The Powder Toy (opens in new tab)

I actually made a bi-propellant rocket engine in this sim, though I had to use a lua script to get the hydrogen to be in liquid form it works surprisingly well. https://twitter.com/Goomanhimer/status/694048595041976320

the 3rd one, microcomputer, is pretty amazing.

http://dan-ball.jp/en/javagame/dust2/ also exists.

Everything's on the CPU right now. Since the interactions between particles is incredibly complex and is designed for serial execution, the best place to start is rendering visuals like fire and blob effects. However, on my machine there is little difference in performance when toggling this feature on/off.

I have serious doubts a 3d version would be better. It would be hard (if possible at all) to make an equally simple interface that conveys the same information and is equally easy and fast to use while allowing free 3d interaction.

Maybe that becomes a lot easier once virtual reality and 3d input devices become common, but until then I think there are better ways to use extra computation power

From a quick look at the code it seems to be coded as a fairly standard particle system. Modern processors are fast, if you have a million particles, a 2GHz processor, and do 20 simulation steps per second you can spend 100 clock cycles per particle on simulating it. On modern processors 100 clock cycles usually translates to over 100 instructions.

Of course the ~100 clock cycles latency for fetching from main memory has to be avoided, so you code in a language like c++ (like this project) and pack your data in big arrays in the order it's accessed in. Then processor caches and prefetching do the magic.

Particle interactions that usually imply quadratic runtime can be made fast by mapping particle positions to a grid and either looking up neighbouring particles in the grid or calculating large scale effects directly with the grid.

Personally, I think for this project the working whole and the value it provides as a fun educational tool is a bigger deal than architectural or development ideas that went into it (but I'm happy to be proven wrong)

Source is on GitHub if you want to study it: https://github.com/simtr/The-Powder-Toy