blender-to-unity-fbx-exporter.py

bl_info = {
	"name": "Unity FBX format",
	"author": "Angel 'Edy' Garcia (@VehiclePhysics)",
	"version": (1, 4, 1),
	"blender": (3, 0, 0),
	"location": "File > Export > Unity FBX",
	"description": "FBX exporter compatible with Unity's coordinate and scaling system.",
	"warning": "",
	"wiki_url": "",
	"category": "Import-Export",
}


import bpy
import mathutils
import math


# Multi-user datablocks are preserved here. Unique copies are made for applying the rotation.
# Eventually multi-user datablocks become single-user and gets processed.
# Therefore restoring the multi-user data assigns a shared but already processed datablock.
shared_data = dict()

# All objects and collections in this view layer must be visible while being processed.
# apply_rotation and matrix changes don't have effect otherwise.
# Visibility will be restored right before saving the FBX.
hidden_collections = []
hidden_objects = []
disabled_collections = []
disabled_objects = []


def unhide_collections(col):
	global hidden_collections
	global disabled_collections

	# No need to unhide excluded collections. Their objects aren't included in current view layer.
	if col.exclude:
		return

	# Find hidden child collections and unhide them
	hidden = [item for item in col.children if not item.exclude and item.hide_viewport]
	for item in hidden:
		item.hide_viewport = False

	# Add them to the list so they could be restored later
	hidden_collections.extend(hidden)

	# Same with the disabled collections
	disabled = [item for item in col.children if not item.exclude and item.collection.hide_viewport]
	for item in disabled:
		item.collection.hide_viewport = False

	disabled_collections.extend(disabled)

	# Recursively unhide child collections
	for item in col.children:
		unhide_collections(item)


def unhide_objects():
	global hidden_objects
	global disabled_objects

	view_layer_objects = [ob for ob in bpy.data.objects if ob.name in bpy.context.view_layer.objects]

	for ob in view_layer_objects:
		if ob.hide_get():
			hidden_objects.append(ob)
			ob.hide_set(False)
		if ob.hide_viewport:
			disabled_objects.append(ob)
			ob.hide_viewport = False


def make_single_user_data():
	global shared_data

	for ob in bpy.data.objects:
		if ob.data and ob.data.users > 1:
			# Figure out actual users of this datablock (not counting fake users)
			users = [user for user in bpy.data.objects if user.data == ob.data]
			if len(users) > 1:
				# Store shared mesh data (MESH objects only).
				# Other shared datablocks (CURVE, FONT, etc) are always exported as separate meshes
				# by the built-in FBX exporter.
				if ob.type == 'MESH':
					# Shared mesh data will be restored if users have no active modifiers
					modifiers = 0
					for user in users:
						modifiers += len([mod for mod in user.modifiers if mod.show_viewport])
					if modifiers == 0:
						shared_data[ob.name] = ob.data

				# Single-user data is mandatory in all object types, otherwise we can't apply the rotation.
				ob.data = ob.data.copy()


def apply_object_modifiers():
	# Select objects in current view layer not using an armature modifier
	bpy.ops.object.select_all(action='DESELECT')
	for ob in bpy.data.objects:
		if ob.name in bpy.context.view_layer.objects:
			bypass_modifiers = False
			for mod in ob.modifiers:
				if mod.type == 'ARMATURE':
					bypass_modifiers = True
			if not bypass_modifiers:
				ob.select_set(True)

	# Conversion to mesh may not be available depending on the remaining objects
	if bpy.ops.object.convert.poll():
		print("Converting to meshes:", bpy.context.selected_objects)
		bpy.ops.object.convert(target='MESH')


def reset_parent_inverse(ob):
	if (ob.parent):
		mat_world = ob.matrix_world.copy()
		ob.matrix_parent_inverse.identity()
		ob.matrix_basis = ob.parent.matrix_world.inverted() @ mat_world


def apply_rotation(ob):
	bpy.ops.object.select_all(action='DESELECT')
	ob.select_set(True)
	bpy.ops.object.transform_apply(location = False, rotation = True, scale = False)


def fix_object(ob):
	# Only fix objects in current view layer
	if ob.name in bpy.context.view_layer.objects:

		# Reset parent's inverse so we can work with local transform directly
		reset_parent_inverse(ob)

		# Create a copy of the local matrix and set a pure X-90 matrix
		mat_original = ob.matrix_local.copy()
		ob.matrix_local = mathutils.Matrix.Rotation(math.radians(-90.0), 4, 'X')

