Warmer-Colder: Practicing with tf

• Download and unzip the warmer_colder package to your workspace directory: warmer_colder.zip . There is a launch file in place that will start the sound_play and goal_publisher nodes.

• Modify warmer_colder.py so that its behavior matches the documentation.

  The page Using Published Transforms contains the documentation for tf methods that will be useful for transforming the goal point into the robot's /base_footprint coordinate frame.

  If you see ExtrapolationErrors you will need to use the waitForTransform method of the TransformListener class. That method can be called as follows:

  your_tf_listener.waitForTransform(FRAME_ID_THAT_WE_WANT_TO_TRANSFORM_FROM,
                                   FRAME_ID_THAT_WE_WANT_TO_TRANSFORM_TO,
                                   TIME_THAT_WE_WANT_THE_TRANSFORM,
                                   HOW_LONG_TO_WAIT_BEFORE_GIVING_UP)
  

  Both FRAME_ID_THAT_WE_WANT_TO_TRANSFORM_FROM and TIME_THAT_WE_WANT_THE_TRANSFORM can be obtained from the header of the stamped point. HOW_LONG_TO_WAIT_BEFORE_GIVING_UP needs to be a ROS duration object -- something like: rospy.Duration(1.0).
• Once the game is working and tested, modify goal_publisher.py so that it broadcasts a transform at the goal position in addition to publishing the goal point. You can see an example of publishing a transform in a Python node here: Writing a tf broadcaster (Python).
• Use rviz to make sure that your transform is being published correctly. The game should be much easier if you drive the robot while visualizing the goal transform.
• Now copy use svn copy to put a copy of your finished lab into the submit folder and commit.

      $ svn cp warmer_colder submit
      $ svn commit