Piero Cavina wrote:
>
> At 16:07 -0700 31-07-1997, Greg Troutman wrote:
>
> >You got me. This one was my arcade favorite for months and I thought
> >surely it would end up on the VCS eventually...
>
> Don't forget the second phase, when you go back to the mother ship... :)
I know, that's the best part. But the introduction of both missiles
will be a pisser.
> >I wrote a coarse adjustment routine with single-cycle precision, then
> >use one of three copies of a 4 byte sprite (like you would use to draw a
> >logo or something) to provide motion in between coarse adjustments...
> >Boy was that hard. It still isn't working quite right, but it's obvious
> >it will.
>
> When the lander is leaving the mother ship, part of it has to be drawn
> inside the mother ship and part outside. This might not be obvious on the
> 2600, have you already thought about this?
Yeah. The part inside the mothership is drawn in a video buffer where I
ORA the two graphics together (during VBLANK), and the part outside is
drawn in the line by line two sprite repositioning section. Keeping the
two pieces aligned during the transition on the way down the screen is
pretty tricky. The good news is that nothing else occurs on the
scanlines with the mothership, so I've got the time to do it. I'm
struggling with those details now.
>
> [Source]
> >Okay. Where is it?
>
> I posted it to the list (whith comments in ital-english!) some time ago. It
> is the source of an early version, but the kernel is almost the same, maybe
> even more readable than the current one.
> The main difficulty has been to find a way to draw p0 in any vertical
> position while you also have to draw p1 at fixed heights, in various
> colors, and reposition it every 7(x2) lines. Not forgetting the
> non-symmetric playfield.
> Playfield apart, it's not very far from what you'll have to do for your game.
> Clue: look at how is done the pattern for p0, with those zeros before and
> after...
Without seeing the code, I think I know what you are getting at. I plan
to do both P0 and P1 this way. It's the only way I think I'll find
enough cycles to do everything.
--
mor@xxxxxxx
http://www.crl.com/~mor/
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