'Hello World' - CD-i member TwBurn set the goal to himself to create a starting point in CD-i homebrew by coding these lines on the CD-i, and he did it! He hinted at his ambition to start some CD-i homebrew development during the development of his USB2CDi adapter. There are currently only a handful of people who are actually capable of writing CD-i homebrew software these days, so this is a precious effort! TwBurn explains what he did: "[It is] all in C, no machine language was used. It's awfully slow so far. [I used] loops to fill the clut tables and screen patterns, I didn't expect/plan this to be fast, [it is] just a starting point. Just getting something on screen was my goal here. There's some constructs that are still unknown to me, the mattes, regions, draw maps, and the exact meaning of the fact and lct. Those last two I currently understand as graphics code run on line/field transitions . Things like changing a few clut entries on line transition seem possible for some effects . I saw in the SuperQuartet example [that] it allocates 280+2 entries for the LCT, given 280 lines I'd expect that to be one for each line. I'm planning to do some easy stuff to start with, as for the first real game/program I'm going to make (I've got a small idea what my first one is going to be). Most people would consider me mad, doing CDi development in 2021!"
As with all other CD-i homebrew efforts, CD-i member cdifan is the right person to offer help and advice and thankfully he is always willing to help: "Every high-performance CD-i game out there uses some form of direct lct access, it's the most widely used "hack" of CD-i. All developers that I've ever spoken to used it. If you want any fast animation, you'll need optimized blit code or compiled sprites. Drawing performance is the biggest single performance hurdle of CD-i."
CDifan also recommends some ICDIA documents for the next steps:
- For improving the speed: TN #061 - Software Sprites in CD-I
- And also: The Apprentice - some technical information.
- For the best display sync I recommend TN #089 - A New Method for Video Scan Synchronization in CD-i
- For best performance you need to use Direct LCT Access. See Interactive Engineer, Volume 5, No. 4, July/August 1996, Direct Line Control Table access
[Thanks, TwBurn and cdifan - To be continued]