export_fbx_bin.py

        except Exception as e:
            print("WARNING: embeding file {} failed ({})".format(vid.filepath, e))
            elem_data_single_byte_array(fbx_vid, b"Content", b"")
    else:
        elem_data_single_byte_array(fbx_vid, b"Content", b"")


def fbx_data_armature_elements(root, arm_obj, scene_data):
    """
    Write:
        * Bones "data" (NodeAttribute::LimbNode, contains pretty much nothing!).
        * Deformers (i.e. Skin), bind between an armature and a mesh.
        ** SubDeformers (i.e. Cluster), one per bone/vgroup pair.
        * BindPose.
    Note armature itself has no data, it is a mere "Null" Model...
    """
    mat_world_arm = arm_obj.fbx_object_matrix(scene_data, global_space=True)

    # Bones "data".
    for bo_obj in arm_obj.bones:
        bo = bo_obj.bdata
        bo_data_key = scene_data.data_bones[bo_obj]
        fbx_bo = elem_data_single_int64(root, b"NodeAttribute", get_fbxuid_from_key(bo_data_key))
        fbx_bo.add_string(fbx_name_class(bo.name.encode(), b"NodeAttribute"))
        fbx_bo.add_string(b"LimbNode")
        elem_data_single_string(fbx_bo, b"TypeFlags", b"Skeleton")

        tmpl = elem_props_template_init(scene_data.templates, b"Bone")
        props = elem_properties(fbx_bo)
        elem_props_template_set(tmpl, props, "p_double", b"Size", (bo.tail_local - bo.head_local).length)
        elem_props_template_finalize(tmpl, props)

        # Custom properties.
        if scene_data.settings.use_custom_properties:
            fbx_data_element_custom_properties(props, bo)

    # Deformers and BindPoses.
    # Note: we might also use Deformers for our "parent to vertex" stuff???
    deformer = scene_data.data_deformers.get(arm_obj, None)
    if deformer is not None:
        for me, (skin_key, ob_obj, clusters) in deformer.items():
            # BindPose.
            # We assume bind pose for our bones are their "Editmode" pose...
            # All matrices are expected in global (world) space.
            bindpose_key = get_blender_armature_bindpose_key(arm_obj.bdata, me)
            fbx_pose = elem_data_single_int64(root, b"Pose", get_fbxuid_from_key(bindpose_key))
            fbx_pose.add_string(fbx_name_class(me.name.encode(), b"Pose"))
            fbx_pose.add_string(b"BindPose")

            elem_data_single_string(fbx_pose, b"Type", b"BindPose")
            elem_data_single_int32(fbx_pose, b"Version", FBX_POSE_BIND_VERSION)
            elem_data_single_int32(fbx_pose, b"NbPoseNodes", 1 + len(arm_obj.bdata.data.bones))

            # First node is mesh/object.
            mat_world_obj = obj.fbx_object_matrix(scene_data, global_space=True)
            fbx_posenode = elem_empty(fbx_pose, b"PoseNode")
            elem_data_single_int64(fbx_posenode, b"Node", obj.fbx_uuid)
            elem_data_single_float64_array(fbx_posenode, b"Matrix", matrix_to_array(mat_world_obj))
            # And all bones of armature!
            mat_world_bones = {}
            for bo_obj in arm_obj.bones:
                bomat = bo_obj.fbx_object_matrix(scene_data, global_space=True)
                mat_world_bones[bo_obj] = bomat
                fbx_posenode = elem_empty(fbx_pose, b"PoseNode")
                elem_data_single_int64(fbx_posenode, b"Node", bo_obj.fbx_uuid)
                elem_data_single_float64_array(fbx_posenode, b"Matrix", matrix_to_array(bomat))

            # Deformer.
            fbx_skin = elem_data_single_int64(root, b"Deformer", get_fbxuid_from_key(skin_key))
            fbx_skin.add_string(fbx_name_class(arm_obj.name.encode(), b"Deformer"))
            fbx_skin.add_string(b"Skin")

            elem_data_single_int32(fbx_skin, b"Version", FBX_DEFORMER_SKIN_VERSION)
            elem_data_single_float64(fbx_skin, b"Link_DeformAcuracy", 50.0)  # Only vague idea what it is...

