Table of Contents

RandomContext is a component that contains methods for pseudo-random number generation.

Learning Objectives

  • Understanding random number generators
  • Die roll simulation
  • Using random seeds
  • Random distribution

Level Setup

RandomContext

RandomContext is a component for creating unique scenarios, such as when a random number of enemies are created, or a random amount of gold is given to a player.

Using Int

Int is a function that returns a pseudo-random number between 0 and MaxInt.

  • In the NumberGenerator script
  • Update the NumberGenerator class to the following:
class RandomGenerator : NadaComponent
{
  [Dependency] var RandomContext : RandomContext;

  function Initialize(init : CogInitializer)
  {
    var number = this.RandomContext.Int();
    Console.WriteLine("Random Number: `number`");
  }
}

---------------- Begin Game ----------------
Random Number: 26581
Level 'Level' was loaded.
Loaded level 0.00s

Notice how a random positive integer is returned.

Using the Modulo Operator

Modulo is represented by the % operator. Using modulo returns the remainder when a number is divided by another number.

  • In the NumberGenerator script
  • Update the NumberGenerator class to the following:
class RandomGenerator : NadaComponent
{
  [Dependency] var RandomContext : RandomContext;
    
  function Initialize(init : CogInitializer)
  {
    var number = this.RandomContext.Int();
    Console.WriteLine("Number: `number`");
    Console.WriteLine("Mod 10: \t`number % 10`");
    Console.WriteLine("Mod 100: \t`number % 100`");
    Console.WriteLine("Mod 1000: \t`number % 1000`");
    Console.WriteLine("Mod 10000: \t`number % 10000`");
  }
}

---------------- Begin Game ----------------
Number: 30796
Mod 10:   6
Mod 100:  96
Mod 1000:   796
Mod 10000:  796
Level 'Level' was loaded.
Loaded level 0.00s

Notice how the random integer given is then divided by various powers of 10 and the remainder is printed out. This is how a pseudo-random value can be constrained to a range starting at 0 and ending one before the applied value.

Using Range

Range is a function that returns a Real number between the lower number given (inclusive) and the higher number (exclusive).

  • In the NumberGenerator script
  • Update the NumberGenerator class to the following:
class NumberGenerator : NadaComponent
{
  [Dependency] var RandomContext : RandomContext;
  
  var EnemyCount : Integer;
  
  function Initialize(init : CogInitializer)
  {
    // This will pick a random number between 1 and 10
    var randomEnemyCount = this.RandomContext.Range(1, 11) as Integer;
    
    // Loop to create enemies based on the random counter
    for(var i= 0; i < randomEnemyCount; ++i)
    {
      Console.WriteLine("Spawned An Enemy");
      this.EnemyCount += 1;
    }
    
    // Display how many enemies were spawned
    Console.WriteLine("Spawned `this.EnemyCount` enemies");
  }
}

---------------- Begin Game ----------------
Spawned An Enemy
Spawned An Enemy
Spawned 2 enemies
Level 'Level' was loaded.
Loaded level 0.00s

Notice how the output displays a random number of enemies created each time you start the game. In this example, a pseudo-random number is found between 1 and 10, but another scenario could include finding between 1 and 5 enemies, and then adding 5 to it. That way, the end result will be between 6 and 10. However, this could just be accomplished by finding a Range value between 6 and 10.

Seeding

Rolling a six-sided die should generally result in a random value in the range [1, 6]. However, if that die is thrown under the same conditions every time, then theoretically the die should always result in the same value, removing randomness.

This is accomplished in code by setting a Seed. All projects already have a seed pseudo-randomly assigned at run-time, but applying a custom seeded value ensures all further randomness can instead be predicted.

  • In the NumberGenerator script
  • Update the NumberGenerator class to the following:
class NumberGenerator : NadaComponent
{
  [Dependency] var RandomContext : RandomContext;
  
  var EnemyCount : Integer;
  
  function Initialize(init : CogInitializer)
  {
    this.RandomContext.Seed = 54321;
    
    // Find four pseudo-random numbers and print to console.
    for(var i = 0; i < 4; ++i)
    {
      // This will pick a random number between 1 and 5
      var randomNumber = this.RandomContext.Range(1, 6) as Integer;
      
      // Display how many enemies were spawned
      Console.WriteLine("Number: `randomNumber`");
    }
  }
}

---------------- Begin Game ----------------
Number: 3
Number: 2
Number: 5
Number: 5
Level 'Level' was loaded.
Loaded level 0.00s

Notice the number sequence that is printed.

---------------- Begin Game ----------------
Number: 3
Number: 2
Number: 5
Number: 5
Level 'Level' was loaded.
Loaded level 0.00s

Notice how the number sequence was exactly the same as the first time.

---------------- Begin Game ----------------
Number: 3
Number: 2
Number: 5
Number: 5
Level 'Level' was loaded.
Loaded level 0.00s

Notice that once again the number sequence was exactly the same. Continue this process to your heart's content.

Due to how the seed was set to 54321, the pattern was the same throughout. However, it was not the same number repeated each time. This is due to how RandomContent is still referred to for a unique value.

Seeding is important in many different video games to recreate previous experiences. Games that rely upon seeding for Procedural Generation to create a level or determine gameplay sometimes also inform the player the seed used, allowing them to input that seed later and replay the exact same scenario.

Convenience Functions

Die Roll

DieRoll is a simple function that returns an integer between 1 and a specified number of sides. It is intended for novice users, as it functions the same as the Range function, except that:

  • The value returned is inclusive of the maximum value
  • The lowest value possible is 1 instead of 0
  • The value returned is an Integer rather than a Real that must be cast into an Integer

Coin Flip

CoinFlip is a simple function that returns true or false.

Related Materials

Manual

Reference

Commands

Classes

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