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During its 40 years long lifespan, Atari ST programmers invented several truely outstanding demo coding techniques.

In early 1989, Ilja from Germany or the Swedish guys from Omega managed to show graphics in all four borders of the screen, a groundbreaking technique now known as fullscreen or overscan. Only a few months later, legendary Swedish Carebears coder Nic invented the so called 'sync scrolling' technique which enabled fine scrolling on a simple Atari ST - despite the missing video low byte in the video hardware.

Who's that girl?

 

Another outstanding invention was the so called chunky-to-planar (C2P) technique by Kalms (or Chaos?) to code fast paced new school effects. And last but not least not to forget the impressive and extremely versatile sound effect called 'Sync Buzzer', invented by German chiptune wizzard Tao that lets the soundchip of your Atari ST create sounds nobody ever thought it could make!

Then in July 2024, demoscene veteran tIn (the Innovator) from Germany released ‘Ika I Compofylla’ at the Sommarhack demoparty in Sweden which caused a big stir with yet not fully forseeable consequence of possible usecases in the future.

At first glance, the demo only appears like another rotozoomer - however, a very smooth one with open borders and very high pixel precision. But the technique behind it is both groundbreaking and breathtaking. It's a true revolution, not a simple evolution of what has been done before!

To keep it simple, what we see on the screen is the cleverly manipulated ‘bus noise’ of the CPU - we are observing bitmap data without anything being written to the screen RAM at this moment. Yes, we are really only watching graphic patterns of the bus data! 😳 Thankfully tIn published a comprehensive and easy to read text about his invention that can also be understood by non-coders. 😄

In February 2025, ‘Ika I Compofylla’ was nominated in the ‘Outstanding Technical Achievement’ category of the Meteoriks 2025 awards. Let's cross fingers that the jury (unlike some commentators on Pouet 😉) realize it's not your common zoom rotator, and handle it as what IMHO it really is: one of the best, if not the best technical achievement ever on the Atari ST! 

 

🔗 'Ika I Compofylla' on Demozoo
🔗 In-depth explanation of the technique by tIn

Addendum: So who really is that girl? It's Ika Nord, a 1960 born Swedish actress, mime, clown and director. She is best known for her appearances in Swedish kids television shows.

 

 

Editor's note: This article was published post-mortem - Rest in peace, mOdmate ❤️

Comments

0
Anonymous
Saturday, 15 March 2025 20:56
Fascinating stuff, still don't quite get how the data read pushes to the screen but that's on me. 
And the idea of writing code that could be displayed as a graphic is joyous.
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evldhs
Saturday, 15 March 2025 23:23
The screenpointer is set outside of available ram.  Then any data that passes through the bus will end up on screen, so called "bus noise". By reading graphic datas (not writing) with the CPU, it will be visible on screen. The problem is that the opcode to read data (the move instruction) will also end up on screen as that too passes through the bus! There lies one of the challenges to make something useful out of the technique :)

tIn is amazing.
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tom-
Sunday, 16 March 2025 01:51
I wanna see someone do this as two 1bpl "writes", rather than a single 2bpl write.  Come on guys!
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