export_fbx_bin.py

    scene = scene_data.scene
    animations = []
    animated = set()
    frame_start = 1e100
    frame_end = -1e100

    def add_anim(animations, animated, anim):
        nonlocal frame_start, frame_end
        if anim is not None:
            animations.append(anim)
            f_start, f_end = anim[4:6]
            if f_start < frame_start:
                frame_start = f_start
            if f_end > frame_end:
                frame_end = f_end

            _astack_key, astack, _alayer_key, _name, _fstart, _fend = anim
            for elem_key, (alayer_key, acurvenodes) in astack.items():
                for fbx_prop, (acurvenode_key, acurves, acurvenode_name) in acurvenodes.items():
                    animated.add((elem_key, fbx_prop))

    # Per-NLA strip animstacks.
    if scene_data.settings.bake_anim_use_nla_strips:
        strips = []
        ob_actions = []
        for ob_obj in scene_data.objects:
            # NLA tracks only for objects, not bones!
            if not ob_obj.is_object:
                continue
            ob = ob_obj.bdata  # Back to real Blender Object.
            if not ob.animation_data:
                continue
            # We have to remove active action from objects, it overwrites strips actions otherwise...
            ob_actions.append((ob, ob.animation_data.action))
            ob.animation_data.action = None
            for track in ob.animation_data.nla_tracks:
                if track.mute:
                    continue
                for strip in track.strips:
                    if strip.mute:
                        continue
                    strips.append(strip)
                    strip.mute = True

        for strip in strips:
            strip.mute = False
            add_anim(animations, animated,
                     fbx_animations_do(scene_data, strip, strip.frame_start, strip.frame_end, True, force_keep=True))
            strip.mute = True
            scene.frame_set(scene.frame_current, subframe=0.0)

        for strip in strips:
            strip.mute = False

        for ob, ob_act in ob_actions:
            ob.animation_data.action = ob_act

    # All actions.
    if scene_data.settings.bake_anim_use_all_actions:
        def validate_actions(act, path_resolve):
            for fc in act.fcurves:
                data_path = fc.data_path
                if fc.array_index:
                    data_path = data_path + "[%d]" % fc.array_index
                try:
                    path_resolve(data_path)
                except ValueError:
                    return False  # Invalid.
            return True  # Valid.

        def restore_object(ob_to, ob_from):
            # Restore org state of object (ugh :/ ).
            props = (
                'location', 'rotation_quaternion', 'rotation_axis_angle', 'rotation_euler', 'rotation_mode', 'scale',
                'delta_location', 'delta_rotation_euler', 'delta_rotation_quaternion', 'delta_scale',
                'lock_location', 'lock_rotation', 'lock_rotation_w', 'lock_rotations_4d', 'lock_scale',
                'tag', 'track_axis', 'up_axis', 'active_material', 'active_material_index',
                'matrix_parent_inverse', 'empty_display_type', 'empty_display_size', 'empty_image_offset', 'pass_index',
                'color', 'hide_viewport', 'hide_select', 'hide_render', 'instance_type',
                'use_instance_vertices_rotation', 'use_instance_faces_scale', 'instance_faces_scale',
                'display_type', 'show_bounds', 'display_bounds_type', 'show_name', 'show_axis', 'show_texture_space',
                'show_wire', 'show_all_edges', 'show_transparent', 'show_in_front',
                'show_only_shape_key', 'use_shape_key_edit_mode', 'active_shape_key_index',
            )
            for p in props:
                if not ob_to.is_property_readonly(p):
                    setattr(ob_to, p, getattr(ob_from, p))

        for ob_obj in scene_data.objects:
            # Actions only for objects, not bones!
            if not ob_obj.is_object:
                continue

            ob = ob_obj.bdata  # Back to real Blender Object.

            if not ob.animation_data:
                continue  # Do not export animations for objects that are absolutely not animated, see T44386.

            if ob.animation_data.is_property_readonly('action'):
                continue  # Cannot re-assign 'active action' to this object (usually related to NLA usage, see T48089).

            # We can't play with animdata and actions and get back to org state easily.
            # So we have to add a temp copy of the object to the scene, animate it, and remove it... :/
            ob_copy = ob.copy()
            # Great, have to handle bones as well if needed...
            pbones_matrices = [pbo.matrix_basis.copy() for pbo in ob.pose.bones] if ob.type == 'ARMATURE' else ...

            org_act = ob.animation_data.action
            path_resolve = ob.path_resolve

            for act in bpy.data.actions:
                # For now, *all* paths in the action must be valid for the object, to validate the action.
                # Unless that action was already assigned to the object!
                if act != org_act and not validate_actions(act, path_resolve):
                    continue
                ob.animation_data.action = act
                frame_start, frame_end = act.frame_range  # sic!
                add_anim(animations, animated,
                         fbx_animations_do(scene_data, (ob, act), frame_start, frame_end, True,
                                           objects={ob_obj}, force_keep=True))
                # Ugly! :/
                if pbones_matrices is not ...:
                    for pbo, mat in zip(ob.pose.bones, pbones_matrices):
                        pbo.matrix_basis = mat.copy()
                ob.animation_data.action = org_act
                restore_object(ob, ob_copy)
                scene.frame_set(scene.frame_current, subframe=0.0)

            if pbones_matrices is not ...:
                for pbo, mat in zip(ob.pose.bones, pbones_matrices):
                    pbo.matrix_basis = mat.copy()
            ob.animation_data.action = org_act

            bpy.data.objects.remove(ob_copy)
            scene.frame_set(scene.frame_current, subframe=0.0)

    # Global (containing everything) animstack, only if not exporting NLA strips and/or all actions.
    if not scene_data.settings.bake_anim_use_nla_strips and not scene_data.settings.bake_anim_use_all_actions:
        add_anim(animations, animated, fbx_animations_do(scene_data, None, scene.frame_start, scene.frame_end, False))

    # Be sure to update all matrices back to org state!
    scene.frame_set(scene.frame_current, subframe=0.0)

    return animations, animated, frame_start, frame_end


def fbx_data_from_scene(scene, depsgraph, settings):
    """
    Do some pre-processing over scene's data...
    """
    objtypes = settings.object_types
    dp_objtypes = objtypes - {'ARMATURE'}  # Armatures are not supported as dupli instances currently...
    perfmon = PerfMon()
    perfmon.level_up()

    # ##### Gathering data...

    perfmon.step("FBX export prepare: Wrapping Objects...")

