I'd imagine that this, like all the other 3D JS libraries, use WebGL under the hood, which is quite fast, hardware accelerated, and just exposes a JS API. You w

I'd imagine that this, like all the other 3D JS libraries, use WebGL under the hood, which is quite fast, hardware accelerated, and just exposes a JS API. You wouldn't actually write your shader in JS, unless it happened to be asm.js which allows the browser to get close to C level performance.