@myasga @LegionGamingDev The optimization uses built-in UE method which is SLOW - MaskedMaterialToNanite/README.md at master · krojew/MaskedMaterialToNanite · GitHub talks about this issue. With big meshes and large tessellation levels the triangle count can reach many millions. In such cases, it’s better to use something that’s faster than UE for mesh optimization, e.g. Blender. Unfortunately, that’s how the engine does it at the moment and there’s nothing we can do 