Task: Explore Demoscene Demos
Needed: Altirra
Time: 15-30 mins
Introduction
The demoscene is notorious for pushing the limits of 8-bit computer hardware. Fortunately, there are a number of demos from this community for the Atari computers. I find these mesmerizing and inspiring. How do they program demos which seem impossible on the Atari? One trick is they take advantage of additional RAM through upgrades such as the Ultimate 1MB. Many of these demos use as much as 320KB of RAM which is more than the stock 128KB on the Atari 130XE. This makes it possible to devote a lot of RAM to screen memory making page flipping and scrolling much more effective. For example, a Graphics 5 80×40 screen with four colors takes up about 1K of memory. You could algorithmically generate about 200 screens of data beyond the stock 128K and then rapidly flip from one to the next in a loop by increasing the memory address of the screen data in the display list. Since the screens are pre-drawn, this would happen as fast as the screen can be drawn with a really nice animation effect. Set that to a techno beat and you have a demo. The key of course is the algorithm for pre-drawing the screens in memory. That takes some programming skill. Some of these demos are way more complicated than that. The good news is that these demos are all online. Give them a try!
Instructions
Navigate to the pouet.net web page and start downloading! The link I have provided is to the Atari 8-bit page with the demos sorted by the popularity. You can click on the different columns and sort them however you want.
You can run the ATR or XEX files on Altirra using the 320K Rambo RAM option. You can locate the memory options under the SYSTEM menu option and then CONFIGURE SYSTEM. Click on MEMORY and choose the 320K option.
Note most of these were developed for PAL systems so you will need to select than option as well from SYSTEM menu -> CONFIGURE SYSTEM -> SYSTEM-> VIDEO STANDARD -> select PAL.
Two of my favorites are Cyperpunk and Pure.
Comments
Definitely give these a try. Would love take a deep dive into the source code for some of these to see how they are done. I imagine each is an enormous amount of work.
Here is the Cyberpunk demo on Youtube if you don’t want to load the ATR file.
Here are more Atari demoscene demos on Youtube.