[Coco] Max Video Resolution

[Glen Hewlett]

Hi All,

Thanks for the feedback on the screen size, I didn’t think there was a larger screen but it’s better to check since it would make it a lot nicer.

Thanks for the suggestions below Mark, I think I’ll try the 8x8 character version with scrolling first…

Cheers,
Glen

> On Jan 4, 2017, at 7:42 AM, Mark McDougall <msmcdoug at iinet.net.au> wrote:
> 
> On 4/01/2017 3:57 AM, Glen Hewlett wrote:
> 
>> I’m at the point in my Z80 Pac Man translation to 6809 and I am stuck
>> trying to figure out the best way to deal with the rotated screen of
>> the original Pac Man.  What I need is screen resolution that is
>> 320x256.  Over the years has anyone found any hidden graphics modes
>> to give you more rows then the documented 320x225?
> 
> If you saw my Pacman project photos for the Model 4, you'll see that I had a similar problem (640x240), and I didn't even realise it until I'd gotten a little further into it! Unfortunately scrolling on that hardware is not an option. :(
> 
> I'm assuming you're rotating the screen to show it in the correct orientation; ie. 28x32 tiles or 224x256 pixels for the maze, and displaying the other 4 rows of text/icons on the RHS of the screen like pretty much every other console port in the history of consoles?!? ;)
> 
> I notice Nick's Pacman page mentions "the tallest vertical resolution I could muster... 320x225 pixels" so unless he or others have learned more since, I guess that's it?!? The GIME register reference also suggests 225 is the limit...
> 
>> If not I’m either going to have to shrink all the character data from
>> 8x8 to 7x7. The other thing I’ve thought of is scrolling the screen
>> vertically, so that if you are in the top half of the screen you will
>> see everything but the 4 character rows at the bottom and vice versa
>> if you are at the bottom of the screen.  This will also mess with any
>> score or level info I might have on the right of the Maze though.  I
>> really need a bigger screen.
> 
> I'm assuming Nick shrunk the character data to 7 pixels; I'd be tempted to keep it at 8x7 or your screen calcs and tile/sprite data will be worse than the Apple II! ;)
> 
> Scrolling is not a bad idea, even if you implement that as a 1st-pass (it will be a lot easier) and a novel approach to the game. You could use a similar display to Nick's, but more centered, and all info should still be visible whilst scrolling.
> 
> I have actually done exactly this for an FPGA implementation I did for Pacman to run on a 320x240 LCD (on the terASIC DE2) many years ago. It was a quick hack of the standard VGA version (of course the method has absolutely no relevance to a software implementation) but the point is, it was still quite playable. Of course it was a slightly different experience as sometimes one or more of the ghosts weren't visible, plus you couldn't immediately see how many dots or power pills you had left. But again, I think worth tackling first since it would be a relatively small enhancement to a non-scrolling display of 8x8 tiles that simply cut off the bottom edge. From there you could decide whether 8x7/7x7 was worth the effort?!?
> 
> Very interested to see your results!
> 
> Regards,
> 
> -- 
> Mark McDougall
> <http://retroports.blogspot.com.au>
> 
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