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tracker.py Usage Guide

This project currently provides SteamVR tracking through tracker.py and ViveTrackerModule.

The examples below are aligned with how we uses the tracker pipeline.

Provenance

tracker.py is adapted from the SteamVR_Tracking GitHub repository and then updated locally for this project.

Quick Start

from tracker import ViveTrackerModule

v_tracker = ViveTrackerModule()
v_tracker.print_discovered_objects()

# Typical key names: tracker_1, controller_1, hmd_1, tracking_reference_1
tracker = v_tracker.devices["tracker_1"]

pose_euler = tracker.get_pose_euler()        # [x, y, z, yaw, pitch, roll]
pose_quat = tracker.get_pose_quaternion()    # [x, y, z, qx, qy, qz, qw]
pose_T = tracker.get_T()                     # 4x4 homogeneous transform

Use with the robot control script

We uses the tracker in three phases:

  1. Initialize tracker module and select a device:
v_tracker = ViveTrackerModule()
v_tracker.print_discovered_objects()
tracker = v_tracker.devices["tracker_1"]
  1. Capture baseline state before teleop loop:
tracker_init_state = tracker.get_pose_euler()
init_rotation = tracker.get_pose_quaternion()[3:7]
  1. Read tracker pose continuously in control loop:
position = tracker.get_pose_euler()
rotation = tracker.get_pose_quaternion()[3:7]

Then robot-specific code maps tracker deltas to robot commands (for Franka this is done in control_franka.py).

API Notes

  • ViveTrackerModule():
    • Initializes OpenVR (openvr.init(...)), discovers connected devices, and populates devices.
  • print_discovered_objects():
    • Prints all discovered devices by class.
  • devices:
    • Dictionary of tracked devices keyed by generated names, for example tracker_1.
  • get_pose_euler():
    • Returns [x, y, z, yaw, pitch, roll] if pose is valid; otherwise None.
  • get_pose_quaternion():
    • Returns [x, y, z, qx, qy, qz, qw] if pose is valid; otherwise None.
  • get_T():
    • Returns a 4x4 homogeneous transform matrix as numpy.ndarray.

Important Quaternion Convention

In this repository's track.py, quaternion output order is:

  • qx, qy, qz, qw (with position prepended to make [x, y, z, qx, qy, qz, qw])

If you integrate with code expecting qw, qx, qy, qz, reorder explicitly.

Known Caveats

  • get_pose_euler() currently prints every valid reading to stdout before returning the value.
  • controller_state_to_dict() is a placeholder and does not expose full controller button parsing.
  • Device names like tracker_1 depend on discovery order; use print_discovered_objects() to confirm names.

Minimal Environment For Track-Only Use

Use a clean Python environment and install only the runtime packages needed by tracker.py:

pip install numpy openvr

Quick check (with SteamVR running and tracker powered on):

python -c "from tracker import ViveTrackerModule; v=ViveTrackerModule(); v.print_discovered_objects()"