Hello OpenSim testers, We are happy to announce the upcoming release of OpenSim 4.6, and we’re looking for your help with beta testing the software before a wider release. OpenSim 4.6 will include a brand new visualizer with improved visualization quality and media creation tools, several updates to the OpenSim API and Moco, and new Python packaging options. To test the new application: 1. Go to downloads page for the OpenSim project <https://simtk.org/frs/?group_id=91>. 2. Scroll down to the section titled “OpenSim Release Betas”. 3. Download the application installer for your platform (Windows or Mac), and install. 4. If installing on Mac, note that you will need to allow installation in the Privacy & Security settings (i.e., click “Open Anyway” under “Security” for the package when prompted). A detailed list of changes coming with OpenSim 4.6 can be found on the following Confluence page: What’s New in OpenSim 4.6? <https://opensimconfluence.atlassian.net/wiki/spaces/OpenSim/pages/1274118147/Whats+New+in+OpenSim+4.6>. The changes on this page include the addition of PyPI packages to support pip-installation of OpenSim, but they are not currently available for testing. However, these packages will be included in the wider OpenSim 4.6 release. We would greatly appreciate anyone willing to test the new features described above. For those willing to participate, please go to the following Google sheet to provide your name, platform information, and testing feedback: OpenSim 4.6 Beta Testing Tasks <https://docs.google.com/spreadsheets/d/1xBr-TGytDs7Sj8cH1yNabNWwUy2x08bP459sWYQXdZs/edit?gid=9#gid=9>. The sheet contains many predefined testing tasks, but feel free to test your own models, motions, and research workflows too. If you do perform any predefined testing tasks, please try to prioritize tests that others have not covered already. Looking forward to hearing your feedback! Cheers, The OpenSim Team