ROS 2 Bridge in Standalone Workflow
Learning Objectives
Run standalone ROS2 python examples
Manually step ROS2 components
Getting Started
Important
Make sure to source your ROS 2 installation from the terminal before running Isaac Sim. If sourcing ROS 2 is a part of your bashrc then Isaac Sim can be run directly.
Prerequisite
Completed Isaac Sim Workflows and Hello World to understand the two workflows (Standalone and Extension).
Set the environment variables needed to enable ROS2 messaging with the following steps.
Create a file named
fastdds.xmlunder~/.ros/if you haven’t already, paste the following snippet link into the file.<?xml version="1.0" encoding="UTF-8" ?> <license>Copyright (c) 2022, NVIDIA CORPORATION. All rights reserved. NVIDIA CORPORATION and its licensors retain all intellectual property and proprietary rights in and to this software, related documentation and any modifications thereto. Any use, reproduction, disclosure or distribution of this software and related documentation without an express license agreement from NVIDIA CORPORATION is strictly prohibited.</license> <profiles xmlns="http://www.eprosima.com/XMLSchemas/fastRTPS_Profiles" > <transport_descriptors> <transport_descriptor> <transport_id>UdpTransport</transport_id> <type>UDPv4</type> </transport_descriptor> </transport_descriptors> <participant profile_name="udp_transport_profile" is_default_profile="true"> <rtps> <userTransports> <transport_id>UdpTransport</transport_id> </userTransports> <useBuiltinTransports>false</useBuiltinTransports> </rtps> </participant> </profiles>
In every terminal that Isaac Sim will be launched by the script, run
unset LD_LIBRARY_PATHandexport FASTRTPS_DEFAULT_PROFILES_FILE=~/.ros/fastdds.xml.
Note
In Windows 10 or 11, depending on your machine’s configuration, RViz2 may not open properly.
Manually Stepping ROS2 Components
One major usage for standalone scripting is to manually control the simulation steps. An OnImpulseEvent OmniGraph node can be connected to any ROS2 OmniGraph node so that the frequency of the publishers and subscribers can be carefully controlled.
An example of how a new action graph with a ROS2 Publish Clock node can be setup to be precisely controlled with a ROS2 Domain ID of 1:
import omni.graph.core as og
# Create a new graph with the path /ActionGraph
og.Controller.edit(
{"graph_path": "/ActionGraph", "evaluator_name": "execution"},
{
og.Controller.Keys.CREATE_NODES: [
("ReadSimTime", "omni.isaac.core_nodes.IsaacReadSimulationTime"),
("Context", "omni.isaac.ros2_bridge.ROS2Context"),
("PublishClock", "omni.isaac.ros2_bridge.ROS2PublishClock"),
("OnImpulseEvent", "omni.graph.action.OnImpulseEvent"),
],
og.Controller.Keys.CONNECT: [
# Connecting execution of OnImpulseEvent node to PublishClock so it will only publish when an impulse event is triggered
("OnImpulseEvent.outputs:execOut", "PublishClock.inputs:execIn"),
# Connecting simulationTime data of ReadSimTime to the clock publisher node
("ReadSimTime.outputs:simulationTime", "PublishClock.inputs:timeStamp"),
# Connecting the ROS2 Context to the clock publisher node so it will run under the specified ROS2 Domain ID
("Context.outputs:context", "PublishClock.inputs:context"),
],
og.Controller.Keys.SET_VALUES: [
# Assigning topic name to clock publisher
("PublishClock.inputs:topicName", "/clock"),
# Assigning a Domain ID of 1 to Context node
("Context.inputs:domain_id", 1),
],
},
)
On any frame, run the following to set an impulse event which will tick the clock publisher once:
og.Controller.set(og.Controller.attribute("/ActionGraph/OnImpulseEvent.state:enableImpulse"), True)
Note
Due to the explicit control of rendering and physics simulation steps in standalone scripting, the time it takes to complete each step will depend on the computation load and will likely not match real time. This may cause discrepancy in observed speed of action when running the same application via standalone scripting versus using the GUI. When that occurs, use the simulation clock as reference.
Examples
We converted a few of the tutorial examples into standalone python examples. Here are the instructions for running them.
ROS2 Clock
This sample demonstrates how to create a action graph with ROS2 component nodes and then tick them at different rates.
