Overview

Vellum is a scripting language created for the Creation Kit. Vellum keeps compatibility with the Papyrus ecosystem and offers clearer syntax and tooling.

For now, only the Skyrim PEX subset is supported. Support for Fallout 4 and Starfield is planned.

Script declaration

See Inheritance for extending base scripts and script attachment.

Put your script inside a .vel file. Classic hello world example in Vellum:

script HelloWorld : ObjectReference {
    event onActivate(actionRef: ObjectReference) {
        Debug.MessageBox("Hello, World!")
    }
}

Functions and events

See Functions.

You can define a function using the fun keyword. A function that takes two Int parameters and returns an Int:

fun sum(a: Int, b: Int) -> Int {
    return a + b
}

Event definitions start with the event keyword:

event OnActivate(activator: ObjectReference) {
  PlayAnimation("CoolStuff")
}

Variables

See Variables.

In Vellum, you declare a variable using the var keyword followed by the name of the variable:

var x: Int = 4
var m: String = "Hello"

Vellum supports type inference, so you can omit the type after the variable name:

var x = 4 // type `Int` is inferred

Properties

See Properties.

Properties are defined using the var keyword followed by name, type, and accessors:

var myProperty: String {get set} // defines auto property myProperty with type String

var anotherProperty: Float {get} // defines readonly property anotherProperty with type Float

Arrays

See Arrays.

Arrays can hold multiple items of the same type:

var numbers = [Int; 10] // defines array of 10 Ints

numbers[0] = 5 // assign 5 to the first element of array numbers

var x = numbers[9] // assign array last element value to new variable x

You can use the length property to get the number of elements:

var numbersCount = numbers.length

For loop

See Control flow.

Use a for loop to iterate over an array:

var messages = [String; 5] // array of 5 String objects

// fill messages array somehow
// ...
// ...

for message in messages {
    processMessage(message)
}

While loop

See Control flow.

A while loop runs the code inside the loop body continuously while the condition is satisfied:

var x = 0
while x < 10 {
    x += 1
}

You can use break and continue statements to control the flow of loops (like for and while).

If statement

See Control flow.

// assume value is set
var x: Int
if value > 10 {
    x = 1
} else {
    x = 0
}

Ternary conditional operator

See Control flow.

In some cases you can shorten your if statement:

// assume value is set
var x = value > 10 ? 1 : 0

You can also use it in a return statement:

fun max(a: Int, b: Int) -> Int {
    return a > b ? a : b
}

States

See States.

script MyScript {

}

state MyState {
    event onInit() {

    }

    fun foo() {

    }
}

If you want your script to start in a particular state, put the auto keyword before state:

script MyScript {

}

auto state InitialState {

}

Casts

See Casts.

Write expression as Type when the compiler allows that conversion, for example obj as Actor to narrow a reference.