            # Pre-process vertex weights (also to check vertices assigned ot more than four bones).
            ob = ob_obj.bdata
            bo_vg_idx = {bo_obj.bdata.name: ob.vertex_groups[bo_obj.bdata.name].index
                         for bo_obj in clusters.keys() if bo_obj.bdata.name in ob.vertex_groups}
            valid_idxs = set(bo_vg_idx.values())
            vgroups = {vg.index: OrderedDict() for vg in ob.vertex_groups}
            verts_vgroups = (sorted(((vg.group, vg.weight) for vg in v.groups if vg.weight and vg.group in valid_idxs),
                                    key=lambda e: e[1], reverse=True)
                             for v in me.vertices)
            for idx, vgs in enumerate(verts_vgroups):
                for vg_idx, w in vgs:
                    vgroups[vg_idx][idx] = w

            for bo_obj, clstr_key in clusters.items():
                bo = bo_obj.bdata
                # Find which vertices are affected by this bone/vgroup pair, and matching weights.
                # Note we still write a cluster for bones not affecting the mesh, to get 'rest pose' data
                # (the TransformBlah matrices).
                vg_idx = bo_vg_idx.get(bo.name, None)
                indices, weights = ((), ()) if vg_idx is None or not vgroups[vg_idx] else zip(*vgroups[vg_idx].items())

                # Create the cluster.
                fbx_clstr = elem_data_single_int64(root, b"Deformer", get_fbxuid_from_key(clstr_key))
                fbx_clstr.add_string(fbx_name_class(bo.name.encode(), b"SubDeformer"))
                fbx_clstr.add_string(b"Cluster")

                elem_data_single_int32(fbx_clstr, b"Version", FBX_DEFORMER_CLUSTER_VERSION)
                # No idea what that user data might be...
                fbx_userdata = elem_data_single_string(fbx_clstr, b"UserData", b"")
                fbx_userdata.add_string(b"")
                elem_data_single_int32_array(fbx_clstr, b"Indexes", indices)
                elem_data_single_float64_array(fbx_clstr, b"Weights", weights)
                # Transform, TransformLink and TransformAssociateModel matrices...
                # They seem to be doublons of BindPose ones??? Have armature (associatemodel) in addition, though.
                # WARNING! Even though official FBX API presents Transform in global space,
                #          **it is stored in bone space in FBX data!** See:
                #          http://area.autodesk.com/forum/autodesk-fbx/fbx-sdk/why-the-values-return-
                #                 by-fbxcluster-gettransformmatrix-x-not-same-with-the-value-in-ascii-fbx-file/
                elem_data_single_float64_array(fbx_clstr, b"Transform",
                                               matrix_to_array(mat_world_bones[bo_obj].inverted() * mat_world_obj))
                elem_data_single_float64_array(fbx_clstr, b"TransformLink", matrix_to_array(mat_world_bones[bo_obj]))
                elem_data_single_float64_array(fbx_clstr, b"TransformAssociateModel", matrix_to_array(mat_world_arm))


def fbx_data_object_elements(root, ob_obj, scene_data):
    """
    Write the Object (Model) data blocks.
    Note this "Model" can also be bone or dupli!
    """
    obj_type = b"Null"  # default, sort of empty...
    if ob_obj.is_bone:
        obj_type = b"LimbNode"
    elif (ob_obj.type in BLENDER_OBJECT_TYPES_MESHLIKE):
        obj_type = b"Mesh"
    elif (ob_obj.type == 'LAMP'):
        obj_type = b"Light"
    elif (ob_obj.type == 'CAMERA'):
        obj_type = b"Camera"
    model = elem_data_single_int64(root, b"Model", ob_obj.fbx_uuid)
    model.add_string(fbx_name_class(ob_obj.name.encode(), b"Model"))
    model.add_string(obj_type)

    elem_data_single_int32(model, b"Version", FBX_MODELS_VERSION)

    # Object transform info.
    loc, rot, scale, matrix, matrix_rot = ob_obj.fbx_object_tx(scene_data)
    rot = tuple(units_convert_iter(rot, "radian", "degree"))

    tmpl = elem_props_template_init(scene_data.templates, b"Model")
    # For now add only loc/rot/scale...
    props = elem_properties(model)
    elem_props_template_set(tmpl, props, "p_lcl_translation", b"Lcl Translation", loc)
    elem_props_template_set(tmpl, props, "p_lcl_rotation", b"Lcl Rotation", rot)
    elem_props_template_set(tmpl, props, "p_lcl_scaling", b"Lcl Scaling", scale)

    # Custom properties.
    if scene_data.settings.use_custom_properties:
        fbx_data_element_custom_properties(props, ob_obj.bdata)

