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Live-visualize the robot

Two interchangeable viewers ride on /lite/joint_states + /robot_description and render the live kinematic chain. Pick whichever fits your workflow; run two terminals if you want both at once.

rerun_vizviser_viz
ViewerNative rerun window (auto-opens)Browser at http://<host>:8080
Best forLocal desktop; timeline scrubbing; replay-style debuggingHeadless robot machine; share over SSH tunnel; URL-shareable
URDF parserrerun.urdf.UrdfTree (bundled with rerun-sdk)yourdfpy.URDF
Dep sourcererun-sdk (pixi pypi)viser, yourdfpy, scipy (pixi pypi)

Dependencies​

Both viewers' dependencies ship in the pixi env — pixi install already pulled them in. No extra pip install step is needed.

Run from the host (tethered deployment default)​

viz.launch.py is the host-side entrypoint of the two-machine tethered split: it subscribes over DDS to the /lite/joint_states stream real.launch.py publishes from the onboard computer and renders the live pose on the operator workstation.

Inside the workspace env (cd bar_ws && pixi shell):

# Default — viser, browser at http://localhost:8080
ros2 launch bar_bringup_lite viz.launch.py

# Native rerun window instead
ros2 launch bar_bringup_lite viz.launch.py viewer:=rerun

# Multi-robot or non-Lite — override the topic
ros2 launch bar_bringup_lite viz.launch.py joint_state_topic:=/<owner>/joint_states

viewer:= mirrors mjlab's --viewer flag so the same vocabulary moves between training-time and deployment-time scripts. Pick viser for headless / screen-recorded / shareable sessions; pick rerun for local timeline scrubbing on a workstation with a display.

real.launch.py itself does not spawn the viewers — visualisers are host-side by deployment policy. See AGENTS.md §"Deployment topology" for the rationale.

Run standalone (any bringup, single-machine sim/dev)​

For MuJoCo or any single-machine path, start the viewer node directly instead of the launch wrapper. ROS_DOMAIN_ID matching is on you — these talk to whatever's already on the local domain.

ros2 run bar_bringup_lite rerun_viz
ros2 run bar_bringup_lite viser_viz

Both work against any bringup that publishes /robot_description (latched) and /lite/joint_states — silicon, MuJoCo, or mock_components.

Using viser_viz over SSH​

viser serves the viewer on 0.0.0.0:8080 by default — so from any machine with route to the robot:

http://<robot-ip>:8080

When you're remote, an SSH tunnel keeps the port off the LAN:

# On the laptop:
ssh -L 8080:localhost:8080 user@robot
# Now visit http://localhost:8080 in the laptop's browser.

The viewer is read-only — there's no command surface in either tool. For drag-to-command interaction use rqt_joint_trajectory_controller (stock) or mit_slider_gui (project).

Performance notes​

ViewerTypical CPU on a workstation
rerun_viz~5% per core for 14 joints @ 50 Hz; renders on GPU
viser_viz~10% per core; mostly websocket/JSON overhead

Both subscribe /robot_description with TRANSIENT_LOCAL QoS and parse the URDF once at startup; runtime cost is just the per-/lite/joint_states callback + a tf update.

Failure modes​

SymptomCause
Window opens but robot is blank / collapsedMesh package:// URLs not resolving. Make sure bar_description_lite's install is on AMENT_PREFIX_PATH (pixi activation does this automatically once you pixi shell into bar_ws/).
rerun_viz says ModuleNotFoundError: No module named 'rerun'The pixi env wasn't entered — run cd bar_ws && pixi shell first, then ros2 run bar_bringup_lite rerun_viz.
viser_viz complains about a missing scipy symbolStale env. Re-run pixi install to resync against pixi.lock.
Browser at :8080 shows "this site can't be reached"viser_viz not running — start it via ros2 launch bar_bringup_lite viz.launch.py (default viewer is viser), or wrong host in the URL.
Joints visible in ros2 topic echo /lite/joint_states but not moving in viewerTF buffer staleness — restart the viewer; the URDF subscription may have been late to the latched message.

See also​