I’m attempting to diagnose a problem with a game engine model exporter I’ve written for Natural Selection 2. The exporter uses the normals, tangents and bitangents generated in Blender via the mesh.calc_tangents() function – it does not calculate its own tangent vectors. It works flawlessly for dozens of other models I have exported with it, yet for some reason, this newest model is exhibiting some tangent/normal mapping mismatches.
I tried importing the exported file and to my surprise, the problem remained!
I wrote a python script that mimics the effects of what exporting and re-importing the mesh is doing. Super un-optimized, it’s just something I threw together in 5 minutes to see if the issue could be replicated wholly inside blender – it can!
I would appreciate any insight into this problem, it’s very frustrating for me.