Godot Facts

Godot 3 to 4 rename

BakedLightmapData in Godot 4: it is LightmapGIData now

BakedLightmapData is LightmapGIData in Godot 4.7.2, and BakedLightmap is LightmapGI. Do not create it in code: a bake writes it into the LightmapGI node's light_data, which is null until then, as the fix printed.

What Godot prints

A Godot 3 script that creates a BakedLightmapData in code, on a Node3D.

repro.gd
extends Node3D

func _ready():
	var data = BakedLightmapData.new()
	print(data)
Output, Godot 4.7.2
Godot Engine v4.7.2.stable.mono.official.ed1daf0bf - https://godotengine.org

SCRIPT ERROR: Parse Error: Identifier "BakedLightmapData" not declared in the current scope. Did you mean to use "LightmapGIData"?
   at: GDScript::reload (res://answers/bakedlightmapdata-in-godot-4/repro.gd:4)
ERROR: Failed to load script "res://answers/bakedlightmapdata-in-godot-4/repro.gd" with error "Parse error".
   at: load (modules/gdscript/gdscript_resource_format.cpp:46)

The fix

In Godot 4 the data belongs to a LightmapGI node and is written by a bake. The fix adds a LightmapGI and reads its light_data, typed as LightmapGIData.

fix.gd
extends Node3D

func _ready() -> void:
	var gi := LightmapGI.new()
	add_child(gi)
	var data: LightmapGIData = gi.light_data
	print("light_data before a bake: ", data)
	print("LightmapGIData extends ", ClassDB.get_parent_class("LightmapGIData"))
Output, Godot 4.7.2
Godot Engine v4.7.2.stable.mono.official.ed1daf0bf - https://godotengine.org

light_data before a bake: <Object#null>
LightmapGIData extends Resource

Why it happens

GDScript's analyzer resolves every identifier when the script loads. BakedLightmapData is not a class in Godot 4.7.2, so the script fails to parse and Godot does not load it. The editor build adds the new name from Godot's 3 to 4 rename table: Did you mean to use "LightmapGIData"?

The table maps BakedLightmap to LightmapGI and BakedLightmapData to LightmapGIData.

LightmapGIData holds the baked lightmap and the dynamic object probe data of a LightmapGI, and every bake replaces it. The class reference says light_data is created automatically after baking and is not meant to be created manually. It is a Resource, as the fix printed.

Baking a LightmapGI is only available in the editor, so an exported game cannot bake lightmaps. For procedurally generated or user-built levels, the class reference points to VoxelGI or SDFGI instead.

Sources

Run on Godot 4.7.2, .

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