Re: [stella] Supercharger screens...

Subject: Re: [stella] Supercharger screens...
From: "John Saeger" <john@xxxxxxxxxxx>
Date: Mon, 11 Jan 1999 09:32:14 -0800
-----Original Message-----
From: Eckhard Stolberg <Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx>

>If you hit RESPx to position a sprite in the scanline, the sprite
>will be positioned at the pixel where the hit occured plus the
>five pixel delay. This happens everytime you hit RESPx in a scanline.
>If the hit happens during the five pixel delay before any displayed
>copy of the sprite, you will get the full set of sprites to be displayed.
>If you hit RESPx at any other time, the display of the first copy of that
>sprite will be ommitted. The positioning will be as if the ommitted copy
>was there, though.

Hmmm, as I recall the window of opportunity to get a complete display of the
second set of sprites is only one pixel wide, but I forget the exact timing.
The demo earlyb.bin rings a bell though...  But I think more experimentation
is necessary.  I haven't tested all possible positions of the second RESPx
so there may be other places that the second RESPx could produce a complete
set of sprites.  But I'm just guessing.  But until all possible combinations
have been tested, one really can't be sure.

And of course missiles, as well as the other values of NUSIZ that can
produce more than one sprite need to be tested as well.  Actually I think it
would be cool if there were a demo that could independently position two
groups of sprites at any possible position of RESPx with joystick control
and a scoreboard display of the clock positions of the RESPx.  That way it
would be much easier to do all of the testing.  Unfortunately I'm not clever
enough to do it myself. :=(

>This is the reason why there is no sprite in the line where you hit
>RESPx to position a single copy of a sprite. It is the copy, that gets
>ommitted,when you don't hit RESPx during the five pixel delay.
>What happens when you position a set of sprites over the right border
>(especially when one copy of the sprite gets displayed half on both
>sides of the screen) and you hit RESPx during HBLANK, I don't know.
>It might be that the area, where you can hit for a full set of spites,
>can be bigger than five pixel. There might also be circumstances where
>the display of the first two copies of a sprite would be ommitted.
>(At least on some VCSs.)

Yes, this is definitely a gray area ;-)


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