Re: [stella] Star Fire 2600: Return of the Crosshair

Subject: Re: [stella] Star Fire 2600: Return of the Crosshair
From: Manuel Polik <cybergoth@xxxxxxxx>
Date: Wed, 10 Jul 2002 22:33:07 +0200
Hi Clay!

>> Even though I have 16 Bit resolution for the sprites,
>> right now they have to be mirrored. That is the main
>> problem at the moment. You just can't draw a Star
>> Destroyer from the side if it has to be displayed 
>> mirrored sprites.

>Ah. Okay, I assumed you were still using the sprite 
engine from the last
>demo you posted. Hmmm, 16-bit sprites... very cool. But 
won't that make the
>flicker even worse?

Not at all. Those intelligent Anti-flicker algorithms as 
the one I wrote, are only able to re-use one sprite. 
Consider you lose two complete scannlines for 1 
repositioning. Doing two repositionings, for both 
sprites, would create lots of overhead and not really 
gain you that much in terms of really reducing flicker.

Now my trick is, that I found a way, to reposition both 
sprites at _once_ in only two scannlines! 

So you see, I get the 16-bit resolution for free :-)

The flicker gets the worse, the bigger the sprites get. 
Even if it looks horrible on the emulator right now, 
it'll be way better in the end on the real thing. Both 
because it flickers less on a TV and because with the 
final movement schemes of the enemies, I'll greatly 
reduce any flicker situations in general.

>Why the mirrored sprites? If there's no way to specify 
mirroring on a
>per-sprite basis, you could manually mirror all the 
sprite data. It's not
>like there will be a huge amount of graphic data 

Both to save time and space.

If you fit everything into a single page, you never need 
to alter the sprite pointer MSB _during_ the kernel.

And, as I already said, you only need to load the data 

>Something else to maybe add to each sprite definition 
would be a vertical
>offset value so objects don't appear to drop as they 
move closer.

Again, I'll hope that the final movement patterns will 
make you no longer notice that phenomenon. Take a look 
at the diagonal moving ships, you can't see that they're 
*dropping* too, right? ;-)


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