UE 5.4 backwards compatibility: bundled .uasset files not loading

[1820026296]

UE5.4.4 cannot use UI assets in the plugin, unable to display, unable to run demo

[jonathanembleyriches]

Thanks for reporting this. The plugin was originally developed on UE 5.4 but was upgraded to 5.7 for the open-source release. Unfortunately .uasset files are not backwards compatible between engine versions, so the bundled UI widgets, materials, and input mappings won't load on 5.4.

The C++ code, physics, MJCF import, ZMQ networking, and Blueprint API all compile and run on 5.4. You just won't have the dashboard widget. You can control the simulation through the details panel on the MjManager and articulation actors, or via ZMQ from Python.

If you have UE 5.7 installed alongside 5.4, it is possible to recreate the assets by opening them in 5.7, copying all nodes (Ctrl+A, Ctrl+C), then pasting into a new asset of the same type in your 5.4 project. However we'd strongly recommend just upgrading to 5.7 as we can only test and support that version.

Documented in the Getting Started troubleshooting guide. Also see #7.