Hi salvob,
the smoothing in FBX includes two types: by polygon and by edge.

“by Edge” represents the hard/soft edge in Maya. It’s 0/1 flag for each edge:) such as:

LayerElementSmoothing: 0 {
Version: 102
Name: “”
MappingInformationType: “ByEdge”
ReferenceInformationType: “Direct”
Smoothing: *12 {a: 0,0,0,0,1,0,0,0,0,0,0,0}
}

“by polygon” represents the smoothing groups in 3ds Max. It recorded an ID for each face. The ID could be used in 3ds Max and converted to corresponding smoothing group ID. Such as:
LayerElementSmoothing: 0 {
Version: 102
Name: “”
MappingInformationType: “ByPolygon”
ReferenceInformationType: “Direct”
Smoothing: *12 {
a: 2,2,4,4,8,8,16,16,32,32,64,64
}

Thanks Zhihao for your reply,

i need to understand how to catch the smoothing from the nodes, tell me if i am wrong:

KFbxMesh* param_Mesh = (KFbxMesh*) something->GetMesh()

KFbxLayer* param_Layer = param_Mesh-> getLayer()

KFbxLayerElementSmoothing* pLayerSmooth = param_Layer->GetSmoothing()

pLayerSmooth->GetMappingMode()

pLayerSmooth->GetReferenceMode()

pLayerSmooth->GetDirectArray()

so i have the three parameters, but, is it right to say that they are not related with vectors, because in other API (LIGHTWORKS) you need the vectors and the angle limit to define the shadow smoothing.