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Contributors: Please read the Terminology Style Guide.


  • Abstract class – a class which can't be added to a map or spawned in game and is thus only useful as a base class. See Class Syntax.
  • Accessed None – UnrealScript warning message, meaning that code attempted to retrieve or alter data via an invalid object reference (also see Log Warnings)
  • Active brush – another name for the red builder brush
  • Actor – object in three-dimensional virtual space
  • Algorithm – implementation, procedure, protocol, or sequence of rules or instructions, (usually for accomplishing a maths-oriented task) that specify the order and kind of arithmetic operations that are used on specified set of data, though technically, a cooking recipe is an example
  • Alpha version – unfinished software version, not yet feature-complete; not ready for public release.
  • Animation – Series of pre-generated, articulated graphic components that convey character motion or behavior, during a scene display, and are called by the animation subsystem in specific game situations
  • Assertions – code expression that usually evaluates to true or false. Utilized to ensure that components behave properly; typically, checks on execution conditions and performance
  • Array – variable containing an ordered set of values of the same type, indexed by an integer
  • AI – Artificial Intelligence; in game development, AI is a code subsystem that controls the behavior of agents (or Bot (UT)s, see bot navigation), objects, and numerous actors; the AI is responsible for realistic, or, intelligent, behavior of opponents during gameplay
  • Attribute – synonymous to Property


  • Base class – higher level, generalized class; used to define characteristics common to all its subclasses. ScriptedPawn is the base class for Unreal I monsters, for example.
  • Beta version – unfinished software version, yet considered feature-complete, that's still in testing stage; not yet ready for public release
  • BMP – bitmap file format (with no or lossless compression)
  • Boolean – value that is either true or false
  • Bone – An object which describes the relationship of itself to other "bones." Bones usually have vertexes attached which move with the bone, thus creating an animation without worrying about the placment of each vertex
  • Brush – piece of geometry that builds the virtual space
  • BSP – Binary Space Partition; static data structure method used by game programmers to determine correct front-to-back polygon visibility, so that scenes are rendered realistically
  • BSP hole – building bug, yields unwanted invisible obstacles and players falling into geometry and dying


  • Canvas – the class in the Unreal engine that is responsible for drawing items directly onto a player's display. The most common use of the canvas is in the creation and modification of a HUD.
  • Casting – see Typecasting
  • Class – type of an object, an object's class defines how an object is implemented; derived from or instantiated by an object, from which it inherits clearly defined attributes. A class can contain: static data members, objects of another class, pointers and references to types and objects of the same or another class, declarations of another class, member functions, and friend classes. All Classes are listed in the Actor browser.
  • Client – any linked user (another remote computer terminal, or program, or even another class) of another server, or program, or class is said to be a client of that entity
  • Compiler – software that parses a high-level language, and converts source code to a binary executable program, that will run on Windows, Unix, or some operating system
  • Constructor – method that is automatically called when an object is created; responsible for initializing this object; see Creating Actors And Objects
  • CSG – Constructive Solid Geometry, the general idea behind building geometry in UnrealED


  • Declaration – code statement that doesn't produce executable code when compiled, but informs the compiler about new variables and functions (and their types, parameters, and so on)
  • Destructor – method that is automatically called when an object is destroyed; responsible for releasing resources (memory, sockets, other objects) used by this object; see destroying objects
  • DLL – Dynamic Link Library, file containing native executable code that is bound to another application (or UnrealScript) at runtime
  • DXT – some sort of texture compression mojo
  • Dynamics – Effects in the map that the map designer put in to make the map more pleasing to the eyes and ears. Examples are Movers, Emitters, and Sounds


  • Emitter – an Actor responsible for creating a particle effect; there are two emitter classes in UT2003: Emitter and xEmitter
  • Engine – the underlying code framework which makes a complex computer program run
  • Enumeration – ordered set of numeric constants whose values are automatically assigned during compilation (declared with the enum keyword)
  • Environment mapping – dynamic UV mapping of a skin on a mesh, depending on the viewer's relative position, producing a mirror-like effect.
  • Event – (1) an actor's or trigger's reaction to something, broadcast to actors with matching tags; (2) UnrealScript function called from native code


  • Face – see polygon
  • FinalBlend – a texture Modifier
  • Float – numerical value capable of storing numbers with digits after the decimal point (like 3.142)
  • Forward kinematics (FK) – A term used in skeletal animation, indicating that motion in a skeletal hierarchy (a set of connected bones) is transferred down the hierarchy. Example: rotation applied to a shoulder joint results in rotation of the bones below that joint in the skeletal chain – upper arm, forearm, hands, fingers or claws, etc. See also Inverse kinematics (IK).
  • FOV – Field Of Vision (or: Field Of View)
  • Function – piece of code with a defined entry point and one or more exit points
  • Function call – request for an object to carry out one of its operations. Code command within a program that jumps to a different portion of the code and returns to the statement following the call after executing that code (and may return a data value to it). The function return can be a value, a reference, or a pointer.
  • Function overriding – see Overriding
  • Function prototype – see Prototype


  • G16 – 16 bit grayscale texture
  • Garbage collection – automatic destruction of unreferenced objects (as in Java, Perl or UnrealScript)
  • Gimbal lock – occurs when rotations in successive axes make further rotations either impossible or produce undesired results.
  • Gibs – Body parts that fly every where when you blow up somebody.


