  int TextureIndex() const {
    const auto it = json_double_value.find("index");
    if (it != std::end(json_double_value)) {
      return int(it->second);
    }
    return -1;
  }
  int TextureIndex() const {
    const auto it = json_double_value.find("index");
    if (it != std::end(json_double_value)) {
      return int(it->second);
    }
    return -1;
  }