    # Those settings would obviously need to be edited in a complete version of the exporter, may depends on
    # object type, etc.
    elem_data_single_int32(model, b"MultiLayer", 0)
    elem_data_single_int32(model, b"MultiTake", 0)
    elem_data_single_bool(model, b"Shading", True)
    elem_data_single_string(model, b"Culling", b"CullingOff")

    if obj_type == b"Camera":
        # Why, oh why are FBX cameras such a mess???
        # And WHY add camera data HERE??? Not even sure this is needed...
        render = scene_data.scene.render
        width = render.resolution_x * 1.0
        height = render.resolution_y * 1.0
        elem_props_template_set(tmpl, props, "p_enum", b"ResolutionMode", 0)  # Don't know what it means
        elem_props_template_set(tmpl, props, "p_double", b"AspectW", width)
        elem_props_template_set(tmpl, props, "p_double", b"AspectH", height)
        elem_props_template_set(tmpl, props, "p_bool", b"ViewFrustum", True)
        elem_props_template_set(tmpl, props, "p_enum", b"BackgroundMode", 0)  # Don't know what it means
        elem_props_template_set(tmpl, props, "p_bool", b"ForegroundTransparent", True)

    elem_props_template_finalize(tmpl, props)


def fbx_data_animation_elements(root, scene_data):
    """
    Write animation data.
    """
    animations = scene_data.animations
    if not animations:
        return
    scene = scene_data.scene

    fps = scene.render.fps / scene.render.fps_base

    def keys_to_ktimes(keys):
        return (int(v) for v in units_convert_iter((f / fps for f, _v in keys), "second", "ktime"))

    # Animation stacks.
    for astack_key, alayers, alayer_key, name, f_start, f_end in animations:
        astack = elem_data_single_int64(root, b"AnimationStack", get_fbxuid_from_key(astack_key))
        astack.add_string(fbx_name_class(name, b"AnimStack"))
        astack.add_string(b"")

        astack_tmpl = elem_props_template_init(scene_data.templates, b"AnimationStack")
        astack_props = elem_properties(astack)
        r = scene_data.scene.render
        fps = r.fps / r.fps_base
        start = int(units_convert(f_start / fps, "second", "ktime"))
        end = int(units_convert(f_end / fps, "second", "ktime"))
        elem_props_template_set(astack_tmpl, astack_props, "p_timestamp", b"LocalStart", start)
        elem_props_template_set(astack_tmpl, astack_props, "p_timestamp", b"LocalStop", end)
        elem_props_template_set(astack_tmpl, astack_props, "p_timestamp", b"ReferenceStart", start)
        elem_props_template_set(astack_tmpl, astack_props, "p_timestamp", b"ReferenceStop", end)
        elem_props_template_finalize(astack_tmpl, astack_props)

        # For now, only one layer for all animations.
        alayer = elem_data_single_int64(root, b"AnimationLayer", get_fbxuid_from_key(alayer_key))
        alayer.add_string(fbx_name_class(name, b"AnimLayer"))
        alayer.add_string(b"")

        for ob_obj, (alayer_key, acurvenodes) in alayers.items():
            # Animation layer.
            # alayer = elem_data_single_int64(root, b"AnimationLayer", get_fbxuid_from_key(alayer_key))
            # alayer.add_string(fbx_name_class(ob_obj.name.encode(), b"AnimLayer"))
            # alayer.add_string(b"")

            for fbx_prop, (acurvenode_key, acurves, acurvenode_name) in acurvenodes.items():
                # Animation curve node.
                acurvenode = elem_data_single_int64(root, b"AnimationCurveNode", get_fbxuid_from_key(acurvenode_key))
                acurvenode.add_string(fbx_name_class(acurvenode_name.encode(), b"AnimCurveNode"))
                acurvenode.add_string(b"")

                acn_tmpl = elem_props_template_init(scene_data.templates, b"AnimationCurveNode")
                acn_props = elem_properties(acurvenode)

                for fbx_item, (acurve_key, def_value, keys, _acurve_valid) in acurves.items():
                    elem_props_template_set(acn_tmpl, acn_props, "p_number", fbx_item.encode(),
                                            def_value, animatable=True)

                    # Only create Animation curve if needed!
                    if keys:
                        acurve = elem_data_single_int64(root, b"AnimationCurve", get_fbxuid_from_key(acurve_key))
                        acurve.add_string(fbx_name_class(b"", b"AnimCurve"))
                        acurve.add_string(b"")

                        # key attributes...
                        nbr_keys = len(keys)
                        # flags...
                        keyattr_flags = (
                            1 << 3 |   # interpolation mode, 1 = constant, 2 = linear, 3 = cubic.
                            1 << 8 |   # tangent mode, 8 = auto, 9 = TCB, 10 = user, 11 = generic break,
                            1 << 13 |  # tangent mode, 12 = generic clamp, 13 = generic time independent,
                            1 << 14 |  # tangent mode, 13 + 14 = generic clamp progressive.
                            0,
                        )
                        # Maybe values controlling TCB & co???
                        keyattr_datafloat = (0.0, 0.0, 9.419963346924634e-30, 0.0)

