington Downs Road SBaker++at++link.com (eMail)
Arlington, Texas. TX 76005-6171 SJBaker1++at++airmail.net (Personal eMail)
http://www.hti.com http://web2.airmail.net/sjbaker1 (personal)
** Beware of Geeks bearing GIF's. **
=======================================================================
List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/
Submissions: info-performer++at++sgi.com
Admin. requests: info-performer-request++at++sgi.com
This archive was generated by hypermail 2.0b2 on Mon Aug 10 1998 - 17:57:03 PDT