		# Apply the rotation to the object
		apply_rotation(ob)

		# Reapply the previous local transform with an X+90 rotation
		ob.matrix_local = mat_original @ mathutils.Matrix.Rotation(math.radians(90.0), 4, 'X')

	# Recursively fix child objects in current view layer.
	# Children may be in the current view layer even if their parent isn't.
	for child in ob.children:
		fix_object(child)


def export_unity_fbx(context, filepath, active_collection, selected_objects, deform_bones, leaf_bones, primary_bone_axis, secondary_bone_axis, tangent_space, triangulate_faces):
	global shared_data
	global hidden_collections
	global hidden_objects
	global disabled_collections
	global disabled_objects

	print("Preparing 3D model for Unity...")

	# Root objects: Empty, Mesh, Curve, Surface, Font or Armature without parent
	root_objects = [item for item in bpy.data.objects if (item.type == "EMPTY" or item.type == "MESH" or item.type == "ARMATURE" or item.type == "FONT" or item.type == "CURVE" or item.type == "SURFACE") and not item.parent]

	# Preserve current scene
	# undo_push examples, including exporters' execute:
	# https://programtalk.com/python-examples/bpy.ops.ed.undo_push  (Examples 4, 5 and 6)
	# https://sourcecodequery.com/example-method/bpy.ops.ed.undo  (Examples 1 and 2)

	bpy.ops.ed.undo_push(message="Prepare Unity FBX")

	shared_data = dict()
	hidden_collections = []
	hidden_objects = []
	disabled_collections = []
	disabled_objects = []

	selection = bpy.context.selected_objects

	# Object mode
	if bpy.ops.object.mode_set.poll():
		bpy.ops.object.mode_set(mode="OBJECT")

	# Ensure all the collections and objects in this view layer are visible
	unhide_collections(bpy.context.view_layer.layer_collection)
	unhide_objects()

	# Create a single copy in multi-user datablocks. Will be restored after fixing rotations.
	make_single_user_data()

	# Apply modifiers to objects (except those affected by an armature)
	apply_object_modifiers()

	try:
		# Fix rotations
		for ob in root_objects:
			print(ob.name, ob.type)
			fix_object(ob)

		# Restore multi-user meshes
		for item in shared_data:
			bpy.data.objects[item].data = shared_data[item]

		# Recompute the transforms out of the changed matrices
		bpy.context.view_layer.update()

		# Restore hidden and disabled objects
		for ob in hidden_objects:
			ob.hide_set(True)
		for ob in disabled_objects:
			ob.hide_viewport = True

		# Restore hidden and disabled collections
		for col in hidden_collections:
			col.hide_viewport = True
		for col in disabled_collections:
			col.collection.hide_viewport = True

		# Restore selection
		bpy.ops.object.select_all(action='DESELECT')
		for ob in selection:
			ob.select_set(True)

		# Export FBX file
		params = dict(filepath=filepath, apply_scale_options='FBX_SCALE_UNITS', object_types={'EMPTY', 'MESH', 'ARMATURE'}, use_active_collection=active_collection, use_selection=selected_objects, use_armature_deform_only=deform_bones, add_leaf_bones=leaf_bones, primary_bone_axis=primary_bone_axis, secondary_bone_axis=secondary_bone_axis, use_tspace=tangent_space, use_triangles=triangulate_faces)

		print("Invoking default FBX Exporter:", params)
		bpy.ops.export_scene.fbx(**params)

	except Exception as e:
		bpy.ops.ed.undo_push(message="")
		bpy.ops.ed.undo()
		bpy.ops.ed.undo_push(message="Export Unity FBX")
		print(e)
		print("File not saved.")
		# Always finish with 'FINISHED' so Undo is handled properly
		return {'FINISHED'}

	# Restore scene and finish

	bpy.ops.ed.undo_push(message="")
	bpy.ops.ed.undo()
	bpy.ops.ed.undo_push(message="Export Unity FBX")
	print("FBX file for Unity saved.")
	return {'FINISHED'}


#---------------------------------------------------------------------------------------------------
# Exporter stuff (from the Operator File Export template)

# ExportHelper is a helper class, defines filename and
# invoke() function which calls the file selector.
from bpy_extras.io_utils import ExportHelper
from bpy.props import StringProperty, BoolProperty, EnumProperty
from bpy.types import Operator


class ExportUnityFbx(Operator, ExportHelper):
	"""FBX exporter compatible with Unity's coordinate and scaling system"""
	bl_idname = "export_scene.unity_fbx"
	bl_label = "Export Unity FBX"
	bl_options = {'UNDO_GROUPED'}

