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====== FBX Importing ======

Importing FBX files in Unity with the correct scale, rotation, and axis is fraught.

===== Scaling =====

FBX is in cm by default, but can support other units. Other unit scales are achieved in FBX by by setting ''GlobalSettings->Properties70->UnitScaleFactor'' property in the fbx. For example, a 1 meter cube in 'meters' should be stored in an fbx file like:
<code yaml>
GlobalSettings:
  Properties70:
    UnitScaleFactor = (100.0)   # The 'unit' is 100 * 1cm 
CubeObject:
  Lcl Scaling = (1,1,1)
</code>

This file will show up in Unity's importer as '1m (File)'.

++++ Instructions for Blender

In order to achieve the above scaling (scale of 1 on objects, UnitScaleFactor=100), in the export settings set one of the following for ''Transform->Apply Scaling'':
  * FBX Units Scale
  * FBX All

++++

===== Rotation =====

In the FBX file format, global axis alignment is stored in the GlobalSettings:
  * UpAxis: 0,0,1 (+Z)
  * FrontAxis: 0,1,0 (+Y)
  * CoordAxis: -1,0,0 (-X)
  * OriginalUpAxis: ??? <sup>[//[[:wiki:tag:research-needed|research needed]]//]</sup>

Unity uses these properties to determine the coordinate system for the file. On import, the asset will be rotated to convert it from the file-coordinate system, to the Unity coordinate system. __As of 2020.1, when "Bake Axis Conversion" is checked, these rotations will be baked into the meshes, rather than applied in the transforms.__

++++ Instructions for Blender ~2.92 |
In Blender 2.92, the export behavior changed slightly, so we can simply:
  * Axis must be set as -Y Forward, and Z Up. ((Blender coordinates))
  * "Use Space Transform" **must** be off. ((This feature was, [[https://forum.unity.com/threads/bake-axis-conversion-defaults-to-models-looking-backwards.910298/|interestingly]], built to help export to Unity properly. However, this actually adds a root rotation to the file, which can confuse other tools))
  * In Unity, select: "Bake Axis Conversion"
{{ :blender_6pdtp5vutg.png }}
{{ :unity_4iszlno6j5.png }}
++++
++++ Instructions for Blender ~2.83 |
In Blender 2.83:
  * Select "!Experimental! Apply Transforms". 
  * Axis must be set as -Z Forward, and Y Up.
  * In Unity, "Bake Axis Conversion" must be **off**.
{{ :blender_5lcugkdlz1.png }}
{{ :unity_4iszlno6j5.png }}

//Note: If your object does not support Apply Transforms, you should either [[https://www.immersivelimit.com/tutorials/blender-to-unity-export-correct-scale-rotation|counter-rotate]] the object, or upgrade to Blender >2.92.//
++++

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