    # This is rather simple for now, maybe we could end generating templates with most-used values
    # instead of default ones?
    objects = {}  # Because we do not have any ordered set...
    for ob in settings.context_objects:
        if ob.type not in objtypes:
            continue
        ob_obj = ObjectWrapper(ob)
        objects[ob_obj] = None
        # Duplis...
        for dp_obj in ob_obj.dupli_list_gen(depsgraph):
            if dp_obj.type not in dp_objtypes:
                continue
            objects[dp_obj] = None

    perfmon.step("FBX export prepare: Wrapping Data (lamps, cameras, empties)...")

    data_lights = {ob_obj.bdata.data: get_blenderID_key(ob_obj.bdata.data)
                   for ob_obj in objects if ob_obj.type == 'LIGHT'}
    # Unfortunately, FBX camera data contains object-level data (like position, orientation, etc.)...
    data_cameras = {ob_obj: get_blenderID_key(ob_obj.bdata.data)
                    for ob_obj in objects if ob_obj.type == 'CAMERA'}
    # Yep! Contains nothing, but needed!
    data_empties = {ob_obj: get_blender_empty_key(ob_obj.bdata)
                    for ob_obj in objects if ob_obj.type == 'EMPTY'}

    perfmon.step("FBX export prepare: Wrapping Meshes...")

    data_meshes = {}
    for ob_obj in objects:
        if ob_obj.type not in BLENDER_OBJECT_TYPES_MESHLIKE:
            continue
        ob = ob_obj.bdata
        use_org_data = True
        org_ob_obj = None

        # Do not want to systematically recreate a new mesh for dupliobject instances, kind of break purpose of those.
        if ob_obj.is_dupli:
            org_ob_obj = ObjectWrapper(ob)  # We get the "real" object wrapper from that dupli instance.
            if org_ob_obj in data_meshes:
                data_meshes[ob_obj] = data_meshes[org_ob_obj]
                continue

        is_ob_material = any(ms.link == 'OBJECT' for ms in ob.material_slots)

        if settings.use_mesh_modifiers or ob.type in BLENDER_OTHER_OBJECT_TYPES or is_ob_material:
            # We cannot use default mesh in that case, or material would not be the right ones...
            use_org_data = not (is_ob_material or ob.type in BLENDER_OTHER_OBJECT_TYPES)
            tmp_mods = []
            if use_org_data and ob.type == 'MESH':
                # No need to create a new mesh in this case, if no modifier is active!
                for mod in ob.modifiers:
                    # For meshes, when armature export is enabled, disable Armature modifiers here!
                    # XXX Temp hacks here since currently we only have access to a viewport depsgraph...
                    if mod.type == 'ARMATURE' and 'ARMATURE' in settings.object_types:
                        tmp_mods.append((mod, mod.show_render, mod.show_viewport))
                        mod.show_render = False
                        mod.show_viewport = False
                    if mod.show_render or mod.show_viewport:
                        use_org_data = False
            if not use_org_data:
                tmp_me = ob.to_mesh(
                    depsgraph,
                    apply_modifiers=settings.use_mesh_modifiers)
                data_meshes[ob_obj] = (get_blenderID_key(tmp_me), tmp_me, True)
            # Re-enable temporary disabled modifiers.
            for mod, show_render, show_viewport in tmp_mods:
                mod.show_render = show_render
                mod.show_viewport = show_viewport
        if use_org_data:
            data_meshes[ob_obj] = (get_blenderID_key(ob.data), ob.data, False)

        # In case "real" source object of that dupli did not yet still existed in data_meshes, create it now!
        if org_ob_obj is not None:
            data_meshes[org_ob_obj] = data_meshes[ob_obj]

    perfmon.step("FBX export prepare: Wrapping ShapeKeys...")

    # ShapeKeys.
    data_deformers_shape = {}
    geom_mat_co = settings.global_matrix if settings.bake_space_transform else None
    for me_key, me, _free in data_meshes.values():
        if not (me.shape_keys and len(me.shape_keys.key_blocks) > 1):  # We do not want basis-only relative skeys...
            continue
        if me in data_deformers_shape:
            continue

        shapes_key = get_blender_mesh_shape_key(me)
        # We gather all vcos first, since some skeys may be based on others...
        _cos = array.array(data_types.ARRAY_FLOAT64, (0.0,)) * len(me.vertices) * 3
        me.vertices.foreach_get("co", _cos)
        v_cos = tuple(vcos_transformed_gen(_cos, geom_mat_co))
        sk_cos = {}
        for shape in me.shape_keys.key_blocks[1:]:
            shape.data.foreach_get("co", _cos)
            sk_cos[shape] = tuple(vcos_transformed_gen(_cos, geom_mat_co))
        sk_base = me.shape_keys.key_blocks[0]

        for shape in me.shape_keys.key_blocks[1:]:
            # Only write vertices really different from org coordinates!
            shape_verts_co = []
            shape_verts_idx = []

            sv_cos = sk_cos[shape]
            ref_cos = v_cos if shape.relative_key == sk_base else sk_cos[shape.relative_key]
            for idx, (sv_co, ref_co) in enumerate(zip(sv_cos, ref_cos)):
                if similar_values_iter(sv_co, ref_co):
                    # Note: Maybe this is a bit too simplistic, should we use real shape base here? Though FBX does not
                    #       have this at all... Anyway, this should cover most common cases imho.
                    continue
                shape_verts_co.extend(Vector(sv_co) - Vector(ref_co))
                shape_verts_idx.append(idx)