  • Hidden variable – a variable defined in a class but not accessible in UnrealEd's Actor Properties Window. This is done with the variable syntax var instead of var().
  • Hierarchy – an ordering of things (such as objects, classes, people) in a tree-like structure, where things descend or depend on their superiors. Examples: a family tree, the military chain of command. Superseding values affect preceding values, but not vice versa.
  • HOM – Hall Of Mirrors (effect), a rendering bug
  • HUD – Heads-Up Display, rendered on top of the in-game 3D viewport and displaying in-game data like frags, weapons, ammo and scores


  • Implementation – program code structure that accomplishes some task or sequence of functions (see also Interface)
  • Inheritance – relationship among classes wherein one class shares the structure and/or behavior defined in one or more other superclasses
  • Instantiation – creation of an object from a class, each object having a copy of its own (non-static) data members
  • Integer – numerical value, a whole number without decimals (like 10)
  • Interface – user's or client's perception of an object; object-oriented data abstraction is to provide a clean and efficient interface that allows the user to access the underlying implementation
  • Inverse kinematics (IK) – A term used in skeletal animation, indicating that motion in a skeletal hierarchy (a set of connected bones) is transferred up the hierarchy. Example: Positioning a hand bone at the end of a skeletal chain results in joints further up the chain (e.g., forearm and upper arm) being relocated as needed. See also Forward kinematics (FK).
  • Iterator – special function that allows iteration over all or a given subset of all objects, using a foreach loop


  • Lighting – A combination of the lights in the levels, and the light-maps that are overlayed onto walls, giving the impression of lights on those walls.
  • Linked List – List consisting of objects where each item has a reference (link) to the next one.


  • Masked – color blending type; makes part of a Texture (UT) transparent (see color blending)
  • Material – rectangular image (bitmap) that can be applied to brush surfaces and meshes or directly drawn on a canvas; also see texture
  • Mesh – three-dimensional representation of an Actor in virtual space (like weapons, pickups, players)
  • Method – function (piece of code) that deals with objects of a given class; defined by the object's class
  • Mod – custom-made modification of a game (like Unreal or Unreal Tournament) by adding new game types, weapons, player models and so on
  • Modulated – color blending type; mid-gray is transparent, black and white are opaque (see color blending)
  • Mover – movable Brush (for doors, elevators and visual effects)
  • Mutator – small plug-in mod (for Unreal Tournament) that just changes a certain aspect of the game; stackable with other mutators to combine their modifications
  • MyLevel – a special name for a package. Using this tells UnrealEd to embed a resource in the current map file.


  • Name – unique specifier for an object or class (or something else) in UnrealScript; unlike strings, can't be modified like a string value and may not contain anything except letters, numbers and underscores
  • Native code – code that can be interpreted by a computer's processor without any intermediate steps. In Unreal, this is C++ code in DLL files.
  • Newbie – a person that's new to and hence unexperienced in something.
    • N00b – same as Newbie, but is compulsive (is that a good word for them?) about being that. They are sometimes [poseurs].
  • Node – the polys that are seen in Zone/Portal view. They correspond to surface polygons split by BSP cuts. See polygon and node count.
  • Node count – a measure of how much rendering work the engine has to perform to display a view of a map. Also the total number of nodes in the name.
  • Null – Texture(s) that is missing or can not be found. These null textures are given a defualt texture used by the engine (The green bubbly texture).


  • Obfuscation – Creating code that, while working, is very hard to understand, and work out what it actually does.
  • Object – abstraction that typically is assigned clearly specified characteristics; in other words, a chunk of data with a certain class associated to it; the class describes the data structure and contains the code that deals with objects of that class
  • OCD – Object Collision Detection
  • OOP – Object Oriented Programming
  • Overloading (a function) – redeclaring and reimplementing a function with the same name as an existing function, but a distinguishable set of parameters (like having two versions of a function, one of them working for float parameters, one of them for integer parameters)
  • Overriding (a method) – redeclaring and reimplementing a method in a subclass
  • Overwriting (a method) – see Overriding (a method)


  • Package – a file containing resources for Unreal engine games (like code, decorations, sound, music, maps, or all of it)
  • Pathnoding – making levels playable with bots.
  • Palette – look-up table of colors used in a bitmap
  • PCX – bitmap file format (with no or lossless compression)
  • Pivot – point about which a brush is rotated or scaled.
  • Pointer –
  • Polycount – either number of polys currently drawn on screen by the engine, or the total number of polygons in the map.
  • Polygon – two-dimensional, flat, closed shape in three-dimensional space, like a brush surface. Currently Unreal Tournament only supports convex polygons.
  • Prefab – A collection of Actors, such as CSG brushes and/or lights that can be copied and used over and over again in a map. ( Useful for distributing map parts without sacrificing storage space since a .t3d (Unreal Text) file is much smaller than a .ut2 file )
  • Private (method or property) – not accessible from outside the class this method or property has been declared in (see Public (method or property))
  • Probe function – A function that can be enabled or disabled using the Enable and Disable methods. These functions are usually defined as "events" and are called by native engine code.
  • Property – individual item of an object's data; defined by the object's class
  • Prototype – number, order and types of function parameters
  • Projector – UT2003's replacement for the deprecated Decal class. Allows for projected shadows (ShadowProjector class) and other neat stuff.
  • Public (method or property) – accessible from outside the class this method or property has been declared in (see Private (method or property))


