There always some problems when using mirrored UV on assets. I know it is tangent bi-normal problem and try to fix it. Even though I adjust tangents in XSI, it seems Unreal doesn’t import them correctly or is there any other way I should be aware of? FYI I enable import tangents and bi-normals in import settings without any luck.
Unreal preview:
Before tangent editing
After tangent editing