            # FBX does not like empty shapes (makes Unity crash e.g.).
            # To prevent this, we add a vertex that does nothing, but it keeps the shape key intact
            if not shape_verts_co:
                shape_verts_co.extend((0, 0, 0))
                shape_verts_idx.append(0)

            channel_key, geom_key = get_blender_mesh_shape_channel_key(me, shape)
            data = (channel_key, geom_key, shape_verts_co, shape_verts_idx)
            data_deformers_shape.setdefault(me, (me_key, shapes_key, {}))[2][shape] = data

    perfmon.step("FBX export prepare: Wrapping Armatures...")

    # Armatures!
    data_deformers_skin = {}
    data_bones = {}
    arm_parents = set()
    for ob_obj in tuple(objects):
        if not (ob_obj.is_object and ob_obj.type in {'ARMATURE'}):
            continue
        fbx_skeleton_from_armature(scene, settings, ob_obj, objects, data_meshes,
                                   data_bones, data_deformers_skin, data_empties, arm_parents)

    # Generate leaf bones
    data_leaf_bones = []
    if settings.add_leaf_bones:
        data_leaf_bones = fbx_generate_leaf_bones(settings, data_bones)

    perfmon.step("FBX export prepare: Wrapping World...")

    # Some world settings are embedded in FBX materials...
    if scene.world:
        data_world = {scene.world: get_blenderID_key(scene.world)}
    else:
        data_world = {}

    perfmon.step("FBX export prepare: Wrapping Materials...")

    # TODO: Check all the material stuff works even when they are linked to Objects
    #       (we can then have the same mesh used with different materials...).
    #       *Should* work, as FBX always links its materials to Models (i.e. objects).
    #       XXX However, material indices would probably break...
    data_materials = {}
    for ob_obj in objects:
        # If obj is not a valid object for materials, wrapper will just return an empty tuple...
        for ma_s in ob_obj.material_slots:
            ma = ma_s.material
            if ma is None:
                continue  # Empty slots!
            # Note theoretically, FBX supports any kind of materials, even GLSL shaders etc.
            # However, I doubt anything else than Lambert/Phong is really portable!
            # Note we want to keep a 'dummy' empty material even when we can't really support it, see T41396.
            ma_data = data_materials.setdefault(ma, (get_blenderID_key(ma), []))
            ma_data[1].append(ob_obj)

    perfmon.step("FBX export prepare: Wrapping Textures...")

    # Note FBX textures also hold their mapping info.
    # TODO: Support layers?
    data_textures = {}
    # FbxVideo also used to store static images...
    data_videos = {}
    # For now, do not use world textures, don't think they can be linked to anything FBX wise...
    for ma in data_materials.keys():
        # Note: with nodal shaders, we'll could be generating much more textures, but that's kind of unavoidable,
        #       given that textures actually do not exist anymore in material context in Blender...
        ma_wrap = node_shader_utils.PrincipledBSDFWrapper(ma, is_readonly=True)
        for sock_name, fbx_name in PRINCIPLED_TEXTURE_SOCKETS_TO_FBX:
            tex = getattr(ma_wrap, sock_name)
            if tex is None or tex.image is None:
                continue
            blender_tex_key = (ma, sock_name)
            data_textures[blender_tex_key] = (get_blender_nodetexture_key(*blender_tex_key), fbx_name)

            img = tex.image
            vid_data = data_videos.setdefault(img, (get_blenderID_key(img), []))
            vid_data[1].append(blender_tex_key)

    perfmon.step("FBX export prepare: Wrapping Animations...")

    # Animation...
    animations = ()
    animated = set()
    frame_start = scene.frame_start
    frame_end = scene.frame_end
    if settings.bake_anim:
        # From objects & bones only for a start.
        # Kind of hack, we need a temp scene_data for object's space handling to bake animations...
        tmp_scdata = FBXExportData(
            None, None, None,
            settings, scene, depsgraph, objects, None, None, 0.0, 0.0,
            data_empties, data_lights, data_cameras, data_meshes, None,
            data_bones, data_leaf_bones, data_deformers_skin, data_deformers_shape,
            data_world, data_materials, data_textures, data_videos,
        )
        animations, animated, frame_start, frame_end = fbx_animations(tmp_scdata)

    # ##### Creation of templates...

    perfmon.step("FBX export prepare: Generating templates...")

