Last I looked, the vector math part of 3D wasn't handled by webGL, this uses Three.js to handle that, and looks to be the main bottleneck. Until you can do matrix/vector math using hardware, webGL is pretty much useless.
use typed arrays effectively to do very fast matrix and vector math in JS. A modern JS engine can transform such code into something very efficient, more than fast enough to do things like even first person shooters.
That is pretty much about right. I wrote a bit about the implementation[1], and the discussion went over how to optimize this (including, but not limited to, using shaders to do the drawing and not relying on Three.js so much).
Would be interested if its worthwhile/possible using shaders as a wrapper for three.js. All I got when I was searching was there was a mozilla bug report and a hacked patch to expose SIMD through js[1], and a project to add SIMD support to vectors in Dart[2].
