import_fbx.py

# ##### BEGIN GPL LICENSE BLOCK #####
#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU General Public License
#  as published by the Free Software Foundation; either version 2
#  of the License, or (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program; if not, write to the Free Software Foundation,
#  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
#
# ##### END GPL LICENSE BLOCK #####

# <pep8 compliant>

# Script copyright (C) Blender Foundation

# FBX 7.1.0 -> 7.4.0 loader for Blender

# Not totally pep8 compliant.
#   pep8 import_fbx.py --ignore=E501,E123,E702,E125

if "bpy" in locals():
    import importlib
    if "parse_fbx" in locals():
        importlib.reload(parse_fbx)
    if "fbx_utils" in locals():
        importlib.reload(fbx_utils)

import bpy
from mathutils import Matrix, Euler, Vector

# -----
# Utils
from . import parse_fbx, fbx_utils

from .parse_fbx import data_types, FBXElem
from .fbx_utils import (
    units_convertor_iter,
    array_to_matrix4,
    similar_values,
    similar_values_iter,
    FBXImportSettings
)

# global singleton, assign on execution
fbx_elem_nil = None

# Units convertors...
convert_deg_to_rad_iter = units_convertor_iter("degree", "radian")

MAT_CONVERT_BONE = fbx_utils.MAT_CONVERT_BONE.inverted()
MAT_CONVERT_LAMP = fbx_utils.MAT_CONVERT_LAMP.inverted()
MAT_CONVERT_CAMERA = fbx_utils.MAT_CONVERT_CAMERA.inverted()


def elem_find_first(elem, id_search, default=None):
    for fbx_item in elem.elems:
        if fbx_item.id == id_search:
            return fbx_item
    return default


def elem_find_iter(elem, id_search):
    for fbx_item in elem.elems:
        if fbx_item.id == id_search:
            yield fbx_item


def elem_find_first_string(elem, id_search):
    fbx_item = elem_find_first(elem, id_search)
    if fbx_item is not None:
        assert(len(fbx_item.props) == 1)
        assert(fbx_item.props_type[0] == data_types.STRING)
        return fbx_item.props[0].decode('utf-8')
    return None


def elem_find_first_bytes(elem, id_search, decode=True):
    fbx_item = elem_find_first(elem, id_search)
    if fbx_item is not None:
        assert(len(fbx_item.props) == 1)
        assert(fbx_item.props_type[0] == data_types.STRING)
        return fbx_item.props[0]
    return None


def elem_repr(elem):
    return "%s: props[%d=%r], elems=(%r)" % (
        elem.id,
        len(elem.props),
        ", ".join([repr(p) for p in elem.props]),
        # elem.props_type,
        b", ".join([e.id for e in elem.elems]),
        )


def elem_split_name_class(elem):
    assert(elem.props_type[-2] == data_types.STRING)
    elem_name, elem_class = elem.props[-2].split(b'\x00\x01')
    return elem_name, elem_class


def elem_name_ensure_class(elem, clss=...):
    elem_name, elem_class = elem_split_name_class(elem)
    if clss is not ...:
        assert(elem_class == clss)
    return elem_name.decode('utf-8')


def elem_split_name_class_nodeattr(elem):
    assert(elem.props_type[-2] == data_types.STRING)
    elem_name, elem_class = elem.props[-2].split(b'\x00\x01')
    assert(elem_class == b'NodeAttribute')
    assert(elem.props_type[-1] == data_types.STRING)
    elem_class = elem.props[-1]
    return elem_name, elem_class


def elem_uuid(elem):
    assert(elem.props_type[0] == data_types.INT64)
    return elem.props[0]


def elem_prop_first(elem, default=None):
    return elem.props[0] if (elem is not None) and elem.props else default


# ----
# Support for
# Properties70: { ... P:
def elem_props_find_first(elem, elem_prop_id):

    # support for templates (tuple of elems)
    if type(elem) is not FBXElem:
        assert(type(elem) is tuple)
        for e in elem:
            result = elem_props_find_first(e, elem_prop_id)
            if result is not None:
                return result
        assert(len(elem) > 0)
        return None

    for subelem in elem.elems:
        assert(subelem.id == b'P')
        if subelem.props[0] == elem_prop_id:
            return subelem
    return None


def elem_props_get_color_rgb(elem, elem_prop_id, default=None):
    elem_prop = elem_props_find_first(elem, elem_prop_id)
    if elem_prop is not None:
        assert(elem_prop.props[0] == elem_prop_id)
        if elem_prop.props[1] == b'Color':
            # FBX version 7300
            assert(elem_prop.props[1] == b'Color')
            assert(elem_prop.props[2] == b'')
            assert(elem_prop.props[3] in {b'A', b'A+', b'AU'})
        else:
            assert(elem_prop.props[1] == b'ColorRGB')
            assert(elem_prop.props[2] == b'Color')
        assert(elem_prop.props_type[4:7] == bytes((data_types.FLOAT64,)) * 3)
        return elem_prop.props[4:7]
    return default


