urlab_bridge

Python middleware for Unreal Robotics Lab (URLab) -- connects neural-network policies to MuJoCo-in-Unreal simulations over ZeroMQ.

Run pretrained locomotion policies, visualize joint states and camera streams, or bridge everything to ROS 2 -- all from a single Python package.

Installation

# Recommended (uv)
cd urlab_bridge
uv sync                          # core deps (ZMQ, NumPy, OpenCV, DearPyGui)

# To run policies (optional):
uv sync --extra policy            # + PyTorch, ONNX, etc.
uv pip install -e ./RoboJuDo     # policy framework (bundled submodule)

The dashboard (joints, sensors, cameras, actuator control) works without the policy extras. RoboJuDo is only needed if you want to run neural-network policies.

Requires Python 3.11+.

Quick Start

# Launch the dashboard (joint/sensor/camera viewer, actuator control, optional policy runner)
uv run src/run.py --ui

# Run a specific policy headless
uv run src/run.py --policy unitree_12dof --prefix g1

# Test ZMQ connection
uv run src/run.py --test --prefix g1

Available Policies

Key	Robot	DOF	Description	Requires PHC
unitree_12dof	G1	12	Basic walking -- WASD twist control
unitree_wo_gait	G1	29	Full body walking without gait clock
smooth	G1	29	Smoother walking policy
beyondmimic_dance	G1	29	Motion imitation -- dance	Y
h2h	G1	21	Human motion retargeting	Y
amo	G1	29	Adaptive motion optimization	Y
twist_tracker	G1	12	Motion tracker with twist	Y
go2_wtw	Go2	12	Walk-These-Ways rough-terrain locomotion

Policies marked PHC require the PHC submodule installed inside RoboJuDo.

ZMQ Protocol

URLab publishes binary-packed data over ZeroMQ PUB/SUB sockets. All topics are prefixed with the articulation name (e.g. g1/).

Topic Pattern	Direction	Payload Format
{prefix}/joint/{id}	Unreal -> Python	<Ifff (ID, pos, vel, acc)
{prefix}/sensor/{name}	Unreal -> Python	<I ID + <I dim + f*N floats
{prefix}/camera/{name}	Unreal -> Python	Raw BGRA bytes (dedicated socket)
{prefix}/control	Python -> Unreal	<I count + (<If)*N (ID, value) pairs

• State socket (default tcp://127.0.0.1:5555): joints + sensors at up to 1000 Hz.
• Control socket (default tcp://127.0.0.1:5556): policy sends target positions.
• Camera socket (default tcp://127.0.0.1:5558): high-bandwidth image stream on a separate socket.

ROS 2 Bridge

ros2_broadcaster.py republishes ZMQ streams as standard ROS 2 topics (JointState, Image, Float64MultiArray). Requires a sourced ROS 2 workspace (Humble/Jazzy).

source /opt/ros/humble/setup.bash
uv run src/ros2_broadcaster.py

License

Apache 2.0 -- see LICENSE.

Copyright 2026 Jonathan Embley-Riches.

Related

This package is the Python companion to Unreal Robotics Lab, an Unreal Engine plugin embedding MuJoCo physics for sim-to-real robotics research.