[Coco] Documentation of "complex" artifacting (i.e. more than black/white/blue/red)?

[John W. Linville]

On Fri, May 21, 2010 at 05:49:12PM -0500, Joel Ewy wrote:
> Brian wrote:
> >Hi John,
> >
> >On my website there's a link to a Rainbow article on artifacting.
> >
> >http://coco.randomrodder.com
> >
> >Sent from Brian's iPhone
> >
> >On May 21, 2010, at 5:05 PM, "John W. Linville"
> ><linville at tuxdriver.com> wrote:
> >
> >>Are there any articles in Rainbow or similar CoCo-oriented publications
> >>that documented use of "complex" artifacting for producing additional
> >>colors (e.g. purple, green, etc) with a CoCo?  Can anyone refer me
> >>to one?
> >>
> >>There was a thread on the list back in July of 2004 that touched on the
> >>issue, but other than some sample programs for testing there wasn't
> >>much discussion of the technique or how to exploit it.  It looks
> >>to me that unlike the "simple" artifacting (which exploits the NTSC
> >>color signal itself), "complex" artifacting relies on the physical
> >>characteristics of a CRT display and possibly on some sloppiness in
> >>the video hardware on the CoCo itself...?
> >>
> 
> Well, the effect does show up on a video capture card, so it is
> present in the NTSC signal, not just in the CRT.  It may be that
> sloppiness in the CoCo video circuitry is responsible, but it's not
> an effect that takes place in the picture tube.

Hmmm...well, I'll have to take your word for it.  The test program
in the thread mentioned above barely tinted the areas that were
supposed to be green and purple, and even that was only noticeable
from a distance. It still looked like a mostly-white checkerboard.

The thing that seems the most strange is the notion that the pattern
of vertically adjacent pixels somehow matters -- I don't see how the
NTSC decoder would somehow "remember" what was on a previous line
when deciding which color gun to fire next...?  So, I presumed that
the effect relied on POV and/or color bleed from adjacent phosphors?

Surely someone put pen to paper regarding this technique? :-)

John
-- 
John W. Linville		Someday the world will need a hero, and you
linville at tuxdriver.com			might be all we have.  Be ready.