Add 2D/3D Lidar Launch Arg in iris_with_lidar.launch.py

[tejalbarnwal]

Description

This PR addresses #63 and implements the following:

• Adds two new models: iris_with_2d_lidar and iris_with_3d_lidar, which only include the lidar link and sensor.
• Updates iris_with_lidar.launch.py and iris_maze.launch.py to select the appropriate model (2D or 3D) based on a launch argument.

Testing

Modify the lidar_dim argument passed to iris_with_lidar.launch.py in iris_maze.launch.py to either 2 or 3.
Any other value prevents the robot_state_publisher node from launching, leading to:

[rviz2-7] [INFO] [1732732583.933054374] [rviz]: Message Filter dropping message: frame 'base_scan' at time 2.773 for reason 'discarding message because the queue is full'

This occurs because no TF data is published.

Work in Progress

I am working on raising a ValueError if an invalid lidar_dim (other than 2 or 3) is passed. However, a challenge remains: Gazebo launches the iris model even if a ValueError is raised, and the launch process exits in the terminal. Manually killing the Gazebo process (ruby PID) is currently required to stop it. I am actively working on resolving this issue.

Potential Improvements

One concern is ensuring consistency between the model selected via the launch argument and the model referenced in the world files (e.g., iris_maze.sdf, iris_runway.sdf). For instance, iris_maze.sdf references iris_with_lidar and defines its pose in the environment, requiring manual verification.
A possible improvement could involve enabling the independent spawning of the iris model in the world, decoupling it from other Gazebo components, to simplify integration.

[srmainwaring]

Thanks for the PR @tejalbarnwal. I'm wondering whether we can save some duplication and future maintenance overhead by using an <include> element similar to how we do for the iris_with_gimbal model in the ardupilot_gazebo repo.

We would need to create additional models for the 2D and 3D Lidar, each would need to have a canonical link called base_scan to be consistent with the expected TF tree.

    <include merge="true">
      <uri>model://lidar_3d</uri>
      <name>lidar</name>
      <pose degrees="true">0 0 0 0 0 0</pose>    
    </include>

The remainder of the common SDF can be factored out.

We may only need a model expressed for either 2d or 3d, because in the launch file we can use standard python string replacement to substitute the desired model at launch time (using replace on <uri>model://lidar_3d</uri>).

To resolve the consistency concern we should use the gz launch spawn model capability and load the model into the maze at the desired location. There is an example of how to do this for multiple robots here: https://github.com/srmainwaring/ardupilot_gz/blob/prs/pr-multi-vehicle/ardupilot_gz_bringup/launch/robots/iris.launch.py

If you like I can help you rework this to implement the suggestions above.

[Ryanf55]

This is off to a great start! Thanks for spending the time to submit your changes for a 3D Lidar Iris model! This is a nice capability addition that will go well with your bonxai demo.

I agree with Rhys on the requested changes, and can also help if you get stuck.

[tejalbarnwal]

Hi,
I have implemented the requested changes to dynamically replace the <uri>model://lidar_3d</uri> string. Additionally, the launch files now use the ros_gz_sim create executable to spawn the iris_with_lidar model. Please let me know your feedback on the updates.

[tejalbarnwal]

Hi @srmainwaring and @Ryanf55 ,
I would greatly appreciate any feedback on the latest commit I pushed, so we can refine it further for merging the PR at your convenience.

[tejalbarnwal]

Hi @srmainwaring and @Ryanf55 ,
Just checking in, did you get a chance to look at the PR? Let me know if there is anything specific you would like me to address.

[Ryanf55]

Sorry for the very long delay, here's some initial feedback. Once I'm back at my desktop in a few days, I can provide more feedback by testing the changes. Nice improvements!

[tejalbarnwal]

Hi @srmainwaring and @Ryanf55 , I have incorporated the changes you suggested into the code. Could you please review them?