Rerun

Loading URDF models

Rerun features a built-in data-loader for URDF files.

A robot model loaded from an URDF file visualized in Rerun.

Overview overview

Using a URDF in Rerun only requires you to load the file with the logging API. This will automatically invoke the data-loader, which will take care of:

  • resolving paths to meshes
  • loading meshes and shapes as Rerun entities
  • loading the joint transforms and associated frame IDs of links

Once that is done, the joints can be updated by sending Transform3Ds, where you have to set the parent_frame and child_frame fields explicitly to each joint's specific frame IDs.

⚠️ Note: previous versions required you to send transforms with implicit frame IDs, i.e. having to send each joint transform on a specific entity path. This was dropped in favor of explicitly-named frame IDs, which is more in line with ROS and allows you to send all transform updates on one entity (e.g. a transforms entity like in the example below).

Example example

Here is an example that demonstrates how to load and update a URDF with the Python SDK:

from pathlib import Path

import rerun as rr

rr.init("urdf_example", spawn=True)

# `log_file_from_path` automatically uses the built-in URDF data-loader.
urdf_path = Path("/path/to/robot.urdf")
rr.log_file_from_path(urdf_path, static=True)

# Later, in your logging code, you'll update the joints using transforms.
# A minimal example for updating a revolute joint that connects two links:
joint_axis = [0, 1, 0]  # comes from URDF
joint_angle = 1.216     # radians
rotation = rr.RotationAxisAngle(axis=joint_axis, angle=joint_angle)
# Make sure that `parent_frame` and `child_frame` match the joint's frame IDs in the URDF file.
rr.log(
  "transforms",
  rr.Transform3D(
    rotation=rotation,
    parent_frame="link_1",
    child_frame="link_2"
  )
)

For similar code in Rust, we have a full example here.

References references

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