    templates = {}
    templates[b"GlobalSettings"] = fbx_template_def_globalsettings(scene, settings, nbr_users=1)

    if data_empties:
        templates[b"Null"] = fbx_template_def_null(scene, settings, nbr_users=len(data_empties))

    if data_lights:
        templates[b"Light"] = fbx_template_def_light(scene, settings, nbr_users=len(data_lights))

    if data_cameras:
        templates[b"Camera"] = fbx_template_def_camera(scene, settings, nbr_users=len(data_cameras))

    if data_bones:
        templates[b"Bone"] = fbx_template_def_bone(scene, settings, nbr_users=len(data_bones))

    if data_meshes:
        nbr = len({me_key for me_key, _me, _free in data_meshes.values()})
        if data_deformers_shape:
            nbr += sum(len(shapes[2]) for shapes in data_deformers_shape.values())
        templates[b"Geometry"] = fbx_template_def_geometry(scene, settings, nbr_users=nbr)

    if objects:
        templates[b"Model"] = fbx_template_def_model(scene, settings, nbr_users=len(objects))

    if arm_parents:
        # Number of Pose|BindPose elements should be the same as number of meshes-parented-to-armatures
        templates[b"BindPose"] = fbx_template_def_pose(scene, settings, nbr_users=len(arm_parents))

    if data_deformers_skin or data_deformers_shape:
        nbr = 0
        if data_deformers_skin:
            nbr += len(data_deformers_skin)
            nbr += sum(len(clusters) for def_me in data_deformers_skin.values() for a, b, clusters in def_me.values())
        if data_deformers_shape:
            nbr += len(data_deformers_shape)
            nbr += sum(len(shapes[2]) for shapes in data_deformers_shape.values())
        assert(nbr != 0)
        templates[b"Deformers"] = fbx_template_def_deformer(scene, settings, nbr_users=nbr)

    # No world support in FBX...
    """
    if data_world:
        templates[b"World"] = fbx_template_def_world(scene, settings, nbr_users=len(data_world))
    """

    if data_materials:
        templates[b"Material"] = fbx_template_def_material(scene, settings, nbr_users=len(data_materials))

    if data_textures:
        templates[b"TextureFile"] = fbx_template_def_texture_file(scene, settings, nbr_users=len(data_textures))

    if data_videos:
        templates[b"Video"] = fbx_template_def_video(scene, settings, nbr_users=len(data_videos))

    if animations:
        nbr_astacks = len(animations)
        nbr_acnodes = 0
        nbr_acurves = 0
        for _astack_key, astack, _al, _n, _fs, _fe in animations:
            for _alayer_key, alayer in astack.values():
                for _acnode_key, acnode, _acnode_name in alayer.values():
                    nbr_acnodes += 1
                    for _acurve_key, _dval, acurve, acurve_valid in acnode.values():
                        if acurve:
                            nbr_acurves += 1

        templates[b"AnimationStack"] = fbx_template_def_animstack(scene, settings, nbr_users=nbr_astacks)
        # Would be nice to have one layer per animated object, but this seems tricky and not that well supported.
        # So for now, only one layer per anim stack.
        templates[b"AnimationLayer"] = fbx_template_def_animlayer(scene, settings, nbr_users=nbr_astacks)
        templates[b"AnimationCurveNode"] = fbx_template_def_animcurvenode(scene, settings, nbr_users=nbr_acnodes)
        templates[b"AnimationCurve"] = fbx_template_def_animcurve(scene, settings, nbr_users=nbr_acurves)

    templates_users = sum(tmpl.nbr_users for tmpl in templates.values())

    # ##### Creation of connections...

    perfmon.step("FBX export prepare: Generating Connections...")

    connections = []

    # Objects (with classical parenting).
    for ob_obj in objects:
        # Bones are handled later.
        if not ob_obj.is_bone:
            par_obj = ob_obj.parent
            # Meshes parented to armature are handled separately, yet we want the 'no parent' connection (0).
            if par_obj and ob_obj.has_valid_parent(objects) and (par_obj, ob_obj) not in arm_parents:
                connections.append((b"OO", ob_obj.fbx_uuid, par_obj.fbx_uuid, None))
            else:
                connections.append((b"OO", ob_obj.fbx_uuid, 0, None))

    # Armature & Bone chains.
    for bo_obj in data_bones.keys():
        par_obj = bo_obj.parent
        if par_obj not in objects:
            continue
        connections.append((b"OO", bo_obj.fbx_uuid, par_obj.fbx_uuid, None))

    # Object data.
    for ob_obj in objects:
        if ob_obj.is_bone:
            bo_data_key = data_bones[ob_obj]
            connections.append((b"OO", get_fbx_uuid_from_key(bo_data_key), ob_obj.fbx_uuid, None))
        else:
            if ob_obj.type == 'LIGHT':
                light_key = data_lights[ob_obj.bdata.data]
                connections.append((b"OO", get_fbx_uuid_from_key(light_key), ob_obj.fbx_uuid, None))
            elif ob_obj.type == 'CAMERA':
                cam_key = data_cameras[ob_obj]
                connections.append((b"OO", get_fbx_uuid_from_key(cam_key), ob_obj.fbx_uuid, None))
            elif ob_obj.type == 'EMPTY' or ob_obj.type == 'ARMATURE':
                empty_key = data_empties[ob_obj]
                connections.append((b"OO", get_fbx_uuid_from_key(empty_key), ob_obj.fbx_uuid, None))
            elif ob_obj.type in BLENDER_OBJECT_TYPES_MESHLIKE:
                mesh_key, _me, _free = data_meshes[ob_obj]
                connections.append((b"OO", get_fbx_uuid_from_key(mesh_key), ob_obj.fbx_uuid, None))

    # Leaf Bones
    for (_node_name, par_uuid, node_uuid, attr_uuid, _matrix, _hide, _size) in data_leaf_bones:
        connections.append((b"OO", node_uuid, par_uuid, None))
        connections.append((b"OO", attr_uuid, node_uuid, None))

