Supporting Purple Planet Yo demo

[lance.ewing]

Not really certain what the best section to post this under is. It kind of spans a few different areas. I was watching the recent Purple Planet Yo demo on Youtube and thinking that looks and sounds really cool. But when I tried it on VICE, it didn't work the same. I then tried it on my in progress emulator and it also didn't look the same. It made me start wondering how on earth they're doing some of the things that they're doing in that demo.

http://sleepingelephant.com/ipw-web/bul ... yo#p103682

https://www.youtube.com/watch?v=KmaK8ru2pz8

For starters, my emulator now has sound emulation, and it is based on our recent discoveries. It sounds pretty good for other demos, but it is completely silent on Purple Planet Yo. Not sure why yet.

Then for the graphics, almost immediately we have this kind of copperbar effect on the Youtube video, but on my emulator that area is completely black, and on VICE it is a non moving section of multiple coloured lines. Clearly there is something being used here that I haven't yet understood, and that VICE and my emulator isn't catering for.

Any thoughts on how that copperbar effect is done, and why VICE isn't able to handle it?

Then we come to the "Good ol Mister Twister" effect. VICE can't handle that either. What are we missing?

I'm really looking forward to the upcoming release of the source code for this demo.

[Mike]

Any thoughts on how that copperbar effect is done, and why VICE isn't able to handle it?

Haven't checked on real hardware, anyhow with my installation of VICE (WinVICE 3.1 x86 r34289, on Win10) the demo works. No issues with audio, either.

I didn't look deeply into the code, but from the 2-line granularity of the raster bar effect and glitches mostly apparent in NTSC I'd gather they are actually polling the raster register in $9004 to wait for the next colour change. This isn't exactly state of the art. Look here for a slightly more refined example of raster tech: press SPACE when the picture has loaded, source is included.

[lance.ewing]

I have got it working in VICE now. Previously I was loading it with only 24K RAM. I didn't see the comment with the Youtube video stating that it required the full 32K RAM, and on the Denial releases topic.

Edit: Actually it seems to require the full 35K RAM. I tried it on my emulator with only 32K, and although it ran, certain parts weren't working. It wasn't until I set it to 35K that everything started working. Sound was there with only 32K, but some of the visual effects were not working until I set it to 35K. I verified this in VICE as well.

[Mike]

Edit: Actually it seems to require the full 35K RAM.

Prefilling $0400..$0FFF with a marker character (I use ASCII 42 for this ... it's full of stars!) shows that $0400..$07FF are being written to, so they were a bit inaccurate about the memory requirements ... ... a good case for MINIMON, which sits comfortably at $9800.

Did you try out my raster demo with your emulator in the meantime?

[lance.ewing]

Did you try out my raster demo with your emulator in the meantime?

I haven't implemented support for disk images yet, or for the disk drive, so at the moment I can only run standalone program files or cartridge images.

The disk drive is probably the next thing on my list to take a look at.