Tutorial for Visual SLAM with Isaac Sim
=======================================

.. figure:: :ir_lfs:`<resources/isaac_ros_docs/concepts/visual_slam/cuvslam/After_localization.png>`
    :align: center
    :alt: After Localization
    :width: 600px

Overview
------------

This tutorial walks you through a graph to estimate 3D pose of the
camera with :ir_repo:`Visual SLAM <isaac_ros_visual_slam>`
using images from Isaac Sim.

Tutorial Walkthrough
--------------------

1.  Complete the :ref:`quickstart <repositories_and_packages/isaac_ros_visual_slam/isaac_ros_visual_slam/index:quickstart>`.

2.  Launch the Docker container using the ``run_dev.sh`` script:

    .. code:: bash

       cd ${ISAAC_ROS_WS}/src/isaac_ros_common && \
         ./scripts/run_dev.sh

3.  Install and launch Isaac Sim following the steps in the :doc:`Isaac ROS Isaac Sim Setup Guide </getting_started/isaac_sim/index>`

4.  Press **Play** to start publishing data from the Isaac Sim.

    .. figure:: :ir_lfs:`<resources/isaac_ros_docs/getting_started/isaac_sim_sample_scene.png>`
        :align: center
        :width: 600px

5.  In a separate terminal, start ``isaac_ros_visual_slam`` using the
    launch files:

    .. code:: bash

       ros2 launch isaac_ros_visual_slam isaac_ros_visual_slam_isaac_sim.launch.py

7.  In a separate terminal, send the signal to move the robot about as follows:

    .. code:: bash

       ros2 topic pub --once /cmd_vel geometry_msgs/msg/Twist "{linear: {x: 0.2, y: 0.0, z: 0.0}, angular: {x: 0.0, y: 0.0, z: 0.2}}""

7.  In a separate terminal, spin up RViz with default configuration file
    to see the rich visualizations as the robot moves.

    .. code:: bash

       rviz2 -d src/isaac_ros_visual_slam/isaac_ros_visual_slam/rviz/isaac_sim.cfg.rviz

    .. figure:: :ir_lfs:`<resources/isaac_ros_docs/concepts/visual_slam/cuvslam/Rviz_isaac_sim.png>`
        :align: center
        :width: 600px

8.  To see the odometry messages, in a separate terminal echo the contents of the ``/visual_slam/tracking/odometry`` topic with the
    following command:

    .. code:: bash

       ros2 topic echo /visual_slam/tracking/odometry

    .. figure:: :ir_lfs:`<resources/isaac_ros_docs/concepts/visual_slam/cuvslam/Terminal_output.png>`
        :align: center
        :width: 600px

Saving and Using the Map
------------------------

As soon as you start the visual SLAM node, it starts storing the
landmarks and the pose graph. You can save them in a map and store the
map onto a disk. Make a call to the ``SaveMap`` ROS 2 Action with the
following command:

  .. note::

    ``/path/to/save/the/map`` must be a new empty directory
    every time you call this action because this action overwrites the
    existing contents.

.. code:: bash

   ros2 action send_goal /visual_slam/save_map isaac_ros_visual_slam_interfaces/action/SaveMap "{map_url: /path/to/save/the/map}"


.. figure:: :ir_lfs:`<resources/isaac_ros_docs/concepts/visual_slam/cuvslam/Save_map.png>`
    :align: center
    :width: 600px

.. figure:: :ir_lfs:`<resources/isaac_ros_docs/concepts/visual_slam/cuvslam/Rviz_isaac_sim_mapping.png>`
    :align: center
    :width: 600px

Try to load and localize in the previously saved map.
Stop the ``visual_slam`` node launched for creating and saving the
map, then relaunch it.

Use the following command to load the map from the disk and provide an
approximate start location (prior):

.. code:: bash

   ros2 action send_goal /visual_slam/load_map_and_localize isaac_ros_visual_slam_interfaces/action/LoadMapAndLocalize "{map_url: /path/to/save/the/map, localize_near_point: {x: x_val, y: y_val, z: z_val}}"


.. figure:: :ir_lfs:`<resources/isaac_ros_docs/concepts/visual_slam/cuvslam/Load_and_localize.png>`
    :align: center
    :width: 600px

After the above step returns success, you have successfully loaded and
localized your robot in the map. If it results in failure, there might
be a possibility that the current landmarks from the approximate start
location are not matching with stored landmarks and you need to provide
another valid value.

.. figure:: :ir_lfs:`<resources/isaac_ros_docs/concepts/visual_slam/cuvslam/Before_localization.png>`
    :align: center
    :alt: Before Localization
    :width: 600px

.. figure:: :ir_lfs:`<resources/isaac_ros_docs/concepts/visual_slam/cuvslam/After_localization.png>`
    :align: center
    :alt: After Localization
    :width: 600px