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12 Random

Kyra Ma; Hasan Malik; and Rutwa Engineer

Learning Objectives

  • Learn about math.random() and Random.new()
  • Generate random values using both methods
  • Use the Random object for controlled randomness in game mechanics, e.g. spawning and drops

Introduction

The Random module in Roblox Lua is essential for generating random numbers, which can be used for procedural generation, game mechanics (like random loot drops or enemy spawn locations), and adding unpredictability to gameplay. Roblox provides two main ways to generate random values: the global math.random() function and the Random object (Random.new()). While both serve similar purposes, the Random object offers better randomness control and reproducibility.

Math-Based Random Generation: math.random()

Lua provides a simple way to generate random numbers using the built-in math.random() function:

Example

local randomValue = math.random(1, 10) -- Generates a random number between 1 and 10
print(randomValue)

The numbers contained inside the brackets represent the range of random numbers to choose from. In this case, each random number is between 1 and 10.

If the brackets are left empty, Roblox by default will pick a random decimal number between 0 and 1. Try this out for yourself in Roblox Studio!

We can even use this random function to change physical properties of our world. For example, let’s change the Baseplate to random colors every few seconds! The program is shown below.

Example

local baseplate = game.Workspace.Baseplate
while true do
local redValue = math.random(0, 255)
local greenValue = math.random(0, 255)
local blueValue = math.random(0, 255)
baseplate.Color = Color3.fromRGB(redValue, greenValue, blueValue)
task.wait(3)
end

Let’s break this down!

This script works by first creating a variable called baseplate, which stores a reference to the Baseplate object in the game. This lets us access and change the Baseplate’s properties later in the code.

Next, we use a while true do loop, which runs forever. Inside the loop, we generate three random numbers between 0 and 255—one for red, one for green, and one for blue. These values are used to change the color of the Baseplate.

We use a function called Color3.fromRGB() to create a color from those three values. This function is part of how Roblox handles colors. It takes three numbers — red, green, and blue — and mixes them to make a color. Each value must be between 0 and 255:

  • 0 means none of that color
  • 255 means the full strength of that color

For example:

  • Color3.fromRGB(255, 0, 0) gives you pure red.
  • Color3.fromRGB(0, 255, 0) gives you pure green.
  • Color3.fromRGB(0, 0, 255) gives you pure blue.
  • Color3.fromRGB(255, 255, 255) gives you white (all colors at full strength)
  • Color3.fromRGB(0, 0, 0) gives you black (no color at all)

By using random values, we’re creating a new, random color each time the loop runs. The Baseplate’s Color property is updated with that new color, so it keeps changing every few seconds.

Lastly, we use task.wait(3). This pauses the loop for 3 seconds before it repeats. Without this pause, the color would change constantly at full speed, which could cause the game to lag or crash. Adding a delay makes the color changes smoother and keeps the game running well.

Limitations of math.random()

However, math.random() relies on a global random seed, which means its randomness is not truly unpredictable. If a game starts with the same seed, it may generate identical random sequences.

To make results more unpredictable, math.randomseed() can be used to initialize the random generator with a changing value, like the current time:

math.randomseed(tick()) -- Seeds the generator with time
local randomNumber = math.random(1, 100)
print(randomNumber)

While math.random() is quick and useful for simple cases, it has limitations in security and reproducibility.

The Random Object: Random.new()

 Roblox introduced Random.new() as a more advanced and controlled way of generating random values. Unlike math.random(), Random.new() creates an independent random generator instance, which prevents interference from other scripts modifying the random seed.

Example

local rng = Random.new() -- Creates a new random generator
local value = rng:NextInteger(1, 10) -- Generates a random number between 1 and 10
print(value)

Each instance of Random.new() has its own unique random state, meaning different scripts can maintain independent randomness without affecting each other.

Why Use Random.new() Instead of math.random()?

  • Better Control – You can create independent random generators without affecting other parts of the game.
  • Reproducibility – If you provide a specific seed (Random.new(seed)), you can generate the same random sequence every time, which is useful for debugging.
  • No Interference – Unlike math.random(), which shares a global state, Random.new() prevents other scripts from unintentionally changing the randomness of your system.

Randomness for Different Data Types

The Random object provides different functions for generating values.

Generating Random Integers (NextInteger)

This function returns a whole number (integer) within the specified range:

local rng = Random.new()
local randomInt = rng:NextInteger(1, 100) -- Random number between 1 and 100
print(randomInt)

This is useful for cases like:

  • Rolling a dice (1-6).
  • Selecting a random item from a list (use as an index).
  • Generating procedural enemy levels or NPC stats.

Generating Random Decimal Numbers (NextNumber)

If you need a decimal value, use NextNumber(). By default, it generates numbers between 0 and 1:

local rng = Random.new()
local randomDecimal = rng:NextNumber() -- Generates a random number between 0 and 1
print(randomDecimal)

To get a random decimal between two values, you can scale and shift it:

local randomScaled = rng:NextNumber() * (10 - 5) + 5 -- Generates a number between 5 and 10
print(randomScaled)

This is useful for:

  • Randomizing object sizes.
  • Smooth procedural animations.
  • Generating natural-looking numbers for physics effects.

So, how would all this look inside a game? Let’s say you want to generate different coordinates for each enemy to spawn in!

local rng = Random.new()
local spawnX = rng:NextInteger(-50, 50) -- Random X position
local spawnZ = rng:NextInteger(-50, 50) -- Random Z position

local enemy = game.ReplicatedStorage.Enemy:Clone()
enemy.Position = Vector3.new(spawnX, 10, spawnZ) -- Spawn at a random location
enemy.Parent = game.Workspace

Or, let’s say you want to implement Randomized Loot Drops! You can use random numbers to determine the probability of item drops.

local rng = Random.new()
local dropChance = rng:NextNumber() -- Random number between 0 and 1
if dropChance < 0.1 then -- 10% chance for a rare item
print("Rare item dropped!")
elseif dropChance < 0.5 then -- 40% chance for a common item
print("Common item dropped!")
else
print("No item dropped.")
end

Say you want a game’s weather to change randomly—you can use Random.new() to determine transitions!

local rng = Random.new()
local weatherType = rng:NextInteger(1, 3) -- 1 = Sunny, 2 = Rainy, 3 = Stormy
if weatherType == 1 then
print("It's a sunny day!")
elseif weatherType == 2 then
print("Rain is starting.")
else
print("A storm is approaching!")
end

Common Mistakes

Don’t Overuse math.random()

If you’re working with multiple scripts, math.random() can create inconsistent random results due to shared randomness. Instead, use Random.new() to ensure each script has its own independent randomness.

Avoid Infinite Waits with Random Events

When using randomness for game logic, always make sure all conditions are eventually met. For example, if you keep waiting for a rare event that has a very low probability, the event might never happen, leading to bad player experiences.

Consider:

 

local rng = Random.new()
while rng:NextNumber() > 0.99 do -- 1% chance of breaking loop
print("Still waiting for event...")
task.wait(1)
end
print("The rare event has happened!")
Balance Randomness for Fairness

While randomness is fun, it should be balanced so that players don’t feel frustrated. If a drop rate is too low, players might quit; if it’s too high, items lose value. Fine-tune probabilities based on gameplay testing.

Congratulations—you are now familiar with the Random function in Roblox Studio!

 

 

License

Learn Coding and Animations in Lua Code Copyright © by Kyra Ma; Hasan Malik; and Rutwa Engineer. All Rights Reserved.

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