[stella] missile bit width

Subject: [stella] missile bit width
From: Glenn Saunders <krishna@xxxxxxxxxxxx>
Date: Sun, 7 Sep 1997 17:13:19 -0700 (PDT)
On Sun, 7 Sep 1997, Erik Mooney wrote:
> The missiles can be 1, 2, 4, or 8 bits wide.  Check the references
> again.. bits 4 and 5 of NUSIZx control missile width.  By altering the
> width and HMOVEing the missile every line, you can do tricks like:
> 
> ......XX
> .....XX.
> ....XX..
> ..XXXX..
> XXXXXXXX
> XXXXXXXX
> XXXXXXXX
> ..XXXX..

Yes, this gives you the illusion of having a 8-bits to play with, just
like players, but you can't do shapes like: 

XX  XX  

Or odd widths like:

XXX

This is an innovative technique here, to be sure.  And you are probably
right that it's never been done before.  It would be quite a feat to pull
it off.

> Or, you could combine the 8 bits of player gfx with the missile to
> create wider objects.  Such as a 16-pixel wide tank:
> 
> .............X..
> ............XXXX
> ............XX..
> X..........XX...
> X.........XX....
> X...XXXXXX......
> X..XXXXXXXXX....
> X.XX........XX..
> XXX.X.XXXXXX....
> XX.X.........X..
> ..X.X.XX..XX....
> ...X.........X..
> .....XXX.XXXX...
> 
> It looks better onscreen than here, but you get the idea.  The
> right half of the tank is done solely with the missile.

Yes, this could translate into other games as a way to create more
detailed objects.  The missiles and ball have often been underutilized by
programmers, IMHO.

What if you combined this technique with copies?  3 copies of players,
missiles, and ball would = 12 total copies.

Can the missiles and ball be copied as well?

Maybe doing this, and changing the shapes on the fly, it might be possible
to do a flicker-free 12-character credit scroll after all.

Some characters could be done with the missiles: 1, l, i, t, j, -, (, ),
",", "'", +, =, /, \, |.  If you fudge it with "filled" characters you can
do most of them with the missiles.


They didn't have to be missiles since there are only two maximum per
scanline.

I still think that Warlords is a game that needs to be rewritten.  If I
ever do figure out how to program the 2600, I will cut my teeth on
rewriting Warlords as an exercise.


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