# Psychtoolbox 3.0.20.4 release "Sleight of Hand" 🫶

**URL:** <https://psychtoolbox.discourse.group/t/psychtoolbox-3-0-20-4-release-sleight-of-hand/5670>\
**Category:** Announcements\
**Tags:** release\
**Created:** [March 21, 2025, 7:31am UTC](https://psychtoolbox.discourse.group/t/psychtoolbox-3-0-20-4-release-sleight-of-hand/5670 "2025-03-21T07:31:14Z")\
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**Author:** ![mariokleiner](https://avatars.discourse-cdn.com/v4/letter/m/13edae/32.png) [@mariokleiner](https://psychtoolbox.discourse.group/u/mariokleiner)\
**Post date:** [March 21, 2025, 7:31am UTC](https://psychtoolbox.discourse.group/t/psychtoolbox-3-0-20-4-release-sleight-of-hand/5670/1 "2025-03-21T07:31:14Z")

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Psychtoolbox 3.0.20.4 “Sleight of Hand” 🫶 was released at 21st March 2025.

The complete development history can be found in our GitHub repository.  
The release tag is “3.0.20.4”, with the full tree and commit logs under the URL:

[https://github.com/Psychtoolbox-3/Psychtoolbox-3/tree/3.0.20.4](https://github.com/Psychtoolbox-3/Psychtoolbox-3/tree/3.0.20.4)

[This Psychtoolbox release was sponsored by Mathworks under the year 2024/2025  
contract for significant enhancements, sponsoring the OpenXR hand tracking  
support as major new feature.](https://www.mathworks.com/solutions/neuroscience.html)

### Compatibility changes wrt. Psychtoolbox 3.0.20.3:

- None.

### Highlights:

- OpenXR articulated handtracking and fingertracking support for VR applications.  
Sponsored by Mathworks.

### All:

- We now have OpenXR hand tracking support via our OpenXR driver, utilizing  
the XR\_EXT\_hand\_tracking OpenXR extension! This works on Linux and Windows with any articulated hand tracking device that has suitable runtime support.  
Tested with Monado Mercury computer vision hand tracker and UltraLeap  
Leapmotion v2 vision based hand tracker on Linux Ubuntu 22.04/24.04 and on  
MS-Windows 10, both with Monado and SteamVR, Octave and Matlab.

- PsychLicenseHandling(): Refine auto download and install for LM client libs.

- Various other smaller refinements, bug fixes and documentation updates.

### Linux:

- Psychtoolbox was built and tested against Matlab R2024a and Octave 5.2 and later.

- Our OpenXR VR/AR/MR/XR driver can now use articulated hand trackers to track  
a users hand and finger movements and configuration. Tested with a Ultraleap  
Leapmotion v2 controller under SteamVR and Monado runtimes with a real VR HMD and a simulated HMD, as well as under Monado with Monado’s Open source Mercury hand tracker on a simulated NorthStar HMD and with a Luxonis W-Pro smart camera.

### Windows:

- Psychtoolbox was built and tested against Matlab R2024a and Octave 7.3.

- Screen(): Improve/Fix per-pixel alpha for onscreen window transparency, now also on Matlab, not just Octave!

- Screen(): Whenever GStreamer is used, disallow MMCSS scheduling. This is a  
workaround for a GStreamer bug present since at least GStreamer 1.22. If `Priority(1)` was called in a script before `Screen('OpenMovie')` to enable Realtime scheduling, it would end with a crash during movie playback. See GitHub issue #857 reported by Diederick Niehorster for the background info.

- Our OpenXR VR/AR/MR/XR driver can now use articulated hand trackers to track  
a users hand and finger movements and configuration. Tested with a Ultraleap  
Leapmotion v2 controller under SteamVR runtime with a real VR HMD.

### macOS:

- Psychtoolbox was built and tested against native Matlab R2024a and against native Octave 9.4 from HomeBrew, on macOS 13.7.1 Ventura for Intel Macs, and on macOS 14.5 Sonoma for Apple Silicon Macs.

Enjoy!