add BoneFlipper for flipping bone poses

scripts/effects/bones/bone_flattener.gd

@@ -93,7 +93,7 @@ func _ready() -> void:
 			continue
 		for bone_name in bone_to_flatten.bone_names:
 			var bone_idx := _skeleton.find_bone(bone_name)
-			assert(bone_idx != -1, bone_name + " missing!")
+			assert(bone_idx != -1, str(self) + ": bone " + bone_name + " missing!")
 
 
 func _process_modification() -> void:

scripts/effects/bones/bone_flipper.gd

@@ -0,0 +1,93 @@
+@tool
+class_name BoneFlipper
+extends SkeletonModifier3D
+
+@export var flip: bool = false
+
+@export_enum(" ") var _bones_to_flip: Array[String] = []
+@export var _flip_all_bones: bool = true
+@export_enum(" ") var _bones_to_exclude: Array[String] = []
+@export var _bone_prefixes_to_exclude: Array[String] = []
+
+var _skeleton: Skeleton3D
+
+
+func _validate_property(property: Dictionary) -> void:
+	if property.name == "_bones_to_flip" or property.name == "_bones_to_exclude":
+		if _skeleton:
+			property.hint = PROPERTY_HINT_TYPE_STRING
+			property.hint_string = (
+				"%d/%d:%s"
+				% [
+					TYPE_STRING,
+					PROPERTY_HINT_ENUM,
+					_skeleton.get_concatenated_bone_names()
+				]
+			)
+
+
+func _ready() -> void:
+	_skeleton = get_skeleton()
+	assert(_skeleton, str(self) + ": _skeleton missing!")
+
+	for bone_name in _bones_to_flip:
+		var bone_idx := _skeleton.find_bone(bone_name)
+		assert(bone_idx != -1, str(self) + ": bone " + bone_name + " missing!")
+	for bone_name in _bones_to_exclude:
+		var bone_idx := _skeleton.find_bone(bone_name)
+		assert(bone_idx != -1, str(self) + ": bone " + bone_name + " missing!")
+
+
+func _process_modification() -> void:
+	if !_skeleton or !flip:
+		for bone_idx in range(_skeleton.get_bone_count()):
+			_skeleton.set_bone_pose(bone_idx, _skeleton.get_bone_pose(bone_idx))
+		return
+
+	if _flip_all_bones:
+		for bone_idx in range(_skeleton.get_bone_count()):
+			_flip_bone_if_not_excluded(bone_idx)
+	else:
+		for bone_name in _bones_to_flip:
+			var bone_idx := _skeleton.find_bone(bone_name)
+			if bone_idx == -1:
+				continue
+			_flip_bone(bone_idx, bone_name)
+
+
+func _flip_bone_if_not_excluded(bone_idx: int) -> void:
+	var bone_name := _skeleton.get_bone_name(bone_idx)
+	if bone_name in _bones_to_exclude:
+		return
+	for bone_prefix in _bone_prefixes_to_exclude:
+		if bone_prefix and bone_name.begins_with(bone_prefix):
+			return
+	_flip_bone(bone_idx, bone_name)
+
+
+func _flip_bone(bone_idx: int, bone_name: String) -> void:
+	var pose: Transform3D = _skeleton.get_bone_pose(bone_idx)
+
+	if bone_name.ends_with("_R") or (bone_name.ends_with("_L") and !_flip_all_bones):
+		var other_side_bone_name: String = (
+			bone_name.replace("_R", "_L")
+			if bone_name.ends_with("_R")
+			else bone_name.replace("_L", "_R")
+		)
+		var other_side_bone_idx := _skeleton.find_bone(other_side_bone_name)
+		if other_side_bone_idx == -1:
+			return
+		var other_side_pose: Transform3D = _skeleton.get_bone_pose(other_side_bone_idx)
+		_mirror_bone_transform(bone_idx, other_side_pose)
+		_mirror_bone_transform(other_side_bone_idx, pose)
+	elif !bone_name.ends_with("_R") and !bone_name.ends_with("_L"):
+		_mirror_bone_transform(bone_idx, pose)
+
+
+func _mirror_bone_transform(bone_idx: int, pose: Transform3D) -> void:
+	pose.origin.x = -pose.origin.x
+	var pose_rot := pose.basis.get_euler()
+	pose_rot.z = -pose_rot.z
+	pose_rot.y = -pose_rot.y
+	pose.basis = Basis.from_euler(pose_rot)
+	_skeleton.set_bone_pose(bone_idx, pose)

scripts/effects/bones/bone_flipper.gd.uid

@@ -0,0 +1 @@
+uid://bmbbkpkqtugwy