    # 'Shape' deformers (shape keys, only for meshes currently)...
    for me_key, shapes_key, shapes in data_deformers_shape.values():
        # shape -> geometry
        connections.append((b"OO", get_fbx_uuid_from_key(shapes_key), get_fbx_uuid_from_key(me_key), None))
        for channel_key, geom_key, _shape_verts_co, _shape_verts_idx in shapes.values():
            # shape channel -> shape
            connections.append((b"OO", get_fbx_uuid_from_key(channel_key), get_fbx_uuid_from_key(shapes_key), None))
            # geometry (keys) -> shape channel
            connections.append((b"OO", get_fbx_uuid_from_key(geom_key), get_fbx_uuid_from_key(channel_key), None))

    # 'Skin' deformers (armature-to-geometry, only for meshes currently)...
    for arm, deformed_meshes in data_deformers_skin.items():
        for me, (skin_key, ob_obj, clusters) in deformed_meshes.items():
            # skin -> geometry
            mesh_key, _me, _free = data_meshes[ob_obj]
            assert(me == _me)
            connections.append((b"OO", get_fbx_uuid_from_key(skin_key), get_fbx_uuid_from_key(mesh_key), None))
            for bo_obj, clstr_key in clusters.items():
                # cluster -> skin
                connections.append((b"OO", get_fbx_uuid_from_key(clstr_key), get_fbx_uuid_from_key(skin_key), None))
                # bone -> cluster
                connections.append((b"OO", bo_obj.fbx_uuid, get_fbx_uuid_from_key(clstr_key), None))

    # Materials
    mesh_material_indices = {}
    _objs_indices = {}
    for ma, (ma_key, ob_objs) in data_materials.items():
        for ob_obj in ob_objs:
            connections.append((b"OO", get_fbx_uuid_from_key(ma_key), ob_obj.fbx_uuid, None))
            # Get index of this material for this object (or dupliobject).
            # Material indices for mesh faces are determined by their order in 'ma to ob' connections.
            # Only materials for meshes currently...
            # Note in case of dupliobjects a same me/ma idx will be generated several times...
            # Should not be an issue in practice, and it's needed in case we export duplis but not the original!
            if ob_obj.type not in BLENDER_OBJECT_TYPES_MESHLIKE:
                continue
            _mesh_key, me, _free = data_meshes[ob_obj]
            idx = _objs_indices[ob_obj] = _objs_indices.get(ob_obj, -1) + 1
            mesh_material_indices.setdefault(me, {})[ma] = idx
    del _objs_indices

    # Textures
    for (ma, sock_name), (tex_key, fbx_prop) in data_textures.items():
        ma_key, _ob_objs = data_materials[ma]
        # texture -> material properties
        connections.append((b"OP", get_fbx_uuid_from_key(tex_key), get_fbx_uuid_from_key(ma_key), fbx_prop))

    # Images
    for vid, (vid_key, blender_tex_keys) in data_videos.items():
        for blender_tex_key in blender_tex_keys:
            tex_key, _fbx_prop = data_textures[blender_tex_key]
            connections.append((b"OO", get_fbx_uuid_from_key(vid_key), get_fbx_uuid_from_key(tex_key), None))

    # Animations
    for astack_key, astack, alayer_key, _name, _fstart, _fend in animations:
        # Animstack itself is linked nowhere!
        astack_id = get_fbx_uuid_from_key(astack_key)
        # For now, only one layer!
        alayer_id = get_fbx_uuid_from_key(alayer_key)
        connections.append((b"OO", alayer_id, astack_id, None))
        for elem_key, (alayer_key, acurvenodes) in astack.items():
            elem_id = get_fbx_uuid_from_key(elem_key)
            # Animlayer -> animstack.
            # alayer_id = get_fbx_uuid_from_key(alayer_key)
            # connections.append((b"OO", alayer_id, astack_id, None))
            for fbx_prop, (acurvenode_key, acurves, acurvenode_name) in acurvenodes.items():
                # Animcurvenode -> animalayer.
                acurvenode_id = get_fbx_uuid_from_key(acurvenode_key)
                connections.append((b"OO", acurvenode_id, alayer_id, None))
                # Animcurvenode -> object property.
                connections.append((b"OP", acurvenode_id, elem_id, fbx_prop.encode()))
                for fbx_item, (acurve_key, default_value, acurve, acurve_valid) in acurves.items():
                    if acurve:
                        # Animcurve -> Animcurvenode.
                        connections.append((b"OP", get_fbx_uuid_from_key(acurve_key), acurvenode_id, fbx_item.encode()))

    perfmon.level_down()

    # ##### And pack all this!

    return FBXExportData(
        templates, templates_users, connections,
        settings, scene, depsgraph, objects, animations, animated, frame_start, frame_end,
        data_empties, data_lights, data_cameras, data_meshes, mesh_material_indices,
        data_bones, data_leaf_bones, data_deformers_skin, data_deformers_shape,
        data_world, data_materials, data_textures, data_videos,
    )


def fbx_scene_data_cleanup(scene_data):
    """
    Some final cleanup...
    """
    # Delete temp meshes.
    done_meshes = set()
    for me_key, me, free in scene_data.data_meshes.values():
        if free and me_key not in done_meshes:
            bpy.data.meshes.remove(me)
            done_meshes.add(me_key)


# ##### Top-level FBX elements generators. #####

def fbx_header_elements(root, scene_data, time=None):
    """
    Write boiling code of FBX root.
    time is expected to be a datetime.datetime object, or None (using now() in this case).
    """
    app_vendor = "Blender Foundation"
    app_name = "Blender (stable FBX IO)"
    app_ver = bpy.app.version_string

    import addon_utils
    import sys
    addon_ver = addon_utils.module_bl_info(sys.modules[__package__])['version']

    # ##### Start of FBXHeaderExtension element.
    header_ext = elem_empty(root, b"FBXHeaderExtension")

    elem_data_single_int32(header_ext, b"FBXHeaderVersion", FBX_HEADER_VERSION)

    elem_data_single_int32(header_ext, b"FBXVersion", FBX_VERSION)

