tf2 tutorials: Consistency fixes in Python and C++ tutorials (#1936)

* check and update consistency in Writing-A-Tf2-Static-Broadcaster Python and C++ tutorials

* check and update consistency in Writing-A-Tf2-Broadcaster Python and C++ tutorials

* check and update consistency in Writing-A-Tf2-Listener Python and C++ tutorials and update code snippet to match update in geopmetry_tutorials

* check and update consistency in Adding-A-Frame Python and C++ tutorials

* check and update consistency in Time-Travel-With-Tf2 Python and C++ tutorials

* use lowercase in titles in Introduction-To-Tf2 tutorial

* lowercase in title in Tf2-Main

* update tutorial time estimation in Adding-A-Frame tutorials

* update depend type in package.xml snippet

* update title Tf2 introduction

* update colon in Time-Travel-With-Tf2

* update text in Writing-A-Tf2-Static-Broadcaster

* move all images to folder and update links

source/Tutorials/Tf2/Adding-A-Frame-Cpp.rst

@@ -7,7 +7,7 @@ Adding a frame (C++)
 
 **Tutorial level:** Intermediate
 
-**Time:** 10 minutes
+**Time:** 15 minutes
 
 .. contents:: Contents
    :depth: 3
@@ -34,7 +34,7 @@ Currently, our tf2 tree contains three frames: ``world``, ``turtle1`` and ``turt
 The two turtle frames are children of the ``world`` frame.
 If we want to add a new frame to tf2, one of the three existing frames needs to be the parent frame, and the new one will become its child frame.
 
-.. image:: turtlesim_frames.png
+.. image:: images/turtlesim_frames.png
 
 Tasks
 -----
@@ -211,7 +211,7 @@ Rebuild the package and start the turtle broadcaster demo:
 
 You should notice that the new ``carrot1`` frame appeared in the transformation tree.
 
-.. image:: turtlesim_frames_carrot.png
+.. image:: images/turtlesim_frames_carrot.png
 