def elem_props_get_vector_3d(elem, elem_prop_id, default=None):
    elem_prop = elem_props_find_first(elem, elem_prop_id)
    if elem_prop is not None:
        assert(elem_prop.props_type[4:7] == bytes((data_types.FLOAT64,)) * 3)
        return elem_prop.props[4:7]
    return default


def elem_props_get_number(elem, elem_prop_id, default=None):
    elem_prop = elem_props_find_first(elem, elem_prop_id)
    if elem_prop is not None:
        assert(elem_prop.props[0] == elem_prop_id)
        if elem_prop.props[1] == b'double':
            assert(elem_prop.props[1] == b'double')
            assert(elem_prop.props[2] == b'Number')
        else:
            assert(elem_prop.props[1] == b'Number')
            assert(elem_prop.props[2] == b'')
            assert(elem_prop.props[3] in {b'A', b'A+', b'AU'})

        # we could allow other number types
        assert(elem_prop.props_type[4] == data_types.FLOAT64)

        return elem_prop.props[4]
    return default


def elem_props_get_integer(elem, elem_prop_id, default=None):
    elem_prop = elem_props_find_first(elem, elem_prop_id)
    if elem_prop is not None:
        assert(elem_prop.props[0] == elem_prop_id)
        if elem_prop.props[1] == b'int':
            assert(elem_prop.props[1] == b'int')
            assert(elem_prop.props[2] == b'Integer')
        elif elem_prop.props[1] == b'ULongLong':
            assert(elem_prop.props[1] == b'ULongLong')
            assert(elem_prop.props[2] == b'')

        # we could allow other number types
        assert(elem_prop.props_type[4] in {data_types.INT32, data_types.INT64})

        return elem_prop.props[4]
    return default


def elem_props_get_bool(elem, elem_prop_id, default=None):
    elem_prop = elem_props_find_first(elem, elem_prop_id)
    if elem_prop is not None:
        assert(elem_prop.props[0] == elem_prop_id)
        assert(elem_prop.props[1] == b'bool')
        assert(elem_prop.props[2] == b'')
        assert(elem_prop.props[3] == b'')

        # we could allow other number types
        assert(elem_prop.props_type[4] == data_types.INT32)
        assert(elem_prop.props[4] in {0, 1})

        return bool(elem_prop.props[4])
    return default


def elem_props_get_enum(elem, elem_prop_id, default=None):
    elem_prop = elem_props_find_first(elem, elem_prop_id)
    if elem_prop is not None:
        assert(elem_prop.props[0] == elem_prop_id)
        assert(elem_prop.props[1] == b'enum')
        assert(elem_prop.props[2] == b'')
        assert(elem_prop.props[3] == b'')

        # we could allow other number types
        assert(elem_prop.props_type[4] == data_types.INT32)

        return elem_prop.props[4]
    return default


def elem_props_get_visibility(elem, elem_prop_id, default=None):
    elem_prop = elem_props_find_first(elem, elem_prop_id)
    if elem_prop is not None:
        assert(elem_prop.props[0] == elem_prop_id)
        assert(elem_prop.props[1] == b'Visibility')
        assert(elem_prop.props[2] == b'')
        assert(elem_prop.props[3] in {b'A', b'A+', b'AU'})

        # we could allow other number types
        assert(elem_prop.props_type[4] == data_types.FLOAT64)

        return elem_prop.props[4]
    return default


# ----------------------------------------------------------------------------
# Blender

# ------
# Object
from collections import namedtuple


FBXTransformData = namedtuple("FBXTransformData", (
    "loc",
    "rot", "rot_ofs", "rot_piv", "pre_rot", "pst_rot", "rot_ord", "rot_alt_mat",
    "sca", "sca_ofs", "sca_piv",
))


def blen_read_custom_properties(fbx_obj, blen_obj, settings):
    # There doesn't seem to be a way to put user properties into templates, so this only get the object properties:
    fbx_obj_props = elem_find_first(fbx_obj, b'Properties70')
    if fbx_obj_props:
        for fbx_prop in fbx_obj_props.elems:
            assert(fbx_prop.id == b'P')

