[FBX] Imported Null Sockets Transforms are not Converted to Unreal Axis Orientation

When importing Meshes through FBX, Unreal correctly convert the transforms to its axis orientation. It is not the case for Nulls.

For example, from Houdini to Unreal, a Y translation in Houdini should be converted to a Z translation in Unreal. This is the case for imported Meshes, but not for imported Null (used for Mesh Sockets for instance).

I’ve checked an ASCII FBX and for instance I have this property - among others - for the Mesh:
P: “Lcl Translation”, “Lcl Translation”, “”, “A”,0,25,0

and this one for the Null:
P: “Lcl Translation”, “Lcl Translation”, “”, “A”,0,100,0

In Unreal, the Mesh is correctly translated to Z:25 but the Null has Y:100 which is wrong as it should be its Z as well.

Using Unreal 4.13.2 and FBX 2014.

Hi grabiller,

I was unable to reproduce your issue by using other software, and there may be a possibility that I will be unable to test in Houdini.

Is it possible you could try using a bone instead of a null object that has nothing weighted to it?

Just make sure you have the bone as a child of a bone in your skeleton so the engine doesn’t discard it. Also, make sure that you have " Use T0 as Reference pose" checked.

If that doesn’t work I will see what I can do about testing on Houdini.


Hello Ed,

Perhaps it will be easier for you to reproduce it with the FBX I was talking about UnitCube1m.fbx.

You will see in the ‘Object definitions’ there are FbxNull and FbxMesh objects, with their transforms in the ‘Object properties’ section. They are expressed in the Houdini axis orientation (+x towards right, +y up and +z towards camera back.

Yet only the Mesh transforms are correctly converted to the Unreal axis orientation after import.

Hi grabkiller,

Thank you for submitting a bug report. I logged the issue here with the asset you provided: Unreal Engine Issues and Bug Tracker (UE-38566)

You can track the report’s status as the issue is reviewed by our development staff. Also, be sure to let me know if this report properly addresses the issue.


Ed, Cheers.Guy.