import_fbx.py

        _(); del _

    perfmon.step("FBX import: Assign materials...")

    def _():
        # link Material's to Geometry (via Model's)
        for fbx_uuid, fbx_item in fbx_table_nodes.items():
            fbx_obj, blen_data = fbx_item
            if fbx_obj.id != b'Geometry':
                continue

            mesh = fbx_table_nodes.get(fbx_uuid, (None, None))[1]

            # can happen in rare cases
            if mesh is None:
                continue

            # In Blender, we link materials to data, typically (meshes), while in FBX they are linked to objects...
            # So we have to be careful not to re-add endlessly the same material to a mesh!
            # This can easily happen with 'baked' dupliobjects, see T44386.
            # TODO: add an option to link materials to objects in Blender instead?
            done_materials = set()

            for (fbx_lnk, fbx_lnk_item, fbx_lnk_type) in connection_filter_forward(fbx_uuid, b'Model'):
                # link materials
                fbx_lnk_uuid = elem_uuid(fbx_lnk)
                for (fbx_lnk_material, material, fbx_lnk_material_type) in connection_filter_reverse(fbx_lnk_uuid, b'Material'):
                    if material not in done_materials:
                        mesh.materials.append(material)
                        done_materials.add(material)

            # We have to validate mesh polygons' ma_idx, see T41015!
            # Some FBX seem to have an extra 'default' material which is not defined in FBX file.
            if mesh.validate_material_indices():
                print("WARNING: mesh '%s' had invalid material indices, those were reset to first material" % mesh.name)
    _(); del _

    perfmon.step("FBX import: Assign textures...")

    def _():
        material_images = {}

        fbx_tmpl = fbx_template_get((b'Material', b'KFbxSurfacePhong'))
        # b'KFbxSurfaceLambert'

        def texture_mapping_set(fbx_obj, node_texture):
            assert(fbx_obj.id == b'Texture')

            fbx_props = (elem_find_first(fbx_obj, b'Properties70'),
                         elem_find_first(fbx_tmpl, b'Properties70', fbx_elem_nil))
            loc = elem_props_get_vector_3d(fbx_props, b'Translation', (0.0, 0.0, 0.0))
            rot = tuple(-r for r in elem_props_get_vector_3d(fbx_props, b'Rotation', (0.0, 0.0, 0.0)))
            scale = tuple(((1.0 / s) if s != 0.0 else 1.0)
                          for s in elem_props_get_vector_3d(fbx_props, b'Scaling', (1.0, 1.0, 1.0)))
            clamp = (bool(elem_props_get_enum(fbx_props, b'WrapModeU', 0)) or
                     bool(elem_props_get_enum(fbx_props, b'WrapModeV', 0)))

            if (loc == (0.0, 0.0, 0.0) and
                rot == (0.0, 0.0, 0.0) and
                scale == (1.0, 1.0, 1.0) and
                clamp == False):
                return

            node_texture.translation = loc
            node_texture.rotation = rot
            node_texture.scale = scale
            if clamp:
                node_texture.extension = 'EXTEND'

        for fbx_uuid, fbx_item in fbx_table_nodes.items():
            fbx_obj, blen_data = fbx_item
            if fbx_obj.id != b'Material':
                continue

            material = fbx_table_nodes.get(fbx_uuid, (None, None))[1]
            for (fbx_lnk,
                 image,
                 fbx_lnk_type) in connection_filter_reverse(fbx_uuid, b'Texture'):

                if fbx_lnk_type.props[0] == b'OP':
                    lnk_type = fbx_lnk_type.props[3]

                    ma_wrap = nodal_material_wrap_map[material]

                    if lnk_type in {b'DiffuseColor', b'3dsMax|maps|texmap_diffuse'}:
                        ma_wrap.base_color_texture.image = image
                        texture_mapping_set(fbx_lnk, ma_wrap.base_color_texture)
                    elif lnk_type in {b'SpecularColor', b'SpecularFactor'}:
                        # Intensity actually, not color...
                        ma_wrap.specular_texture.image = image
                        texture_mapping_set(fbx_lnk, ma_wrap.specular_texture)
                    elif lnk_type in {b'ReflectionColor', b'ReflectionFactor', b'3dsMax|maps|texmap_reflection'}:
                        # Intensity actually, not color...
                        ma_wrap.metallic_texture.image = image
                        texture_mapping_set(fbx_lnk, ma_wrap.metallic_texture)
                    elif lnk_type in {b'TransparentColor', b'TransparentFactor'}:
                        ma_wrap.alpha_texture.image = image
                        texture_mapping_set(fbx_lnk, ma_wrap.alpha_texture)
                        if use_alpha_decals:
                            material_decals.add(material)
                    elif lnk_type == b'ShininessExponent':
                        # That is probably reversed compared to expected results? TODO...
                        ma_wrap.roughness_texture.image = image
                        texture_mapping_set(fbx_lnk, ma_wrap.roughness_texture)
                    # XXX, applications abuse bump!
                    elif lnk_type in {b'NormalMap', b'Bump', b'3dsMax|maps|texmap_bump'}:
                        ma_wrap.normalmap_texture.image = image
                        texture_mapping_set(fbx_lnk, ma_wrap.normalmap_texture)
                        """
                    elif lnk_type == b'Bump':
                        # TODO displacement...
                        """
                    else:
                        print("WARNING: material link %r ignored" % lnk_type)

                    material_images.setdefault(material, {})[lnk_type] = image

        # Check if the diffuse image has an alpha channel,
        # if so, use the alpha channel.

        # Note: this could be made optional since images may have alpha but be entirely opaque
        for fbx_uuid, fbx_item in fbx_table_nodes.items():
            fbx_obj, blen_data = fbx_item
            if fbx_obj.id != b'Material':
                continue
            material = fbx_table_nodes.get(fbx_uuid, (None, None))[1]
            image = material_images.get(material, {}).get(b'DiffuseColor', None)
            # do we have alpha?
            if image and image.depth == 32:
                if use_alpha_decals:
                    material_decals.add(material)

                ma_wrap = nodal_material_wrap_map[material]
                ma_wrap.alpha_texture.use_alpha = True
                ma_wrap.alpha_texture.copy_from(ma_wrap.base_color_texture)

            # Propagate mapping from diffuse to all other channels which have none defined.
            # XXX Commenting for now, I do not really understand the logic here, why should diffuse mapping
            #     be applied to all others if not defined for them???
            # ~ ma_wrap = nodal_material_wrap_map[material]
            # ~ ma_wrap.mapping_set_from_diffuse()

    _(); del _

    perfmon.step("FBX import: Cycles z-offset workaround...")

    def _():
        # Annoying workaround for cycles having no z-offset
        if material_decals and use_alpha_decals:
            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':
                    mesh = fbx_item[1]

                    if decal_offset != 0.0:
                        for material in mesh.materials:
                            if material in material_decals:
                                for v in mesh.vertices:
                                    v.co += v.normal * decal_offset
                                break

                    for obj in (obj for obj in bpy.data.objects if obj.data == mesh):
                        obj.cycles_visibility.shadow = False
    _(); del _

    perfmon.level_down()

    perfmon.level_down("Import finished.")
    return {'FINISHED'}