Serialize model transform as 16-bit floats

This reads / writes a float in the range of 0.0 to 1.0, but
with a uniform distribution instead of whatever it's called
that floating point values do.

This allows us to more efficiently store euler angles, which
can only have values between 0.0 and TAU. No more wasted bits!

copyMultiplayer.gd

@@ -11,6 +11,12 @@ var main_controller: ModelController
 ## Hardcoded list of bone names that will get syncronized.
 var tracked_bones: Array[String]
 
+var version: int = -1
+var bone_lookup: Array[String] = []
+var bone_to_lookup: Dictionary = {}
+var blendshape_lookup: Array[String] = []
+var blendshape_to_lookup: Dictionary = {}
+
 # Temporary positioning system.
 # TODO: Add a setting that allows syncing model positions, as an alternative
 #       to letting the local player choose where each model is going to appear.
@@ -43,6 +49,7 @@ func _ready() -> void:
 	# FIXME: Hardcoded way to get the main model controller.
 	main_controller = $"/root/SnekStudio_Main/ModelController"
 	main_controller.child_entered_tree.connect(on_model_controller_child_added)
+	on_model_controller_child_added(main_controller.get_node_or_null("Model"))
 
 	setup_setting_widget("cache"   , "Cache/LineEdit", true )
 	setup_setting_widget("nickname", "Name/LineEdit" , false)
@@ -137,7 +144,7 @@ func on_peer_connected(id: int) -> void:
 	# (Technically this doesn't need to be relayed through the server, but oh well.)
 	if nickname: change_nickname.rpc_id(id, nickname)
 	var filename = main_controller._last_loaded_vrm.get_file()
-	if filename.is_valid_filename(): change_model.rpc_id(id, filename)
+	if filename.is_valid_filename(): change_model.rpc_id(id, version, bone_lookup, blendshape_lookup, filename)
 
 	update_status()
 	print_log("%s connected" % sync_controller.get_display_name())
@@ -216,11 +223,30 @@ func _process(_delta: float) -> void:
 	SyncController.send_model_animation(self)
 
 func on_model_controller_child_added(child: Node) -> void:
-	if child.name != "Model": return
+	if (child == null) or (child.name != "Model"): return
+
+	var skeleton: Skeleton3D = main_controller._get_model_skeleton()
+	if not skeleton: return # Do nothing, I guess? Unsure if potential bug.
+
+	version = (version + 1) % 256
+
+	bone_lookup.clear()
+	bone_to_lookup.clear()
+	for bone_name in tracked_bones:
+		bone_lookup.append(bone_name)
+		var bone_idx := skeleton.find_bone(bone_name)
+		if bone_idx == -1: continue # Need bone in bone_lookup, but not in bone_to_lookup!
+		bone_to_lookup[bone_name] = bone_lookup.size() - 1
+
+	blendshape_lookup.clear()
+	blendshape_to_lookup.clear()
+	# TODO: Redo the blendshapes. Consider grabbing data from animations directly?
+
 	# Wait for one frame, then "_last_loaded_vrm" is updated.
 	await get_tree().process_frame
 	var filename = main_controller._last_loaded_vrm.get_file()
-	if filename.is_valid_filename(): change_model.rpc(filename)
+
+	change_model.rpc(version, bone_lookup, blendshape_lookup, filename)
 
 
 ## Gets the SyncController for the player with the specified peer id.
@@ -236,13 +262,22 @@ func change_nickname(new_nickname: String) -> void:
 	if controller: controller.change_nickname(new_nickname)
 
 @rpc("any_peer", "reliable")
-func change_model(filename: String) -> void:
+func change_model(
+	new_version: int,
+	new_bone_lookup: Array[String],
+	new_blendshape_lookup: Array[String],
+	filename: String,
+) -> void:
 	var peer_id := multiplayer.get_remote_sender_id()
 	var controller := get_sync_controller(peer_id)
-	if controller: controller.change_model(filename)
+	if controller: controller.change_model(new_version, new_bone_lookup, new_blendshape_lookup, filename)
 
 @rpc("any_peer", "unreliable_ordered")
-func sync_model_animation(uncompressed_length: int, buffer: PackedByteArray) -> void:
+func sync_model_animation(
+	current_version: int,
+	uncompressed_length: int,
+	buffer: PackedByteArray,
+) -> void:
 	var peer_id := multiplayer.get_remote_sender_id()
 	var controller := get_sync_controller(peer_id)
-	if controller: controller.sync_model_animation(uncompressed_length, buffer)
+	if controller: controller.sync_model_animation(current_version, uncompressed_length, buffer)

stream_buffer.gd

@@ -77,6 +77,16 @@ func write_float16(value: float) -> void: ensure_capacity(2); buffer.encode_half
 func write_float32(value: float) -> void: ensure_capacity(4); buffer.encode_float(size, value); size += 4; bit = 0
 func write_float64(value: float) -> void: ensure_capacity(8); buffer.encode_double(size, value); size += 8; bit = 0
 
