Subject: Re: [stella] Re: supercharger line definition From: Rob <kudla@xxxxxxxxx> Date: Mon, 10 Jan 2000 00:25:07 -0500 |
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/
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