URDFRenderer::URDFRenderer (std::string model_description, 
                             std::string tf_prefix,
                             std::string cam_frame,
                             std::string fixed_frame,
                             tf::TransformListener &tf)
   : model_description_(model_description)
   , tf_prefix_(tf_prefix)
   , camera_frame_ (cam_frame)
   , fixed_frame_(fixed_frame)
   , tf_(tf)
 {
   initURDFModel ();
 }
 URDFRenderer::URDFRenderer (std::string model_description, 
                             std::string tf_prefix,
                             std::string cam_frame,
                             std::string fixed_frame,
                             tf::TransformListener &tf)
   : model_description_(model_description)
   , tf_prefix_(tf_prefix)
   , camera_frame_ (cam_frame)
   , fixed_frame_(fixed_frame)
   , tf_(tf)
 {
   initURDFModel ();
   tf_.setExtrapolationLimit (ros::Duration (5.0));
 }