                        # And now, the *real* data!
                        elem_data_single_float64(acurve, b"Default", def_value)
                        elem_data_single_int32(acurve, b"KeyVer", FBX_ANIM_KEY_VERSION)
                        elem_data_single_int64_array(acurve, b"KeyTime", keys_to_ktimes(keys))
                        elem_data_single_float32_array(acurve, b"KeyValueFloat", (v for _f, v in keys))
                        elem_data_single_int32_array(acurve, b"KeyAttrFlags", keyattr_flags)
                        elem_data_single_float32_array(acurve, b"KeyAttrDataFloat", keyattr_datafloat)
                        elem_data_single_int32_array(acurve, b"KeyAttrRefCount", (nbr_keys,))

                elem_props_template_finalize(acn_tmpl, acn_props)


##### Top-level FBX data container. #####

# Helper container gathering some data we need multiple times:
#     * templates.
#     * objects.
#     * connections.
#     * takes.
FBXData = namedtuple("FBXData", (
    "templates", "templates_users", "connections",
    "settings", "scene", "objects", "animations", "frame_start", "frame_end",
    "data_empties", "data_lamps", "data_cameras", "data_meshes", "mesh_mat_indices",
    "data_bones", "data_deformers",
    "data_world", "data_materials", "data_textures", "data_videos",
))


def fbx_mat_properties_from_texture(tex):
    """
    Returns a set of FBX metarial properties that are affected by the given texture.
    Quite obviously, this is a fuzzy and far-from-perfect mapping! Amounts of influence are completely lost, e.g.
    Note tex is actually expected to be a texture slot.
    """
    # Tex influence does not exists in FBX, so assume influence < 0.5 = no influence... :/
    INFLUENCE_THRESHOLD = 0.5

    # Mapping Blender -> FBX (blend_use_name, blend_fact_name, fbx_name).
    blend_to_fbx = (
        # Lambert & Phong...
        ("diffuse", "diffuse", b"DiffuseFactor"),
        ("color_diffuse", "diffuse_color", b"DiffuseColor"),
        ("alpha", "alpha", b"TransparencyFactor"),
        ("diffuse", "diffuse", b"TransparentColor"),  # Uses diffuse color in Blender!
        ("emit", "emit", b"EmissiveFactor"),
        ("diffuse", "diffuse", b"EmissiveColor"),  # Uses diffuse color in Blender!
        ("ambient", "ambient", b"AmbientFactor"),
        #("", "", b"AmbientColor"),  # World stuff in Blender, for now ignore...
        ("normal", "normal", b"NormalMap"),
        # Note: unsure about those... :/
        #("", "", b"Bump"),
        #("", "", b"BumpFactor"),
        #("", "", b"DisplacementColor"),
        #("", "", b"DisplacementFactor"),
        # Phong only.
        ("specular", "specular", b"SpecularFactor"),
        ("color_spec", "specular_color", b"SpecularColor"),
        # See Material template about those two!
        ("hardness", "hardness", b"Shininess"),
        ("hardness", "hardness", b"ShininessExponent"),
        ("mirror", "mirror", b"ReflectionColor"),
        ("raymir", "raymir", b"ReflectionFactor"),
    )

    tex_fbx_props = set()
    for use_map_name, name_factor, fbx_prop_name in blend_to_fbx:
        if getattr(tex, "use_map_" + use_map_name) and getattr(tex, name_factor + "_factor") >= INFLUENCE_THRESHOLD:
            tex_fbx_props.add(fbx_prop_name)

    return tex_fbx_props


def fbx_skeleton_from_armature(scene, settings, arm_obj, objects, data_meshes,
                               data_bones, data_deformers, arm_parents):
    """
    Create skeleton from armature/bones (NodeAttribute/LimbNode and Model/LimbNode), and for each deformed mesh,
    create Pose/BindPose(with sub PoseNode) and Deformer/Skin(with Deformer/SubDeformer/Cluster).
    Also supports "parent to bone" (simple parent to Model/LimbNode).
    arm_parents is a set of tuples (armature, object) for all successful armature bindings.
    """
    arm_data = arm_obj.bdata.data
    bones = OrderedDict()  # Because we do not have any ordered set :/
    for bo in arm_obj.bones:
        data_key = get_blender_bone_key(arm_obj.bdata, bo.bdata)
        data_bones[bo] = data_key
        bones[bo] = None

    if not bones:
        return

    for ob_obj in objects:
        if not (ob_obj.is_object and ob_obj.type in {'MESH'} and ob_obj.parent == arm_obj):
            continue

        # Always handled by an Armature modifier...
        ob = ob_obj.bdata
        found = False
        for mod in ob.modifiers:
            if mod.type not in {'ARMATURE'}:
                continue
            # We only support vertex groups binding method, not bone envelopes one!
            if mod.object == arm_obj and mod.use_vertex_groups:
                found = True
                break

        if not found:
            continue

        # Now we have a mesh using this armature.
        # Note: bindpose have no relations at all (no connections), so no need for any preprocess for them.
        # Create skin & clusters relations (note skins are connected to geometry, *not* model!).
        _key, me, _free = data_meshes[ob]
        clusters = OrderedDict((bo, get_blender_bone_cluster_key(arm_obj.bdata, me, bo.bdata)) for bo in bones)
        data_deformers.setdefault(arm_obj, OrderedDict())[me] = (get_blender_armature_skin_key(arm_obj.bdata, me),
                                                                 ob_obj, clusters)

