Fix T42135: FBX Exporter Armature not linked to mesh.

This time, it was exporter that did not support bone parenting of mere objects.

Also fixes a more general bug about parenting - matrix_parent_inverse
was not taken into account at all for child objects!

io_scene_fbx/fbx_utils.py

@@ -881,7 +881,17 @@ class ObjectWrapper(metaclass=MetaObjectWrapper):
 
     def get_parent(self):
         if self._tag == 'OB':
-            return ObjectWrapper(self.bdata.parent)
+            if (self.bdata.parent and self.bdata.parent.type == 'ARMATURE' and
+                self.bdata.parent_type == 'BONE' and self.bdata.parent_bone):
+                # Try to parent to a bone.
+                bo_par = self.bdata.parent.pose.bones.get(self.bdata.parent_bone, None)
+                if (bo_par):
+                    return ObjectWrapper(bo_par, self.bdata.parent)
+                else:  # Fallback to mere object parenting.
+                    return ObjectWrapper(self.bdata.parent)
+            else:
+                # Mere object parenting.
+                return ObjectWrapper(self.bdata.parent)
         elif self._tag == 'DP':
             return ObjectWrapper(self.bdata.parent or self._ref)
         else:  # self._tag == 'BO'
@@ -983,6 +993,14 @@ class ObjectWrapper(metaclass=MetaObjectWrapper):
         elif self.bdata.type == 'CAMERA':
             matrix = matrix * MAT_CONVERT_CAMERA
 
+        if self._tag in {'DP', 'OB'} and parent:
+            # To get *real* local matrix of a child object, we also need to take into account its inverted par mat!
+            matrix = self.bdata.matrix_parent_inverse * matrix
+            if parent._tag == 'BO':
+                # In bone parent case, we get transformation in **bone tip** space (sigh).
+                # Have to bring it back into bone root, which is FBX expected value.
+                matrix = Matrix.Translation((0, (parent.bdata.tail - parent.bdata.head).length, 0)) * matrix
+
         # Our matrix is in local space, time to bring it in its final desired space.
         if parent:
             if is_global:

io_scene_fbx/import_fbx.py

@@ -1288,6 +1288,12 @@ class FbxImportHelperNode:
         if self._parent is not None:
             self._parent.children.append(self)
 
+    def __repr__(self):
+        if self.fbx_elem:
+            return self.fbx_elem.props[1].decode()
+        else:
+            return "None"
+
     def print_info(self, indent=0):
         print(" " * indent + (self.fbx_name if self.fbx_name else "(Null)")
               + ("[root]" if self.is_root else "")
@@ -1636,6 +1642,7 @@ class FbxImportHelperNode:
                         child.pre_matrix = self.bone_child_matrix
 
                     child_obj.matrix_basis = child.get_matrix()
+            return None
         else:
             # child is not a bone
             obj = self.build_node(fbx_tmpl, settings)