@Override
    public void update(float tpf) {

        if (environment != null) {

            if (environment.hasTraditionalGUIOverlay()) {
                // update the mouse?
                environment.getVRMouseManager().update(tpf);

                // update GUI position?
                if (environment.getVRGUIManager().isWantsReposition() || environment.getVRGUIManager().getPositioningMode() != VRGUIPositioningMode.MANUAL) {
                    environment.getVRGUIManager().positionGuiNow(tpf);
                    environment.getVRGUIManager().updateGuiQuadGeometricState();
                }
            }
        } else {
            throw new IllegalStateException("This VR view manager is not attached to any VR environment.");
        }
    }
Replaces rootNode with the distortion mesh as the main camera's scene.
jme3-vr/src/main/java/com/jme3/input/vr/lwjgl_openvr/LWJGLOpenVRViewManager.java