            if b'U' in fbx_prop.props[3]:
                if fbx_prop.props[0] == b'UDP3DSMAX':
                    # Special case for 3DS Max user properties:
                    assert(fbx_prop.props[1] == b'KString')
                    assert(fbx_prop.props_type[4] == data_types.STRING)
                    items = fbx_prop.props[4].decode('utf-8')
                    for item in items.split('\r\n'):
                        if item:
                            prop_name, prop_value = item.split('=', 1)
                            blen_obj[prop_name.strip()] = prop_value.strip()
                else:
                    prop_name = fbx_prop.props[0].decode('utf-8')
                    prop_type = fbx_prop.props[1]
                    if prop_type in {b'Vector', b'Vector3D', b'Color', b'ColorRGB'}:
                        assert(fbx_prop.props_type[4:7] == bytes((data_types.FLOAT64,)) * 3)
                        blen_obj[prop_name] = fbx_prop.props[4:7]
                    elif prop_type in {b'Vector4', b'ColorRGBA'}:
                        assert(fbx_prop.props_type[4:8] == bytes((data_types.FLOAT64,)) * 4)
                        blen_obj[prop_name] = fbx_prop.props[4:8]
                    elif prop_type == b'Vector2D':
                        assert(fbx_prop.props_type[4:6] == bytes((data_types.FLOAT64,)) * 2)
                        blen_obj[prop_name] = fbx_prop.props[4:6]
                    elif prop_type in {b'Integer', b'int'}:
                        assert(fbx_prop.props_type[4] == data_types.INT32)
                        blen_obj[prop_name] = fbx_prop.props[4]
                    elif prop_type == b'KString':
                        assert(fbx_prop.props_type[4] == data_types.STRING)
                        blen_obj[prop_name] = fbx_prop.props[4].decode('utf-8')
                    elif prop_type in {b'Number', b'double', b'Double'}:
                        assert(fbx_prop.props_type[4] == data_types.FLOAT64)
                        blen_obj[prop_name] = fbx_prop.props[4]
                    elif prop_type in {b'Float', b'float'}:
                        assert(fbx_prop.props_type[4] == data_types.FLOAT32)
                        blen_obj[prop_name] = fbx_prop.props[4]
                    elif prop_type in {b'Bool', b'bool'}:
                        assert(fbx_prop.props_type[4] == data_types.INT32)
                        blen_obj[prop_name] = fbx_prop.props[4] != 0
                    elif prop_type in {b'Enum', b'enum'}:
                        assert(fbx_prop.props_type[4:6] == bytes((data_types.INT32, data_types.STRING)))
                        val = fbx_prop.props[4]
                        if settings.use_custom_props_enum_as_string:
                            enum_items = fbx_prop.props[5].decode('utf-8').split('~')
                            assert(val >= 0 and val < len(enum_items))
                            blen_obj[prop_name] = enum_items[val]
                        else:
                            blen_obj[prop_name] = val
                    else:
                        print ("WARNING: User property type '%s' is not supported" % prop_type.decode('utf-8'))


def blen_read_object_transform_do(transform_data):
    # translation
    lcl_translation = Matrix.Translation(transform_data.loc)

    # rotation
    to_rot = lambda rot, rot_ord: Euler(convert_deg_to_rad_iter(rot), rot_ord).to_matrix().to_4x4()
    lcl_rot = to_rot(transform_data.rot, transform_data.rot_ord) * transform_data.rot_alt_mat
    pre_rot = to_rot(transform_data.pre_rot, transform_data.rot_ord)
    pst_rot = to_rot(transform_data.pst_rot, transform_data.rot_ord)

    rot_ofs = Matrix.Translation(transform_data.rot_ofs)
    rot_piv = Matrix.Translation(transform_data.rot_piv)
    sca_ofs = Matrix.Translation(transform_data.sca_ofs)
    sca_piv = Matrix.Translation(transform_data.sca_piv)

    # scale
    lcl_scale = Matrix()
    lcl_scale[0][0], lcl_scale[1][1], lcl_scale[2][2] = transform_data.sca

    return (
        lcl_translation *
        rot_ofs *
        rot_piv *
        pre_rot *
        lcl_rot *
        pst_rot *
        rot_piv.inverted_safe() *
        sca_ofs *
        sca_piv *
        lcl_scale *
        sca_piv.inverted_safe()
    )


# XXX This might be weak, now that we can add vgroups from both bones and shapes, name collisions become
#     more likely, will have to make this more robust!!!
def add_vgroup_to_objects(vg_indices, vg_weights, vg_name, objects):
    assert(len(vg_indices) == len(vg_weights))
    if vg_indices:
        for obj in objects:
            # We replace/override here...
            vg = obj.vertex_groups.get(vg_name)
            if vg is None:
                vg = obj.vertex_groups.new(vg_name)
            for i, w in zip(vg_indices, vg_weights):
                vg.add((i,), w, 'REPLACE')


def blen_read_object_transform_preprocess(fbx_props, fbx_obj, rot_alt_mat, use_prepost_rot):
    # This is quite involved, 'fbxRNode.cpp' from openscenegraph used as a reference
    const_vector_zero_3d = 0.0, 0.0, 0.0
    const_vector_one_3d = 1.0, 1.0, 1.0

    loc = list(elem_props_get_vector_3d(fbx_props, b'Lcl Translation', const_vector_zero_3d))
    rot = list(elem_props_get_vector_3d(fbx_props, b'Lcl Rotation', const_vector_zero_3d))
    sca = list(elem_props_get_vector_3d(fbx_props, b'Lcl Scaling', const_vector_one_3d))

