import_fbx.py

                for child_bone in connected[1]:
                    if similar_values_iter(par_tail, child_bone.head):
                        child_bone.use_connect = True

        # Create the (edit)bone.
        bone = arm.bl_data.edit_bones.new(name=self.fbx_name)
        bone.select = True
        self.bl_obj = arm.bl_obj
        self.bl_data = arm.bl_data
        self.bl_bone = bone.name  # Could be different from the FBX name!

        # get average distance to children
        bone_size = 0.0
        bone_count = 0
        for child in self.children:
            if child.is_bone:
                bone_size += child.get_bind_matrix().to_translation().magnitude
                bone_count += 1
        if bone_count > 0:
            bone_size /= bone_count
        else:
            bone_size = parent_bone_size

        # So that our bone gets its final length, but still Y-aligned in armature space.
        # 0-length bones are automatically collapsed into their parent when you leave edit mode,
        # so this enforces a minimum length.
        bone_tail = Vector((0.0, 1.0, 0.0)) * max(0.01, bone_size)
        bone.tail = bone_tail

        # And rotate/move it to its final "rest pose".
        bone_matrix = parent_matrix @ self.get_bind_matrix().normalized()

        bone.matrix = bone_matrix

        # Correction for children attached to a bone. FBX expects to attach to the head of a bone,
        # while Blender attaches to the tail.
        self.bone_child_matrix = Matrix.Translation(-bone_tail)

        connect_ctx = [force_connect_children, ...]
        for child in self.children:
            if child.is_leaf and force_connect_children:
                # Arggggggggggggggggg! We do not want to create this bone, but we need its 'virtual head' location
                # to orient current one!!!
                child_head = (bone_matrix @ child.get_bind_matrix().normalized()).translation
                child_connect(bone, None, child_head, connect_ctx)
            elif child.is_bone and not child.ignore:
                child_bone = child.build_skeleton(arm, bone_matrix, bone_size,
                                                  force_connect_children=force_connect_children)
                # Connection to parent.
                child_connect(bone, child_bone, None, connect_ctx)

        child_connect_finalize(bone, connect_ctx)
        return bone

    def build_node_obj(self, fbx_tmpl, settings):
        if self.bl_obj:
            return self.bl_obj

        if self.is_bone or not self.fbx_elem:
            return None

        # create when linking since we need object data
        elem_name_utf8 = self.fbx_name

        # Object data must be created already
        self.bl_obj = obj = bpy.data.objects.new(name=elem_name_utf8, object_data=self.bl_data)

        fbx_props = (elem_find_first(self.fbx_elem, b'Properties70'),
                     elem_find_first(fbx_tmpl, b'Properties70', fbx_elem_nil))

        # ----
        # Misc Attributes

        obj.color[0:3] = elem_props_get_color_rgb(fbx_props, b'Color', (0.8, 0.8, 0.8))
        obj.hide_viewport = not bool(elem_props_get_visibility(fbx_props, b'Visibility', 1.0))

        obj.matrix_basis = self.get_matrix()

        if settings.use_custom_props:
            blen_read_custom_properties(self.fbx_elem, obj, settings)

        return obj

    def build_skeleton_children(self, fbx_tmpl, settings, scene, view_layer):
        if self.is_bone:
            for child in self.children:
                if child.ignore:
                    continue
                child.build_skeleton_children(fbx_tmpl, settings, scene, view_layer)
            return None
        else:
            # child is not a bone
            obj = self.build_node_obj(fbx_tmpl, settings)

            if obj is None:
                return None

            for child in self.children:
                if child.ignore:
                    continue
                child.build_skeleton_children(fbx_tmpl, settings, scene, view_layer)

            # instance in scene
            view_layer.active_layer_collection.collection.objects.link(obj)
            obj.select_set(True)

            return obj

    def link_skeleton_children(self, fbx_tmpl, settings, scene):
        if self.is_bone:
            for child in self.children:
                if child.ignore:
                    continue
                child_obj = child.bl_obj
                if child_obj and child_obj != self.bl_obj:
                    child_obj.parent = self.bl_obj  # get the armature the bone belongs to
                    child_obj.parent_bone = self.bl_bone
                    child_obj.parent_type = 'BONE'
                    child_obj.matrix_parent_inverse = Matrix()

                    # Blender attaches to the end of a bone, while FBX attaches to the start.
                    # bone_child_matrix corrects for that.
                    if child.pre_matrix:
                        child.pre_matrix = self.bone_child_matrix @ child.pre_matrix
                    else:
                        child.pre_matrix = self.bone_child_matrix

                    child_obj.matrix_basis = child.get_matrix()
                child.link_skeleton_children(fbx_tmpl, settings, scene)
            return None
        else:
            obj = self.bl_obj

            for child in self.children:
                if child.ignore:
                    continue
                child_obj = child.link_skeleton_children(fbx_tmpl, settings, scene)
                if child_obj:
                    child_obj.parent = obj

            return obj

    def set_pose_matrix(self, arm):
        pose_bone = arm.bl_obj.pose.bones[self.bl_bone]
        pose_bone.matrix_basis = self.get_bind_matrix().inverted_safe() @ self.get_matrix()

