Fix display in mobile devices

Example:

https://bulebule.readthedocs.io/en/latest/building.html#rim

Try to reduce the window width to find the issue (3D models nor properly displayed).

Maybe better, have a look at:

https://threejsfundamentals.org/threejs/lessons/threejs-multiple-scenes.html

In particular, render to an off screen canvas and copy the result to a 2D canvas at each element. If performance is not too bad, it could be worth it.