    # No encryption!
    elem_data_single_int32(header_ext, b"EncryptionType", 0)

    if time is None:
        time = datetime.datetime.now()
    elem = elem_empty(header_ext, b"CreationTimeStamp")
    elem_data_single_int32(elem, b"Version", 1000)
    elem_data_single_int32(elem, b"Year", time.year)
    elem_data_single_int32(elem, b"Month", time.month)
    elem_data_single_int32(elem, b"Day", time.day)
    elem_data_single_int32(elem, b"Hour", time.hour)
    elem_data_single_int32(elem, b"Minute", time.minute)
    elem_data_single_int32(elem, b"Second", time.second)
    elem_data_single_int32(elem, b"Millisecond", time.microsecond // 1000)

    elem_data_single_string_unicode(header_ext, b"Creator", "%s - %s - %d.%d.%d"
                                                % (app_name, app_ver, addon_ver[0], addon_ver[1], addon_ver[2]))

    # 'SceneInfo' seems mandatory to get a valid FBX file...
    # TODO use real values!
    # XXX Should we use scene.name.encode() here?
    scene_info = elem_data_single_string(header_ext, b"SceneInfo", fbx_name_class(b"GlobalInfo", b"SceneInfo"))
    scene_info.add_string(b"UserData")
    elem_data_single_string(scene_info, b"Type", b"UserData")
    elem_data_single_int32(scene_info, b"Version", FBX_SCENEINFO_VERSION)
    meta_data = elem_empty(scene_info, b"MetaData")
    elem_data_single_int32(meta_data, b"Version", FBX_SCENEINFO_VERSION)
    elem_data_single_string(meta_data, b"Title", b"")
    elem_data_single_string(meta_data, b"Subject", b"")
    elem_data_single_string(meta_data, b"Author", b"")
    elem_data_single_string(meta_data, b"Keywords", b"")
    elem_data_single_string(meta_data, b"Revision", b"")
    elem_data_single_string(meta_data, b"Comment", b"")

    props = elem_properties(scene_info)
    elem_props_set(props, "p_string_url", b"DocumentUrl", "/foobar.fbx")
    elem_props_set(props, "p_string_url", b"SrcDocumentUrl", "/foobar.fbx")
    original = elem_props_compound(props, b"Original")
    original("p_string", b"ApplicationVendor", app_vendor)
    original("p_string", b"ApplicationName", app_name)
    original("p_string", b"ApplicationVersion", app_ver)
    original("p_datetime", b"DateTime_GMT", "01/01/1970 00:00:00.000")
    original("p_string", b"FileName", "/foobar.fbx")
    lastsaved = elem_props_compound(props, b"LastSaved")
    lastsaved("p_string", b"ApplicationVendor", app_vendor)
    lastsaved("p_string", b"ApplicationName", app_name)
    lastsaved("p_string", b"ApplicationVersion", app_ver)
    lastsaved("p_datetime", b"DateTime_GMT", "01/01/1970 00:00:00.000")

    # ##### End of FBXHeaderExtension element.

    # FileID is replaced by dummy value currently...
    elem_data_single_bytes(root, b"FileId", b"FooBar")

    # CreationTime is replaced by dummy value currently, but anyway...
    elem_data_single_string_unicode(root, b"CreationTime",
                                    "{:04}-{:02}-{:02} {:02}:{:02}:{:02}:{:03}"
                                    "".format(time.year, time.month, time.day, time.hour, time.minute, time.second,
                                              time.microsecond * 1000))

    elem_data_single_string_unicode(root, b"Creator", "%s - %s - %d.%d.%d"
                                          % (app_name, app_ver, addon_ver[0], addon_ver[1], addon_ver[2]))

    # ##### Start of GlobalSettings element.
    global_settings = elem_empty(root, b"GlobalSettings")
    scene = scene_data.scene

    elem_data_single_int32(global_settings, b"Version", 1000)

    props = elem_properties(global_settings)
    up_axis, front_axis, coord_axis = RIGHT_HAND_AXES[scene_data.settings.to_axes]
    #~ # DO NOT take into account global scale here! That setting is applied to object transformations during export
    #~ # (in other words, this is pure blender-exporter feature, and has nothing to do with FBX data).
    #~ if scene_data.settings.apply_unit_scale:
        #~ # Unit scaling is applied to objects' scale, so our unit is effectively FBX one (centimeter).
        #~ scale_factor_org = 1.0
        #~ scale_factor = 1.0 / units_blender_to_fbx_factor(scene)
    #~ else:
        #~ scale_factor_org = units_blender_to_fbx_factor(scene)
        #~ scale_factor = scale_factor_org
    scale_factor = scale_factor_org = scene_data.settings.unit_scale
    elem_props_set(props, "p_integer", b"UpAxis", up_axis[0])
    elem_props_set(props, "p_integer", b"UpAxisSign", up_axis[1])
    elem_props_set(props, "p_integer", b"FrontAxis", front_axis[0])
    elem_props_set(props, "p_integer", b"FrontAxisSign", front_axis[1])
    elem_props_set(props, "p_integer", b"CoordAxis", coord_axis[0])
    elem_props_set(props, "p_integer", b"CoordAxisSign", coord_axis[1])
    elem_props_set(props, "p_integer", b"OriginalUpAxis", -1)
    elem_props_set(props, "p_integer", b"OriginalUpAxisSign", 1)
    elem_props_set(props, "p_double", b"UnitScaleFactor", scale_factor)
    elem_props_set(props, "p_double", b"OriginalUnitScaleFactor", scale_factor_org)
    elem_props_set(props, "p_color_rgb", b"AmbientColor", (0.0, 0.0, 0.0))
    elem_props_set(props, "p_string", b"DefaultCamera", "Producer Perspective")

