Armature and bone transformations cancel each other out

[emeiri]

Hi,

I created a very simple model in Blender of a box with a single bone in it, exported it to FBX and loaded with Assimp (Ubuntu package 5.0.1~ds0-1build1). The bone hierarchy is as follows:

Node name: RootNode num children 4 num meshes 0
Node transformation:
1.000000 0.000000 0.000000 0.000000
0.000000 1.000000 0.000000 0.000000
0.000000 0.000000 1.000000 0.000000
0.000000 0.000000 0.000000 1.000000

--- 0 ---
Node name: Cube num children 0 num meshes 1
Node transformation:
-1.000000 -0.000000 -0.000000 0.000000
-0.000000 0.000000 1.000000 0.000000
0.000000 1.000000 -0.000000 0.000000
0.000000 0.000000 0.000000 1.000000

--- 1 ---
Node name: Light num children 0 num meshes 0
Node transformation:
0.290865 -0.566393 -0.771101 -4.076245
-0.055189 0.794672 -0.604525 5.903862
0.955171 0.218391 0.199883 1.005454
0.000000 0.000000 0.000000 1.000000

--- 2 ---
Node name: Camera num children 0 num meshes 0
Node transformation:
0.651558 0.324014 -0.685921 -7.358891
-0.445271 0.895396 0.000000 4.958309
0.614170 0.305421 0.727676 -6.925791
0.000000 0.000000 0.000000 1.000000

--- 3 ---
Node name: Armature num children 1 num meshes 0
Node transformation:
-1.000000 -0.000000 -0.000000 0.000000
-0.000000 0.000000 1.000000 0.000000
0.000000 1.000000 -0.000000 0.000000
0.000000 0.000000 0.000000 1.000000

    --- 0 ---
    Node name: Bone num children 1 num meshes 0
    Node transformation:
    1.000000 0.000000 0.000000 0.000000
    0.000000 -0.000000 -1.000000 0.000000
    0.000000 1.000000 -0.000000 0.000000
    0.000000 0.000000 0.000000 1.000000

        --- 0 ---
        Node name: Bone_end num children 0 num meshes 0
        Node transformation:
        1.000000 0.000000 0.000000 0.000000
        0.000000 1.000000 0.000000 1.000000
        0.000000 0.000000 1.000000 0.000000
        0.000000 0.000000 0.000000 1.000000

Looks like the transformations of 'Bone' and 'Armature' cancel each other out. Could you please explain why is that?

Thanks,

Etay