Thank you for your suggestion!
Unfortunately, your shader doesn’t use a framebuffer. It just takes time and particle index and calculates this particle coordinates. Then it has to measure distance from every pixel to every of these points, so to decide, light the pixel or not.
It’s not effective, 600 particles are already slow, 1000000 are impossible.
Here is a link to a rendered video of webgl shader, which moves 1M particles with ease https://www.instagram.com/p/B3pxMEiIZgA/