 1.4 Checking the results
 ~~~~~~~~~~~~~~~~~~~~~~~~
@@ -240,7 +240,7 @@ To do so, open the ``turtle_tf2_fixed_frame_demo.launch.py`` file, and add the `
 
 Now just rebuild the package, restart the ``turtle_tf2_fixed_frame_demo.launch.py``, and you'll see the second turtle following the carrot instead of the first turtle!
 
-.. image:: carrot_static.png
+.. image:: images/carrot_static.png
 
 2 Write the dynamic frame broadcaster
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -388,7 +388,7 @@ To test this code, create a new launch file ``turtle_tf2_dynamic_frame_demo.laun
 
 Rebuild the package, and start the ``turtle_tf2_dynamic_frame_demo.launch.py`` launch file, and now you’ll see that the second turtle is following the carrot's position that is constantly changing.
 
-.. image:: carrot_dynamic.png
+.. image:: images/carrot_dynamic.png
 
 Summary
 -------

source/Tutorials/Tf2/Adding-A-Frame-Py.rst

@@ -7,7 +7,7 @@ Adding a frame (Python)
 
 **Tutorial level:** Intermediate
 
-**Time:** 10 minutes
+**Time:** 15 minutes
 
 .. contents:: Contents
    :depth: 3
@@ -17,27 +17,24 @@ Background
 ----------
 
 In previous tutorials, we recreated the turtle demo by writing a :ref:`tf2 broadcaster <WritingATf2BroadcasterPy>` and a :ref:`tf2 listener <WritingATf2ListenerPy>`.
-This tutorial will teach you how to add an extra frame to the transformation tree.
+This tutorial will teach you how to add extra fixed and dynamic frames to the transformation tree.
 In fact, adding a frame in tf2 is very similar to creating the tf2 broadcaster, but this example will show you some additional features of tf2.
 
-1 Why add frames?
-^^^^^^^^^^^^^^^^^
-
 For many tasks related to transformations, it is easier to think inside a local frame.
 For example, it is easiest to reason about laser scan measurements in a frame at the center of the laser scanner.
 tf2 allows you to define a local frame for each sensor, link, or joint in your system.
 When transforming from one frame to another, tf2 will take care of all the hidden intermediate frame transformations that are introduced.
 
-2 Where to add frames
-^^^^^^^^^^^^^^^^^^^^^
+tf2 tree
+--------
 
-tf2 builds up a tree structure of frames, and thus does not allow a closed loop in the frame structure.
+tf2 builds up a tree structure of frames and, thus, does not allow a closed loop in the frame structure.
 This means that a frame only has one single parent, but it can have multiple children.
 Currently, our tf2 tree contains three frames: ``world``, ``turtle1`` and ``turtle2``.
 The two turtle frames are children of the ``world`` frame.
 If we want to add a new frame to tf2, one of the three existing frames needs to be the parent frame, and the new one will become its child frame.
 
-.. image:: turtlesim_frames.png
+.. image:: images/turtlesim_frames.png
 
 Tasks
 -----
@@ -49,7 +46,37 @@ In our turtle example, we'll add a new frame ``carrot1``, which will be the chil
 This frame will serve as the goal for the second turtle.
 
 Let's first create the source files. Go to the ``learning_tf2_py`` package we created in the previous tutorials.
-Fire up your favorite editor and paste the following code into a new file called ``fixed_frame_tf2_broadcaster.py``.
+Download the fixed frame broadcaster code by entering the following command:
+
+.. tabs::
+
+   .. group-tab:: Linux
+
+      .. code-block:: console
+
+         wget https://raw.githubusercontent.com/ros/geometry_tutorials/ros2/turtle_tf2_py/turtle_tf2_py/fixed_frame_tf2_broadcaster.py
+
+   .. group-tab:: macOS
+
+      .. code-block:: console
+
+         wget https://raw.githubusercontent.com/ros/geometry_tutorials/ros2/turtle_tf2_py/turtle_tf2_py/fixed_frame_tf2_broadcaster.py
+
+   .. group-tab:: Windows
+
+      In a Windows command line prompt:
+
+      .. code-block:: console
+
+         curl -sk https://raw.githubusercontent.com/ros/geometry_tutorials/ros2/turtle_tf2_py/turtle_tf2_py/fixed_frame_tf2_broadcaster.py -o fixed_frame_tf2_broadcaster.py
+
+      Or in powershell:
+
+      .. code-block:: console
+
+         curl https://raw.githubusercontent.com/ros/geometry_tutorials/ros2/turtle_tf2_py/turtle_tf2_py/fixed_frame_tf2_broadcaster.py -o fixed_frame_tf2_broadcaster.py
+
+Now open the file called ``fixed_frame_tf2_broadcaster.py``.
 
 .. code-block:: python
 
@@ -150,7 +177,7 @@ With your text editor, create a new file called ``turtle_tf2_fixed_frame_demo.la
       ])
 
 
-This launch file first imports the required packages, then creates a ``demo_nodes`` variable that will store nodes that we created in the previous tutorial's launch file.
+This launch file imports the required packages and then creates a ``demo_nodes`` variable that will store nodes that we created in the previous tutorial's launch file.
 
 The last part of the code will add our fixed ``carrot1`` frame to the turtlesim world using our ``fixed_frame_tf2_broadcaster`` node.
 
@@ -165,21 +192,21 @@ The last part of the code will add our fixed ``carrot1`` frame to the turtlesim
 1.3 Build and run
 ~~~~~~~~~~~~~~~~~
 
-Rebuild the package, and start the turtle broadcaster demo:
+Rebuild the package and start the turtle broadcaster demo:
 
 .. code-block:: console
 
    ros2 launch learning_tf2_py turtle_tf2_fixed_frame_demo.launch.py
 
 You should notice that the new ``carrot1`` frame appeared in the transformation tree.
 
-.. image:: turtlesim_frames_carrot.png
+.. image:: images/turtlesim_frames_carrot.png
 
 1.4 Checking the results
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
 If you drive the first turtle around, you should notice that the behavior didn't change from the previous tutorial, even though we added a new frame.
-That's because adding an extra frame does not affect the other frames, and our listener is still using the previously defined frames.
+That's because adding an extra frame does not affect the other frames and our listener is still using the previously defined frames.
 
 Therefore if we want our second turtle to follow the carrot instead of the first turtle, we need to change value of the ``target_frame``.
 This can be done two ways.
@@ -202,16 +229,45 @@ To do so, open the ``turtle_tf2_fixed_frame_demo.launch.py`` file, and add the `
 
 Now just rebuild the package, restart the ``turtle_tf2_fixed_frame_demo.launch.py``, and you'll see the second turtle following the carrot instead of the first turtle!
 
