At 03:20 PM 1/4/00 -0800, Glenn Saunders wrote:
[Supercharger RAM as framebuffer concept snipped]
>I think this is how Suicide Mission does it, and other Supercharger games
>may take advantage of the RAM in similar ways.
This is kind of a tangent because I haven't looked at any of this code, but
I was just thinking about this very subject. I was looking at Suicide
Mission the other day when I got my fabulous new Stella Gets a New Brain 2
disc, and it seems to me that it's not quite as straightforward as using
the RAM as a framebuffer, even with the Supercharger.
It seems to me that Suicide Mission is using a similar mechanism to games
like Stellar Track and Dark Mage, which appear to simulate a 12-character
display like this:
frame 1 - X = 8 pixels (a player)
X X X X X X scanline 1 (reusing player 1 and player 2 over and over)
X X X X X X scanline 2 (ditto)
frame 2
X X X X X X scanline 1 (drawing the places skipped in the other scanline)
X X X X X X scanline 2 (ditto)
Apologies to the folks reading this in a proportional font.
Suicide Mission actually doesn't do it quite as convincingly, just
alternating columns every frame instead of also crisscrossing every other
scanline, and might appear more flickery as a result. But Suicide Mission
also covers the entire screen (5 copies of each player, I assume) instead
of just doing 96 pixels across like the above games. I didn't know you
could rewrite the horizontal player position register like that (I don't
know that's what they're doing but it seems the only obvious method.) I
also assume they're copying each scanline from Supercharger RAM to
zero-page RAM before writing the registers (to save cycles) and that's why
they skip every other scanline.
I don't want to look at the code because I want to implement something like
this one of these days and GPL it. (Sorry, but I don't ever agree with
holding back code for an out of production machine.) Back when I was still
doing my game hacks I wanted to do a demo that would do nothing but draw an
arbitrary fullscreen 160x192 bitmap and maybe scroll it; now I know you'd
have to jump through mega hoops to do such a thing if it's possible at all
(and unless it was a static bitmap the Supercharger is definitely
required.) But I'd totally dismissed the idea until rediscovering Suicide
Mission.
Anyway, before I revolutionize 2600 programming I'll have to learn how to
output the right number of scanlines every frame ;)
Rob
kudla@xxxxxxxxx ... http://kudla.org/raindog ... Rob
--
Archives (includes files) at http://www.biglist.com/lists/stella/archives/
Unsub & more at http://www.biglist.com/lists/stella/
