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   REPLYADDR tlake@twcny.rr.com   
   REPLYTO 3:770/3.0 UUCP   
   MSGID: <205441fe-8b09-4e38-a993-c087195b9076@googlegroups.com> f7bbefc1   
   REPLY: <87muiqjwtd.fsf@usenet.ankman.de> 8098ef17   
   PID: SoupGate-Win32 v1.05   
   On Sunday, June 9, 2019 at 5:03:27 PM UTC-4, Andreas Kohlbach wrote:   
   > On Sat, 08 Jun 2019 20:32:30 +1300, Frank Linhares wrote:   
   > >   
   > >  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   
      
   --- SoupGate-Win32 v1.05   
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