    # Global timing data.
    r = scene.render
    _, fbx_fps_mode = FBX_FRAMERATES[0]  # Custom framerate.
    fbx_fps = fps = r.fps / r.fps_base
    for ref_fps, fps_mode in FBX_FRAMERATES:
        if similar_values(fps, ref_fps):
            fbx_fps = ref_fps
            fbx_fps_mode = fps_mode
    elem_props_set(props, "p_enum", b"TimeMode", fbx_fps_mode)
    elem_props_set(props, "p_timestamp", b"TimeSpanStart", 0)
    elem_props_set(props, "p_timestamp", b"TimeSpanStop", FBX_KTIME)
    elem_props_set(props, "p_double", b"CustomFrameRate", fbx_fps)

    # ##### End of GlobalSettings element.


def fbx_documents_elements(root, scene_data):
    """
    Write 'Document' part of FBX root.
    Seems like FBX support multiple documents, but until I find examples of such, we'll stick to single doc!
    time is expected to be a datetime.datetime object, or None (using now() in this case).
    """
    name = scene_data.scene.name

    # ##### Start of Documents element.
    docs = elem_empty(root, b"Documents")

    elem_data_single_int32(docs, b"Count", 1)

    doc_uid = get_fbx_uuid_from_key("__FBX_Document__" + name)
    doc = elem_data_single_int64(docs, b"Document", doc_uid)
    doc.add_string_unicode(name)
    doc.add_string_unicode(name)

    props = elem_properties(doc)
    elem_props_set(props, "p_object", b"SourceObject")
    elem_props_set(props, "p_string", b"ActiveAnimStackName", "")

    # XXX Some kind of ID? Offset?
    #     Anyway, as long as we have only one doc, probably not an issue.
    elem_data_single_int64(doc, b"RootNode", 0)


def fbx_references_elements(root, scene_data):
    """
    Have no idea what references are in FBX currently... Just writing empty element.
    """
    docs = elem_empty(root, b"References")


def fbx_definitions_elements(root, scene_data):
    """
    Templates definitions. Only used by Objects data afaik (apart from dummy GlobalSettings one).
    """
    definitions = elem_empty(root, b"Definitions")

    elem_data_single_int32(definitions, b"Version", FBX_TEMPLATES_VERSION)
    elem_data_single_int32(definitions, b"Count", scene_data.templates_users)

    fbx_templates_generate(definitions, scene_data.templates)


def fbx_objects_elements(root, scene_data):
    """
    Data (objects, geometry, material, textures, armatures, etc.).
    """
    perfmon = PerfMon()
    perfmon.level_up()
    objects = elem_empty(root, b"Objects")

    perfmon.step("FBX export fetch empties (%d)..." % len(scene_data.data_empties))

    for empty in scene_data.data_empties:
        fbx_data_empty_elements(objects, empty, scene_data)

    perfmon.step("FBX export fetch lamps (%d)..." % len(scene_data.data_lights))

    for lamp in scene_data.data_lights:
        fbx_data_light_elements(objects, lamp, scene_data)

    perfmon.step("FBX export fetch cameras (%d)..." % len(scene_data.data_cameras))

    for cam in scene_data.data_cameras:
        fbx_data_camera_elements(objects, cam, scene_data)

    perfmon.step("FBX export fetch meshes (%d)..."
                 % len({me_key for me_key, _me, _free in scene_data.data_meshes.values()}))

    done_meshes = set()
    for me_obj in scene_data.data_meshes:
        fbx_data_mesh_elements(objects, me_obj, scene_data, done_meshes)
    del done_meshes

    perfmon.step("FBX export fetch objects (%d)..." % len(scene_data.objects))

    for ob_obj in scene_data.objects:
        if ob_obj.is_dupli:
            continue
        fbx_data_object_elements(objects, ob_obj, scene_data)
        for dp_obj in ob_obj.dupli_list_gen(scene_data.depsgraph):
            if dp_obj not in scene_data.objects:
                continue
            fbx_data_object_elements(objects, dp_obj, scene_data)

    perfmon.step("FBX export fetch remaining...")

    for ob_obj in scene_data.objects:
        if not (ob_obj.is_object and ob_obj.type == 'ARMATURE'):
            continue
        fbx_data_armature_elements(objects, ob_obj, scene_data)

    if scene_data.data_leaf_bones:
        fbx_data_leaf_bone_elements(objects, scene_data)

    for ma in scene_data.data_materials:
        fbx_data_material_elements(objects, ma, scene_data)

    for blender_tex_key in scene_data.data_textures:
        fbx_data_texture_file_elements(objects, blender_tex_key, scene_data)

    for vid in scene_data.data_videos:
        fbx_data_video_elements(objects, vid, scene_data)

    perfmon.step("FBX export fetch animations...")
    start_time = time.process_time()

    fbx_data_animation_elements(objects, scene_data)

    perfmon.level_down()


def fbx_connections_elements(root, scene_data):
    """
    Relations between Objects (which material uses which texture, and so on).
    """
    connections = elem_empty(root, b"Connections")

    for c in scene_data.connections:
        elem_connection(connections, *c)


def fbx_takes_elements(root, scene_data):
    """
    Animations.
    """
    # XXX Pretty sure takes are no more needed...
    takes = elem_empty(root, b"Takes")
    elem_data_single_string(takes, b"Current", b"")

    animations = scene_data.animations
    for astack_key, animations, alayer_key, name, f_start, f_end in animations:
        scene = scene_data.scene
        fps = scene.render.fps / scene.render.fps_base
        start_ktime = int(convert_sec_to_ktime(f_start / fps))
        end_ktime = int(convert_sec_to_ktime(f_end / fps))

        take = elem_data_single_string(takes, b"Take", name)
        elem_data_single_string(take, b"FileName", name + b".tak")
        take_loc_time = elem_data_single_int64(take, b"LocalTime", start_ktime)
        take_loc_time.add_int64(end_ktime)
        take_ref_time = elem_data_single_int64(take, b"ReferenceTime", start_ktime)
        take_ref_time.add_int64(end_ktime)


