Out of the box, Unreal Engine supports creating game logic in C++ and Blueprints, but sometimes it's useful to be able to write some game logic in another scripting language.

Thanks to Impromptu Games Discord for starting me down this rabbit-hole again.

Why use a scripting language?

Why would you want to add scripting support to your game?

  • Empower Designers: Some technical designers may have experience in scripting languages and want to create game logic themselves, without having to go to Blueprints or rely on C++ engineers.
  • Easier Mod Support: The same tools that you give designers to implement custom behaviour can also be used by modders. For example a strategy game could allow players to define new unit types in a scripting language. Scripting languages are often simpler in syntax than C++ and are much easier to drop into a specific folder and get running.
  • Easier collaboration: Text-based scripts (in contrast to binary Blueprint assets) can be easily merged, so multiple people can work on the same logic at the same time.

How to choose a language?

There is no "right answer", despite what some passionate supporters of a particular language might tell you. There are many factors, so think which ones are most important to you.

  • Previous Experience: Who will be using the scripting tools? What languages do they have experience with?
  • Documentation: How good is the documentation? If the language is more niche there will be less documentation online, making it harder to on-board new team members.
  • Long-term Support: Is the Unreal integration still maintained? When was the last update? Otherwise do you have enough engineers to support it in-house?

Languages

I found all the languages that have plugins or integrations with a decent amount of support and active maintenance.

Lua

Lua has a long history as a language that is commonly integrated with games for scripting purposes. The documentation and online resources are excellent, but I have found it somewhat lacking in libraries for solving problems.

-- Silly example code
function draw_woof(canvas, dog, ntimes)
	for i=1, ntimes do
		local woof_text = dog:get_woof_text()
		canvas:draw(woof_text)
	end
end

For Unreal, LuaMachine is a fantastic plugin that I found straightforward to integrate with Industries of Titan. It even has an active Discord channel for support.

AngelScript

AngelScript has been around for a while, its list of games go back to Turok 2. It is actively maintained and seems very highly recommended.

Its list of features includes:

  • Looks a lot like C/C++.
  • Statically typed.
  • Object oriented.
  • No pointers, instead has object handles.
void DoSomething()
{ 
	SomeObject myObj;
	// AngelScript
	SomeObject@ myObjHandle = null;
	@myObjHandle = SomeObject();
}

Unfortunately integrating AngelScript into Unreal isn't quite as simple as dropping in a plugin. Hazelight have made a set of modifications to Unreal Engine and published it as a fork of Unreal Engine, so you will have to be comfortable building a custom version of the engine.

Their version of the language has a lot of tight integration with Unreal Engine so it differs slightly from the original language.

JavaScript

NCSoft's Unreal.js seems like a very actively-maintained and well-used JavaScript plugin.

  • Great for anything that needs to communicate with the web.
  • Full access to the whole UnrealEngine API.
  • Live reload.
  • Supports debugging within Visual Studio, Visual Studio Code.
  • Access to existing JavaScript libraries via npm, bower, etc.
  • Installable through a plugin.
class MyActor extends Actor {
	properties() {
		this.MyProp/*EditAnywhere+Replicated+int*/;
	}
	RPC(x/*int*/) /*Server+Reliable*/ {
		console.log('This function is replicated',this.MyProp++);
	}
}
let MyActor_C = require('uclass')()(global,MyActor);
if (GWorld.IsServer()) { 
	new MyActor_C(GWorld);
}

SkookumScript

SkookumScript is a custom scripting language that is now Epic-owned and community-maintained. It was used in Sleeping Dogs and seems really battle-tested.

That being said, it seems that it has not been updated in a while, the last supported version on the Marketplace is 4.24

Some Features (the full list is available on the Features page):

  • Concurrency at language-level. See the example below, it's really easy to set up code to execute simultaneously, for things to wait for each other, or be cancelled if one finishes first
  • Can make changes to the code and see it update live while the game is running.
  • Compile-time type checking.
  • Can be installed via a plugin.
// Person and car both start at same time.
// Next line is run after whichever one completes first
// and any remaining commands are cancelled.
race
  [
  person._walk
  car._drive
  ]
println("Completed")

Verse

At the time I'm writing this in January 2022, Epic have announced a new scripting language called Verse. It is not yet released but it does look very interesting.

It's got a very… unique syntax.

BoxFight = class(FortGameScriptBase):
	GameStarted^ : bool = false
	CurrentRound^ : int = 0

	RunGame()<latent>=

		# Pause until all players are in the matchmaking session
		WaitForPlayersToJoin()
		GameStarted := true

		for(i = 1..NumberOfRounds):

			if(!SetupPlayersAndSpawnPoints()?):

Python

Unreal has great built-in support for Python as an Editor scripting tool. As far as I know none of the Python-related code is available at runtime.

Blueprints

Blueprints aren't a scripting language in the same vein as the ones listed above but it's important to not discount them when considering what to use. If your designers are most comfortable with Blueprints, stick with them and see what else you can do to empower them!

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