RandomNumberGenerator is a class for generating pseudo-random numbers. It currently uses [http://www.pcg-random.org/](PCG32).
Note: The underlying algorithm is an implementation detail. As a result, it should not be depended upon for reproducible random streams across Godot versions.
To generate a random float number (within a given range) based on a time-dependant seed:
var rng = RandomNumberGenerator.new()
func _ready():
rng.randomize()
var my_random_number = rng.randf_range(-10.0, 10.0)
Note: The default values of godot.RandomNumberGenerator.seed
and godot.RandomNumberGenerator.state
properties are pseudo-random, and changes when calling godot.RandomNumberGenerator.randomize
. The 0
value documented here is a placeholder, and not the actual default seed.
Constructor
Variables
seed:UInt64
Initializes the random number generator state based on the given seed value. A given seed will give a reproducible sequence of pseudo-random numbers.
Note: The RNG does not have an avalanche effect, and can output similar random streams given similar seeds. Consider using a hash function to improve your seed quality if they're sourced externally.
Note: Setting this property produces a side effect of changing the internal godot.RandomNumberGenerator.state
, so make sure to initialize the seed before modifying the godot.RandomNumberGenerator.state
:
var rng = RandomNumberGenerator.new()
rng.seed = hash("Godot")
rng.state = 100 # Restore to some previously saved state.
Warning: the getter of this property returns the previous godot.RandomNumberGenerator.state
, and not the initial seed value, which is going to be fixed in Godot 4.0.
state:UInt64
The current state of the random number generator. Save and restore this property to restore the generator to a previous state:
var rng = RandomNumberGenerator.new()
print(rng.randf())
var saved_state = rng.state # Store current state.
print(rng.randf()) # Advance internal state.
rng.state = saved_state # Restore the state.
print(rng.randf()) # Prints the same value as in previous.
Note: Do not set state to arbitrary values, since the random number generator requires the state to have certain qualities to behave properly. It should only be set to values that came from the state property itself. To initialize the random number generator with arbitrary input, use godot.RandomNumberGenerator.seed
instead.
Methods
randfRange(from:Single, to:Single):Single
Generates a pseudo-random float between from
and to
(inclusive).
randfn(?mean:Single, ?deviation:Single):Single
Generates a [https://en.wikipedia.org/wiki/Normal_distribution](normally-distributed) pseudo-random number, using Box-Muller transform with the specified mean
and a standard deviation
. This is also called Gaussian distribution.
randiRange(from:Int, to:Int):Int
Generates a pseudo-random 32-bit signed integer between from
and to
(inclusive).