RandomNumberGenerator¶

A class for generating pseudo-random numbers.

Description¶

RandomNumberGenerator is a class for generating pseudo-random numbers. It currently uses 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 seed and state properties are pseudo-random, and changes when calling randomize. The 0 value documented here is a placeholder, and not the actual default seed.

Tutorials¶

Random number generation

Properties¶

int	seed	`0`
int	state	`0`

Methods¶

float	randf ( )
float	randf_range ( float from, float to )
float	randfn ( float mean=0.0, float deviation=1.0 )
int	randi ( )
int	randi_range ( int from, int to )
void	randomize ( )

Property Descriptions¶

int seed = 0

void set_seed ( int value )
int get_seed ( )

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 state, so make sure to initialize the seed before modifying the 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 state, and not the initial seed value, which is going to be fixed in Godot 4.0.

int state = 0

void set_state ( int value )
int get_state ( )

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 seed instead.

Method Descriptions¶

float randf ( )

Generates a pseudo-random float between 0.0 and 1.0 (inclusive).

float randf_range ( float from, float to )

Generates a pseudo-random float between from and to (inclusive).

float randfn ( float mean=0.0, float deviation=1.0 )

Generates a normally-distributed pseudo-random number, using Box-Muller transform with the specified mean and a standard deviation. This is also called Gaussian distribution.

int randi ( )

Generates a pseudo-random 32-bit unsigned integer between 0 and 4294967295 (inclusive).

int randi_range ( int from, int to )

Generates a pseudo-random 32-bit signed integer between from and to (inclusive).

void randomize ( )

Setups a time-based seed to generator.