Hey guys,

I’ve got some problems with the fbx sdk when importing scenes with different coordinate systems. For example Maya uses a righthanded and Max a lefthanded coordinate system. If I export the same scene from both packages as fbx with y-up I expected the exported fbxs to be almost the same. For the transformations this is true since they are converted by the exporter. But what about the vertices and normals and stuff like that? In Max a vertex with position (0,0,1) is exported as (0,0,1) although I defined Y to be the up axis (in my opinion this should be exported as (0,1,0)). Is this the common way of exporting scenes in Max as fbx? I think it doesn’t make sense to double check the coordinate system in my app since the scene should be converted already.
Any suggestions?

Thanks in advance.

Hi, DP007, we got an FAQ now and it happens to be able to answer your question :)

2.2 Why doesn’t ConvertScene() modify any vertices?
The ConvertScene() functions do not change vertex values. But simply apply a rotation/scale to imitate Axis or unit conversion.
There are 2 ConvertScene() functions.
KFbxAxisSystem::ConvertScene() acts on the node transforms (pre-rotation) and animations.
KFbxSystemUnit::ConvertScene() acts on the node transforms (scale) and animations.
Of course, if the scene is already in the required axis system or required unit system, ConvertScene() does not change anything. For example:
- If the scene is already in the MayaZUp axis system, the code
KFbxAxisSystem::MayaZUp.ConvertScene(scene);
will not change anything.
- If the scene units is already centimeters, the code
KFbxSystemUnit::cm.ConvertScene(scene);
will not change anything.

BTW: both May and Max are right-handed, just Maya is Y-up, Max is Z-up.

Jiayang Xu
Maya Data Platform
Autodesk