        for child in self.children:
            if child.ignore:
                continue
            if child.is_bone:
                child.set_pose_matrix(arm)

    def merge_weights(self, combined_weights, fbx_cluster):
        indices = elem_prop_first(elem_find_first(fbx_cluster, b'Indexes', default=None), default=())
        weights = elem_prop_first(elem_find_first(fbx_cluster, b'Weights', default=None), default=())

        for index, weight in zip(indices, weights):
            w = combined_weights.get(index)
            if w is None:
                combined_weights[index] = [weight]
            else:
                w.append(weight)

    def set_bone_weights(self):
        ignored_children = tuple(child for child in self.children
                                       if child.is_bone and child.ignore and len(child.clusters) > 0)

        if len(ignored_children) > 0:
            # If we have an ignored child bone we need to merge their weights into the current bone weights.
            # This can happen both intentionally and accidentally when skinning a model. Either way, they
            # need to be moved into a parent bone or they cause animation glitches.
            for fbx_cluster, meshes in self.clusters:
                combined_weights = {}
                self.merge_weights(combined_weights, fbx_cluster)

                for child in ignored_children:
                    for child_cluster, child_meshes in child.clusters:
                        if not meshes.isdisjoint(child_meshes):
                            self.merge_weights(combined_weights, child_cluster)

                # combine child weights
                indices = []
                weights = []
                for i, w in combined_weights.items():
                    indices.append(i)
                    if len(w) > 1:
                        weights.append(sum(w) / len(w))
                    else:
                        weights.append(w[0])

                add_vgroup_to_objects(indices, weights, self.bl_bone, [node.bl_obj for node in meshes])

            # clusters that drive meshes not included in a parent don't need to be merged
            all_meshes = set().union(*[meshes for _, meshes in self.clusters])
            for child in ignored_children:
                for child_cluster, child_meshes in child.clusters:
                    if all_meshes.isdisjoint(child_meshes):
                        indices = elem_prop_first(elem_find_first(child_cluster, b'Indexes', default=None), default=())
                        weights = elem_prop_first(elem_find_first(child_cluster, b'Weights', default=None), default=())
                        add_vgroup_to_objects(indices, weights, self.bl_bone, [node.bl_obj for node in child_meshes])
        else:
            # set the vertex weights on meshes
            for fbx_cluster, meshes in self.clusters:
                indices = elem_prop_first(elem_find_first(fbx_cluster, b'Indexes', default=None), default=())
                weights = elem_prop_first(elem_find_first(fbx_cluster, b'Weights', default=None), default=())
                add_vgroup_to_objects(indices, weights, self.bl_bone, [node.bl_obj for node in meshes])

        for child in self.children:
            if child.is_bone and not child.ignore:
                child.set_bone_weights()

    def build_hierarchy(self, fbx_tmpl, settings, scene, view_layer):
        if self.is_armature:
            # create when linking since we need object data
            elem_name_utf8 = self.fbx_name

            self.bl_data = arm_data = bpy.data.armatures.new(name=elem_name_utf8)

            # Object data must be created already
            self.bl_obj = arm = bpy.data.objects.new(name=elem_name_utf8, object_data=arm_data)

            arm.matrix_basis = self.get_matrix()

            if self.fbx_elem:
                fbx_props = (elem_find_first(self.fbx_elem, b'Properties70'),
                             elem_find_first(fbx_tmpl, b'Properties70', fbx_elem_nil))

                if settings.use_custom_props:
                    blen_read_custom_properties(self.fbx_elem, arm, settings)

            # instance in scene
            view_layer.active_layer_collection.collection.objects.link(arm)
            arm.select_set(True)

            # Add bones:

            # Switch to Edit mode.
            view_layer.objects.active = arm
            is_hidden = arm.hide_viewport
            arm.hide_viewport = False  # Can't switch to Edit mode hidden objects...
            bpy.ops.object.mode_set(mode='EDIT')

            for child in self.children:
                if child.ignore:
                    continue
                if child.is_bone:
                    child.build_skeleton(self, Matrix(), force_connect_children=settings.force_connect_children)

            bpy.ops.object.mode_set(mode='OBJECT')

            arm.hide_viewport = is_hidden

            # Set pose matrix
            for child in self.children:
                if child.ignore:
                    continue
                if child.is_bone:
                    child.set_pose_matrix(self)

            # Add bone children:
            for child in self.children:
                if child.ignore:
                    continue
                child_obj = child.build_skeleton_children(fbx_tmpl, settings, scene, view_layer)

            return arm
        elif self.fbx_elem and not self.is_bone:
            obj = self.build_node_obj(fbx_tmpl, settings)

            # walk through children
            for child in self.children:
                child.build_hierarchy(fbx_tmpl, settings, scene, view_layer)

            # instance in scene
            view_layer.active_layer_collection.collection.objects.link(obj)
            obj.select_set(True)

            return obj
        else:
            for child in self.children:
                child.build_hierarchy(fbx_tmpl, settings, scene, view_layer)

            return None

    def link_hierarchy(self, fbx_tmpl, settings, scene):
        if self.is_armature:
            arm = self.bl_obj

