It roughly took 5-6 months in total over a span of 1-2 years (we paused development several times to work on client projects). I recommend diving into Three.js

It roughly took 5-6 months in total over a span of 1-2 years (we paused development several times to work on client projects). I recommend diving into Three.js (or other WebGL libraries), and learning Blender or similar to create your own 3D scenes.