UE5 MaterialMerge and Optimize provides wrong bone weights, Remesh creates wrong Opacity Mask

both the current and the previous versions on UE5 InstaLOD plugins provide wrong results for skeletal meshes, thus the animations are very distorted in an unusable way:


after material merge:

after optimize:

Remesh does the job if “Fuzzy Face Count Target” is set to Highest, but when the material has Opacity Mask, its texture conversion is bad, the mask texture quality results in no masked out pixels:



after tweaking brightness/contrast of mask texture, some area is still opaque:

I would be happy if Material Merge would not do any mesh processing.
As a comparison, with the built-in UE5 or with Simplygons mesh reduction, the resulting LODs are fine for the same skeletal mesh.

I think that might be a recent regression as many studios use InstaLOD for characters. UE often changes APIs so it’s tricky to catch up quickly for the team.

I’ll report this internally as a critical issue, thanks for bringing it up!