Summer Games

[Andreas Kohlbach]

I was recently playing Summer Games by Epyx on the Commodore 64 (well in
an emulator). I noticed again the smooth animation of the guy with the
torch lightning the Olympic Fire. I was stunned back in 1984 when I saw
it on the real machine.

Only today I notice that the guy, the fire and eight doves were on the
screen at the same time at some point. I would imagine these are all
sprites. But the C64 only had eight hardware sprites. But with eight
doves, the torch carrier and possibly the flame after being ignited I
count at least ten sprite. How did they pull it off?

[Tom Lake]

Post by Andreas Kohlbach
I was recently playing Summer Games by Epyx on the Commodore 64 (well in
an emulator). I noticed again the smooth animation of the guy with the
torch lightning the Olympic Fire. I was stunned back in 1984 when I saw
it on the real machine.
Only today I notice that the guy, the fire and eight doves were on the
screen at the same time at some point. I would imagine these are all
sprites. But the C64 only had eight hardware sprites. But with eight
doves, the torch carrier and possibly the flame after being ignited I
count at least ten sprite. How did they pull it off?
--
Andreas
My random thoughts and comments
https://news-commentaries.blogspot.com/

As long as the doves stay in the sky and the fire stays OUT of the sky and away from the ground, they might have used vertical interrupts to switch sprite sets as the electron beam hit certain parts of the screen. Think of it like a layer cake. Each layer can have up to eight sprites which are independent of the sprites in any other layer. On the 64, the layers can be different widths. You can have dozens of sprites on the screen at the same time but each group of eight can only stay in its own layer.

[Frank Linhares]

TL> As long as the doves stay in the sky and the fire stays OUT of the sky
TL> and away from the ground, they might have used vertical interrupts to
TL> switch sprite sets as the electron beam hit certain parts of the screen.
TL> Think of it like a layer cake. Each
TL> layer can have up to eight sprites which are independent of the sprites
TL> in any other layer. On the 64, the layers can be different widths. You
TL> can have dozens of sprites on the screen at the same time but each group
TL> of eight can only stay in its own
TL> layer.

Many of the demo scene demos from back in the day (and currently) took
advantage of vertical interrupts to make incredible demos. I would bet that
Epyx did the same.

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[Andreas Kohlbach]

Post by Frank Linhares
TL> As long as the doves stay in the sky and the fire stays OUT of the sky
TL> and away from the ground, they might have used vertical interrupts to
TL> switch sprite sets as the electron beam hit certain parts of the screen.
TL> Think of it like a layer cake. Each
TL> layer can have up to eight sprites which are independent of the sprites
TL> in any other layer. On the 64, the layers can be different widths. You
TL> can have dozens of sprites on the screen at the same time but each group
TL> of eight can only stay in its own
TL> layer.
Many of the demo scene demos from back in the day (and currently) took
advantage of vertical interrupts to make incredible demos. I would bet that
Epyx did the same.

Thank you and Tom. So vertical interrupts might made this
happen. Amazing, because in 1984 the Commodore 64 was only two years old.

[Tom Lake]

Post by Andreas Kohlbach

Post by Frank Linhares
TL> As long as the doves stay in the sky and the fire stays OUT of the sky
TL> and away from the ground, they might have used vertical interrupts to
TL> switch sprite sets as the electron beam hit certain parts of the screen.
TL> Think of it like a layer cake. Each
TL> layer can have up to eight sprites which are independent of the sprites
TL> in any other layer. On the 64, the layers can be different widths. You
TL> can have dozens of sprites on the screen at the same time but each group
TL> of eight can only stay in its own
TL> layer.
Many of the demo scene demos from back in the day (and currently) took
advantage of vertical interrupts to make incredible demos. I would bet that
Epyx did the same.

Thank you and Tom. So vertical interrupts might made this
happen. Amazing, because in 1984 the Commodore 64 was only two years old.
--
Andreas
My random thoughts and comments
https://news-commentaries.blogspot.com/

The technique was documented in the Commodore 64 Programmer's Reference manual which was available at the beginning of January 1983 so it wasn't one of those hidden features that had to be discovered by users.

Tom L