When T0 is set as Reference Pose in the import settings, on an asset where faces have been rotated significantly (90 or 180 degrees) from the initial bind pose, the result will be some faces inverting.

Steps to Reproduce

*I've included a link to a Maya file in the description so you do not have to set up from scratch, but here's how the test was created:

  1. In Maya, create a box with a side lid that will flip up 90 degrees and a top lid that will flip over 180 degrees (See attached images)
  2. Bind skeleton at the "lids open" stage
  3. On frame zero, rotate and key side lid 90 degrees and top lid 180 degrees so box is "Closed" (See images for clarification)
  4. Show Face Normals to demonstrate that all are facing outward as expected at this point (See attached image)
  5. Export selection from Maya as FBX
  6. Import selection to UE4, setting T0 as the Reference Pose (See image for exact settings)
  7. Open and inspect Box asset with Show>Advanced>Normals in the Viewport
    RESULT: Some face normals have become reversed
    EXPECTED: Face normals to face the same direction from the program the asset was exported from.

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Won't Fix
Affects Versions4.11
CreatedMar 11, 2016
ResolvedAug 18, 2021
UpdatedAug 18, 2021