A bit more info about how you would place a 3D web page inside a PlayCanvas scene:
- Enable transparent canvas in PlayCanvas’ render settings in the Editor.
- Create a div behind the PlayCanvas canvas in script.
- Render the web page into that div using CSS 3D transform.
- Render a quad into your PlayCanvas scene with z-write enabled, and color write for R, G and B disabled, but write 0 for alpha (full transparency). Writing to the z-buffer will enable things to sort correctly. And writing the alpha will effectively punch through the PlayCanvas canvas and allow you to see the CSS 3D transformed div. Note that the quad will have to be transformed identically to the underlying div.
Sounds a little complicated, but it’s definitely possible. Perhaps the hardest thing is matching the CSS 3D transform with the transform of the 3D quad in the PlayCanvas scene.