[dpiers]

WebGL may be good enough if you are producing low-res visualizations/interfaces and using the rest of the CPU/GPU to crunch the simulation.

Epic got the Unreal Engine running in-browser with WebGL and asm.js. The stuff Uber is doing isn't anywhere near as graphically intensive as that.

disclaimer: I work at Uber, but not on this project. Also, I used to work on game engines, which have a lot in common with these types of simulators.