How can I make a custom fbx exporter for unity?

Question

I want to export fbx for unity based on manual way in this video I know there is an option as !!EXPERIMENTAL!!, I don't want to use it because sometimes it doesn't work.

Manual Way

manual way works fine I just want to do manual way by code. because I have to repeat these steps on every 3d models!!!

suppose we have a fish model and we want to export it to untiy

1.Manually rotate the object by -90 degree around X-axis (if you don't see this panel - press N key)

2.press Ctrl + A and Apply => Rotation

3.and set X rotation to 90 degrees (do not apply this time)

Answer 1

you can make steps automatic

1.rotate the object by -90 degree around X-axis

obj.rotation_euler = (math.radians(-90),0,0)

2.press Ctrl + A and Apply => Rotation

bpy.ops.object.transform_apply(location=False, rotation=True, scale=False)

3.and set X rotation to 90 degrees (do not apply this time)

obj.rotation_euler = (math.radians(-90),0,0)

also, you can export it by unit scale

bl_info = {
    "name": "Unity Fix",
    "author": "Kamali",
    "version": (1, 0),
    "blender": (2, 80, 0),
    "location": "File > Export > Export For Unity",
    "description": "Fix Pivot ,Location , Rotation , Scale ",
    "warning": "",
    "doc_url": "",
    "category": "",
}
import bpy
import math
def write_some_data(context, filepath):
    bpy.ops.object.origin_set(type='ORIGIN_CENTER_OF_MASS', center='MEDIAN')
    obj= context.object
# reset location to the center
obj.location = (0,0,0)

# reset everything to make sure it won't change
bpy.ops.object.transform_apply(location=True, rotation=True, scale=True)
# set rotation to -90

obj.rotation_euler = (math.radians(-90),0,0)
# reset everything
bpy.ops.object.transform_apply(location=True, rotation=True, scale=True)

# rotate 90 degree along x axis
obj.rotation_euler = (math.radians(90),0,0)


# apply unit scaling
bpy.ops.export_scene.fbx(filepath=filepath, use_selection=True,apply_scale_options='FBX_SCALE_UNITS',apply_unit_scale=True)
return {'FINISHED'}





from bpy_extras.io_utils import ExportHelper
from bpy.props import StringProperty, BoolProperty, EnumProperty
from bpy.types import Operator
class ExportSomeData(Operator, ExportHelper):
    """Export For Unity"""
    bl_idname = "export_test.some_data"

    bl_label = "Export For Unity"
filename_ext = ".fbx"

filter_glob: StringProperty(
    default="*.fbx",
    options={'HIDDEN'},
    maxlen=255, 
)


def execute(self, context):
    return write_some_data(context, self.filepath)



Only needed if you want to add into a dynamic menu
def menu_func_export(self, context):
    self.layout.operator(ExportSomeData.bl_idname, text="Export For Unity")
def register():
    bpy.utils.register_class(ExportSomeData)
    bpy.types.TOPBAR_MT_file_export.append(menu_func_export)
def unregister():
    bpy.utils.unregister_class(ExportSomeData)
    bpy.types.TOPBAR_MT_file_export.remove(menu_func_export)
if name == "main":
    register()