-.. image:: carrot_static.png
+.. image:: images/carrot_static.png
 
 2 Write the dynamic frame broadcaster
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 The extra frame we published in this tutorial is a fixed frame that doesn't change over time in relation to the parent frame.
 However, if you want to publish a moving frame you can code the broadcaster to change the frame over time.
 Let's change our ``carrot1`` frame so that it changes relative to ``turtle1`` frame over time.
+Now download the dynamic frame broadcaster code by entering the following command:
+
+.. tabs::
+
+   .. group-tab:: Linux
+
+      .. code-block:: console
+
+         wget https://raw.githubusercontent.com/ros/geometry_tutorials/ros2/turtle_tf2_py/turtle_tf2_py/dynamic_frame_tf2_broadcaster.py
+
+   .. group-tab:: macOS
+
+      .. code-block:: console
+
+         wget https://raw.githubusercontent.com/ros/geometry_tutorials/ros2/turtle_tf2_py/turtle_tf2_py/dynamic_frame_tf2_broadcaster.py
+
+   .. group-tab:: Windows
+
+      In a Windows command line prompt:
+
+      .. code-block:: console
+
+         curl -sk https://raw.githubusercontent.com/ros/geometry_tutorials/ros2/turtle_tf2_py/turtle_tf2_py/dynamic_frame_tf2_broadcaster.py -o dynamic_frame_tf2_broadcaster.py
+
+      Or in powershell:
+
+      .. code-block:: console
+
+         curl https://raw.githubusercontent.com/ros/geometry_tutorials/ros2/turtle_tf2_py/turtle_tf2_py/dynamic_frame_tf2_broadcaster.py -o dynamic_frame_tf2_broadcaster.py
 
-Create the file called ``dynamic_frame_tf2_broadcaster.py``:
+Now open the file called ``dynamic_frame_tf2_broadcaster.py``:
 
 .. code-block:: python
 
@@ -314,10 +370,10 @@ To test this code, create a new launch file ``turtle_tf2_dynamic_frame_demo.laun
 
 Rebuild the package, and start the ``turtle_tf2_dynamic_frame_demo.launch.py`` launch file, and now you’ll see that the second turtle is following the carrot's position that is constantly changing.
 
-.. image:: carrot_dynamic.png
+.. image:: images/carrot_dynamic.png
 
 Summary
 -------
 
 In this tutorial, you learned about the tf2 transformation tree, its structure, and its features.
-You also learned how to add extra fixed and dynamic frames to tf2.
+You also learned that it is easiest to think inside a local frame, and learned to add extra fixed and dynamic frames for that local frame.

source/Tutorials/Tf2/Debugging-Tf2-Problems.rst

@@ -195,7 +195,7 @@ If you like to get a graphical representation of this, use ``view_frames`` tool.
 
 Open the generated ``frames.pdf`` file to see the following output:
 
-.. image:: turtlesim_frames.png
+.. image:: images/turtlesim_frames.png
 
 So obviously the problem is that we are requesting transform from frame ``turtle3``, which does not exist.
 To fix this bug, just replace ``turtle3`` with ``turtle2`` in line 67.
@@ -265,7 +265,7 @@ Stop the demo, build and run:
 
 And you should finally see the turtle move!
 
-.. image:: turtlesim_follow1.png
+.. image:: images/turtlesim_follow1.png
 
 That last fix we made is not really what you want to do, it was just to make sure that was our problem.
 The real fix would look like this:

source/Tutorials/Tf2/Introduction-To-Tf2.rst

@@ -13,7 +13,7 @@ Introduction to tf2
    :depth: 2
    :local:
 
-Installing the Demo
+Installing the demo
 -------------------
 
 Let's start by installing the demo package and its dependencies.
@@ -39,7 +39,7 @@ Additionally, install a ``transforms3d`` package, which provides the quaternion
 
    pip3 install transforms3d
 
-Running the Demo
+Running the demo
 ----------------
 
 Now that we've installed the ``turtle_tf2_py`` tutorial package let's run the demo.
@@ -52,7 +52,7 @@ Then run the following command:
 
 You will see the turtlesim start with two turtles.
 
-.. image:: turtlesim_follow1.png
+.. image:: images/turtlesim_follow1.png
 
 In the second terminal window type the following command:
 
@@ -63,17 +63,17 @@ In the second terminal window type the following command:
 Once the turtlesim is started you can drive the central turtle around in the turtlesim using the keyboard arrow keys,
 select the second terminal window so that your keystrokes will be captured to drive the turtle.
 
-.. image:: turtlesim_follow2.png
+.. image:: images/turtlesim_follow2.png
 
 You can see that one turtle continuously moves to follow the turtle you are driving around.
 
-What is Happening
------------------
+What is happening?
+------------------
 
 This demo is using the tf2 library to create three coordinate frames: a ``world`` frame, a ``turtle1`` frame, and a ``turtle2`` frame.
 This tutorial uses a tf2 broadcaster to publish the turtle coordinate frames and a tf2 listener to compute the difference in the turtle frames and move one turtle to follow the other.
 