    rot_ofs = elem_props_get_vector_3d(fbx_props, b'RotationOffset', const_vector_zero_3d)
    rot_piv = elem_props_get_vector_3d(fbx_props, b'RotationPivot', const_vector_zero_3d)
    sca_ofs = elem_props_get_vector_3d(fbx_props, b'ScalingOffset', const_vector_zero_3d)
    sca_piv = elem_props_get_vector_3d(fbx_props, b'ScalingPivot', const_vector_zero_3d)

    is_rot_act = elem_props_get_bool(fbx_props, b'RotationActive', False)

    if is_rot_act:
        if use_prepost_rot:
            pre_rot = elem_props_get_vector_3d(fbx_props, b'PreRotation', const_vector_zero_3d)
            pst_rot = elem_props_get_vector_3d(fbx_props, b'PostRotation', const_vector_zero_3d)
        else:
            pre_rot = const_vector_zero_3d
            pst_rot = const_vector_zero_3d
        rot_ord = {
            0: 'XYZ',
            1: 'XYZ',
            2: 'XZY',
            3: 'YZX',
            4: 'YXZ',
            5: 'ZXY',
            6: 'ZYX',
            }.get(elem_props_get_enum(fbx_props, b'RotationOrder', 0))
    else:
        pre_rot = const_vector_zero_3d
        pst_rot = const_vector_zero_3d
        rot_ord = 'XYZ'

    return FBXTransformData(loc,
                            rot, rot_ofs, rot_piv, pre_rot, pst_rot, rot_ord, rot_alt_mat,
                            sca, sca_ofs, sca_piv)


# ---------
# Animation
def blen_read_animations_curves_iter(fbx_curves, blen_start_offset, fbx_start_offset, fps):
    """
    Get raw FBX AnimCurve list, and yield values for all curves at each singular curves' keyframes,
    together with (blender) timing, in frames.
    blen_start_offset is expected in frames, while fbx_start_offset is expected in FBX ktime.
    """
    # As a first step, assume linear interpolation between key frames, we'll (try to!) handle more
    # of FBX curves later.
    from .fbx_utils import FBX_KTIME
    timefac = fps / FBX_KTIME

    curves = tuple([0,
                    elem_prop_first(elem_find_first(c[2], b'KeyTime')),
                    elem_prop_first(elem_find_first(c[2], b'KeyValueFloat')),
                    c]
                   for c in fbx_curves)

    allkeys = sorted({item for sublist in curves for item in sublist[1]})
    for curr_fbxktime in allkeys:
        curr_values = []
        for item in curves:
            idx, times, values, fbx_curve = item

            if times[idx] < curr_fbxktime:
                if idx >= 0:
                    idx += 1
                    if idx >= len(times):
                        # We have reached our last element for this curve, stay on it from now on...
                        idx = -1
                    item[0] = idx

            if times[idx] >= curr_fbxktime:
                if idx == 0:
                    curr_values.append((values[idx], fbx_curve))
                else:
                    # Interpolate between this key and the previous one.
                    ifac = (curr_fbxktime - times[idx - 1]) / (times[idx] - times[idx - 1])
                    curr_values.append(((values[idx] - values[idx - 1]) * ifac + values[idx - 1], fbx_curve))
        curr_blenkframe = (curr_fbxktime - fbx_start_offset) * timefac + blen_start_offset
        yield (curr_blenkframe, curr_values)


def blen_read_animations_action_item(action, item, cnodes, fps):
    """
    'Bake' loc/rot/scale into the action,
    taking any pre_ and post_ matrix into account to transform from fbx into blender space.
    """
    from bpy.types import Object, PoseBone, ShapeKey
    from itertools import chain

    fbx_curves = []
    for curves, fbxprop in cnodes.values():
        for (fbx_acdata, _blen_data), channel in curves.values():
            fbx_curves.append((fbxprop, channel, fbx_acdata))

    # Leave if no curves are attached (if a blender curve is attached to scale but without keys it defaults to 0).
    if len(fbx_curves) == 0:
        return

    blen_curves = []
    props = []

    if isinstance(item, ShapeKey):
        props = [(item.path_from_id("value"), 1, "Key")]
    else:  # Object or PoseBone:
        if item.is_bone:
            bl_obj = item.bl_obj.pose.bones[item.bl_bone]
        else:
            bl_obj = item.bl_obj

        # We want to create actions for objects, but for bones we 'reuse' armatures' actions!
        grpname = item.bl_obj.name

        # Since we might get other channels animated in the end, due to all FBX transform magic,
        # we need to add curves for whole loc/rot/scale in any case.
        props = [(bl_obj.path_from_id("location"), 3, grpname or "Location"),
                 None,
                 (bl_obj.path_from_id("scale"), 3, grpname or "Scale")]
        rot_mode = bl_obj.rotation_mode
        if rot_mode == 'QUATERNION':
            props[1] = (bl_obj.path_from_id("rotation_quaternion"), 4, grpname or "Quaternion Rotation")
        elif rot_mode == 'AXIS_ANGLE':
            props[1] = (bl_obj.path_from_id("rotation_axis_angle"), 4, grpname or "Axis Angle Rotation")
        else:  # Euler
            props[1] = (bl_obj.path_from_id("rotation_euler"), 3, grpname or "Euler Rotation")