            # Link bone children:
            for child in self.children:
                if child.ignore:
                    continue
                child_obj = child.link_skeleton_children(fbx_tmpl, settings, scene)
                if child_obj:
                    child_obj.parent = arm

            # Add armature modifiers to the meshes
            if self.meshes:
                for mesh in self.meshes:
                    (mmat, amat) = mesh.armature_setup[self]
                    me_obj = mesh.bl_obj

                    # bring global armature & mesh matrices into *Blender* global space.
                    # Note: Usage of matrix_geom (local 'diff' transform) here is quite brittle.
                    #       Among other things, why in hell isn't it taken into account by bindpose & co???
                    #       Probably because org app (max) handles it completely aside from any parenting stuff,
                    #       which we obviously cannot do in Blender. :/
                    if amat is None:
                        amat = self.bind_matrix
                    amat = settings.global_matrix @ (Matrix() if amat is None else amat)
                    if self.matrix_geom:
                        amat = amat @ self.matrix_geom
                    mmat = settings.global_matrix @ mmat
                    if mesh.matrix_geom:
                        mmat = mmat @ mesh.matrix_geom

                    # Now that we have armature and mesh in there (global) bind 'state' (matrix),
                    # we can compute inverse parenting matrix of the mesh.
                    me_obj.matrix_parent_inverse = amat.inverted_safe() @ mmat @ me_obj.matrix_basis.inverted_safe()

                    mod = mesh.bl_obj.modifiers.new(arm.name, 'ARMATURE')
                    mod.object = arm

            # Add bone weights to the deformers
            for child in self.children:
                if child.ignore:
                    continue
                if child.is_bone:
                    child.set_bone_weights()

            return arm
        elif self.bl_obj:
            obj = self.bl_obj

            # walk through children
            for child in self.children:
                child_obj = child.link_hierarchy(fbx_tmpl, settings, scene)
                if child_obj:
                    child_obj.parent = obj

            return obj
        else:
            for child in self.children:
                child.link_hierarchy(fbx_tmpl, settings, scene)

            return None


def load(operator, context, filepath="",
         use_manual_orientation=False,
         axis_forward='-Z',
         axis_up='Y',
         global_scale=1.0,
         bake_space_transform=False,
         use_custom_normals=True,
         use_image_search=False,
         use_alpha_decals=False,
         decal_offset=0.0,
         use_anim=True,
         anim_offset=1.0,
         use_subsurf=False,
         use_custom_props=True,
         use_custom_props_enum_as_string=True,
         ignore_leaf_bones=False,
         force_connect_children=False,
         automatic_bone_orientation=False,
         primary_bone_axis='Y',
         secondary_bone_axis='X',
         use_prepost_rot=True):

    global fbx_elem_nil
    fbx_elem_nil = FBXElem('', (), (), ())

    import os
    import time
    from bpy_extras.io_utils import axis_conversion

    from . import parse_fbx
    from .fbx_utils import RIGHT_HAND_AXES, FBX_FRAMERATES

    start_time_proc = time.process_time()
    start_time_sys = time.time()

    perfmon = PerfMon()
    perfmon.level_up()
    perfmon.step("FBX Import: start importing %s" % filepath)
    perfmon.level_up()

    # Detect ASCII files.

    # Typically it's bad practice to fail silently on any error,
    # however the file may fail to read for many reasons,
    # and this situation is handled later in the code,
    # right now we only want to know if the file successfully reads as ascii.
    try:
        with open(filepath, 'r', encoding="utf-8") as fh:
            fh.read(24)
        is_ascii = True
    except Exception:
        is_ascii = False

    if is_ascii:
        operator.report({'ERROR'}, "ASCII FBX files are not supported %r" % filepath)
        return {'CANCELLED'}
    del is_ascii
    # End ascii detection.

    try:
        elem_root, version = parse_fbx.parse(filepath)
    except Exception as e:
        import traceback
        traceback.print_exc()

        operator.report({'ERROR'}, "Couldn't open file %r (%s)" % (filepath, e))
        return {'CANCELLED'}

    if version < 7100:
        operator.report({'ERROR'}, "Version %r unsupported, must be %r or later" % (version, 7100))
        return {'CANCELLED'}

    print("FBX version: %r" % version)

    if bpy.ops.object.mode_set.poll():
        bpy.ops.object.mode_set(mode='OBJECT', toggle=False)

    # deselect all
    if bpy.ops.object.select_all.poll():
        bpy.ops.object.select_all(action='DESELECT')

    basedir = os.path.dirname(filepath)

    nodal_material_wrap_map = {}
    image_cache = {}

    # Tables: (FBX_byte_id -> [FBX_data, None or Blender_datablock])
    fbx_table_nodes = {}

    if use_alpha_decals:
        material_decals = set()
    else:
        material_decals = None

    scene = context.scene
    view_layer = context.view_layer

    # #### Get some info from GlobalSettings.

    perfmon.step("FBX import: Prepare...")

