While a development bug fix is underway, there is a external workaround plugin in order to accommodate stick skeletons exported into Unreal Engine 5.1. This is not a perfect solution, but will offer a way to use a properly scaled skeletal mesh to use in retargeting an animation.
The Live Link Skeletal Mesh Generator is a third-party plugin and is not supported by OptiTrack. More details of this plugin can be found here: Live Link Skeletal Mesh Generator Plugin.
Unreal Engine 5.1
Motive 3.0
Visual Studio 2019+
Install Visual Studio 2019 or higher
During installation, from the Workloads tab make sure to select 'Game Development with C++'
Disable any OptiTrack plugins in UE5.1
From your project navigate to Tools > New C++ Class
Select 'None' from the Add C++ Class window
Name your class (i.e. 'StarterClass')
In order for this to be applied, you'll need to save and close Unreal
Find your project in the file directory you chose to save it in
Open the generated solution file and verify that you can select the green play button from top toolbar
This will open the Unreal Editor, close the Unreal Editor and the solution
Move the Skeletal Mesh Generator Plugin into the Plugins folder of your project files.
Restart the solution/editor and enable: The 'Skeletal Mesh Generator Plugin', 'Geometry script', and 'Skeletal Mesh Modeling tools'.
Re-enabled OptiTrack LiveLink Plugin.
You should now be able to use the Skeletal Mesh Generator Plugin under Plugins > SkeletonGenerator Content > Widgets.
To view the Skeletal Mesh Generator widget, right click on the BLU_SkelmeshFromLiveLink and select Run Editor Utility Widget.
Please note you'll need to bind the mesh to the skeleton in order for your skeletal mesh asset to properly work.