    blen_curves = [action.fcurves.new(prop, channel, grpname)
                   for prop, nbr_channels, grpname in props for channel in range(nbr_channels)]

    if isinstance(item, ShapeKey):
        # We assume for now blen init point is frame 1.0, while FBX ktime init point is 0.
        for frame, values in blen_read_animations_curves_iter(fbx_curves, 1.0, 0, fps):
            value = 0.0
            for v, (fbxprop, channel, _fbx_acdata) in values:
                assert(fbxprop == b'DeformPercent')
                assert(channel == 0)
                value = v / 100.0

            for fc, v in zip(blen_curves, (value,)):
                fc.keyframe_points.insert(frame, v, {'NEEDED', 'FAST'}).interpolation = 'LINEAR'

    else:  # Object or PoseBone:
        if item.is_bone:
            bl_obj = item.bl_obj.pose.bones[item.bl_bone]
        else:
            bl_obj = item.bl_obj

        transform_data = item.fbx_transform_data
        rot_prev = bl_obj.rotation_euler.copy()

        # Pre-compute inverted local rest matrix of the bone, if relevant.
        restmat_inv = item.get_bind_matrix().inverted_safe() if item.is_bone else None

        # We assume for now blen init point is frame 1.0, while FBX ktime init point is 0.
        for frame, values in blen_read_animations_curves_iter(fbx_curves, 1.0, 0, fps):
            for v, (fbxprop, channel, _fbx_acdata) in values:
                if fbxprop == b'Lcl Translation':
                    transform_data.loc[channel] = v
                elif fbxprop == b'Lcl Rotation':
                    transform_data.rot[channel] = v
                elif fbxprop == b'Lcl Scaling':
                    transform_data.sca[channel] = v
            mat = blen_read_object_transform_do(transform_data)

            # compensate for changes in the local matrix during processing
            if item.anim_compensation_matrix:
                mat = mat * item.anim_compensation_matrix

            # apply pre- and post matrix
            # post-matrix will contain any correction for lights, camera and bone orientation
            # pre-matrix will contain any correction for a parent's correction matrix or the global matrix
            if item.pre_matrix:
                mat = item.pre_matrix * mat
            if item.post_matrix:
                mat = mat * item.post_matrix

            # And now, remove that rest pose matrix from current mat (also in parent space).
            if restmat_inv:
                mat = restmat_inv * mat

            # Now we have a virtual matrix of transform from AnimCurves, we can insert keyframes!
            loc, rot, sca = mat.decompose()
            if rot_mode == 'QUATERNION':
                pass  # nothing to do!
            elif rot_mode == 'AXIS_ANGLE':
                vec, ang = rot.to_axis_angle()
                rot = ang, vec.x, vec.y, vec.z
            else:  # Euler
                rot = rot.to_euler(rot_mode, rot_prev)
                rot_prev = rot
            for fc, value in zip(blen_curves, chain(loc, rot, sca)):
                fc.keyframe_points.insert(frame, value, {'NEEDED', 'FAST'}).interpolation = 'LINEAR'

    # Since we inserted our keyframes in 'FAST' mode, we have to update the fcurves now.
    for fc in blen_curves:
        fc.update()


def blen_read_animations(fbx_tmpl_astack, fbx_tmpl_alayer, stacks, scene):
    """
    Recreate an action per stack/layer/object combinations.
    Only the first found action is linked to objects, more complex setups are not handled,
    it's up to user to reproduce them!
    """
    from bpy.types import ShapeKey

    actions = {}
    for as_uuid, ((fbx_asdata, _blen_data), alayers) in stacks.items():
        stack_name = elem_name_ensure_class(fbx_asdata, b'AnimStack')
        for al_uuid, ((fbx_aldata, _blen_data), items) in alayers.items():
            layer_name = elem_name_ensure_class(fbx_aldata, b'AnimLayer')
            for item, cnodes in items.items():
                if isinstance(item, ShapeKey):
                    id_data = item.id_data
                else:
                    id_data = item.bl_obj
                if id_data is None:
                    continue
                # Create new action if needed (should always be needed!
                key = (as_uuid, al_uuid, id_data)
                action = actions.get(key)
                if action is None:
                    action_name = "|".join((id_data.name, stack_name, layer_name))
                    actions[key] = action = bpy.data.actions.new(action_name)
                    action.use_fake_user = True
                # If none yet assigned, assign this action to id_data.
                if not id_data.animation_data:
                    id_data.animation_data_create()
                if not id_data.animation_data.action:
                    id_data.animation_data.action = action
                # And actually populate the action!
                blen_read_animations_action_item(action, item, cnodes, scene.render.fps)


