Blueprint Variables

Variables are properties that hold a value or reference an Object or Actor in the world. These properties can be accessible internally to the Blueprint containing them, or they can be made accessible externally so that their values can be modified by designers working with instances of the Blueprint placed in a level.

Variables are displayed as rounded boxes that contain the name of the variable:

Variable Types

Variables can be created in a variety of different types, including data types - such as Boolean, integer, and float - as well as reference types for holding things like Objects, Actors, and particular Classes. Arrays of each variable type can also be created. Each type is color coded for easy identification:

Variable Type	Color	Example	Represents
Boolean	Maroon		True or false value (bool).
Byte	Sherpa blue		Whole number value between 0 and 255 (unsigned char).
Integer	Sea green		Whole number value between −2,147,483,648 and 2,147,483,647 (int).
Integer64	Moss green		Whole number value between −9,223,372,036,854,775,808 and 9,223,372,036,854,775,807 (long).
Float	Yellow green		Number value with a decimal such as 0.0553, 101.2887, and -78.322 (float).
Name	Mauve		Piece of text used to identify something in the game.
String	Magenta		Group of alphanumeric characters such as Hello World (string).
Text	Pink		Text that you display to users. Use this type for text that you want to localize.
Vector	Gold		Set of three numbers (X, Y, and Z). This type is useful for 3D coordinates and RGB color data.
Rotator	Cornflower blue		Group of numbers that define rotation in 3D space.
Transform	Orange		Set of data that combines translation (3D position), rotation, and scale.
Object	Blue		Blueprint objects such as Lights, Actors, StaticMeshes, Cameras, and SoundCues.

Variables in the My Blueprint Tab

The My Blueprint tab allows custom variables to be added to the Blueprint and lists any existing variables, including component instance variables added in the Components List or variables created by promoting a value to a variable in the graph.

Public Variables

To allow a variable to be modified from outside its Blueprint, make it public.

By default the eye is closed (private); select the eye to open it and make it public. You can also select or clear the Instance Editable box to make the variable private or public.

After you've made the variable public, you can modify its value from the Details panel of the Main Editor window.

Above, the variable LightColor has been set to Editable and we can now set this value in the Details panel of the Level Editor.

Variable Tooltips

You can also add a Tooltip for your variables that will appear when mousing over the variable in the editor.

You can add the Tooltip from the Details panel of the variable. When doing so, if the variable is set to Public, the Eye Icon will change from yellow to green indicating that a Tooltip has been written for the variable.

Expose on Spawn

Expose on Spawn enables you to set if the variable should be accessible at the time of spawning the Blueprint it sits in.

Above we have a variable called LightColor which is a Linear Color property that is set to Expose on Spawn. This variable is implemented in a Blueprint for a Point Light that uses the Set Light Color node and the LightColor variable to determine the color the light should be.

Below, inside a different Blueprint, a script is used to spawn the Point Light Blueprint and since the LightColor variable was set to Expose on Spawn, the option to set the value is made available on the Spawn Actor from Class node, allowing us to set its color when the light spawns in the game world.

Private Variables

With the Private option checked on a variable, this prevents the variable from being modified from external Blueprints.

For example, we have a variable below that is not set to private:

Inside another Blueprint, we spawn the Blueprint that contains the variable, then off the Return Value we can access our variable.

If we were to set it Private however:

And spawn the Blueprint again and try to access that variable, we cannot.

Expose to Cinematics

If you want the value of your variable to be affected by Sequencer, select Expose to Cinematics.

To learn more about the sequencer, see Real-Time Compositing with Sequencer.

Promoting to Variable

You can also create variables by using Promote to Variable.

Right-click any input or output data pins on a Blueprint node and select Promote to Variable.

By right-clicking the New Light Color pin and selecting Promote to Variable, we can assign a variable as the New Light Color value.

Alternatively, you can drag off an input or output pin and select Promote to Variable.

Accessing Variables in Blueprints

When working with variables in Blueprints, you will access them in one of two ways: by using the Get node (referred to as a Getter) to get the value of the variable or by using the Set node (referred to as a Setter) to set the value of the variable.

You can create a Set node (1 above) or Get node (2 above) for a variable by right-clicking in the graph and typing either Set (variable name) or Get (variable name). Another method you can use is to hold down the Ctrl key and drag in the variable from the MyBlueprint window to create a Get node or hold down the Alt key and drag in the variable from MyBlueprint window to create a Set node.

Editing Variables

Variable values can be set either as a part of the Blueprint node network or as a default value prior to execution. To set variable default values:

1. Click Class Defaults on the Blueprint Editor Toolbar to open the Defaults in the Details panel.

2. In the Details panel, enter the desired default values to the right of your variable name.

   

   Above, we highlight our Color variable in which we can set its default color.

If you do not see your variable listed in the defaults, make sure to click Compile.

Renaming Variables

To rename a variable:

1. Right-click the variable name in the My Blueprint tab and select Rename in the menu that appears.

   

2. Type the new variable name in the text box and then press Enter.

   

Variable Properties

You can set all the properties for a variable in the Details panel. Some variables may have more properties than those shown here, such as Expose to Cinematics for Vectors or a Slider Range for numeric variables like Integers or Floats.

Advanced Variable Properties

Getting & Setting Variable Values

Variables can also be edited as a part of your Blueprint network by way of Get and Set nodes. The easiest way to create these is by dragging a variable from the Variables tab directly into the Event Graph. A small menu will appear asking if you would like to create a Get or Set node.

Get Nodes

Get nodes supply portions of the network with a variable value. Once created, these nodes can be plugged into any node that takes the appropriate type.

Set Nodes

Set nodes enable you to change the value of a variable. Note that these must be called by an execution wire in order to execute.