+func write_vector16(value: Vector3) -> void: write_float16(value.x); write_float16(value.y); write_float16(value.z)
+func write_vector32(value: Vector3) -> void: write_float32(value.x); write_float32(value.y); write_float32(value.z)
+
+func write_transform16(value: Transform3D) -> void: write_vector16(value.basis.x); write_vector16(value.basis.y); write_vector16(value.basis.z); write_vector16(value.origin)
+func write_transform32(value: Transform3D) -> void: write_vector32(value.basis.x); write_vector32(value.basis.y); write_vector32(value.basis.z); write_vector32(value.origin)
+
+func write_range8(value: float) -> void: write_uint8(roundi(value * 255))
+func write_range16(value: float) -> void: write_uint16(roundi(value * 65535))
+func write_range32(value: float) -> void: write_uint32(roundi(value * 4294967295))
+
 
 func read_int8() -> int: assert(remaining_bytes() >= 1); var result := buffer.decode_s8(cursor); cursor += 1; bit = 0; return result
 func read_int16() -> int: assert(remaining_bytes() >= 2); var result := buffer.decode_s16(cursor); cursor += 2; bit = 0; return result
@@ -93,19 +103,24 @@ func read_float16() -> float: assert(remaining_bytes() >= 2); var result := buff
 func read_float32() -> float: assert(remaining_bytes() >= 4); var result := buffer.decode_float(cursor); cursor += 4; bit = 0; return result
 func read_float64() -> float: assert(remaining_bytes() >= 8); var result := buffer.decode_double(cursor); cursor += 8; bit = 0; return result
 
+func read_vector16() -> Vector3: return Vector3(read_float16(), read_float16(), read_float16())
+func read_vector32() -> Vector3: return Vector3(read_float32(), read_float32(), read_float32())
+
+func read_transform16() -> Transform3D: return Transform3D(Basis(read_vector16(), read_vector16(), read_vector16()), read_vector16())
+func read_transform32() -> Transform3D: return Transform3D(Basis(read_vector32(), read_vector32(), read_vector32()), read_vector32())
+
+func read_range8() -> float: return float(read_uint8()) / 255
+func read_range16() -> float: return float(read_uint16()) / 65535
+func read_range32() -> float: return float(read_uint32()) / 4294967295
+
 
 func write_bit(value: bool) -> void:
-	if bit == 0:
-		ensure_capacity(1)
-		buffer[size] = 0
-		size += 1
+	if bit == 0: ensure_capacity(1); buffer[size] = 0; size += 1
 	buffer[size - 1] = buffer[size - 1] | (int(value) << bit)
 	bit = (bit + 1) % 8
 
 func read_bit() -> bool:
-	if bit == 0:
-		assert(remaining_bytes() >= 1)
-		cursor += 1
+	if bit == 0: assert(remaining_bytes() >= 1); cursor += 1
 	var result := bool((buffer[cursor - 1] >> bit) & 1)
 	bit = (bit + 1) % 8
 	return result
@@ -138,21 +153,6 @@ func read_string() -> String:
 	return bytes.get_string_from_utf8()
 
 
-func write_transform32(value: Transform3D) -> void:
-	write_float32(value.basis.x.x); write_float32(value.basis.x.y); write_float32(value.basis.x.z)
-	write_float32(value.basis.y.x); write_float32(value.basis.y.y); write_float32(value.basis.y.z)
-	write_float32(value.basis.z.x); write_float32(value.basis.z.y); write_float32(value.basis.z.z)
-	write_float32(value.origin.x);  write_float32(value.origin.y);  write_float32(value.origin.z)
-
-func read_transform32() -> Transform3D:
-	var result := Transform3D.IDENTITY
-	result.basis.x = Vector3(read_float32(), read_float32(), read_float32())
-	result.basis.y = Vector3(read_float32(), read_float32(), read_float32())
-	result.basis.z = Vector3(read_float32(), read_float32(), read_float32())
-	result.origin  = Vector3(read_float32(), read_float32(), read_float32())
-	return result
-
-
 # Optimized way to write a bone transform, since bones are likely to not contain offset or scale.
 
