XRView.isFirstPersonObserver

The XRView interface's read-only isFirstPersonObserver property is a boolean indicating if the XRView is a first-person observer view.

To create video recordings of AR device cameras, you can't simply use one of the rendered eyes, as there often will be a physical offset. Some devices expose a secondary view, the first-person observer view, which has an eye of none.

To receive a first-person observer view, you need to enable the "secondary-views" feature descriptor explicitly (typically as an optional feature). See XRSystem.requestSession() for details.

The isFirstPersonObserver property then allows you to check which secondary view is a first-person observer view.

// Make sure to enable "secondary-view"
navigator.xr.requestSession("immersive-ar", {
  optionalFeatures: ["secondary-views"]
});

// ...

session.requestAnimationFrame(function(frame) {
  let views = frame.getViewerPose(space);
  // Make sure to iterate over all views
  for (view of views) {
    if (view.isFirstPersonObserver) {
      renderFPO();
    } else {
      render());
    }
  }
});