    fbx_settings = elem_find_first(elem_root, b'GlobalSettings')
    fbx_settings_props = elem_find_first(fbx_settings, b'Properties70')
    if fbx_settings is None or fbx_settings_props is None:
        operator.report({'ERROR'}, "No 'GlobalSettings' found in file %r" % filepath)
        return {'CANCELLED'}

    # FBX default base unit seems to be the centimeter, while raw Blender Unit is equivalent to the meter...
    unit_scale = elem_props_get_number(fbx_settings_props, b'UnitScaleFactor', 1.0)
    unit_scale_org = elem_props_get_number(fbx_settings_props, b'OriginalUnitScaleFactor', 1.0)
    global_scale *= (unit_scale / units_blender_to_fbx_factor(context.scene))
    # Compute global matrix and scale.
    if not use_manual_orientation:
        axis_forward = (elem_props_get_integer(fbx_settings_props, b'FrontAxis', 1),
                        elem_props_get_integer(fbx_settings_props, b'FrontAxisSign', 1))
        axis_up = (elem_props_get_integer(fbx_settings_props, b'UpAxis', 2),
                   elem_props_get_integer(fbx_settings_props, b'UpAxisSign', 1))
        axis_coord = (elem_props_get_integer(fbx_settings_props, b'CoordAxis', 0),
                      elem_props_get_integer(fbx_settings_props, b'CoordAxisSign', 1))
        axis_key = (axis_up, axis_forward, axis_coord)
        axis_up, axis_forward = {v: k for k, v in RIGHT_HAND_AXES.items()}.get(axis_key, ('Z', 'Y'))
    global_matrix = (Matrix.Scale(global_scale, 4) @
                     axis_conversion(from_forward=axis_forward, from_up=axis_up).to_4x4())

    # To cancel out unwanted rotation/scale on nodes.
    global_matrix_inv = global_matrix.inverted()
    # For transforming mesh normals.
    global_matrix_inv_transposed = global_matrix_inv.transposed()

    # Compute bone correction matrix
    bone_correction_matrix = None  # None means no correction/identity
    if not automatic_bone_orientation:
        if (primary_bone_axis, secondary_bone_axis) != ('Y', 'X'):
            bone_correction_matrix = axis_conversion(from_forward='X',
                                                     from_up='Y',
                                                     to_forward=secondary_bone_axis,
                                                     to_up=primary_bone_axis,
                                                     ).to_4x4()

    # Compute framerate settings.
    custom_fps = elem_props_get_number(fbx_settings_props, b'CustomFrameRate', 25.0)
    time_mode = elem_props_get_enum(fbx_settings_props, b'TimeMode')
    real_fps = {eid: val for val, eid in FBX_FRAMERATES[1:]}.get(time_mode, custom_fps)
    if real_fps <= 0.0:
        real_fps = 25.0
    scene.render.fps = round(real_fps)
    scene.render.fps_base = scene.render.fps / real_fps

    # store global settings that need to be accessed during conversion
    settings = FBXImportSettings(
        operator.report, (axis_up, axis_forward), global_matrix, global_scale,
        bake_space_transform, global_matrix_inv, global_matrix_inv_transposed,
        use_custom_normals, use_image_search,
        use_alpha_decals, decal_offset,
        use_anim, anim_offset,
        use_subsurf,
        use_custom_props, use_custom_props_enum_as_string,
        nodal_material_wrap_map, image_cache,
        ignore_leaf_bones, force_connect_children, automatic_bone_orientation, bone_correction_matrix,
        use_prepost_rot,
    )

    # #### And now, the "real" data.

    perfmon.step("FBX import: Templates...")

    fbx_defs = elem_find_first(elem_root, b'Definitions')  # can be None
    fbx_nodes = elem_find_first(elem_root, b'Objects')
    fbx_connections = elem_find_first(elem_root, b'Connections')

    if fbx_nodes is None:
        operator.report({'ERROR'}, "No 'Objects' found in file %r" % filepath)
        return {'CANCELLED'}
    if fbx_connections is None:
        operator.report({'ERROR'}, "No 'Connections' found in file %r" % filepath)
        return {'CANCELLED'}

    # ----
    # First load property templates
    # Load 'PropertyTemplate' values.
    # Key is a tuple, (ObjectType, FBXNodeType)
    # eg, (b'Texture', b'KFbxFileTexture')
    #     (b'Geometry', b'KFbxMesh')
    fbx_templates = {}

    def _():
        if fbx_defs is not None:
            for fbx_def in fbx_defs.elems:
                if fbx_def.id == b'ObjectType':
                    for fbx_subdef in fbx_def.elems:
                        if fbx_subdef.id == b'PropertyTemplate':
                            assert(fbx_def.props_type == b'S')
                            assert(fbx_subdef.props_type == b'S')
                            # (b'Texture', b'KFbxFileTexture') - eg.
                            key = fbx_def.props[0], fbx_subdef.props[0]
                            fbx_templates[key] = fbx_subdef
    _(); del _

    def fbx_template_get(key):
        ret = fbx_templates.get(key, fbx_elem_nil)
        if ret is fbx_elem_nil:
            # Newest FBX (7.4 and above) use no more 'K' in their type names...
            key = (key[0], key[1][1:])
            return fbx_templates.get(key, fbx_elem_nil)
        return ret

    perfmon.step("FBX import: Nodes...")

