Re: [stella] Star Fire - Return of the Starfield ?!? (was: Strange Z26 (real thing?) behaviour discovered...)

Subject: Re: [stella] Star Fire - Return of the Starfield ?!? (was: Strange Z26 (real thing?) behaviour discovered...)
From: Manuel Polik <cybergoth@xxxxxxxx>
Date: Wed, 24 Jul 2002 22:04:59 +0200
Hi Thomas!

>Manuel wrote:
>> -> Attached is my current Starfield WIP. After moving 
>> 160 pixels, the horizontal *reset* of is not as 
>> as it should be, but apart from that I'm very pleased 
>> for the start :-)

>You will know that already, but I think, there are far 
too many stars and 
>it's looking much to symmetric.

100% agreed. I'm working on it ;-)

>For making the thing looking less symmetric, you could 
change the HMOVE 
>values inside a frame or use two different values (e.g 
on even frames +8 
>and -5 on odd ones). 

That won't work. +8 does the trick, nothing else.

Consider this:

Horizontal scrolling works with +-1 and vertical 
scrolling with +-8 pixels. 

If you shift only a single line with anything else than 
+8, the vertical scrolling is out of sync immediately.

>Then you should try to display only every ~4th star 
>(perferable randomly, starting with different vertical 
offsets on odd/even 

Hm... that's ~ how I'll try to work. 
Total randomness won't work, since you've to *repeat* 
what you're doing every frame, but I'll experiment with 
that. I certainly won't sacrifice any RAM for that, but 
maybe one can just scan bitwise somehow through a 
randomly chosen part of the ROM for example. Or maybe 
writing a *sequence-generator*, though I fear that any 
possible implementation of that'll cost way to much 
execution time during the display kernel.

> and maybe try to give the stars different colors.

Depends on how many cycles remain in the end.
Non-mirrored sprites first, then fancy colors :-)

>I think, that is what Solaris does too.

I'm too lazy studying the Solaris source because of all 
the renamed TIA registers, but I analyzed the general 
idea behind this technique in 'Earth Dies Screaming'. 
I'd assume Solaris does similar.


Archives (includes files) at
Unsub & more at

Current Thread