When importing a mesh as skeletal mesh and using any of the MikkTSpace or option to "Import Normals and Tangents" will cause the normals to import incorrectly. If using the Compute Normals or Import Normals option and setting it to "Built in" rather than MikkTSpace the normals will calculate correctly for the skeletal mesh.

Example asset attached, simple box mesh.

Image comparison of Static Mesh vs Skeletal Mesh import of same mesh. Static Mesh on the Left and Skeletal Mesh on the right.

Tested in:
4.11 Preview 1 CL- 2810555
4.11 releases CL-2824708
4.12 - Dev-Rendering CL-2824562

Steps to Reproduce

1. Open UE4
2. Import any mesh asset as Skeletal Mesh (box mesh attached to this report)
3. In the import options use any fo the "Normal Import Methods" with MikkTSpace set

Regression: Yes

Results: When using the MikkTSpace Normal Generation Method or Import Normals and Tangents will result in incorrect normals

Expected: Normals should look correct based on the mesh

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Cannot Reproduce
ComponentUE - Graphics Features
Affects Versions4.114.12
Target Fix4.11
Fix Commit2871852
Main Commit2873884
CreatedJan 12, 2016
ResolvedApr 11, 2016
UpdatedMay 2, 2018
View Jira Issue