Material Expression Reference | Unreal Engine 4.27 Documentation

This page is a reference for all material expression nodes available in the Material Editor. Material Expressions are the building blocks for creating fully functional materials in Unreal Engine 4. Each material expression is a self-contained black box that either outputs a set of one or more specific values, or performs a single operation on one or more inputs and then outputs the results of that operation.

Parameters

Certain material expressions are parameters, meaning their values can be modified (dynamically during runtime in some cases) in a Material Instance of the base material containing the parameter. These expressions should be given unique names, via the Parameter Name property, to be used when identifying the specific parameter in the Material Instance. If two parameters of the same type have the same name in the same material, they will be assumed to be the same parameter. Changing the value of the parameter in the Material Instance would change the value of both the parameter expressions in the material. A default value for the parameter will also be set in the base material. This will be the value of the parameter in the Material Instance unless it is overridden and modified there.

Material Expression Properties

All Material Expression nodes contain the same properties that provide different kinds of information. Below, we use a Texture Sample node to highlight these on properties.

Number	Property Name	Description
1	Description	All materials expressions have a common Desc (Description) property, which is accessible from the Details Panel. Any text entered into this in this property displays in the Material Editor just above the expression in the workspace. It can be used for any purpose, but usually serves as a good way to leave short notes about the purpose or function of the expression.
2	Title bar	Displays the name and/or pertinent information about the the Material Expression.
3	Inputs	Links to any values used by the Material Expression.
4	Preview	Displays a preview of the values that are output by the Material Expression. This updates automatically when realtime update is enabled and can be manually updated using the Spacebar.
5	Outputs	Links that output the results of the Material Expression operation.

Expression Types

Expression Index

This is a reference list of many, but not all, Material Expressions. All links shown here can also be accessed through the Expression Types pages listed above. Additionally, you can use Ctrl+F to find the expression node you need and follow the link to its description.

Atmosphere