        # We don't want a regular parent relationship for those in FBX...
        arm_parents.add((arm_obj, ob_obj))

    objects.update(bones)


def fbx_animations_simplify(scene_data, animdata):
    """
    Simplifies FCurves!
    """
    fac = scene_data.settings.bake_anim_simplify_factor
    step = scene_data.settings.bake_anim_step
    # So that, with default factor and step values (1), we get:
    max_frame_diff = step * fac * 10  # max step of 10 frames.
    value_diff_fac = fac / 1000  # min value evolution: 0.1% of whole range.

    for keys in animdata.values():
        if not keys:
            continue
        extremums = [(min(values), max(values)) for values in zip(*(k[1] for k in keys))]
        min_diffs = [max((mx - mn) * value_diff_fac, 0.000001) for mx, mn in extremums]
        p_currframe, p_key, p_key_write = keys[0]
        p_keyed = [(p_currframe - max_frame_diff, val) for val in p_key]
        for currframe, key, key_write in keys:
            for idx, (val, p_val) in enumerate(zip(key, p_key)):
                p_keyedframe, p_keyedval = p_keyed[idx]
                if val == p_val:
                    # Never write keyframe when value is exactly the same as prev one!
                    continue
                if abs(val - p_val) >= min_diffs[idx]:
                    # If enough difference from previous sampled value, key this value *and* the previous one!
                    key_write[idx] = True
                    p_key_write[idx] = True
                    p_keyed[idx] = (currframe, val)
                elif (abs(val - p_keyedval) >= min_diffs[idx]) or (currframe - p_keyedframe >= max_frame_diff):
                    # Else, if enough difference from previous keyed value (or max gap between keys is reached),
                    # key this value only!
                    key_write[idx] = True
                    p_keyed[idx] = (currframe, val)
            p_currframe, p_key, p_key_write = currframe, key, key_write
        # Always key last sampled values (we ignore curves with a single valid key anyway).
        p_key_write[:] = [True] * len(p_key_write)


def fbx_animations_objects_do(scene_data, ref_id, f_start, f_end, start_zero, objects=None, force_keep=False):
    """
    Generate animation data (a single AnimStack) from objects, for a given frame range.
    """
    bake_step = scene_data.settings.bake_anim_step
    scene = scene_data.scene

    if objects is not None:
        # Add bones and duplis!
        for ob_obj in tuple(objects):
            if not ob_obj.is_object:
                continue
            if ob_obj.type == 'ARMATURE':
                objects |= set(ob_obj.bones)
            ob_obj.dupli_list_create(scene, 'RENDER')
            for dp_obj in ob_obj.dupli_list:
                if dp_obj in scene_data.objects:
                    objects.add(dp_obj)
            ob_obj.dupli_list_clear()
    else:
        objects = scene_data.objects

    # FBX mapping info: Property affected, and name of the "sub" property (to distinguish e.g. vector's channels).
    fbx_names = (
        ("Lcl Translation", "T", "d|X"), ("Lcl Translation", "T", "d|Y"), ("Lcl Translation", "T", "d|Z"),
        ("Lcl Rotation", "R", "d|X"), ("Lcl Rotation", "R", "d|Y"), ("Lcl Rotation", "R", "d|Z"),
        ("Lcl Scaling", "S", "d|X"), ("Lcl Scaling", "S", "d|Y"), ("Lcl Scaling", "S", "d|Z"),
    )

    back_currframe = scene.frame_current
    animdata = OrderedDict((obj, []) for obj in objects)

    p_rots = {}

    currframe = f_start
    while currframe < f_end:
        real_currframe = currframe - f_start if start_zero else currframe
        scene.frame_set(int(currframe), currframe - int(currframe))

        for ob_obj in objects:
            ob_obj.dupli_list_create(scene, 'RENDER')
        for ob_obj in objects:
            # We compute baked loc/rot/scale for all objects (rot being euler-compat with previous value!).
            p_rot = p_rots.get(ob_obj, None)
            loc, rot, scale, _m, _mr = ob_obj.fbx_object_tx(scene_data, rot_euler_compat=p_rot)
            p_rots[ob_obj] = rot
            tx = tuple(loc) + tuple(units_convert_iter(rot, "radian", "degree")) + tuple(scale)
            animdata[ob_obj].append((real_currframe, tx, [False] * len(tx)))
        for ob_obj in objects:
            ob_obj.dupli_list_clear()
        currframe += bake_step

    scene.frame_set(back_currframe, 0.0)

    fbx_animations_simplify(scene_data, animdata)

    animations = OrderedDict()