    # ----
    # Build FBX node-table
    def _():
        for fbx_obj in fbx_nodes.elems:
            # TODO, investigate what other items after first 3 may be
            assert(fbx_obj.props_type[:3] == b'LSS')
            fbx_uuid = elem_uuid(fbx_obj)
            fbx_table_nodes[fbx_uuid] = [fbx_obj, None]
    _(); del _

    # ----
    # Load in the data
    # http://download.autodesk.com/us/fbx/20112/FBX_SDK_HELP/index.html?url=
    #        WS73099cc142f487551fea285e1221e4f9ff8-7fda.htm,topicNumber=d0e6388

    perfmon.step("FBX import: Connections...")

    fbx_connection_map = {}
    fbx_connection_map_reverse = {}

    def _():
        for fbx_link in fbx_connections.elems:
            c_type = fbx_link.props[0]
            if fbx_link.props_type[1:3] == b'LL':
                c_src, c_dst = fbx_link.props[1:3]
                fbx_connection_map.setdefault(c_src, []).append((c_dst, fbx_link))
                fbx_connection_map_reverse.setdefault(c_dst, []).append((c_src, fbx_link))
    _(); del _

    perfmon.step("FBX import: Meshes...")

    # ----
    # Load mesh data
    def _():
        fbx_tmpl = fbx_template_get((b'Geometry', b'KFbxMesh'))

        for fbx_uuid, fbx_item in fbx_table_nodes.items():
            fbx_obj, blen_data = fbx_item
            if fbx_obj.id != b'Geometry':
                continue
            if fbx_obj.props[-1] == b'Mesh':
                assert(blen_data is None)
                fbx_item[1] = blen_read_geom(fbx_tmpl, fbx_obj, settings)
    _(); del _

    perfmon.step("FBX import: Materials & Textures...")

    # ----
    # Load material data
    def _():
        fbx_tmpl = fbx_template_get((b'Material', b'KFbxSurfacePhong'))
        # b'KFbxSurfaceLambert'

        for fbx_uuid, fbx_item in fbx_table_nodes.items():
            fbx_obj, blen_data = fbx_item
            if fbx_obj.id != b'Material':
                continue
            assert(blen_data is None)
            fbx_item[1] = blen_read_material(fbx_tmpl, fbx_obj, settings)
    _(); del _

    # ----
    # Load image & textures data
    def _():
        fbx_tmpl_tex = fbx_template_get((b'Texture', b'KFbxFileTexture'))
        fbx_tmpl_img = fbx_template_get((b'Video', b'KFbxVideo'))

        # Important to run all 'Video' ones first, embedded images are stored in those nodes.
        # XXX Note we simplify things here, assuming both matching Video and Texture will use same file path,
        #     this may be a bit weak, if issue arise we'll fallback to plain connection stuff...
        for fbx_uuid, fbx_item in fbx_table_nodes.items():
            fbx_obj, blen_data = fbx_item
            if fbx_obj.id != b'Video':
                continue
            fbx_item[1] = blen_read_texture_image(fbx_tmpl_img, fbx_obj, basedir, settings)
        for fbx_uuid, fbx_item in fbx_table_nodes.items():
            fbx_obj, blen_data = fbx_item
            if fbx_obj.id != b'Texture':
                continue
            fbx_item[1] = blen_read_texture_image(fbx_tmpl_tex, fbx_obj, basedir, settings)
    _(); del _

    perfmon.step("FBX import: Cameras & Lamps...")

    # ----
    # Load camera data
    def _():
        fbx_tmpl = fbx_template_get((b'NodeAttribute', b'KFbxCamera'))

        for fbx_uuid, fbx_item in fbx_table_nodes.items():
            fbx_obj, blen_data = fbx_item
            if fbx_obj.id != b'NodeAttribute':
                continue
            if fbx_obj.props[-1] == b'Camera':
                assert(blen_data is None)
                fbx_item[1] = blen_read_camera(fbx_tmpl, fbx_obj, global_scale)
    _(); del _

    # ----
    # Load lamp data
    def _():
        fbx_tmpl = fbx_template_get((b'NodeAttribute', b'KFbxLight'))

        for fbx_uuid, fbx_item in fbx_table_nodes.items():
            fbx_obj, blen_data = fbx_item
            if fbx_obj.id != b'NodeAttribute':
                continue
            if fbx_obj.props[-1] == b'Light':
                assert(blen_data is None)
                fbx_item[1] = blen_read_light(fbx_tmpl, fbx_obj, global_scale)
    _(); del _

    # ----
    # Connections
    def connection_filter_ex(fbx_uuid, fbx_id, dct):
        return [(c_found[0], c_found[1], c_type)
                for (c_uuid, c_type) in dct.get(fbx_uuid, ())
                # 0 is used for the root node, which isnt in fbx_table_nodes
                for c_found in (() if c_uuid == 0 else (fbx_table_nodes.get(c_uuid, (None, None)),))
                if (fbx_id is None) or (c_found[0] and c_found[0].id == fbx_id)]

    def connection_filter_forward(fbx_uuid, fbx_id):
        return connection_filter_ex(fbx_uuid, fbx_id, fbx_connection_map)

    def connection_filter_reverse(fbx_uuid, fbx_id):
        return connection_filter_ex(fbx_uuid, fbx_id, fbx_connection_map_reverse)

    perfmon.step("FBX import: Objects & Armatures...")