# ----
# Mesh

def blen_read_geom_layerinfo(fbx_layer):
    return (
        elem_find_first_string(fbx_layer, b'Name'),
        elem_find_first_bytes(fbx_layer, b'MappingInformationType'),
        elem_find_first_bytes(fbx_layer, b'ReferenceInformationType'),
        )


def blen_read_geom_array_setattr(generator, blen_data, blen_attr, fbx_data, stride, item_size, descr, xform):
    """Generic fbx_layer to blen_data setter, generator is expected to yield tuples (ble_idx, fbx_idx)."""
    if xform is not None:
        for blen_idx, fbx_idx in generator:
            if fbx_idx == -1:
                continue
            setattr(blen_data[blen_idx], blen_attr,
                    xform(fbx_data[fbx_idx] if (item_size == 1) else fbx_data[fbx_idx:fbx_idx + item_size]))
    else:
        for blen_idx, fbx_idx in generator:
            if fbx_idx == -1:
                continue
            setattr(blen_data[blen_idx], blen_attr,
                    fbx_data[fbx_idx] if (item_size == 1) else fbx_data[fbx_idx:fbx_idx + item_size])


# generic generators.
def blen_read_geom_array_gen_direct(fbx_data, stride):
    fbx_data_len = len(fbx_data)
    return zip(*(range(fbx_data_len // stride), range(0, fbx_data_len, stride)))


def blen_read_geom_array_gen_indextodirect(fbx_layer_index, stride):
    return ((bi, fi * stride) for bi, fi in enumerate(fbx_layer_index))


def blen_read_geom_array_gen_direct_looptovert(mesh, fbx_data, stride):
    fbx_data_len = len(fbx_data) // stride
    loops = mesh.loops
    for p in mesh.polygons:
        for lidx in p.loop_indices:
            vidx = loops[lidx].vertex_index
            if vidx < fbx_data_len:
                yield lidx, vidx * stride


# generic error printers.
def blen_read_geom_array_error_mapping(descr, fbx_layer_mapping):
    print("warning layer %r mapping type unsupported: %r" % (descr, fbx_layer_mapping))


def blen_read_geom_array_error_ref(descr, fbx_layer_ref):
    print("warning layer %r ref type unsupported: %r" % (descr, fbx_layer_ref))


def blen_read_geom_array_mapped_vert(
        mesh, blen_data, blen_attr,
        fbx_layer_data, fbx_layer_index,
        fbx_layer_mapping, fbx_layer_ref,
        stride, item_size, descr,
        xform=None,
        ):
    if fbx_layer_mapping == b'ByVertice':
        if fbx_layer_ref == b'Direct':
            assert(fbx_layer_index is None)
            blen_read_geom_array_setattr(blen_read_geom_array_gen_direct(fbx_layer_data, stride),
                                         blen_data, blen_attr, fbx_layer_data, stride, item_size, descr, xform)
            return True
        blen_read_geom_array_error_ref(descr, fbx_layer_ref)
    else:
        blen_read_geom_array_error_mapping(descr, fbx_layer_mapping)

    return False


def blen_read_geom_array_mapped_edge(
        mesh, blen_data, blen_attr,
        fbx_layer_data, fbx_layer_index,
        fbx_layer_mapping, fbx_layer_ref,
        stride, item_size, descr,
        xform=None,
        ):
    if fbx_layer_mapping == b'ByEdge':
        if fbx_layer_ref == b'Direct':
            blen_read_geom_array_setattr(blen_read_geom_array_gen_direct(fbx_layer_data, stride),
                                         blen_data, blen_attr, fbx_layer_data, stride, item_size, descr, xform)
            return True
        blen_read_geom_array_error_ref(descr, fbx_layer_ref)
    else:
        blen_read_geom_array_error_mapping(descr, fbx_layer_mapping)

    return False


def blen_read_geom_array_mapped_polygon(
        mesh, blen_data, blen_attr,
        fbx_layer_data, fbx_layer_index,
        fbx_layer_mapping, fbx_layer_ref,
        stride, item_size, descr,
        xform=None,
        ):
    if fbx_layer_mapping == b'ByPolygon':
        if fbx_layer_ref == b'IndexToDirect':
            # XXX Looks like we often get no fbx_layer_index in this case, shall not happen but happens...
            #     We fallback to 'Direct' mapping in this case.
            #~ assert(fbx_layer_index is not None)
            if fbx_layer_index is None:
                blen_read_geom_array_setattr(blen_read_geom_array_gen_direct(fbx_layer_data, stride),
                                            blen_data, blen_attr, fbx_layer_data, stride, item_size, descr, xform)
            else:
                blen_read_geom_array_setattr(blen_read_geom_array_gen_indextodirect(fbx_layer_index, stride),
                                             blen_data, blen_attr, fbx_layer_data, stride, item_size, descr, xform)
            return True
        elif fbx_layer_ref == b'Direct':
            blen_read_geom_array_setattr(blen_read_geom_array_gen_direct(fbx_layer_data, stride),
                                         blen_data, blen_attr, fbx_layer_data, stride, item_size, descr, xform)
            return True
        blen_read_geom_array_error_ref(descr, fbx_layer_ref)
    else:
        blen_read_geom_array_error_mapping(descr, fbx_layer_mapping)