    # And now, produce final data (usable by FBX export code)...
    for ob_obj, keys in animdata.items():
        if not keys:
            continue
        curves = [[] for k in keys[0][1]]
        for currframe, key, key_write in keys:
            for idx, (val, wrt) in enumerate(zip(key, key_write)):
                if wrt:
                    curves[idx].append((currframe, val))

        obj_key = ob_obj.key
        # Get PoseBone from bone...
        #tobj = bone_map[obj] if isinstance(obj, Bone) else obj
        #loc, rot, scale, _m, _mr = fbx_object_tx(scene_data, tobj)
        #tx = tuple(loc) + tuple(units_convert_iter(rot, "radian", "degree")) + tuple(scale)
        dtx = (0.0, 0.0, 0.0) + (0.0, 0.0, 0.0) + (1.0, 1.0, 1.0)
        # If animation for a channel, (True, keyframes), else (False, current value).
        final_keys = OrderedDict()
        for idx, c in enumerate(curves):
            fbx_group, fbx_gname, fbx_item = fbx_names[idx]
            fbx_item_key = get_blender_anim_curve_key(scene, ref_id, obj_key, fbx_group, fbx_item)
            if fbx_group not in final_keys:
                fbx_group_key = get_blender_anim_curve_node_key(scene, ref_id, obj_key, fbx_group)
                final_keys[fbx_group] = (fbx_group_key, OrderedDict(), fbx_gname)
            final_keys[fbx_group][1][fbx_item] = (fbx_item_key, dtx[idx], c,
                                                  True if (len(c) > 1 or (len(c) > 0 and force_keep)) else False)
        # And now, remove anim groups (i.e. groups of curves affecting a single FBX property) with no curve at all!
        del_groups = []
        for grp, (_k, data, _n) in final_keys.items():
            if True in (d[3] for d in data.values()):
                continue
            del_groups.append(grp)
        for grp in del_groups:
            del final_keys[grp]

        if final_keys:
            #animations[obj] = (get_blender_anim_layer_key(scene, obj.bdata), final_keys)
            animations[ob_obj] = ("dummy_unused_key", final_keys)

    astack_key = get_blender_anim_stack_key(scene, ref_id)
    alayer_key = get_blender_anim_layer_key(scene, ref_id)
    name = (get_blenderID_name(ref_id) if ref_id else scene.name).encode()

    if start_zero:
        f_end -= f_start
        f_start = 0.0

    return (astack_key, animations, alayer_key, name, f_start, f_end) if animations else None


def fbx_animations_objects(scene_data):
    """
    Generate global animation data from objects.
    """
    scene = scene_data.scene
    animations = []
    frame_start = 1e100
    frame_end = -1e100

    def add_anim(animations, 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

    # Per-NLA strip animstacks.
    if scene_data.settings.bake_anim_use_nla_strips:
        strips = []
        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
            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, fbx_animations_objects_do(scene_data, strip, strip.frame_start, strip.frame_end, True))
            strip.mute = True

        for strip in strips:
            strip.mute = False

    # 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', 'layers', 'select', 'track_axis', 'up_axis', 'active_material', 'active_material_index',
                'matrix_parent_inverse', 'empty_draw_type', 'empty_draw_size', 'empty_image_offset', 'pass_index',
                'color', 'hide', 'hide_select', 'hide_render', 'use_slow_parent', 'slow_parent_offset',
                'use_extra_recalc_object', 'use_extra_recalc_data', 'dupli_type', 'use_dupli_frames_speed',
                'use_dupli_vertices_rotation', 'use_dupli_faces_scale', 'dupli_faces_scale', 'dupli_group',
                'dupli_frames_start', 'dupli_frames_end', 'dupli_frames_on', 'dupli_frames_off',
                'draw_type', 'show_bounds', 'draw_bounds_type', 'show_name', 'show_axis', 'show_texture_space',
                'show_wire', 'show_all_edges', 'show_transparent', 'show_x_ray',
                'show_only_shape_key', 'use_shape_key_edit_mode', 'active_shape_key_index',
            )
            for p in props:
                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.