    # -- temporary helper hierarchy to build armatures and objects from
    # lookup from uuid to helper node. Used to build parent-child relations and later to look up animated nodes.
    fbx_helper_nodes = {}

    def _():
        # We build an intermediate hierarchy used to:
        # - Calculate and store bone orientation correction matrices. The same matrices will be reused for animation.
        # - Find/insert armature nodes.
        # - Filter leaf bones.

        # create scene root
        fbx_helper_nodes[0] = root_helper = FbxImportHelperNode(None, None, None, False)
        root_helper.is_root = True

        # add fbx nodes
        fbx_tmpl = fbx_template_get((b'Model', b'KFbxNode'))
        for a_uuid, a_item in fbx_table_nodes.items():
            fbx_obj, bl_data = a_item
            if fbx_obj is None or fbx_obj.id != b'Model':
                continue

            fbx_props = (elem_find_first(fbx_obj, b'Properties70'),
                         elem_find_first(fbx_tmpl, b'Properties70', fbx_elem_nil))

            transform_data = blen_read_object_transform_preprocess(fbx_props, fbx_obj, Matrix(), use_prepost_rot)
            # Note: 'Root' "bones" are handled as (armature) objects.
            # Note: See T46912 for first FBX file I ever saw with 'Limb' bones - thought those were totally deprecated.
            is_bone = fbx_obj.props[2] in {b'LimbNode', b'Limb'}
            fbx_helper_nodes[a_uuid] = FbxImportHelperNode(fbx_obj, bl_data, transform_data, is_bone)

        # add parent-child relations and add blender data to the node
        for fbx_link in fbx_connections.elems:
            if fbx_link.props[0] != b'OO':
                continue
            if fbx_link.props_type[1:3] == b'LL':
                c_src, c_dst = fbx_link.props[1:3]
                parent = fbx_helper_nodes.get(c_dst)
                if parent is None:
                    continue

                child = fbx_helper_nodes.get(c_src)
                if child is None:
                    # add blender data (meshes, lights, cameras, etc.) to a helper node
                    fbx_sdata, bl_data = p_item = fbx_table_nodes.get(c_src, (None, None))
                    if fbx_sdata is None:
                        continue
                    if fbx_sdata.id not in {b'Geometry', b'NodeAttribute'}:
                        continue
                    parent.bl_data = bl_data
                else:
                    # set parent
                    child.parent = parent

        # find armatures (either an empty below a bone or a new node inserted at the bone
        root_helper.find_armatures()

        # mark nodes that have bone children
        root_helper.find_bone_children()

        # mark nodes that need a bone to attach child-bones to
        root_helper.find_fake_bones()

        # mark leaf nodes that are only required to mark the end of their parent bone
        if settings.ignore_leaf_bones:
            root_helper.mark_leaf_bones()

        # What a mess! Some bones have several BindPoses, some have none, clusters contain a bind pose as well,
        # and you can have several clusters per bone!
        # Maybe some conversion can be applied to put them all into the same frame of reference?

        # get the bind pose from pose elements
        for a_uuid, a_item in fbx_table_nodes.items():
            fbx_obj, bl_data = a_item
            if fbx_obj is None:
                continue
            if fbx_obj.id != b'Pose':
                continue
            if fbx_obj.props[2] != b'BindPose':
                continue
            for fbx_pose_node in fbx_obj.elems:
                if fbx_pose_node.id != b'PoseNode':
                    continue
                node_elem = elem_find_first(fbx_pose_node, b'Node')
                node = elem_uuid(node_elem)
                matrix_elem = elem_find_first(fbx_pose_node, b'Matrix')
                matrix = array_to_matrix4(matrix_elem.props[0]) if matrix_elem else None
                bone = fbx_helper_nodes.get(node)
                if bone and matrix:
                    # Store the matrix in the helper node.
                    # There may be several bind pose matrices for the same node, but in tests they seem to be identical.
                    bone.bind_matrix = matrix  # global space

        # get clusters and bind pose
        for helper_uuid, helper_node in fbx_helper_nodes.items():
            if not helper_node.is_bone:
                continue
            for cluster_uuid, cluster_link in fbx_connection_map.get(helper_uuid, ()):
                if cluster_link.props[0] != b'OO':
                    continue
                fbx_cluster, _ = fbx_table_nodes.get(cluster_uuid, (None, None))
                if fbx_cluster is None or fbx_cluster.id != b'Deformer' or fbx_cluster.props[2] != b'Cluster':
                    continue

