My stuff

I gave a “Silly Talk” presentation on my MPP file format, and on the techniques used for encoding multi-palette pictures for the Atari ST, while I was at the Silly Venture 2016 demoparty, in Gdańsk, Poland.

This was a good opportunity to talk about the multi palette technique, and also to give an insight of my job on my research field, which is operations research.

I did a Lua implementation of a depacker for the zlib/deflate algorithm. It’s quite efficient for Lua code, even though it obviously won’t compete with a compiled implementation. It can be useful in Lua environments where no access for native C libraries are possible, like the PICO-8 platform.

Performance tests show that typical run times to depack lua-5.3.3.tar.gz on my 2013 i5 laptop are 0.87s with Lua 5.3, and 0.28s with LuaJIT 2.0.4.

The source code and documentation are available on Github, and is made available under the WTFPL license.

I participated to a Raspberry Pi demo, which just participated to the alternative platform demo competition at the Evoke demoparty in Köln, Germany. We got the fifth place out of six, which is rather logical since this prod was neither technically nor artistically impressive. But it was fun to do anyway, especially on that platform !

You can download and run it on your Pi aswell. It requires a Raspbian Linux system. It can be run directly from the console, and it was successfully tested on a 256 MB model with memory configuration of 64 MB of VRAM and 192 MB of RAM.

Too much time since I haven't written to this blog!

From last time, among other things I have participated to the Antiques demo, an Atari STe demo by Dune and Sector One. This is to my opinion a great Atari demo, which is really worth the look. It features great physics and 3D effects by Chuck, great graphics from Mic and awesome music from Dma-Sc. All of this put together by the Sector One conductor, ST Ghost.

In this demo I have done minor helper animation code, like the intro and the greetings part. I also used a new method for displaying still pictures with a large number of colors available on the screen.

Here is for instance one of such pictures, by Mic:

Can you believe this picture can be displayed by an Atari STe, which is supposed to be able to only display 16 colors per picture, from a palette of 4096 colors? Well it can! Basically, Atari ST coders know from a long time how to display pictures with more than 16 colors. This is done by synchronizing palette changes with the screen refresh. Some graphics programs even take profit from such techniques like the famous Neochrome Master which allows to schedule the palette changes at determined vertical positions in the image, or Spectrum 512 which even allows to display more than 16 colors in a single scanline, typically 44 of them. The method used in Antiques demo allows to display 56 different colors per scanline from 29791 possible shades, making use of the blitter chip for that purpose.

In fact, the display method was not the trickiest part in the project. The biggest challenge was to determine a method to generate the data (pixels and palette) to make images look the best as possible when displayed on the STe. A program like Spectrum 512 uses a very basic method to construct image data. It also behaves badly when it has to deal with numerous colors. Of course it had to run on the Atari, with very limited processing power.

My method uses a heuristic method to generate pixel and palette data. It spends a lot of processing power to run a simulated annealing based search method to try and find the best data for each scanline of the picture. The image generation is written in C language and is rather well optimized, to reduce useless computations and make the overall run time acceptable on a modern computer. The program even works on the Atari, if you have enough patience ;)

I have diversified the display method from a single STe-only method to four different methods, the remaining three being also able to run on a plain ST (only 3375 colors are available on the ST though). One mode supports fullscreen, allowing a picture resolution of 416x273 pixels with 48 different possible colors per scanline. I created my own file format to support the different display modes and image types. This format is called MPP, for "Multi Palette Picture".

I am releasing the code of the image converter and the file viewer running on the ST and STe. The Mega STe is also supported. The code is available under the WTFPL public license, which basically corresponds to the public domain. People can use it for what they want, use the code in file conversion plugins, make better sophisticated viewers, etc. You will find the link to the archive at the bottom of this article. I also provide an archive with different sample images. Hoping people will do funny things with that code!

I made a fractal zoomer on the mandelbrot set for the jailbroken Playstation 3. All the computations are done using the SPU's of the Cell processor. The generator is able to render more than 10 frames per second, and for some parts of the Mandelbrot set the framerate can achieve 60 fps ;)

It works as an installable package, to be installed from USB storage via the "Install Package" game menu option of jailbroken PS3's.

Use the analog sticks to scroll and zoom, then you can make a screenshot using the "square" button. Screenshot images are stored to USB storage. Use the "start" button to reset the original settings, and hit "cross" to exit. Enjoy !

Visit the prod page on pouët.net

See a demonstration video on YouTube

Browse the source code on GitHub

I began playing with ray tracing. Unlike some geeks who almost started programming by writing raytracers, I never thought it would be of any interest, since it generally could not lead to real time animation. Then, the PS3 arrived.

I am very proud to announce the release of my PS3 demo called retrostation.

I know it is a bit late compared to sony's decision to completely remove the Install Other OS functionality from the new firmware release of latest April 1st. However, I started this project more than two years ago, so I definitely wouldn't stop this until it is done. I also know about people who still haven't updated their system, because they are aware of what they will lose, so this is a way to show them what they can do with a ps3 system, even without hardware 3D acceleration.

The demo is an animation of different kinds of 3D objects. Some of these have been designed by Mic of Dune, who did a really good job. Others are coming from old Atari ST demos. I let you try and find out from which demos they come from ! Objects of the last kind are algorithmically generated: blobs and text in separately-animated pieces.

The music has been composed by Dma-Sc of Sector One, who also did a great job in the final design of the whole animation. I personally also use my own demoscene nickname in the demo, which is Zerkman of Sector One.

The demo runs on any PS3 system with a linux OS installed on it. It runs in framebuffer mode. Ensure you set the screen mode to 720p 1280*720, and disabled the Xorg server before running the demo.

I hope you'll like the demo as much as I liked making it.

The entry on the pouët.net website is here. From there, you can download a binary version of the demo, as well as a video of the demo (HD 720p, 60 fps).

Official PlayStation 3 firmware update files basically are uncompressed archives containing different subparts.

The pupextract program I wrote basically is a one-hour project which just takes a firmware update file as input, and separate the different subparts into different files. One of these output files, which I called update.tar, is a simple GNU tar archive, containing the (encrypted) files for the firmware update. Another one contains the end-user licence agreement (EULA), while some contain basic information such as the release version number, and others contain empty or unknown data.

Not sure it will be useful for many people, but I decided to release it under the GPLv3 free software licence.

Download source code of pupextract v0.01

As you may know, it is possible to run user programs on the Sony Playstation 3 console, provided you install a Linux-based system. However, it is not possible to directly access the GPU of the console, meaning hardware 3D rendering is currently impossible for -most- PS3 users.