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Update Random number generation for Godot 4.2+ (#9822)
- Document `Array.pick_random()` as a shorthand. - Use global scope random methods as they are all available in global scope now. - Remove calls to `randomize()` that are not needed for code samples to be functional, as the engine now calls `randomize()` on startup once automatically.
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Hugo Locurcio
GitHub
@@ -33,9 +33,6 @@ Global scope methods are easier to set up, but they don't offer as much control.
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RandomNumberGenerator requires more code to use, but allows creating
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multiple instances, each with their own seed and state.
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This tutorial uses global scope methods, except when the method only exists in
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the RandomNumberGenerator class.
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The randomize() method
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----------------------
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@@ -134,7 +131,7 @@ number between 0 and 1. This is useful to implement a
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:ref:`doc_random_number_generation_weighted_random_probability` system, among
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other things.
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:ref:`randfn() <class_RandomNumberGenerator_method_randfn>` returns a random
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:ref:`randfn() <class_@GlobalScope_method_randfn>` returns a random
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floating-point number following a `normal distribution
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<https://en.wikipedia.org/wiki/Normal_distribution>`__. This means the returned
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value is more likely to be around the mean (0.0 by default),
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@@ -144,16 +141,12 @@ varying by the deviation (1.0 by default):
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.. code-tab:: gdscript GDScript
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# Prints a random floating-point number from a normal distribution with a mean 0.0 and deviation 1.0.
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var random = RandomNumberGenerator.new()
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random.randomize()
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print(random.randfn())
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print(randfn())
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.. code-tab:: csharp
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// Prints a normally distributed floating-point number between 0.0 and 1.0.
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var random = new RandomNumberGenerator();
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random.Randomize();
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GD.Print(random.Randfn());
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GD.Print(GD.Randfn());
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:ref:`randf_range() <class_@GlobalScope_method_randf_range>` takes two arguments
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``from`` and ``to``, and returns a random floating-point number between ``from``
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@@ -165,28 +158,31 @@ and ``to``:
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# Prints a random floating-point number between -4 and 6.5.
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print(randf_range(-4, 6.5))
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:ref:`RandomNumberGenerator.randi_range()
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<class_RandomNumberGenerator_method_randi_range>` takes two arguments ``from``
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.. code-tab:: csharp
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// Prints a random floating-point number between -4 and 6.5.
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GD.Print(GD.RandfRange(-4, 6.5));
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:ref:`randi_range() <class_@GlobalScope_method_randi_range>` takes two arguments ``from``
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and ``to``, and returns a random integer between ``from`` and ``to``:
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.. tabs::
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.. code-tab:: gdscript GDScript
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# Prints a random integer between -10 and 10.
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var random = RandomNumberGenerator.new()
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random.randomize()
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print(random.randi_range(-10, 10))
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print(randi_range(-10, 10))
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.. code-tab:: csharp
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// Prints a random integer number between -10 and 10.
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random.Randomize();
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GD.Print(random.RandiRange(-10, 10));
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GD.Print(GD.RandiRange(-10, 10));
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Get a random array element
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--------------------------
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We can use random integer generation to get a random element from an array:
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We can use random integer generation to get a random element from an array,
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or use the :ref:`Array.pick_random<class_Array_method_pick_random>` method
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to do it for us:
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.. tabs::
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.. code-tab:: gdscript GDScript
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@@ -194,12 +190,14 @@ We can use random integer generation to get a random element from an array:
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var _fruits = ["apple", "orange", "pear", "banana"]
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func _ready():
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randomize()
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for i in range(100):
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# Pick 100 fruits randomly.
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print(get_fruit())
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for i in range(100):
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# Pick 100 fruits randomly, this time using the `Array.pick_random()`
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# helper method. This has the same behavior as `get_fruit()`.
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print(_fruits.pick_random())
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func get_fruit():
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var random_fruit = _fruits[randi() % _fruits.size()]
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@@ -209,29 +207,37 @@ We can use random integer generation to get a random element from an array:
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.. code-tab:: csharp
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private string[] _fruits = { "apple", "orange", "pear", "banana" };
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// Use Godot's Array type instead of a BCL type so we can use `PickRandom()` on it.
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private Godot.Collections.Array<string> _fruits = new Godot.Collections.Array<string> { "apple", "orange", "pear", "banana" };
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public override void _Ready()
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{
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GD.Randomize();
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for (int i = 0; i < 100; i++)
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{
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// Pick 100 fruits randomly.
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GD.Print(GetFruit());
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}
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for (int i = 0; i < 100; i++)
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{
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// Pick 100 fruits randomly, this time using the `Array.PickRandom()`
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// helper method. This has the same behavior as `GetFruit()`.
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GD.Print(_fruits.PickRandom());
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}
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}
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public string GetFruit()
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{
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string randomFruit = _fruits[GD.Randi() % _fruits.Length];
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string randomFruit = _fruits[GD.Randi() % _fruits.Size()];
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// Returns "apple", "orange", "pear", or "banana" every time the code runs.
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// We may get the same fruit multiple times in a row.
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return randomFruit;
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}
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To prevent the same fruit from being picked more than once in a row, we can add
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more logic to this method:
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more logic to the above method. In this case, we can't use
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:ref:`Array.pick_random<class_Array_method_pick_random>` since it lacks a way to
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prevent repetition:
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.. tabs::
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.. code-tab:: gdscript GDScript
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@@ -241,8 +247,6 @@ more logic to this method:
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func _ready():
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randomize()
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# Pick 100 fruits randomly.
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for i in range(100):
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print(get_fruit())
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@@ -270,8 +274,6 @@ more logic to this method:
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public override void _Ready()
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{
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GD.Randomize();
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for (int i = 0; i < 100; i++)
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{
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// Pick 100 fruits randomly.
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@@ -316,8 +318,6 @@ We can apply similar logic from arrays to dictionaries as well:
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func _ready():
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randomize()
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for i in range(20):
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print(get_metal())
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@@ -341,8 +341,6 @@ floating-point number between 0.0 and 1.0. We can use this to create a
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.. code-tab:: gdscript GDScript
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func _ready():
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randomize()
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for i in range(100):
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print(get_item_rarity())
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@@ -364,8 +362,6 @@ floating-point number between 0.0 and 1.0. We can use this to create a
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public override void _Ready()
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{
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GD.Randomize();
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for (int i = 0; i < 100; i++)
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{
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GD.Print(GetItemRarity());
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@@ -413,7 +409,6 @@ ends up empty. When that happens, you reinitialize it to its default value::
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func _ready():
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randomize()
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_fruits_full = _fruits.duplicate()
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_fruits.shuffle()
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@@ -456,7 +451,6 @@ terrain. Godot provides :ref:`class_fastnoiselite` for this, which supports
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var _noise = FastNoiseLite.new()
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func _ready():
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randomize()
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# Configure the FastNoiseLite instance.
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_noise.noise_type = FastNoiseLite.NoiseType.TYPE_SIMPLEX_SMOOTH
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_noise.seed = randi()
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@@ -474,7 +468,6 @@ terrain. Godot provides :ref:`class_fastnoiselite` for this, which supports
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public override void _Ready()
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{
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GD.Randomize();
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// Configure the FastNoiseLite instance.
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_noise.NoiseType = NoiseTypeEnum.SimplexSmooth;
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_noise.Seed = (int)GD.Randi();
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