                # Get the bind pose from the cluster:
                tx_mesh_elem = elem_find_first(fbx_cluster, b'Transform', default=None)
                tx_mesh = array_to_matrix4(tx_mesh_elem.props[0]) if tx_mesh_elem else Matrix()

                tx_bone_elem = elem_find_first(fbx_cluster, b'TransformLink', default=None)
                tx_bone = array_to_matrix4(tx_bone_elem.props[0]) if tx_bone_elem else None

                tx_arm_elem = elem_find_first(fbx_cluster, b'TransformAssociateModel', default=None)
                tx_arm = array_to_matrix4(tx_arm_elem.props[0]) if tx_arm_elem else None

                mesh_matrix = tx_mesh
                armature_matrix = tx_arm

                if tx_bone:
                    mesh_matrix = tx_bone @ mesh_matrix
                    helper_node.bind_matrix = tx_bone  # overwrite the bind matrix

                # Get the meshes driven by this cluster: (Shouldn't that be only one?)
                meshes = set()
                for skin_uuid, skin_link in fbx_connection_map.get(cluster_uuid):
                    if skin_link.props[0] != b'OO':
                        continue
                    fbx_skin, _ = fbx_table_nodes.get(skin_uuid, (None, None))
                    if fbx_skin is None or fbx_skin.id != b'Deformer' or fbx_skin.props[2] != b'Skin':
                        continue
                    for mesh_uuid, mesh_link in fbx_connection_map.get(skin_uuid):
                        if mesh_link.props[0] != b'OO':
                            continue
                        fbx_mesh, _ = fbx_table_nodes.get(mesh_uuid, (None, None))
                        if fbx_mesh is None or fbx_mesh.id != b'Geometry' or fbx_mesh.props[2] != b'Mesh':
                            continue
                        for object_uuid, object_link in fbx_connection_map.get(mesh_uuid):
                            if object_link.props[0] != b'OO':
                                continue
                            mesh_node = fbx_helper_nodes[object_uuid]
                            if mesh_node:
                                # ----
                                # If we get a valid mesh matrix (in bone space), store armature and
                                # mesh global matrices, we need them to compute mesh's matrix_parent_inverse
                                # when actually binding them via the modifier.
                                # Note we assume all bones were bound with the same mesh/armature (global) matrix,
                                # we do not support otherwise in Blender anyway!
                                mesh_node.armature_setup[helper_node.armature] = (mesh_matrix, armature_matrix)
                                meshes.add(mesh_node)

                helper_node.clusters.append((fbx_cluster, meshes))

        # convert bind poses from global space into local space
        root_helper.make_bind_pose_local()

        # collect armature meshes
        root_helper.collect_armature_meshes()

        # find the correction matrices to align FBX objects with their Blender equivalent
        root_helper.find_correction_matrix(settings)

        # build the Object/Armature/Bone hierarchy
        root_helper.build_hierarchy(fbx_tmpl, settings, scene, view_layer)

        # Link the Object/Armature/Bone hierarchy
        root_helper.link_hierarchy(fbx_tmpl, settings, scene)

        # root_helper.print_info(0)
    _(); del _

    perfmon.step("FBX import: ShapeKeys...")

    # We can handle shapes.
    blend_shape_channels = {}  # We do not need Shapes themselves, but keyblocks, for anim.

    def _():
        fbx_tmpl = fbx_template_get((b'Geometry', b'KFbxShape'))

        for s_uuid, s_item in fbx_table_nodes.items():
            fbx_sdata, bl_sdata = s_item = fbx_table_nodes.get(s_uuid, (None, None))
            if fbx_sdata is None or fbx_sdata.id != b'Geometry' or fbx_sdata.props[2] != b'Shape':
                continue

            # shape -> blendshapechannel -> blendshape -> mesh.
            for bc_uuid, bc_ctype in fbx_connection_map.get(s_uuid, ()):
                if bc_ctype.props[0] != b'OO':
                    continue
                fbx_bcdata, _bl_bcdata = fbx_table_nodes.get(bc_uuid, (None, None))
                if fbx_bcdata is None or fbx_bcdata.id != b'Deformer' or fbx_bcdata.props[2] != b'BlendShapeChannel':
                    continue
                meshes = []
                objects = []
                for bs_uuid, bs_ctype in fbx_connection_map.get(bc_uuid, ()):
                    if bs_ctype.props[0] != b'OO':
                        continue
                    fbx_bsdata, _bl_bsdata = fbx_table_nodes.get(bs_uuid, (None, None))
                    if fbx_bsdata is None or fbx_bsdata.id != b'Deformer' or fbx_bsdata.props[2] != b'BlendShape':
                        continue
                    for m_uuid, m_ctype in fbx_connection_map.get(bs_uuid, ()):
                        if m_ctype.props[0] != b'OO':
                            continue
                        fbx_mdata, bl_mdata = fbx_table_nodes.get(m_uuid, (None, None))
                        if fbx_mdata is None or fbx_mdata.id != b'Geometry' or fbx_mdata.props[2] != b'Mesh':
                            continue
                        # Blenmeshes are assumed already created at that time!
                        assert(isinstance(bl_mdata, bpy.types.Mesh))
                        # And we have to find all objects using this mesh!
                        objects = []
                        for o_uuid, o_ctype in fbx_connection_map.get(m_uuid, ()):
                            if o_ctype.props[0] != b'OO':
                                continue
                            node = fbx_helper_nodes[o_uuid]
                            if node:
                                objects.append(node)
                        meshes.append((bl_mdata, objects))
                    # BlendShape deformers are only here to connect BlendShapeChannels to meshes, nothing else to do.

