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FBX static mesh import has incorrect tangents

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    FBX static mesh import has incorrect tangents

    I am running into a reproducible issue where setting the "Import Tangents" flag on static mesh import incorrectly imports tangents. Simply, the checkbox functionality is reversed. Checking the box, which has been part of my normal workflow, seems to now generate new tangent data. Un-checking the box imports the same tangents and binormals that I see in Maya.

    I've tested with FBX vers 2013.1 and 2013.3 also with the July and November UDK builds. Workflow goes like this:

    Maya -> FBX export with "Smoothing Groups" and "Tangents and Binormals" options set -> Static Mesh import with "Import Tangents" and "Explicit Normals" checked

    That workflow in my test case (simple mirrored geometry across the X axis) gives me correct normals and tangents, but reversed binormals.

    Same workflow leaving "Explicit Normals" gives me correct binormals.

    I have tested with FBX 2012 as well, noting your compatibility as stated on UDN.