Babylon.js or Three.js are pure javascript libraries. Unlike Unity, they are light and do not require an IDE. They are free and open source. By the way, I'm thinking of compiling the loader for Babylon or Three. I chose Unity here because I master more and because the integration of C++ (for the libs I bought to decode some formats) is simpler. I also chose Unity because I would like to use my loader to create an augmented/virtual reality 3D model viewer application for Hololens, Open VR, w10 Headsets, ... And Unity can compile the same code for targets that have nothing to do with each other.