Unnecessary floating point digits being serialized in some (but not all) cases

[eigensummer]

Tested versions

• Reproducible in: 4.5.dev5
• Not reproducible in: 4.5.dev4

System information

Godot v4.5.dev5 - Arch Linux #1 ZEN SMP PREEMPT_DYNAMIC Thu, 29 May 2025 21:42:00 +0000 on X11 - X11 display driver, Multi-window, 1 monitor - Vulkan (Forward+) - integrated Intel(R) Iris(R) Xe Graphics (RPL-P) - 13th Gen Intel(R) Core(TM) i9-13900H (20 threads)

Issue description

The new floating point serialization from #98750 has caused a few cases where numbers get serialized with unnecessary digits, causing git noise. Specifically, with shader uniforms (both global and local) and @export variables. It doesn't seem to affect the Environment resource.

Steps to reproduce

1. Create a float global uniform in the project settings
2. Set the value to something else, e.g. 0.02 or 1.2

---

1. Create a script
2. Add a float property with @export_range(0, 2, 0.1) and a default value of 1
3. Add a float property with @export and a default value of 1
4. Use the slider to change both values to 1.2
5. In the .tscn, the first one will be 1.2000000000000002, and the second will be 1.1999999999970896

---

1. Add a WorldEnvironment
2. Change a value (for example, the tonemap exposure) to 1.2
3. Check the .tscn file and see that it has been serialized as 1.2 without any unnecessary digits

Minimal reproduction project (MRP)

float_noise_test.zip

[AThousandShips]

Probably due to floating point precision limitations, but in this case almost certainly due to:

• Use Grisu2 algorithm in String::num_scientific to fix serializing #98750

CC @aaronfranke

This is a bit of a regression in usability, even though the results are technically more "correct", as 1.2 is not representable as a floating point value, it's 1.001100110011..., so 1.2000000000000002 and 1.1999999999970896 are the immediate neighbors of this value, off by one bit (0.02 is also not repsesentable in binary)

This might be an instability issue with the algorithm though

[aaronfranke]

This is actually a bug in Godot's editor sliders, not a bug in the String serialization algorithm. Proof: Add this to your script:

func _ready() -> void:
	print(String.num_scientific(1.2)) # Prints "1.2"
	print(String.num_scientific(number_a)) # Prints "1.2000000000000002"
	print(String.num_scientific(number_b)) # Prints "1.1999999999970896"
	print(number_a == 1.2) # Prints "false"
	print(number_b == 1.2) # Prints "false"

The bug in Godot's editor sliders was masked before by the lack of precision in the String serialization, but it was still there.

[KoBeWi]

That's indeed problem with sliders, or or maybe with Range.

Here's a print of "real" value (using %0.20f) and serialized value, from slider:
1.20000000000000017764 1.2000000000000002
Same, but the value is set in code:
1.19999999999999995559 1.2