# ##### "Main" functions. #####

# This func can be called with just the filepath
def save_single(operator, scene, depsgraph, filepath="",
                global_matrix=Matrix(),
                apply_unit_scale=False,
                global_scale=1.0,
                apply_scale_options='FBX_SCALE_NONE',
                axis_up="Z",
                axis_forward="Y",
                context_objects=None,
                object_types=None,
                use_mesh_modifiers=True,
                use_mesh_modifiers_render=True,
                mesh_smooth_type='FACE',
                use_armature_deform_only=False,
                bake_anim=True,
                bake_anim_use_all_bones=True,
                bake_anim_use_nla_strips=True,
                bake_anim_use_all_actions=True,
                bake_anim_step=1.0,
                bake_anim_simplify_factor=1.0,
                bake_anim_force_startend_keying=True,
                add_leaf_bones=False,
                primary_bone_axis='Y',
                secondary_bone_axis='X',
                use_metadata=True,
                path_mode='AUTO',
                use_mesh_edges=True,
                use_tspace=True,
                embed_textures=False,
                use_custom_props=False,
                bake_space_transform=False,
                armature_nodetype='NULL',
                **kwargs
                ):

    # Clear cached ObjectWrappers (just in case...).
    ObjectWrapper.cache_clear()

    if object_types is None:
        object_types = {'EMPTY', 'CAMERA', 'LIGHT', 'ARMATURE', 'MESH', 'OTHER'}

    if 'OTHER' in object_types:
        object_types |= BLENDER_OTHER_OBJECT_TYPES

    # Default Blender unit is equivalent to meter, while FBX one is centimeter...
    unit_scale = units_blender_to_fbx_factor(scene) if apply_unit_scale else 100.0
    if apply_scale_options == 'FBX_SCALE_NONE':
        global_matrix = Matrix.Scale(unit_scale * global_scale, 4) @ global_matrix
        unit_scale = 1.0
    elif apply_scale_options == 'FBX_SCALE_UNITS':
        global_matrix = Matrix.Scale(global_scale, 4) @ global_matrix
    elif apply_scale_options == 'FBX_SCALE_CUSTOM':
        global_matrix = Matrix.Scale(unit_scale, 4) @ global_matrix
        unit_scale = global_scale
    else: # if apply_scale_options == 'FBX_SCALE_ALL':
        unit_scale = global_scale * unit_scale

    global_scale = global_matrix.median_scale
    global_matrix_inv = global_matrix.inverted()
    # For transforming mesh normals.
    global_matrix_inv_transposed = global_matrix_inv.transposed()

    # Only embed textures in COPY mode!
    if embed_textures and path_mode != 'COPY':
        embed_textures = False

    # Calculate bone correction matrix
    bone_correction_matrix = None  # Default is None = no change
    bone_correction_matrix_inv = None
    if (primary_bone_axis, secondary_bone_axis) != ('Y', 'X'):
        from bpy_extras.io_utils import axis_conversion
        bone_correction_matrix = axis_conversion(from_forward=secondary_bone_axis,
                                                 from_up=primary_bone_axis,
                                                 to_forward='X',
                                                 to_up='Y',
                                                 ).to_4x4()
        bone_correction_matrix_inv = bone_correction_matrix.inverted()


    media_settings = FBXExportSettingsMedia(
        path_mode,
        os.path.dirname(bpy.data.filepath),  # base_src
        os.path.dirname(filepath),  # base_dst
        # Local dir where to put images (medias), using FBX conventions.
        os.path.splitext(os.path.basename(filepath))[0] + ".fbm",  # subdir
        embed_textures,
        set(),  # copy_set
        set(),  # embedded_set
    )

    settings = FBXExportSettings(
        operator.report, (axis_up, axis_forward), global_matrix, global_scale, apply_unit_scale, unit_scale,
        bake_space_transform, global_matrix_inv, global_matrix_inv_transposed,
        context_objects, object_types, use_mesh_modifiers, use_mesh_modifiers_render,
        mesh_smooth_type, use_mesh_edges, use_tspace,
        armature_nodetype, use_armature_deform_only,
        add_leaf_bones, bone_correction_matrix, bone_correction_matrix_inv,
        bake_anim, bake_anim_use_all_bones, bake_anim_use_nla_strips, bake_anim_use_all_actions,
        bake_anim_step, bake_anim_simplify_factor, bake_anim_force_startend_keying,
        False, media_settings, use_custom_props,
    )

    import bpy_extras.io_utils

    print('\nFBX export starting... %r' % filepath)
    start_time = time.process_time()

    # Generate some data about exported scene...
    scene_data = fbx_data_from_scene(scene, depsgraph, settings)

    root = elem_empty(None, b"")  # Root element has no id, as it is not saved per se!

    # Mostly FBXHeaderExtension and GlobalSettings.
    fbx_header_elements(root, scene_data)

    # Documents and References are pretty much void currently.
    fbx_documents_elements(root, scene_data)
    fbx_references_elements(root, scene_data)

    # Templates definitions.
    fbx_definitions_elements(root, scene_data)

    # Actual data.