Subject: Re: [stella] Qb/Demo background animation (very rudimentary) From: "Andrew Davie" <adavie@xxxxxxxxxxxxx> Date: Tue, 6 Feb 2001 01:15:06 +1100 |
> If this demo works in PCAE, you must be using a pretty old version of > this emulator. I tried PUSH.BIN on my 7800 and the sprite positioning I guess it's time to update. Yes, the demo works on my version of PCAE (and I just checked the date - 22/August/1997 !!) so I guess that's basically why it looks good to me. It is quite interesting that, despite what you say about... > Due to the fact that each cycle represents three pixels, you can't > position an object on any pixel with RESxx alone. Therefore you now I could, in fact, do this when using PCAE :)) What I was doing a WSYNC, then an immediate RESPx. Then I did a loop (I only have to position to exact 20-pixel boundaries) which did multiple 4-pixel shifts. Each shift I did a store HMPx followed by an immediate HMOVE. It worked for me - but obviously wrong! I appreciate VERY MUCH your detailed explanation of how it is supposed to work. I am also pleased to find out that my emulator is so old and incorrect - I will update to the new version ASAP! > One other thing that I noticed on your demo is, that it only does about > 249 scanlines per frame, and every couple of scanlines there is a frame > where you do a different number of scanlines, so that the screen jumps. > Z26 displays the number of scanlines in the last completed frame, when > you start it with the -n command line switch. This could help you to > generate a proper display. Thanks for this information - I was aware of the jiggle, but it was one thing to fix up later. I didn't know the jiggle was due to my differing scanlines (accidental), but it is very handy to know that. > Also you should do a STA WSYNC before you turn on VSYNC. Otherwise you > might turn on VSYNC at the end of a scanline and therefore do only > 2 scanlines of VSYNC effectively. Once again, THANKS! Cheers A -- _ _ _| _ _ _| _ * _ _ , (_|| )(_|( (/_\/\/ (_|(_|\/(_(/_ ,~' L_|\ ,-' \ see my Museum of Soviet Calculators at ( \ http://www.taswegian.com/MOSCOW/soviet.html \ __ / L,~' "\__/ @--> v - Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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