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"]
}).then((session) => {
  // …

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