            # 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()

            if ob.animation_data:
                org_act = ob.animation_data.action
            else:
                org_act = ...
                ob.animation_data_create()
            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,
                         fbx_animations_objects_do(scene_data, (ob, act), frame_start, frame_end, True, {ob_obj}, True))
                # Ugly! :/
                ob.animation_data.action = None if org_act is ... else org_act
                restore_object(ob, ob_copy)

            if org_act is ...:
                ob.animation_data_clear()
            else:
                ob.animation_data.action = org_act

            bpy.data.objects.remove(ob_copy)

    # Global (containing everything) animstack.
    if not scene_data.settings.bake_anim_use_nla_strips or not animations:
        add_anim(animations, fbx_animations_objects_do(scene_data, None, scene.frame_start, scene.frame_end, False))

    return animations, frame_start, frame_end


def fbx_data_from_scene(scene, settings):
    """
    Do some pre-processing over scene's data...
    """
    objtypes = settings.object_types

    ##### Gathering data...

    # This is rather simple for now, maybe we could end generating templates with most-used values
    # instead of default ones?
    objects = OrderedDict()  # 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...
        ob_obj.dupli_list_create(scene, 'RENDER')
        for dp_obj in ob_obj.dupli_list:
            objects[dp_obj] = None
        ob_obj.dupli_list_clear()

    data_lamps = OrderedDict((ob_obj.bdata.data, get_blenderID_key(ob_obj.bdata.data))
                             for ob_obj in objects if ob_obj.type == 'LAMP')
    # Unfortunately, FBX camera data contains object-level data (like position, orientation, etc.)...
    data_cameras = OrderedDict((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 = OrderedDict((ob_obj, get_blender_empty_key(ob_obj.bdata))
                               for ob_obj in objects if ob_obj.type == 'EMPTY')

    data_meshes = OrderedDict()
    for ob_obj in objects:
        if ob_obj.type not in BLENDER_OBJECT_TYPES_MESHLIKE:
            continue
        ob = ob_obj.bdata
        if ob in data_meshes:  # Happens with dupli instances.
            continue
        use_org_data = True
        if settings.use_mesh_modifiers or ob.type in BLENDER_OTHER_OBJECT_TYPES:
            use_org_data = False
            tmp_mods = []
            if ob.type == 'MESH':
                # No need to create a new mesh in this case, if no modifier is active!
                use_org_data = True
                for mod in ob.modifiers:
                    # For meshes, when armature export is enabled, disable Armature modifiers here!
                    if mod.type == 'ARMATURE' and 'ARMATURE' in settings.object_types:
                        tmp_mods.append((mod, mod.show_render))
                        mod.show_render = False
                    if mod.show_render:
                        use_org_data = False
            if not use_org_data:
                tmp_me = ob.to_mesh(scene, apply_modifiers=True, settings='RENDER')
                data_meshes[ob] = (get_blenderID_key(tmp_me), tmp_me, True)
            # Re-enable temporary disabled modifiers.
            for mod, show_render in tmp_mods:
                mod.show_render = show_render
        if use_org_data:
            data_meshes[ob] = (get_blenderID_key(ob.data), ob.data, False)

    # Armatures!
    data_bones = OrderedDict()
    data_deformers = OrderedDict()
    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, arm_parents)

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

    # TODO: Check all the mat stuff works even when mats 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 = OrderedDict()
    for ob_obj in objects:
        # If obj is not a valid object for materials, wrapper will just return an empty tuple...
        for mat_s in ob_obj.material_slots:
            mat = mat_s.material
            # Note theoretically, FBX supports any kind of materials, even GLSL shaders etc.
            # However, I doubt anything else than Lambert/Phong is really portable!
            # We support any kind of 'surface' shader though, better to have some kind of default Lambert than nothing.
            # TODO: Support nodes (*BIG* todo!).
            if mat.type in {'SURFACE'} and not mat.use_nodes:
                if mat in data_materials:
                    data_materials[mat][1].append(ob_obj)
                else:
                    data_materials[mat] = (get_blenderID_key(mat), [ob_obj])

    # Note FBX textures also hold their mapping info.
    # TODO: Support layers?
    data_textures = OrderedDict()
    # FbxVideo also used to store static images...
    data_videos = OrderedDict()
    # For now, do not use world textures, don't think they can be linked to anything FBX wise...
    for mat in data_materials.keys():
        for tex in mat.texture_slots:
            if tex is None:
                continue
            # For now, only consider image textures.
            # Note FBX does has support for procedural, but this is not portable at all (opaque blob),
            # so not useful for us.
            # TODO I think ENVIRONMENT_MAP should be usable in FBX as well, but for now let it aside.
            #if tex.texture.type not in {'IMAGE', 'ENVIRONMENT_MAP'}:
            if tex.texture.type not in {'IMAGE'}:
                continue
            img = tex.texture.image
            if img is None:
                continue
            # Find out whether we can actually use this texture for this material, in FBX context.
            tex_fbx_props = fbx_mat_properties_from_texture(tex)
            if not tex_fbx_props:
                continue
            if tex in data_textures:
                data_textures[tex][1][mat] = tex_fbx_props
            else:
                data_textures[tex] = (get_blenderID_key(tex), OrderedDict(((mat, tex_fbx_props),)))
            if img in data_videos:
                data_videos[img][1].append(tex)
            else:
                data_videos[img] = (get_blenderID_key(img), [tex])

