If I’m understanding correctly, you want to suspend the render loop when the viewer does not have
focus. If that’s right, you can definitely do that today. Here is an example:
The Viewer already suspends rendering when it is fully outside of the browser’s viewport (e.g. scrolled out of view). There is also some work already under way to not render when nothing is changing frame to frame (e.g. no animation, no camera movement, etc.). Viewer auto suspend rendering when scene is idle by ryantrem · Pull Request #15864 · BabylonJS/Babylon.js · GitHub