I've shifted the project from C++ to JavaScript during this prototyping phase. I've done this for a few reasons:
- This makes the project incredibly portable, allowing me to work on it on different devices easily.
- Prototyping in JavaScript is easy.
- Threejs is cool and easy to use.
I'm a C++ coder at heart and my ultimate goal is for this to be a C++ project. Pragmatically it hasn't been working for me using C++ for my home projects for the last few years. I find myself needing to upgrade projects and libraries, worry about build processes, ensure Visual Studio is installed on the device etc. Now I can now edit generation scripts almost anywhere, anytime, event on my smart phone. Those little moments of downtime can be much more productive 
I'll take the project to C++ once it has matured - though it will continue to support JavaScript generation scripts so hopefully with a little work I won't have to throw anything away.
Today while eating lunch I read your post, I gotta say I'm pretty excited to see that someone else has decided to make their prototype with these two things. I'm very interested in seeing your progress. What have you cooked up so far?