  • Quaternion – mathematical entity similar to a complex number. These can be used to represent 3D rotations in a way that eliminates the gimbal lock problem with non-l33t rotational matrices; popular with game programmers for this very reason


  • Ray tracing – Calculating the lighting in a level by tracing exactly where the light goes.
  • RBB – red builder brush
  • Rendering – subsystem that actually produces the visible scene that is displayed on the computer terminal for players to yell at; consumes the majority of CPU computing capacity
  • Replication – generic term for sending game-relevant data back and forth between a network server and its clients
  • RGB8 – texture format with three channels (red, green, blue) and 8 bits per channel
  • RGBA8 – texture format with four channels (red, green, blue, alpha) and 8 bits per channel


  • Shader
  • Sheet – a brush which does not enclose a 3D volume, usually because it's a single polygon.
  • Simulation – generic term for simulation or prediction (not authoritative) of game behaviour on network clients
  • Skeletal animation – mesh animation by having vertices attached to interlinked bones; see Animation
  • Skin – set of textures that are applied to a mesh (for instance, a Bot (UT), a player or a decoration)
  • Sky box – see page
  • Solidity – see page
  • Source (code) – original high-level computer language code, like C++ or Java, that is compiled into an executable program
  • Spawn – UnrealScript command for creating a new Actor
  • State – a concept in UnrealScript that allows actors to execute different code in different circumstances. For example, a Bot can be 'Fleeing', 'Attacking', etc. See State and also InitialState
  • State code – code that is outside of functions in a state block
  • Static Mesh – see page.
  • Structure – ordered arrangement of typed data items; similar to a class in UnrealScript, but can't be referenced (only copied) and doesn't have methods
  • String – value of text; for instance, a message somebody typed in
  • Subclass – class derived from another class (its base class, or superclass); inherits properties and methods from the superclass unless they're expressly overwritten
  • Surface – see page.
  • Syntax – the rule of arranging and ordering commands to form a code. UnrealScript grammar, if you will; see class syntax and function syntax


  • Texel – Texture pixel (as opposed to screen pixel)
  • Text Parsing – the act of using a routine or function of some sort to change symbols in a string variable to reflect the values of certain variables, e.g. replacing "%k" in a death message with the killer's name; see Message Placeholder
  • Texture – rectangular image (bitmap) that can be applied to brush surfaces and meshes or directly drawn on a canvas; special type of material
  • Total conversion – mod attempting to totally change the underlying game into a different game by providing all-new content (game types, user interface, weapons, maps, models, menus)
  • Trace – follows a straight line through the world, usually until it hits solid geometry. Used to determine where bullets hit.
  • Translucent – color blending type; black is transparent, white is opaque (see color blending)
  • Trigger – An actor in a level which, when touched, will activate some effect, or other event.
  • Typecasting – converting one type of variable to another (e.g. Float to Integer)


  • UC file – An UnrealScript source code file (Unreal Class), readable in any plain-text editor.
  • UAX – UT's and UT2003's sounds format.
  • UccUnrealScript execution environment, ucc.exe in the System subdirectory
  • UMOD – Unreal Mod installer
  • UMX – UT's music format.
  • Unlit – (Texture (UT)) rendered without any lighting applied to it; yields a bright, uniform appearance
  • USA file – In Unreal 1, Unreal 2, and OldSkool for UT, a file created to save data from a singleplayer game in progress.
  • UT2MODUT2003's UMOD format
  • UU – Unreal units, used to measure and specify lengths within the engine's virtual space
  • UV mapping – two-dimensional application and alignment of a skin on a mesh


  • Variable – memory location with a symbolic name where a program can store information for future retrieval
  • Vertex – point in (normally two- or three-dimensional) space; point where polygon edges meet
  • Vertex animation – mesh animation by playing a set of different, fixed vertex arrangements (like stop-motion animation in movies); see Animation
  • Viewport – Window in UnrealEd which shows one view of the map that is loaded; a class in UnrealScript that represents the local player


  • Wiki – collaborative, open project on the web, gathering knowledge on a certain topic
  • WarpZone – special kind of zone. A WarpZone's portal renders what can be seen from the destination portal, and also teleports players and objects which enter it to the destination portal.


  • Z-axis – the third axis in a 3D co-ordinate system. In FPS games, this also refers to things (architectural detail, enemies, etc) being above or below the player.
  • Zone – portion of a map's space that is sectioned off, either to achieve special effects (gravity, water, etc.) or for engine optimization
  • Zone portal – type of polygon (usually built with a sheet brush) which tells the engine where zone boundaries lie.

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Some other pages that may help:

  • File Format – Summary of all the file formats encountered when working with Unreal

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