    return False


def blen_read_geom_array_mapped_polyloop(
        mesh, blen_data, blen_attr,
        fbx_layer_data, fbx_layer_index,
        fbx_layer_mapping, fbx_layer_ref,
        stride, item_size, descr,
        xform=None,
        ):
    if fbx_layer_mapping == b'ByPolygonVertex':
        if fbx_layer_ref == b'IndexToDirect':
            assert(fbx_layer_index is not None)
            blen_read_geom_array_setattr(blen_read_geom_array_gen_indextodirect(fbx_layer_index, stride),
                                         blen_data, blen_attr, fbx_layer_data, stride, item_size, descr, xform)
            return True
        blen_read_geom_array_error_ref(descr, fbx_layer_ref)
    elif fbx_layer_mapping == b'ByVertice':
        if fbx_layer_ref == b'Direct':
            assert(fbx_layer_index is None)
            blen_read_geom_array_setattr(blen_read_geom_array_gen_direct_looptovert(mesh, fbx_layer_data, stride),
                                         blen_data, blen_attr, fbx_layer_data, stride, item_size, descr, xform)
            return True
        blen_read_geom_array_error_ref(descr, fbx_layer_ref)
    else:
        blen_read_geom_array_error_mapping(descr, fbx_layer_mapping)

    return False


def blen_read_geom_layer_material(fbx_obj, mesh):
    fbx_layer = elem_find_first(fbx_obj, b'LayerElementMaterial')

    if fbx_layer is None:
        return

    (fbx_layer_name,
     fbx_layer_mapping,
     fbx_layer_ref,
     ) = blen_read_geom_layerinfo(fbx_layer)

    if fbx_layer_mapping == b'AllSame':
        # only to quiet warning
        return

    layer_id = b'Materials'
    fbx_layer_data = elem_prop_first(elem_find_first(fbx_layer, layer_id))

    blen_data = mesh.polygons
    blen_read_geom_array_mapped_polygon(
        mesh, blen_data, "material_index",
        fbx_layer_data, None,
        fbx_layer_mapping, fbx_layer_ref,
        1, 1, layer_id,
        )


def blen_read_geom_layer_uv(fbx_obj, mesh):
    for layer_id in (b'LayerElementUV',):
        for fbx_layer in elem_find_iter(fbx_obj, layer_id):
            # all should be valid
            (fbx_layer_name,
             fbx_layer_mapping,
             fbx_layer_ref,
             ) = blen_read_geom_layerinfo(fbx_layer)

            fbx_layer_data = elem_prop_first(elem_find_first(fbx_layer, b'UV'))
            fbx_layer_index = elem_prop_first(elem_find_first(fbx_layer, b'UVIndex'))

            uv_tex = mesh.uv_textures.new(name=fbx_layer_name)
            uv_lay = mesh.uv_layers[-1]
            blen_data = uv_lay.data[:]

            # some valid files omit this data
            if fbx_layer_data is None:
                print("%r %r missing data" % (layer_id, fbx_layer_name))
                continue

            blen_read_geom_array_mapped_polyloop(
                mesh, blen_data, "uv",
                fbx_layer_data, fbx_layer_index,
                fbx_layer_mapping, fbx_layer_ref,
                2, 2, layer_id,
                )


def blen_read_geom_layer_color(fbx_obj, mesh):
    # almost same as UV's
    for layer_id in (b'LayerElementColor',):
        for fbx_layer in elem_find_iter(fbx_obj, layer_id):
            # all should be valid
            (fbx_layer_name,
             fbx_layer_mapping,
             fbx_layer_ref,
             ) = blen_read_geom_layerinfo(fbx_layer)

            fbx_layer_data = elem_prop_first(elem_find_first(fbx_layer, b'Colors'))
            fbx_layer_index = elem_prop_first(elem_find_first(fbx_layer, b'ColorIndex'))

            color_lay = mesh.vertex_colors.new(name=fbx_layer_name)
            blen_data = color_lay.data[:]

            # some valid files omit this data
            if fbx_layer_data is None:
                print("%r %r missing data" % (layer_id, fbx_layer_name))
                continue

            # ignore alpha layer (read 4 items into 3)
            blen_read_geom_array_mapped_polyloop(
                mesh, blen_data, "color",
                fbx_layer_data, fbx_layer_index,
                fbx_layer_mapping, fbx_layer_ref,
                4, 3, layer_id,
                )


def blen_read_geom_layer_smooth(fbx_obj, mesh):
    fbx_layer = elem_find_first(fbx_obj, b'LayerElementSmoothing')

    if fbx_layer is None:
        return False

    # all should be valid
    (fbx_layer_name,
     fbx_layer_mapping,
     fbx_layer_ref,
     ) = blen_read_geom_layerinfo(fbx_layer)

    layer_id = b'Smoothing'
    fbx_layer_data = elem_prop_first(elem_find_first(fbx_layer, layer_id))

