Re: [stella] Supercharger screens...

Subject: Re: [stella] Supercharger screens...
From: Eckhard Stolberg <Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx>
Date: Mon, 11 Jan 1999 16:54:30 +0100
At 12:47 10.01.99 -0500, you wrote:

>I would love to get that trick fixed, however, I'm not sure there's
>enough info on it to emulate it correctly.  Does anyone really understand
>the multisprite trick and how it works?

I don't think that I really understand the multisprite trick, but
here is how I think it works:

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.

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.)

I'm not sure if this helps you, but maybe it is enough to emulate
the figher game kernal, the grid demo and extra18 correctly.

Ciao, Eckhard Stolberg

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