@withADoveInOneHand thanks for the suggestion!
Here’s an example with full interactivity: https://playground.babylonjs.com/#TGZ9GN#25
You click on the iframe to the bring it to the front (you can now interact with it normally), and click out of the iframe to send it back (you can now interact with the WebGL scene).
Hope this helps!
EDIT: if you implement proper mixing in three.js, you will get a similar result in that you need to click to focus and click out to defocus.