-tf2 Tools
+tf2 tools
 ---------
 
 Now let's look at how tf2 is being used to create this demo.
@@ -98,7 +98,7 @@ You will see:
 Here a tf2 listener is listening to the frames that are being broadcasted over ROS and drawing a tree of how the frames are connected.
 To view the tree, open the resulting ``frames.pdf`` with your favorite PDF viewer.
 
-.. image:: turtlesim_frames.png
+.. image:: images/turtlesim_frames.png
 
 Here we can see three frames that are broadcasted by tf2: ``world``, ``turtle1``, and ``turtle2``.
 The ``world`` here is the parent of the ``turtle1`` and ``turtle2`` frames.
@@ -146,6 +146,6 @@ Let's start rviz with the ``turtle_rviz.rviz`` configuration file using the `
 
    ros2 run rviz2 rviz2 -d $(ros2 pkg prefix --share turtle_tf2_py)/rviz/turtle_rviz.rviz
 
-.. image:: turtlesim_rviz.png
+.. image:: images/turtlesim_rviz.png
 
 In the side bar you will see the frames broadcasted by tf2. As you drive the turtle around you will see the frames move in rviz.

source/Tutorials/Tf2/Tf2-Main.rst

@@ -5,8 +5,7 @@ tf2 Tutorials
 
 Many of the tf2 tutorials are available for both C++ and Python.
 The tutorials are streamlined to complete either the C++ track or the Python track.
-If you want to learn both C++ and Python, you should go through the tutorials
-once for C++ and once for Python.
+If you want to learn both C++ and Python, you should go through the tutorials once for C++ and once for Python.
 
 .. contents:: Contents
    :depth: 2
@@ -30,19 +29,18 @@ once for C++ and once for Python.
    Time-Travel-With-Tf2-Cpp
    Debugging-Tf2-Problems
 
-Workspace Setup
+Workspace setup
 ---------------
 
-If you have not yet created a workspace in which to complete the tutorials,
-:ref:`follow this tutorial <ROS2Workspace>`.
+If you have not yet created a workspace in which to complete the tutorials, :ref:`follow this tutorial <ROS2Workspace>`.
 
 Learning tf2
 ------------
 
 #. :ref:`Introduction to tf2 <IntroToTf2>`.
 
-   This tutorial will give you a good idea of what tf2 can do for you. It
-   shows off some of the tf2 power in a multi-robot example using turtlesim.
+   This tutorial will give you a good idea of what tf2 can do for you.
+   It shows off some of the tf2 power in a multi-robot example using turtlesim.
    This also introduces using ``tf2_echo``, ``view_frames``, and ``rviz``.
 
 #. Writing a tf2 static broadcaster :ref:`(Python) <WritingATf2StaticBroadcasterPy>` :ref:`(C++) <WritingATf2StaticBroadcasterCpp>`.
@@ -71,7 +69,7 @@ Learning tf2
    This tutorial teaches you about advanced time travel features of tf2.
 
 Debugging tf2
---------------
+-------------
 
 #. :ref:`Debugging tf2 problems <DebuggingTf2Problems>`.
 

source/Tutorials/Tf2/Time-Travel-With-Tf2-Cpp.rst

@@ -30,7 +30,7 @@ First, let's go back to where we ended in the previous tutorial :ref:`Learning a
 Go to your ``learning_tf2_cpp`` package.
 
 Now, instead of making the second turtle go to where the carrot is now, we will make the second turtle go to where the first carrot was 5 seconds ago.
-Edit the ``lookupTransform()`` call in ``turtle_tf2_listener.cpp`` file to:
+Edit the ``lookupTransform()`` call in ``turtle_tf2_listener.cpp`` file to
 
 .. code-block:: C++
 
@@ -48,7 +48,7 @@ But what happens after these 5 seconds? Let's just give it a try:
 
     ros2 launch learning_tf2_cpp turtle_tf2_fixed_frame_demo.launch.py
 
-.. image:: turtlesim_delay1.png
+.. image:: images/turtlesim_delay1.png
 
 You should now notice that your turtle is driving around uncontrollably like in this screenshot. Let's try to understand reason behind that behavior.
 
@@ -103,7 +103,7 @@ Let's run the simulation again, this time with the advanced time-travel API:
 
     ros2 launch learning_tf2_cpp turtle_tf2_fixed_frame_demo.launch.py
 
-.. image:: turtlesim_delay2.png
+.. image:: images/turtlesim_delay2.png
 
 And yes, the second turtle is directed to where the first carrot was 5 seconds ago!