 func write_bone_pose(value: Transform3D) -> void:
@@ -163,26 +163,11 @@ func write_bone_pose(value: Transform3D) -> void:
 	var has_rot    := !rot.is_zero_approx()
 	var has_scale  := !scale.is_equal_approx(Vector3.ONE)
 	var has_scale3 := !is_equal_approx(scale.x, scale.y) or !is_equal_approx(scale.x, scale.y)
-	write_bit(has_pos)
-	write_bit(has_rot)
-	write_bit(has_scale)
-	write_bit(has_scale3)
-	if has_pos:
-		write_float16(pos.x)
-		write_float16(pos.y)
-		write_float16(pos.z)
-	if has_rot:
-		# TODO: Could optimize this by using 16-bit fixed-point values.
-		#       Since these values can only be in the range 0 to 1.
-		write_float16(rot.x)
-		write_float16(rot.y)
-		write_float16(rot.z)
-	if has_scale3:
-		write_float16(scale.x)
-		write_float16(scale.y)
-		write_float16(scale.z)
-	elif has_scale:
-		write_float16((scale.x + scale.y + scale.z) / 3)
+	write_bit(has_pos); write_bit(has_rot); write_bit(has_scale); write_bit(has_scale3)
+	if has_pos: write_vector16(pos)
+	if has_rot: write_range16(rot.x / TAU); write_range16(rot.y / TAU); write_range16(rot.z / TAU)
+	if has_scale3: write_vector16(scale)
+	elif has_scale: write_float16((scale.x + scale.y + scale.z) / 3)
 
 func read_bone_pose() -> Transform3D:
 	var pos   := Vector3.ZERO
@@ -192,11 +177,9 @@ func read_bone_pose() -> Transform3D:
 	var has_rot    := read_bit()
 	var has_scale  := read_bit()
 	var has_scale3 := read_bit()
-	if has_pos: pos = Vector3(read_float16(), read_float16(), read_float16())
-	if has_rot: rot = Vector3(read_float16(), read_float16(), read_float16())
-	if has_scale3: scale = Vector3(read_float16(), read_float16(), read_float16())
-	elif has_scale:
-		var s := read_float16()
-		scale = Vector3(s, s, s)
+	if has_pos: pos = read_vector16()
+	if has_rot: rot = Vector3(read_range16() * TAU, read_range16() * TAU, read_range16() * TAU)
+	if has_scale3: scale = read_vector16()
+	elif has_scale: var s := read_float16(); scale = Vector3(s, s, s)
 	var basis := Basis.from_scale(scale) * Basis.from_euler(rot)
 	return Transform3D(basis, pos)

sync_controller.gd

@@ -6,6 +6,11 @@ var model_controller: ModelController
 var peer_id: int
 
 var nickname: String
+
+var version: int = -1
+var bone_lookup: Array[String]
+var blendshape_lookup: Array[String]
+
 var model_name: String
 var model: Node
 var skeleton: Skeleton3D
@@ -32,7 +37,18 @@ func change_nickname(new_nickname: String) -> void:
 	nickname = new_nickname
 
 ## Attempts to change the model of this player.
-func change_model(filename: String) -> void:
+func change_model(
+	new_version: int,
+	new_bone_lookup: Array[String],
+	new_blendshape_lookup: Array[String],
+	filename: String,
+) -> void:
+	# These should be safe to update even if the model doesn't load.
+	# We just need to stay in sync with the lookup tables.
+	version           = new_version
+	bone_lookup       = new_bone_lookup
+	blendshape_lookup = new_blendshape_lookup
+
 	if not filename.is_valid_filename():
 		module.print_log("ERROR: '%s' is not a valid file name!" % filename)
 		return
@@ -43,34 +59,52 @@ func change_model(filename: String) -> void:
 	if not model_controller.load_vrm(full_path):
 		module.print_log("ERROR: Model '%s' could not be loaded!" % filename)
 		return
-	module.print_log("%s switched to '%s'" % [ get_display_name(), filename ])
+
 	model_name = filename
 	model      = model_controller.get_node_or_null("Model")
 	skeleton   = model_controller._get_model_skeleton()
 
-func sync_model_animation(uncompressed_length: int, buffer: PackedByteArray) -> void:
+	module.print_log("%s switched to '%s'" % [ get_display_name(), filename ])
+
+func sync_model_animation(
+	current_version: int,
+	uncompressed_length: int,
+	buffer: PackedByteArray,
+) -> void:
+	if version != current_version: return
 	if (not model) or (not skeleton): return
 
 	var uncompressed_buffer := buffer.decompress(uncompressed_length, FileAccess.COMPRESSION_ZSTD);
 	var stream := StreamBuffer.from_buffer(uncompressed_buffer)
-	model.transform = stream.read_transform32()
+
+	model.transform = stream.read_transform16()
+
+	# We skipped some bones, so reset the skipped ones to the rest pose.
+	var all_bones := {}
+	for bone_name in module.bone_to_lookup:
+		var bone_idx  := skeleton.find_bone(bone_name)
+		var bone_rest := skeleton.get_bone_rest(bone_idx)
+		all_bones[bone_name] = { idx = bone_idx, pose = bone_rest }
+
+	# Override rest poses with ones from the packet.
+	var num_bones := stream.read_uint8()
+	for i in num_bones:
+		var bone_name := bone_lookup[stream.read_uint8()]
+		all_bones[bone_name].pose = stream.read_bone_pose()
+
+	# Apply bone poses to skeleton.
+	for bone_name in all_bones:
+		var bone: Dictionary = all_bones[bone_name]
+		skeleton.set_bone_pose(bone.idx, bone.pose)
 
