Subject: Re: [stella] Two triple-copy sprites for 48 horiz. pixels hi-res? From: Greg Troutman <mor@xxxxxxx> Date: Sat, 08 Mar 1997 03:15:02 -0800 |
Nick S Bensema wrote: > > > p0 p1 p0 p1 p0 p1 > > > > 0 1 2 3 4 3 > > (dang, it went too quick for me to read then write a new bit > >pattern in the last spot--I could also have put a four or a two in > >there, but not a 5--just gimme *one* more register...) > > This requires a more intricate system of timing than I've been able to > provide. Yet. > > >The fastest way I've figure so far is to absond with the stack pointer > >and hide away byte 6 long before the time critical stuff: > > > > ldx byte6 > > txs > > .. > > sta GRP0 > > stx GRP1 > > sty GRP0 > > tsx ;2 freaking cycles, and I need it yesterday! > > stx GRP1 > > > >But that's still too slow... > > Try moving your players to the right a little more. Perhaps your aim > is off, so to speak. The question is, if I have a copy of player N at > position X, how soon (in CPU cycles) do I need to modify it to make > the change clearly visible? I'm going to modify my cycle counting > texts to AT LEAST account for the fact that STA's to a register take > place at the LAST cycle, whereas it currently says to put asterisks > around the first cycle. > > It is this way in which the 12-column text from games like Stellar > Track are actually easier timing-wise, because players are spaced > apart further away and you have 16 pixels (5.3333 CPU cycles) between > each copy. Stellar Track uses some sort of frame alternation scheme I think. It doesn't draw two consecutive 8 pixel ranges on any line ever to avoid the tight scheduling. It picks up empty spots on the next frame. But that makes the text flicker. > It is just so incredibly possible. Consult the Defender source code. > In fact, I think I'll look at it tomorrow and add cycle counts. I was just looking at the scoreboard routine and I can't figure out what the variable in $94 does. The game does exactly what I have had to do to get this to work: sta GRP1 stx GRP0 sty GRP1 sta GRP0 (oops. I have no reason/logic to repeat this write though it makes the *display* timing work) If you figure out something about that double STA write which makes sense, let me know. I'll try again tomorrow after some sleep. -- mor@xxxxxxx http://www.crl.com/~mor/ -- To unsubscribe, send the word UNSUBSCRIBE in the body of a message to stella-request@xxxxxxxxxxx
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