ROS topic issues (syncing/hz)

[delenius]

1. The command ros2 topic hz /robot0/front_cam/rgb does not return any info (even though I am getting images through it).
   All the other topics report some data.

2. I am not able to sync the /robot0/front_cam/rgb and /robot0/point_cloud2 topics using message_filters.ApproximateTimeSynchronizer (or plain TimeSynchronizer). I can sync all the other topics. Any idea why?

3. /robot0/point_cloud2 has timestamps of 0 for all messages, like this:

header:
  stamp:
    sec: 0
    nanosec: 0

(perhaps this is why no hz can be computed).

Note: I am using RMW_IMPLEMENTATION=rmw_cyclonedds_cpp as it solved some issues I had (the default dds did not work across different user accounts).

[abizovnuralem]

What Wifi version are you using? Do you ping it while using the dog? What is the average delay in your network? (in ms)

[richard98hess444]

Hi @delenius , I was also facing the same problem, and here's how I fixed it.

Some general information:

• Ubuntu 22.04
• ROS2 Humble
• Isaac Sim 4.1.0
• Situation: running ./run_sim.sh with --robot_amount 1 under the root of go2_omniverse. While echoing the /robot0/point_cloud2 topic, stamp is always 0.

The reason is that ROS_Clock is not set in ./run_sim.sh file, or more precisely, not in the omniverse_sim.py file if we dig into the run_sim.sh file. This webpage from Omniverse shows how to add a ROS_Clock in it. So here are some steps that we have to do.

First, open omnigraph.py in your go2_omniverse workspace and add the following code right under the create_front_cam_omnigraph function. Note that there are some small modifications comparing to omniverse webpage.

def create_ros2_clock():
    graph_path = f"/ROS_Clock"
    og.Controller.edit(
        {"graph_path": graph_path, 
         "evaluator_name": "execution",
         "pipeline_stage": og.GraphPipelineStage.GRAPH_PIPELINE_STAGE_SIMULATION,},
        {
            og.Controller.Keys.CREATE_NODES: [
                ("ReadSimTime", "omni.isaac.core_nodes.IsaacReadSimulationTime"),
                ("Context", "omni.isaac.ros2_bridge.ROS2Context"),
                ("PublishClock", "omni.isaac.ros2_bridge.ROS2PublishClock"),
                ("OnPlaybackTick", "omni.graph.action.OnPlaybackTick"),
            ],
            og.Controller.Keys.CONNECT: [
                ("OnPlaybackTick.outputs:tick", "PublishClock.inputs:execIn"),
                ("ReadSimTime.outputs:simulationTime", "PublishClock.inputs:timeStamp"),
                ("Context.outputs:context", "PublishClock.inputs:context"),
            ],
            og.Controller.Keys.SET_VALUES: [
                ("PublishClock.inputs:topicName", "/clock"),
                ("Context.inputs:domain_id", 1),
            ],
        },
    )

Second, go back to omniverse_sim.py. Find the line that writes from omnigraph import create_front_cam_omnigraph. Import our create_ros2_clock, namely:

from omnigraph import create_front_cam_omnigraph, create_ros2_clock

and add create_ros2_clock() under create_front_cam_omnigraph(i) in the run_sim function.
If we run ./run_sim.sh now, the ROS_Clock action graph can be seen at the stage, which is at the top left of the Isaac Sim window. A /clock topic also appears if you run topic list. However, if you run ros2 topic echo /robot0/point_cloud2, the time stamp is still 0. This is due to RobotBaseNode.

Third, open ros2.py in go2_omniverse workspace and find the RobotBaseNode class. Go to publish_lidar and we see that no time stamp is written (while stamp is defined in imu and odom). Simple add the code

point_cloud.header.stamp = self.get_clock().now().to_msg()

under point_cloud.header = Header(frame_id="odom"). Now the Isaac Sim should publish all the sensor data with time stamp. Hope it works to you!

[abizovnuralem]

Hello @richard98hess444 ! Thanks for your contribution! Could you let me know how you ran this repo on 4.1? In my case, I face freezing and time in simulation is very slow.

[richard98hess444]

Hi @abizovnuralem !
Besides the pre-requirements, I simply followed your instructions and everything was fine. I commanded out some lines like parser.add_argument("--cpu", action="store_true", default=False, help="Use CPU pipeline.") and setup_custom_env() in omniverse_sim.py whenever I met build errors. Isaac Sim is slow especially I load my own map, but still acceptable. It works on my two laptops with RTX3070 and 2060, both using Isaac Sim 4.1.0.

[abizovnuralem]

He @richard98hess444 ! Currently, this repo only supports 4.0 version, if you use 4.1 it will be laggy and slow. This is a known issue with 4.1, your laptop is powerful enough to do real-time. refer to #26 #30

[abizovnuralem]

Just updated the repo and fixed the speed issue.