	# ExportHelper mixin class uses this
	filename_ext = ".fbx"

	filter_glob: StringProperty(
		default="*.fbx",
		options={'HIDDEN'},
		maxlen=255,  # Max internal buffer length, longer would be clamped.
	)

	# List of operator properties, the attributes will be assigned
	# to the class instance from the operator settings before calling.

	active_collection: BoolProperty(
		name="Active Collection Only",
		description="Export objects in the active collection only (and its children). May be combined with Selected Objects Only",
		default=False,
	)

	selected_objects: BoolProperty(
		name="Selected Objects Only",
		description="Export selected objects only. May be combined with Active Collection Only",
		default=False,
	)

	deform_bones: BoolProperty(
		name="Only Deform Bones",
		description="Only write deforming bones (and non-deforming ones when they have deforming children)",
		default=False,
	)

	leaf_bones: BoolProperty(
		name="Add Leaf Bones",
		description="Append a final bone to the end of each chain to specify last bone length (use this when you intend to edit the armature from exported data)",
		default=False,
	)

	primary_bone_axis: EnumProperty(
		name="Primary",
		items=(('X', "X Axis", ""),
				('Y', "Y Axis", ""),
				('Z', "Z Axis", ""),
				('-X', "-X Axis", ""),
				('-Y', "-Y Axis", ""),
				('-Z', "-Z Axis", ""),
		),
		default='Y',
	)

	secondary_bone_axis: EnumProperty(
		name="Secondary",
		items=(('X', "X Axis", ""),
				('Y', "Y Axis", ""),
				('Z', "Z Axis", ""),
				('-X', "-X Axis", ""),
				('-Y', "-Y Axis", ""),
				('-Z', "-Z Axis", ""),
		),
		default='X',
	)

	tangent_space: BoolProperty(
		name="Export tangents",
		description="Add binormal and tangent vectors, together with normal they form the tangent space (tris/quads only). Meshes with N-gons won't export tangents unless the option Triangulate Faces is enabled",
		default=False,
	)

	triangulate_faces: BoolProperty(
		name="Triangulate Faces",
		description="Convert all faces to triangles. This is necessary for exporting tangents in meshes with N-gons. Otherwise Unity will show a warning when importing tangents in these meshes",
		default=False,
	)

	# Custom draw method
	# https://blender.stackexchange.com/questions/55437/add-gui-elements-to-exporter-window
	# https://docs.blender.org/api/current/bpy.types.UILayout.html

	def draw(self, context):
		layout = self.layout
		layout.row().label(text = "Selection")
		layout.row().prop(self, "active_collection")
		layout.row().prop(self, "selected_objects")

		layout.separator()
		layout.row().label(text = "Meshes")
		layout.row().prop(self, "tangent_space")
		layout.row().prop(self, "triangulate_faces")

		layout.separator()
		layout.row().label(text = "Armatures")
		layout.row().prop(self, "deform_bones")
		layout.row().prop(self, "leaf_bones")

		layout.row().label(text = "Bone Axes")
		split = layout.split(factor=0.4)
		col = split.column()
		col.alignment = 'RIGHT'
		col.label(text = "Primary")
		split.column().prop(self, "primary_bone_axis", text="")
		split = layout.split(factor=0.4)
		col = split.column()
		col.alignment = 'RIGHT'
		col.label(text = "Secondary")
		split.column().prop(self, "secondary_bone_axis", text="")

	def execute(self, context):
		return export_unity_fbx(context, self.filepath, self.active_collection, self.selected_objects, self.deform_bones, self.leaf_bones, self.primary_bone_axis, self.secondary_bone_axis, self.tangent_space, self.triangulate_faces)


# Only needed if you want to add into a dynamic menu
def menu_func_export(self, context):
	self.layout.operator(ExportUnityFbx.bl_idname, text="Unity FBX (.fbx)")


def register():
	bpy.utils.register_class(ExportUnityFbx)
	bpy.types.TOPBAR_MT_file_export.append(menu_func_export)


def unregister():
	bpy.utils.unregister_class(ExportUnityFbx)
	bpy.types.TOPBAR_MT_file_export.remove(menu_func_export)


if __name__ == "__main__":
	register()

	# test call
	bpy.ops.export_scene.unity_fbx('INVOKE_DEFAULT')