                # keyblocks is a list of tuples (mesh, keyblock) matching that shape/blendshapechannel, for animation.
                keyblocks = blen_read_shape(fbx_tmpl, fbx_sdata, fbx_bcdata, meshes, scene)
                blend_shape_channels[bc_uuid] = keyblocks
    _(); del _

    if settings.use_subsurf:
        perfmon.step("FBX import: Subdivision surfaces")

        # Look through connections for subsurf in meshes and add it to the parent object
        def _():
            for fbx_link in fbx_connections.elems:
                if fbx_link.props[0] != b'OO':
                    continue
                if fbx_link.props_type[1:3] == b'LL':
                    c_src, c_dst = fbx_link.props[1:3]
                    parent = fbx_helper_nodes.get(c_dst)
                    if parent is None:
                        continue

                    child = fbx_helper_nodes.get(c_src)
                    if child is None:
                        fbx_sdata, bl_data = fbx_table_nodes.get(c_src, (None, None))
                        if fbx_sdata.id != b'Geometry':
                            continue

                        preview_levels = elem_prop_first(elem_find_first(fbx_sdata, b'PreviewDivisionLevels'))
                        render_levels = elem_prop_first(elem_find_first(fbx_sdata, b'RenderDivisionLevels'))
                        if isinstance(preview_levels, int) and isinstance(render_levels, int):
                            mod = parent.bl_obj.modifiers.new('subsurf', 'SUBSURF')
                            mod.levels = preview_levels
                            mod.render_levels = render_levels
                            boundary_rule = elem_prop_first(elem_find_first(fbx_sdata, b'BoundaryRule'), default=1)
                            if boundary_rule == 2:
                                mod.boundary_smooth = "PRESERVE_CORNERS"
                            else:
                                mod.boundary_smooth = "ALL"

        _(); del _

    if use_anim:
        perfmon.step("FBX import: Animations...")

        # Animation!
        def _():
            fbx_tmpl_astack = fbx_template_get((b'AnimationStack', b'FbxAnimStack'))
            fbx_tmpl_alayer = fbx_template_get((b'AnimationLayer', b'FbxAnimLayer'))
            stacks = {}

            # AnimationStacks.
            for as_uuid, fbx_asitem in fbx_table_nodes.items():
                fbx_asdata, _blen_data = fbx_asitem
                if fbx_asdata.id != b'AnimationStack' or fbx_asdata.props[2] != b'':
                    continue
                stacks[as_uuid] = (fbx_asitem, {})

            # AnimationLayers
            # (mixing is completely ignored for now, each layer results in an independent set of actions).
            def get_astacks_from_alayer(al_uuid):
                for as_uuid, as_ctype in fbx_connection_map.get(al_uuid, ()):
                    if as_ctype.props[0] != b'OO':
                        continue
                    fbx_asdata, _bl_asdata = fbx_table_nodes.get(as_uuid, (None, None))
                    if (fbx_asdata is None or fbx_asdata.id != b'AnimationStack' or
                        fbx_asdata.props[2] != b'' or as_uuid not in stacks):
                        continue
                    yield as_uuid
            for al_uuid, fbx_alitem in fbx_table_nodes.items():
                fbx_aldata, _blen_data = fbx_alitem
                if fbx_aldata.id != b'AnimationLayer' or fbx_aldata.props[2] != b'':
                    continue
                for as_uuid in get_astacks_from_alayer(al_uuid):
                    _fbx_asitem, alayers = stacks[as_uuid]
                    alayers[al_uuid] = (fbx_alitem, {})

            # AnimationCurveNodes (also the ones linked to actual animated data!).
            curvenodes = {}
            for acn_uuid, fbx_acnitem in fbx_table_nodes.items():
                fbx_acndata, _blen_data = fbx_acnitem
                if fbx_acndata.id != b'AnimationCurveNode' or fbx_acndata.props[2] != b'':
                    continue
                cnode = curvenodes[acn_uuid] = {}
                items = []
                for n_uuid, n_ctype in fbx_connection_map.get(acn_uuid, ()):
                    if n_ctype.props[0] != b'OP':
                        continue
                    lnk_prop = n_ctype.props[3]
                    if lnk_prop in {b'Lcl Translation', b'Lcl Rotation', b'Lcl Scaling'}:
                        # n_uuid can (????) be linked to root '0' node, instead of a mere object node... See T41712.
                        ob = fbx_helper_nodes.get(n_uuid, None)
                        if ob is None or ob.is_root:
                            continue
                        items.append((ob, lnk_prop))
                    elif lnk_prop == b'DeformPercent':  # Shape keys.
                        keyblocks = blend_shape_channels.get(n_uuid, None)
                        if keyblocks is None:
                            continue
                        items += [(kb, lnk_prop) for kb in keyblocks]
                    elif lnk_prop == b'FocalLength':  # Camera lens.
                        from bpy.types import Camera
                        fbx_item = fbx_table_nodes.get(n_uuid, None)