Hey guys,

I got some issues with the vertex order when importing polygonal meshes via fbx sdk. In my simple example I just created 2 planes in Maya and scaled one plane in x-direction by -1. After that I froze the transformation of the meshes so that the scaling of both is set to (1,1,1). Now if I try to export the scene as fbx and import it in my application the vertex order of the first plane is correct (CCW) while the vertex order of the negatively scaled plane is incorrect. How can this be? Shouldn’t all triangles in a scene have the same vertex order (especially if i freeze transformation on negatively scaled meshes)?
Do I have to manually check the vertex order (can’t imagine that) or is there an option to assure correct vertex order for all triangles contained in a fbx scene?

Thanks in advance.

So the fbx sdk should handle this for me? Or do I have to manually consider the winding order an rearrange the triangle vertices accordingly?

Ok, but as I said I freeze transformation before exporting to fbx, thus the scale is positive. So how do I check for correct winding in that case?

For both meshes I somehow got a rotation pivot and a scaling pivot of (-6.85, 0, -0.22). When running the ImportScene sample from the sdk with that file, the info log for the first plane (which wasn’t negatively scaled) also contains two pivot information, two transformation propagation and two geometric transformation sections. I don’t exactly know how to interpret this. Any suggestions?

I included the ascii version of the fbx file in the zip. Maybe you could have a look on it. That would be very nice.

	Attachment
windingordersample.zip

Hi DP007,

In Maya, when you freeze transforms, you get this warning:
// Warning: Freeze transform with negative scale will set the ‘opposite’ attribute for these nodes: pPlaneShape2
It is at this point that the vertex order is modified, in order to freeze the -1 scaling transform.

When the scene is exported to FBX, the FBX exporter simply prints out vertices in the order that Maya saved them.

Maybe if you check option “Normals”, when freezing transforms, that could solve your problem? The vertex order would still be modified, but the normals would get frozen, too.

Viviane
Maya Data Platform
Autodesk

Viviane Rochon
Maya Data Platform
Autodesk

Thanks for your reply.

I tried freezing with the normal option set. Nothing really changed.

@Rogers: Sure, I could check the surface normal and rearrange the winding order accordingly. But how to do that when storing normals per vertex not per face? Should I average them to get the face normal? I think thats incorrect.