Okay, to cut a long story short: The Bone Rotation issue has all to do with the Fact that 3DSMax/Maya and Blender use different Coordinate Settings.
Blender’s Coord Settings are Z Up, -Y Foward.
I don’t know what 3DSmax / Maya’s Coordinate Settings are. But the point is is that the FFBX Exporter is interpreting Blenders Coords as if they are they same as 3DS and Mayas which they are not, I presume end result = Rotated Bones.
But actually there are two things to consider here:
- The World Rotation of the Armature
- The Rotation of individual Bones.
But these two factors effect each other.
To cut a long story short again, the Armature Object needs to have a World Rotation of 90o X inside Blender to be imported correctly into UDK.
Once that has been achieved the only thing that really needs to be understood is that Bones in Blender and then UE4 have their X and Y axis switched around.
See these two images:
Here in UE4 the Bone has Y Forward, X Down, Z Out.X and Y have been switched.
So for example if you want your Bone to have Y forward in UE4, set X Forward in Blender.
Knowing that should be sufficient to set all bones up correctly in Blender. it works for me. Sorry I can’t give a more exact explanation. But it works! 