 	var shape_dict := {}
-	# 256 blendshapes (and bones) should be enough, right?
-	var num_shapes := stream.read_uint8()
+	var num_shapes := stream.read_uint8() # 256 blendshapes (and bones) should be enough, right?
 	for i in num_shapes:
-		var shape_name  := stream.read_string()
+		var shape_name   := blendshape_lookup[stream.read_uint8()]
 		var shape_alpha  := stream.read_float16()
 		shape_dict[shape_name] = shape_alpha
 	BlendShapes.apply_animations(model, shape_dict)
 
-	var num_bones := stream.read_uint8()
-	for i in num_bones:
-		var bone_name := stream.read_string()
-		var bone_pose := stream.read_bone_pose()
-		var bone_idx  := skeleton.find_bone(bone_name)
-		if bone_idx != -1: skeleton.set_bone_pose(bone_idx, bone_pose)
-
 @warning_ignore("shadowed_variable")
 static func send_model_animation(module: copyMultiplayer) -> void:
 	# Check if there's other players we're connected to.
@@ -81,34 +115,33 @@ static func send_model_animation(module: copyMultiplayer) -> void:
 	var media_pipe = module.get_node("../MediaPipeController")
 	if (not model) or (not skeleton) or (not media_pipe): return
 
-	write_stream.write_transform32(model.transform)
+	write_stream.write_transform16(model.transform)
 
-	# TODO: Do not write full strings. Use a lookup table!
-	# TODO: Only write non-default blendshapes. Anything missing = default.
+	# Pre-filter any bones that are in rest pose.
+	var restless_bones := {}
+	for bone_name in module.bone_to_lookup:
+		var bone_idx  := skeleton.find_bone(bone_name)
+		var bone_pose := skeleton.get_bone_pose(bone_idx)
+		var bone_rest := skeleton.get_bone_rest(bone_idx)
+		if not bone_pose.is_equal_approx(bone_rest):
+			restless_bones[bone_name] = bone_pose
+
+	write_stream.write_uint8(restless_bones.size())
+	for bone_name in restless_bones:
+		write_stream.write_uint8(module.bone_to_lookup[bone_name])
+		write_stream.write_bone_pose(restless_bones[bone_name])
 
+	# TODO: Only write non-default blendshapes. Anything missing = default.
 	var shape_dict: Dictionary = media_pipe.blend_shape_last_values
-	write_stream.write_uint8(shape_dict.size())
-	for shape_name in shape_dict:
+	write_stream.write_uint8(module.blendshape_to_lookup.size())
+	for shape_name in module.blendshape_to_lookup:
 		var shape_alpha: float = shape_dict[shape_name]
-		write_stream.write_string(shape_name)
+		write_stream.write_uint8(module.blendshape_to_lookup[shape_name])
 		write_stream.write_float16(shape_alpha)
 
-	var bone_poses = {}
-	for bone_name in module.tracked_bones:
-		var bone_idx = skeleton.find_bone(bone_name)
-		if bone_idx == -1: continue
-		var bone_pose = skeleton.get_bone_pose(bone_idx)
-		bone_poses[bone_name] = bone_pose
-
-	write_stream.write_uint8(bone_poses.size())
-	for bone_name in bone_poses:
-		var bone_pose: Transform3D = bone_poses[bone_name]
-		write_stream.write_string(bone_name)
-		write_stream.write_bone_pose(bone_pose)
-
-	# TODO: Ideally, compression won't be needed once we remove strings.
+	# The compression still helps, so we'll keep it for now.
 	var compressed_buffer := write_stream.slice().compress(FileAccess.COMPRESSION_ZSTD);
-	# DEBUG: Uncomment this to see packet size (ideally < 1024).
-	# module.set_status("Packet size: %d (%d uncompressed)" % [compressed_buffer.size(), write_stream.size])
-	module.sync_model_animation.rpc(write_stream.size, compressed_buffer)
+	# Uncomment this to see packet size. Can we hit < 256 bytes?
+	# module.set_status("Packet size: %d bytes (%d uncompressed)" % [ compressed_buffer.size(), write_stream.size ])
+	module.sync_model_animation.rpc(module.version, write_stream.size, compressed_buffer)
 	write_stream.clear()