grayscott

Reaction-Diffusion Simulation with Pyglet and GLSL.

This program is motivated by pmneila's Javascript project. Run main.py to play with the simulation.

Keyboard and mouse interface:

• Press s (short for "species") to change to another pattern.

• Press p (short for "palette") to color the pattern another way.

• Press Enter to save a screenshot.

• Press Ctrl + s (short for "save") to save current config to a json file.

• Press Ctrl + o (short for "open") to load a favorable config from the json file. Enter the line number of the config then it will be loaded. The screen might become blank, just draw on it.

• Press Ctrl + r to restore to default config.

• press Esc to close the window.

I put some configs in the palette.json file. Do have a try!

How to save the animation to a video:

1. Set a global variable count=0 as the counter, and in the function on_draw(), write

   global count
   if count % 10 == 0:
       pyglet.image.get_buffer_manager().get_color_buffer().save('screenshot{:04d}.png'.format(count // 10))
   
   count += 1

   This will take a screenshot every 10 frames.

2. Use ffmpeg to convert the images into a video. For example to make a .webm video run command line

   ffmpeg -loglevel quiet -framerate 10 -i screenshot%04d.png -c:v libvpx -crf 10 -b:v 2M grayscott.webm

   -i screenshot%04d.png specifies the images files, -framerate specifies the number of frames persecond, -c:v libvpx is the encoder, -b:v specifies the bitrate (the higher the better quality but larger file).

About the code

pyglet.gl is only a thin wrapper of OpenGL, so one has to write his own helper classes to manage things like vbo, vao, shader, fbo, etc. There are some modules like vispy and gletools that do this job, but that lays the burden of learning one more package.

I wrote two helper classes shader.py (adapted from other people's work) and framebuffer.py. They are not meant to be serious tools, just kept simple and suffice for our work.

The GLSL code borrows heavily from pmneila's work, the most genius part in his code (and also the most tricky thing if you want to understand the code) is the use of a brush variable as the interface between the shader and the mouse.

I found it hard to program buttons and menus in pyglet, so let this be a command line version, pardon me with this.