The sample can be executed by running the following:
./python.sh standalone_examples/api/omni.isaac.ros2_bridge/clock.py
Echo the following topics to see messages being published:
ros2 topic echo /sim_time
ros2 topic echo /manual_time
To create and set up a ROS2 Clock publisher using the Isaac Sim UI, see the ROS2 Clock tutorial.
ROS2 Camera
The following 2 samples demonstrates how to create a action graph with ROS2 Camera Helper and Camera Info Helper OmniGraph nodes which are used to setup ROS2 RGB image, depth image and camera info publishers. Both samples accomplish the same outcome of publishing ROS2 image data at different rates but use different solutions.
On each frame:
Camera Info is published
Every 5 frames:
RGB image is published
Every 60 frames:
Depth image is published
Periodic Image Publishing
The execution rate (every N frames) for each of the ROS2 image and camera info publishers are set by modifying their respective Isaac Simulation Gate OmniGraph nodes in the SDGPipeline graph. By setting the execution rate, an image publisher will automatically be ticked every N rendered frames.
The sample can be executed by running the following:
./python.sh standalone_examples/api/omni.isaac.ros2_bridge/camera_periodic.py
To exit the sample you can terminate via the terminal with CTRL-C
Manual Image Publishing
The ROS2 image and camera info publishers are manually controlled by injecting Branch OmniGraph nodes between each publisher node and their respective Isaac Simulation Gate OmniGraph node. The Branch nodes act like a custom gate and can be enabled/disabled at any time. Whenever a Branch node is enabled, the connected ROS2 publisher node will be ticked.
The sample can be executed by running the following:
./python.sh standalone_examples/api/omni.isaac.ros2_bridge/camera_manual.py
To exit the sample you can terminate via the terminal with CTRL-C
Visualizing Results
To visualize the result of either sample in RViz2, in a new ROS2-sourced terminal navigate to the Isaac Sim package directory and run the following command:
rviz2 -d <ros2_ws>/src/isaac_tutorials/rviz2/camera_manual.rviz
Note
Due to an issue with RViz2, black frames may appear for depth image displays. To verify that Isaac Sim is correctly publishing depth images, run ros2 run rqt_image_view rqt_image_view and set the topic to /depth. In Windows 10 and 11, rqt_image_view is not available.
Carter Stereo
This sample demonstrates how to take an existing USD stage with an action graph containing ROS2 component nodes and modifying the default settings. The stereo camera pair is automatically enabled and the second viewport window is docked in the UI.
On each frame:
The ROS2 clock is published
A ROS2 PointCloud2 message originating from an RTX Lidar is published
Odometry is published
The Twist subscriber is spun
TF messages are published
Left and right cameras are published
Every Two Frames:
The Twist command message is published
The sample can be executed by running the following:
./python.sh standalone_examples/api/omni.isaac.ros2_bridge/carter_stereo.py
To exit the sample you can terminate via the terminal with CTRL-C
To visualize the result:
In a new terminal, run the following command to load RViz2:
rviz2 -d <ros2_ws>/src/isaac_tutorials/rviz2/carter_stereo.rviz
Make sure Right Camera - RGB and Left Camera - RGB within the Displays are enabled to visualize RGB images.
Note
If some of the images don’t show up on RViz2, press Stop and Play in the simulator for the images to show up.
MoveIt2
This sample shows how to add multiple USD stages. It also demonstrates how to manually create a action graph with ROS2 component nodes and then manually tick them.
To visualize the output see the interactive version of the sample:
On each frame:
The ROS clock is published
Joint State messages are published
Joint State subscriber is spun
TF messages are published
The sample can be executed by running the following:
./python.sh standalone_examples/api/omni.isaac.ros2_bridge/moveit.py
To exit the sample you can terminate via the terminal with CTRL-C
Receiving ROS2 Messages
This is a simple subscriber example where upon receiving an empty ROS2 message, a cube in the scene teleports to a random location. This one is running with rendering enabled, so you should be able to see the scene and the cube moving. To run this example
./python.sh standalone_examples/api/omni.isaac.ros2_bridge/subscriber.py
To exit the sample you can terminate via the terminal with CTRL-C
Once the scene with cube is loaded, you can publish the empty message manually from another terminal. We’ll do it at rate of 1Hz.
ros2 topic pub -r 1 /move_cube std_msgs/msg/Empty
Summary
In this tutorial we learned how to manually step ROS2 components and run standalone ROS2 python examples.
Next Steps
Continue on to the next tutorial in our ROS2 Tutorials series, ROS 2 Python Custom Messages.