    # udk has 'Direct' mapped, with no Smoothing, not sure why, but ignore these
    if fbx_layer_data is None:
        return False

    if fbx_layer_mapping == b'ByEdge':
        # some models have bad edge data, we cant use this info...
        if not mesh.edges:
            return False

        blen_data = mesh.edges
        ok_smooth = blen_read_geom_array_mapped_edge(
            mesh, blen_data, "use_edge_sharp",
            fbx_layer_data, None,
            fbx_layer_mapping, fbx_layer_ref,
            1, 1, layer_id,
            xform=lambda s: not s,
            )
        return ok_smooth
    elif fbx_layer_mapping == b'ByPolygon':
        blen_data = mesh.polygons
        return blen_read_geom_array_mapped_polygon(
            mesh, blen_data, "use_smooth",
            fbx_layer_data, None,
            fbx_layer_mapping, fbx_layer_ref,
            1, 1, layer_id,
            xform=lambda s: (s != 0),  # smoothgroup bitflags, treat as booleans for now
            )
    else:
        print("warning layer %r mapping type unsupported: %r" % (fbx_layer.id, fbx_layer_mapping))
        return False


def blen_read_geom_layer_normal(fbx_obj, mesh, xform=None):
    fbx_layer = elem_find_first(fbx_obj, b'LayerElementNormal')

    if fbx_layer is None:
        return False

    (fbx_layer_name,
     fbx_layer_mapping,
     fbx_layer_ref,
     ) = blen_read_geom_layerinfo(fbx_layer)

    layer_id = b'Normals'
    fbx_layer_data = elem_prop_first(elem_find_first(fbx_layer, layer_id))

    blen_data = mesh.vertices

    return blen_read_geom_array_mapped_vert(
        mesh, blen_data, "normal",
        fbx_layer_data, None,
        fbx_layer_mapping, fbx_layer_ref,
        3, 3, layer_id,
        xform
        )


def blen_read_geom(fbx_tmpl, fbx_obj, settings):
    from itertools import chain
    import array

    # Vertices are in object space, but we are post-multiplying all transforms with the inverse of the
    # global matrix, so we need to apply the global matrix to the vertices to get the correct result.
    geom_mat_co = settings.global_matrix if settings.bake_space_transform else None
    # We need to apply the inverse transpose of the global matrix when transforming normals.
    geom_mat_no = Matrix(settings.global_matrix_inv_transposed) if settings.bake_space_transform else None
    if geom_mat_no is not None:
        # Remove translation & scaling!
        geom_mat_no.translation = Vector()
        geom_mat_no.normalize()

    # TODO, use 'fbx_tmpl'
    elem_name_utf8 = elem_name_ensure_class(fbx_obj, b'Geometry')

    fbx_verts = elem_prop_first(elem_find_first(fbx_obj, b'Vertices'))
    fbx_polys = elem_prop_first(elem_find_first(fbx_obj, b'PolygonVertexIndex'))
    fbx_edges = elem_prop_first(elem_find_first(fbx_obj, b'Edges'))

    if geom_mat_co is not None:
        def _vcos_transformed_gen(raw_cos, m=None):
            # Note: we could most likely get much better performances with numpy, but will leave this as TODO for now.
            return chain(*(m * Vector(v) for v in zip(*(iter(raw_cos),) * 3)))
        fbx_verts = array.array(fbx_verts.typecode, _vcos_transformed_gen(fbx_verts, geom_mat_co))

    if fbx_verts is None:
        fbx_verts = ()
    if fbx_polys is None:
        fbx_polys = ()

    mesh = bpy.data.meshes.new(name=elem_name_utf8)
    mesh.vertices.add(len(fbx_verts) // 3)
    mesh.vertices.foreach_set("co", fbx_verts)

    if fbx_polys:
        mesh.loops.add(len(fbx_polys))
        poly_loop_starts = []
        poly_loop_totals = []
        poly_loop_prev = 0
        for i, l in enumerate(mesh.loops):
            index = fbx_polys[i]
            if index < 0:
                poly_loop_starts.append(poly_loop_prev)
                poly_loop_totals.append((i - poly_loop_prev) + 1)
                poly_loop_prev = i + 1
                index ^= -1
            l.vertex_index = index

        mesh.polygons.add(len(poly_loop_starts))
        mesh.polygons.foreach_set("loop_start", poly_loop_starts)
        mesh.polygons.foreach_set("loop_total", poly_loop_totals)

        blen_read_geom_layer_material(fbx_obj, mesh)
        blen_read_geom_layer_uv(fbx_obj, mesh)
        blen_read_geom_layer_color(fbx_obj, mesh)

    if fbx_edges:
        # edges in fact index the polygons (NOT the vertices)
        import array
        tot_edges = len(fbx_edges)
        edges_conv = array.array('i', [0]) * (tot_edges * 2)

        edge_index = 0
        for i in fbx_edges:
            e_a = fbx_polys[i]
            if e_a >= 0:
                e_b = fbx_polys[i + 1]