INCENDIUM is a demoscene 4kb intro, meaning all code that generates the visuals and music fits into 4096 bytes. Participated to 4kb intro category at Revision 2025 demoscene party.
The entry is packaged as Windows PowerShell script which plays the compressed intro in web browser. The visuals and music are both generated using WebGPU.
If you have a powerful GPU, you can run the intro in your browser. Best viewed with 16:9 aspect ratio. Your browser must suppord WebGPU (Chrome, Edge, etc.): https://bercon.github.io/incendium/
You can also checkout a recording at https://youtu.be/U8FXJpO9Vck
The intro is based on heavily optimized and stripped down version of Roquefort, an in browser fluid simlator tech demo that runs even on less powerful hardware, especially if you drop the grid size smaller. Developing the Roquefort first allowed much easier debuging of the fluid simulation code. You can play around with the simulation here: https://bercon.github.io/roquefort/
- Fluid simulation, rendering and music is all done with WebGPU compute shaders
- 3D fluid simulator with multigrid solver that uses red-black Gauss-Seidel iteration to run faster and to read/write same buffer
- Box blur computed using accumulation to get any kernel size at fixed 4 lookups per pixel. Gaussian blur is approximated by running box blur twice
- Volumetric shadows, restricted to primary axis light directions
- Baking lighting makes it possible to do only single vec4 lookup each raymarching step
- 324 byte PowerShell bootstrapper for Brotli compressed webpage (40 bytes less than on used in Felid), might be possible to compress it even more?
- Operating systems default browser must support WebGPU. Currently it means Chrome, Edge, or other new Chromium based browser. Non-nightly/beta Firefox and Safari won't work.
- Nvidia RTX 4080 level GPU to run 1080p 60hz. Running at 60hz is important for smooth artifact free fluid simulation
Building intro and package it (install requirements: pip install -R requirements.txt):
python scripts/build.py
Drag'n'drop build/index.html to browser. To run packaged entry, double click builld/entry.cmd
There also debug version that has seek bar intro_player.html. However, since this is a simulation and seeking simply jumps to given timestamp, it will not look exactly as it would if you let the intro play out.
The final entry was packaged with heavier settings than the defaults, try overkill settings like this to drop the size below 4kb:
python scripts/build.py --slow -s 100000 -D 15
The intro uses Brotli compression that is quite unpredictable, adding characters sometimes decreases the size of the results. Flipping order of rows, using different characters and so on, which don't change the size of the data being compress can change the size of the compressed result by tens of bytes. A packager which is heavily based on Pakettic will suffle rows and try different variants of code to find the optimal layout. Running without this with python scripts/build.py --no_optimization gives 4187 bytes, while with enough suffling, we can drop this to 4093, improving compressiong by 94 bytes.
There is still room for improvement with the packager, it doesn't try variable renaming, swapping operation order, trying different variants such as a/2 and a*.5 which give the same result. All things Pakettic does for TIC-80 code. These could further improve the compression and make using the tool more automatic with less need for manually annotating the code. However, this requires implementing proper WGSL parsing which does take some amount of effort.
The entry is compressed HTML page with brotli. Since brotli compressed content can only be served via web server, not locally opening the file we need a web server. This is achieved with Windows PowerShell script that serves the file itself with suitable offset once as via Windows builtin HTTP server. Technique introduce first (I think?) by Muhmac / Speckdrumm in Felid: https://demozoo.org/graphics/342293/
One downside is that it opens the intro in the default browser. This intro requires WebGPU only supported in Chromium browsers like Edge or Chrome which means if default browser is Firefox, the intro will not work.
- Jerry "Bercon" Ylilammi
- Veikko "pestis" Sariola
MIT license, see LICENSE