updateProjectionMatrix() {
    const projMatrix = this.getProjectionMatrix();
    if (!projMatrix) {
      super.updateProjectionMatrix();
      return;
    }

    this.projectionMatrix.fromArray(projMatrix);
  }
Updates the underlying `projectionMatrix` property from
the AR-enabled VRDisplay, or falls back to
THREE.PerspectiveCamera.prototype.updateProjectionMatrix