message: Disable backplate if there's an HDRI light.
  This mimics previous behavior for our demos as listed on the
  website.
diff: @@ -394,6 +394,10 @@ static void setupLights(const sg::Frame &root)
  tex->setName("map");
  auto &hdri = lights.createChild("hdri", "HDRILight");
  hdri.add(tex);
  +
  + // disable the backplate if there's an HDRI
  + renderer["useBackplate"] = false;
  +
  renderer.verify(); //TODO: this should not be necessary
  sg::Texture2D::clearTextureCache();
  }
  @@ -462,7 +466,7 @@ int main(int argc, const char **argv)
  importFilesFromCommandLine(*root);
  setupLights(*root);
  - // setupCamera(*root);
  + setupCamera(*root);
  MainWindow window(root, pluginsToLoad, tfnsToLoad);
  