Glossary

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A convenient list of common terms. Let's put every entry under header section, so it can be easily linked from other pages.

A

Actor

An object that can be placed into a level, supporting translation, rotation and scale.
All objects in a level inherit from the Actor class.

Apex

Physics engine by Nvidia, more on the Apex Framework.
The plugin is no longer supported and thus disabled by default. It is going to be replaced by Chaos destruction systems.

Asset

An element used when creating a game. Imported or created within the editor. Textures, 3D objects, sounds, blueprints, etc.

Audio Mixer

A brand new audio engine enabled by default in UE 4.24. It comes with many features you would expect from the modern game engine. The previous audio system had very few features. And technically every platform had a separate audio system making difficult to implement new things. For these reasons many studios use 3rd party audio systems, FMOD or Wwise.

B

Blueprint (BP)

Visual Scripting language used in UE4.

Breakpoint

A debugging tool that lets you pause code execution (either C++ or Blueprints) at a specific point.

BRDF

Bidirectional Reflectance Distribution Function is a function that describes the reflectance properties of a surface. Usually used in PBR shaders.

C

Callstack

A list of function calls in the order they were executed.

Class Default Object (CDO)

The template object created for UCLASSs. Can be accessed using UClass::GetDefaultObject or by Get Class Default Object node in blueprints.
Pro-tip: you can get a variable's default value (what was set before running a game) by accessing CDO and then simply getting variable value. This way you need only a single variable "health" instead of "max health" and "current health".

Chaos

Physics and destruction system by Epic Games.

Cascade

Particle effects system used in Unreal Engine 3 and 4, planned to be superseded by Niagara.

D

Digital Content Creation (DCC)

Refers to a category of applications used for digital art and content creation.

F

FMOD

It's a popular and relatively use to use audio engine and editor that can be used by any game engine. It can entirely replace UE4 audio system, which was often unavoidable before introducing Audio Mixer. Learn more at the FMOD website.

G

Gameplay Ability System (GAS)

UE4 Plugin / framework used for implementing gameplay abilities.

Gameplay Framework

The set of foundation classes in UE4 used to build a game. This includes core classes such as GameMode, GameState, PlayerState etc.

Garbage Collection

The process by which no longer needed UObjects are cleaned up during runtime. Both UObjects flagged for destruction as well as the ones not being referenced anymore are removed automatically by UE4.

H

Hot Reloading

Keeping a program running while changes are made to its files and then having it reflect those changes. For example, every time you edit your C++ or Blueprint code and compile, hot reloading lets you see the changes in UE4 Editor without having to restart it.
It's strongly recommended to avoid using the old Hot Reload mechanism in UE4 (rebuilding code from Level Editor's toolbar button while the editor is opened). It often leads to corrupting data.
Use Live Coding instead.

L

Live Coding

It's UE4's implementation of Live++ allowing to safely recompile changes done in .cpp file while editor or game is running. It works even when the game is running, allowing to quickly test many variants of code!
Currently, Live Coding can't reload any changes done in the header, so you can't change the class layout, definitions of properties or functions. Restarting editor is still required in that case.

Logging

Recording internal game events or data in a text file.

M

Matinee

Cinematic production tool in Unreal Engine 3 and 4.
It hasn't been updated at all after the official release of UE4. Entirely replaced by Sequencer and deprecated in UE 4.23.

N

Niagara

New Particle effects system in Unreal Engine 4.

P

PBR

Physically Based Rendering is a method of shading and rendering providing an accurate representation of how light interacts with surfaces. When talking about PBR the aspect of the pipeline that is emphasized refers to rendering and lighting.

PBS

Physically Based Shading. See PBR. When talking about PBS the aspect of the pipeline that is emphasized refers to shading.

Profiler

UE4 tool for collecting information on the performance of your game.

Property Replication

Properties on Actors can be set to replicated. This causes the server to send an update to clients every time the property changes.

R

Remote Procedure Calls (RPC)

RPCs are functions called over the network. Useful when implementing multiplayer to allow the server to execute functions on clients and vice versa.

Replication

The process of synchronizing data between server and clients. This is used in multiplayer games to keep the game state in sync.

Repository (Repo)

The server where your project is stored, usually using a Source Code Control system such as git, Perforce, or Subversion. When submitting our work to server, we often say pushing to repo or committing to repo. And downloading the recent version of project from there is called updating the repo.

S

Slate

C++ UI framework

Sequencer

Cinematic production tool for Unreal Engine 4.

U

Unreal Automation Tool (UAT)

Tool to automate various aspects of UE4 development. For example, the BuildCookRun automation tool Builds, Cooks, and Runs a project.

Unreal Build Tool (UBT)

The build system used by UE4. All other tools, for example Visual Studio projects, end up running UBT to perform the build.

Unreal Game Sync (UGS)

Project synchronization tool for larger teams using Perforce.

Unreal Header Tool (UHT)

A C++ header parser and code-generation tool that is run before the standard C++ compilation. Used to implement parts of the UE4 UObject system.

Unreal Motion Graphics (UMG)

A visual UI authoring tool and collection of widgets. Built on top of Slate.

Unreal Shader File (USF)

HLSL like shader files that implement part of the UE4 rendering system.

Unreal Shader Header (USH)

HLSL like shader files headers that implement a part of the UE4 rendering system.

W

Wwise

Advanced and feature-rich interactive audio engine and editor that can be used by any game engine. Often used by AAA studios. Learn more at the Wwise website. It can entirely replace UE4 audio system, which was often unavoidable before introducing Audio Mixer.