[Coco] The myth of the Coco3 256 color mode :)

[John W. Linville]

On Tue, Apr 16, 2013 at 04:21:36PM -0500, Allen Huffman wrote:
> On Apr 16, 2013, at 9:55 AM, Robert Gault <robert.gault at att.net> wrote:
> 
> > There have been several recent threads about generating multi-color
> > graphics screens on the Coco. One was for the Coco1 or 2, semigraphics
> > was mentioned, and also the 256 color mode on the Coco3 prototype
> > board. Also there is the flicker procedure where several different
> > graphics screens are rapidly switched to yield a blended image.
> 
> So, for those of us not keeping up, how long has this been known
> about? Who figured it out? I think Linville's video player had
> something about this in it, and that was the first I'd ever heard
> of it.

AFAIK, Jason Law discovered this independently around the end
of 2009.  I saw the postings on coco3.com at that time and asked
Jason for info about using the mode.  I used that info to produce
my own slideshow stuff (somewhat similar to Joel Ewy's version).
Since I was developing my coco video player at about that time,
I also added support for that mode to the video player.

Since then I have discovered that Jason thinks that I tried to take
credit for his work or at least that I failed to properly credit him.
I presume that your video is the source of his angst, although I
would refer people to watch it (esp. around the 2:48 mark) and judge
for themselves.  At any rate, from forthwith please let the record
show that Jason provided me with the info I initially used to support
that mode in the programs mentioned above.

Since then, I have educated myself a bit more on such things in an
effort to gain more understanding of how it works.  I still don't have
everything nailed down, but I think that a properly motivated person
could develop a mathematical model of how the colors get generated
without a lot of trouble.  If someone does that, then perhaps the
emulators could be modified to support the mode.  FWIW, I think that
the technology is essentially similar to what the Apple II used for
it's color generation:

	http://en.wikipedia.org/wiki/Apple_II_graphics#Color_on_the_Apple_II

That description doesn't account for the multi-pixel artifacts that
Robert Gault seemed to be inferring.  I'm not sure that those are
observable on all NTSC composite monitors (particularly LCD ones),
but YMMV...

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