    # Animation...
    animations = ()
    frame_start = scene.frame_start
    frame_end = scene.frame_end
    if settings.bake_anim:
        # From objects & bones only for a start.
        tmp_scdata = FBXData(  # Kind of hack, we need a temp scene_data for object's space handling to bake animations...
            None, None, None,
            settings, scene, objects, None, 0.0, 0.0,
            data_empties, data_lamps, data_cameras, data_meshes, None,
            data_bones, data_deformers,
            data_world, data_materials, data_textures, data_videos,
        )
        animations, frame_start, frame_end = fbx_animations_objects(tmp_scdata)

    ##### Creation of templates...

    templates = OrderedDict()
    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_lamps:
        templates[b"Light"] = fbx_template_def_light(scene, settings, nbr_users=len(data_lamps))

    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:
        templates[b"Geometry"] = fbx_template_def_geometry(scene, settings, nbr_users=len(data_meshes))

    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:
        nbr = len(data_deformers)
        nbr += sum(len(clusters) for def_me in data_deformers.values() for a, b, clusters in def_me.values())
        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...

    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_fbxuid_from_key(bo_data_key), ob_obj.fbx_uuid, None))
        else:
            if ob_obj.type == 'LAMP':
                lamp_key = data_lamps[ob_obj.bdata.data]
                connections.append((b"OO", get_fbxuid_from_key(lamp_key), ob_obj.fbx_uuid, None))
            elif ob_obj.type == 'CAMERA':
                cam_key = data_cameras[ob_obj]
                connections.append((b"OO", get_fbxuid_from_key(cam_key), ob_obj.fbx_uuid, None))
            elif ob_obj.type == 'EMPTY':
                empty_key = data_empties[ob_obj]
                connections.append((b"OO", get_fbxuid_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.bdata]
                connections.append((b"OO", get_fbxuid_from_key(mesh_key), ob_obj.fbx_uuid, None))

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

    # Materials
    mesh_mat_indices = OrderedDict()
    _objs_indices = {}
    for mat, (mat_key, ob_objs) in data_materials.items():
        for ob_obj in ob_objs:
            connections.append((b"OO", get_fbxuid_from_key(mat_key), ob_obj.fbx_uuid, None))
            if ob_obj.is_object:
                # Get index of this mat for this object.
                # Mat indices for mesh faces are determined by their order in 'mat to ob' connections.
                # Only mats for meshes currently...
                if ob_obj.type not in BLENDER_OBJECT_TYPES_MESHLIKE:
                    continue
                me = ob_obj.bdata.data
                idx = _objs_indices[ob_obj] = _objs_indices.get(ob_obj, -1) + 1
                mesh_mat_indices.setdefault(me, OrderedDict())[mat] = idx
    del _objs_indices

    # Textures
    for tex, (tex_key, mats) in data_textures.items():
        for mat, fbx_mat_props in mats.items():
            mat_key, _ob_objs = data_materials[mat]
            for fbx_prop in fbx_mat_props:
                # texture -> material properties
                connections.append((b"OP", get_fbxuid_from_key(tex_key), get_fbxuid_from_key(mat_key), fbx_prop))

    # Images
    for vid, (vid_key, texs) in data_videos.items():
        for tex in texs:
            tex_key, _texs = data_textures[tex]
            connections.append((b"OO", get_fbxuid_from_key(vid_key), get_fbxuid_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_fbxuid_from_key(astack_key)
        # For now, only one layer!
        alayer_id = get_fbxuid_from_key(alayer_key)
        connections.append((b"OO", alayer_id, astack_id, None))
        for ob_obj, (alayer_key, acurvenodes) in astack.items():
            ob_id = ob_obj.fbx_uuid
            # Animlayer -> animstack.
            # alayer_id = get_fbxuid_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_fbxuid_from_key(acurvenode_key)
                connections.append((b"OO", acurvenode_id, alayer_id, None))
                # Animcurvenode -> object property.
                connections.append((b"OP", acurvenode_id, ob_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_fbxuid_from_key(acurve_key), acurvenode_id, fbx_item.encode()))

    ##### And pack all this!

    return FBXData(
        templates, templates_users, connections,
        settings, scene, objects, animations, frame_start, frame_end,
        data_empties, data_lamps, data_cameras, data_meshes, mesh_mat_indices,
        data_bones, data_deformers,
        data_world, data_materials, data_textures, data_videos,
    )


def fbx_scene_data_cleanup(scene_data):
    """
    Some final cleanup...
    """
    # Delete temp meshes.
    for _key, me, free in scene_data.data_meshes.values():
        if free:
            bpy.data.meshes.remove(me)


##### 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).
    """
    ##### 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)