At 01:35 PM 8/26/99 -0700, you wrote:
>A couple of questions while I mull this stuff over:
> How does Cubicolor and the RPG demo do it? I'm figuring that the
KLAX is another example, or the TV tester that has the color bars. It's
hard to know what's going on sometimes just by looking at a game visually.
I had no idea Video Chess used the Ball to paint playfield on the left hand
side to avoid having to insert the writes necessary for a nonreflected
playfield (which might have been impossible because of the writes going on
to change the shapes of the chess pieces in mid-scanline) but supposedly it
does this. Sometimes graphics on the VCS can be generated in more than one
way so you may not know without disassembly.
>Missile Command draw the incoming missiles? I'm guessing either a ball
>or a missile graphic.
It would have to be either missiles or players since it uses sprite clones.
It does an HMOVE every few scanlines to draw diagonals. Many games used
this technique, like Jedi Arena, the lasers in Starmaster and Star Voyager,
and so on.
> Also, how many times can I draw the figure for player one at a
>time? I read the part that says you can set a register to display two
>copies/far, etc. (demonstrated in Home Run and the plane battles in
>Combat, right?), but what if I want to draw two to four of them and
>move them independently around the field? Is it possible to do this,
>by constantly reseting the register that tells player 1's horizontal
>position? Please advise.
You have 1, 2, or 3 copies of the player. There are some spacing options
on those copies, and there are width options on the sprites themselves.
The clones refer to the individual scanline. You can not break a clone off
and move it totally independently around the playfield. You don't even
have total freedom on where on that particular scanline the clone appears.
Just a couple of fixed options. The VCS works only on a scanline by
scanline basis. To acheive more totally independent objects you need to
develop a flicker (sprite sharing) routine. The best of these support
variable flicker, where any time sprites are not on the same scanline, they
can be comprised of the same sprite, but with different graphics and
horizontal positions (hence a new sprite for all intents and purposes) but
when they cross into the same scanline, they need to flicker to reuse the
same player over time. Bob Colbert worked on an engine for this
recently... (relatively)
Some games like Super Football help eliminate flicker by using sprite
clones when they cross. In that game, all the players are the same shape,
so clones work well when the players group together at the scrimage line.
Otherwise there would be a LOT of flicker at the scrimage line.
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