FBX Tangent Basis Confusion

2 replies [Last post]

March 29, 2012 - 2:35pm

637 reads

Posts: 2

Hi,

In xNormal 3.17.7, is was stated that the new FBX Importer can load the tangent basis from the files which is good for use with the Unity Engine. This is probably a basic question, but I was wondering how this helps with compatibility with Unity. I read in this post by Farfarer that a tangent basis calculator using Unity's normal map calculation method is needed to compute normal maps so they are synced with the normal map baker, which in this case is xNormal.

I think what I'm confused about is that even if xNormal now loads the tangent basis from an FBX file created in 3D app "X" , if it doesn't utilize the same tangent basis as Unity wouldn't the baked normal map from xNormal still not jive with Unity?

Thanks,

-Wes

jogshy

April 3, 2012 - 9:12pm

Posts: 603

Cuz Unitiy's editor can import models as FBX, so it can read and use the tangent basis from those files.

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http://www.xnormal.net

http://santyhammer.blogspot.com

http://www.ratgpu.com

Farfarer

July 5, 2012 - 6:13am

Posts: 15

Unity does import the tangents from the file, but not the binormals (it only uses them to determine the handedness of the binormals it generates at run-time in the shader).

The upshot of which is that your FBX's tangent basis won't match the one that Unity generates from the same data, as the binormals will have changed.

edit: Heh, I've just realised who you are. So you already know this stuff Never mind.

FBX Tangent Basis Confusion

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