[Coco] 8 color coco 2 graphic display

[Luis Antoniosi (CoCoDemus)]

its similar to programming an Atari vdg2600, where there is no framebuffer,
the video registers must be changed while the scanline draws the image on
screen.


On Sun, Apr 21, 2013 at 9:07 AM, John W. Linville <linville at tuxdriver.com>wrote:

> On Sun, Apr 21, 2013 at 12:12:10AM +0000, Ben wrote:
>
> > I saw a game made for the coco 2 that was able to use 8 colors in a
> game. Is
> > there some sample code around on how to do this? The game I found was
> dragon
> > fire. Of course the trick didn't work in the vcc emulator, but I'd like
> to try
> > and do this on my real coco 2. Also is this trick easy to do? is it worth
> > doing? or is the work involved more trouble then it's worth?
>
> This is half of what I am doing in Sluzzle.  (The other half is the
> flip between CG6 and SG24, FWIW.)
>
> The description given by Torsten is essentially correct.  One must
> time the switching of the CSS bit to correspond to the screen positions
> you want for each color set.  That generally requires cycle counting,
> but other timing mechanisms might work depending on exactly what you
> are trying to accomplish.
>
> I have some description of doing this in the earlier entries at my
> Stupid VDG Tricks blog:
>
>         http://vdgtricks.blogspot.com/
>
> There are also links on the blog to Git trees (both for sluzzle.git and
> the earlier vdgtricks.git) containing code that does the CSS switching.
>
> Good luck!  Feel free to ping me about it or to continue the thread
> here. :-)
>
> John
> --
> John W. Linville                Someday the world will need a hero, and you
> linville at tuxdriver.com                  might be all we have.  Be ready.
>
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