OpenSimplexNoise in Godot 4: it is FastNoiseLite now
By Eduardo Orellana · Updated
OpenSimplexNoise is replaced by FastNoiseLite in Godot 4, and period is gone: frequency is roughly one divided by Godot 3's period. In a Godot 4 project, OpenSimplexNoise.new() fails to parse with Identifier "OpenSimplexNoise" not declared in the current scope. Did you mean to use "FastNoiseLite"?.
AppImage, x86_64. Ubuntu 22.04, Debian 12, Fedora 39 or newer.
Intel or AMD Chromebook, with Linux turned on.
What Godot is checking
GDScript resolves every name when the script loads. OpenSimplexNoise is not a class in Godot 4, so the analyzer stops before anything runs, and because the name is in Godot's own table of Godot 3 renames, the message names the replacement.
The converter carries OpenSimplexNoise to FastNoiseLite. It defaults to simplex-smooth noise; noise_type picks Perlin, cellular, value and others. get_noise_2d() and get_noise_3d() still return values around -1 to 1, and fractal_octaves replaces octaves.
Reproduce it
A Godot 3 script that creates a OpenSimplexNoise in code, in a Godot 4 project.
extends Node
func _ready():
var noise = OpenSimplexNoise.new()
print(noise)
What Godot 4.7.2 prints
Godot Engine v4.7.2.stable.mono.official.ed1daf0bf - https://godotengine.org
SCRIPT ERROR: Parse Error: Identifier "OpenSimplexNoise" not declared in the current scope. Did you mean to use "FastNoiseLite"?
at: GDScript::reload (res://answers/opensimplexnoise-in-godot-4/repro.gd:4)
ERROR: Failed to load script "res://answers/opensimplexnoise-in-godot-4/repro.gd" with error "Parse error".
at: load (modules/gdscript/gdscript_resource_format.cpp:46)Fix it
A seeded FastNoiseLite sampled at two points, so the run prints the same values every time.
extends Node
func _ready() -> void:
var noise := FastNoiseLite.new()
noise.seed = 1
noise.frequency = 1.0 / 64.0
noise.fractal_octaves = 4
print(noise.get_class(), " ", snappedf(noise.get_noise_2d(10, 20), 0.0001), " ", snappedf(noise.get_noise_2d(200, 20), 0.0001))
What the fixed script prints
Godot Engine v4.7.2.stable.mono.official.ed1daf0bf - https://godotengine.org
FastNoiseLite 0.1551 -0.497Verified on Godot 4.7.2
Both scripts on this page were run headless on Godot 4.7.2 (4.7.2.stable.mono.official.ed1daf0bf) on 18 October 2026, and the output above is what Godot printed, unedited.
Where the check lives in Godot's source: [gdscript_analyzer.cpp line 4687, the message with its hint](https://github.com/godotengine/godot/blob/4.7.2-stable/modules/gdscript/gdscript_analyzer.cpp#L4687), [renames_map_3_to_4.cpp line 1557, OpenSimplexNoise to FastNoiseLite](https://github.com/godotengine/godot/blob/4.7.2-stable/editor/project_upgrade/renames_map_3_to_4.cpp#L1557), [FastNoiseLite class reference](https://github.com/godotengine/godot/blob/4.7.2-stable/modules/noise/doc_classes/FastNoiseLite.xml).
Questions
- How do I turn it into a texture?
- Assign it to a NoiseTexture2D's noise property; Godot 3's NoiseTexture is NoiseTexture2D.
- What was period 64 in Godot 3?
- Roughly frequency 1/64 = 0.0156 in Godot 4. The algorithms differ, so the pattern is not identical.