VERC: Glossary of Terms Last edited 1 year ago2022-09-30 03:15:39 UTC

This is a technical document that has definitions and acronyms of common terms that are used within the context of Half-Life related game development. This is not a tutorial or a "How-to" document; its focus is to inform you what something is, not how to use it. For this, it is suggested that you consult a relevant resource or article here on the VERC Collective or elsewhere (although there are many instances where definitions will link you to an appropriate internet resource for more information).

Each definition has the following format:


  1. (Context) A metasyntactic variable. Often used alongside Bar and Wibble.
  1. (Foo) The name of the term.
  2. (Numbers) Some terms may have multiple symbolic meanings. These are split up into separate entries.
  3. (Context) Indicates the context of the particular meaning. eg. Mapping, Programming, Geometry...
  4. (Numbered item)The definition itself.
  5. (See also) A definition may also have relevant information available elsewhere. If you want to know more on a particular topic, then use these links provided.
Tips: Note: The majority of this article is written by a single person. I have devoted a fair amount of effort to validating what is written here, but there are are possibly inaccuracies present, even if it does benefit from the eagle eye verification of the collective editors. While I don't claim to be ultimate authority on Half-Life game development, the article itself does, as it forms a point of reference. Therefore, if you do find any inaccuracies, please jump about and attract some attention, so the article may be amended.



Application Programming Interface (Programming)


Brush Based Entity (Mapping)


Binary Space Parition (Engine)


Counter-Strike (Half-Life)
A popular multi-player based modification for Half-life.


Constructive Solid Geometry (Mapping)


Capture The Flag (Half-Life)
A specific multiplayer gameplay style.


Cyan Magenta Yellow
Subtractive Color Model, Made up of Cyan Magenta and Yellow. Used in systems which absorb light (eg. printed material, etc).


Cyan Magenta Yellow K
Subtractive Color Model, Made up of Cyan Magenta and Yellow with K darkness. Used in systems which absorb light (eg. printed material, etc).


Direct 3D (Engine)


Dynamic Link Library (Programming)


A specific type of gameplay, where opponents battle online against each other for Frags.


DeathMatch Classic (Half-Life)
A modification for Half-Life by Valve Software.


  1. Frames Per Second (Engine)
  2. First Person Shooter


Field Of View (Engine)


Oh, come on.


Hall of Mirrors (Engine)


High Ping Whiner


Hue Saturation Luminance


Heads Up Display


Intergrated Development Environment (Programming)


Local Area Network


Left Mouse Button


Low Ping Bastard


Middle Mouse Button


Gameplay involving other human players either online or over network.


Opposing Force (Half-Life)
A commercial modification for Half-Life by Gearbox Software.


Open Graphics Library (Engine)


Point Based Entity


1. Personal Computer

2. Partial Conversion


Red Green Blue
Additive Color Model created by combining Red Green and Blue. Used in luminous systems (such as monitors, etc.).


Red Green Blue Alpha
Additive Color Model created by combining Red Green and Blue with Alpha brightness. Used in luminous systems (such as monitors, etc.).


Right Mouse Button




Total Conversion


Team Fortress Classic (Half-Life)
A modification for Half-Life by Valve Software.


Valve Editing Resource Center


Visible Information Set (Engine)


Valve Hammer Editor (Mapping)
A map making tool released by Valve.


Worldcraft (Mapping)
A map making tool released by Valve. Later renamed to Valve Hammer Editor, the Worldcraft series of editors are no longer supported.


Zoners Half-Life Compile Tools (Mapping)
A set of map compilation tools specifically for Half-Life maps. They replace the deprecated Quake compile tools (QCSG, QBSP, etc) that are supplied with the VHE.



  1. (Map Compilation) A command-line parameter passed to a particular tool in order to modify a setting within that tool when it is executed. Usually, command-line parameters/arguments are handled by the compilation controller, but in the case of manual or batch file compilations, the mapper must manually specify program arguments though the command-line. An example of an argument for the hlcsg.exe program in ZHLT is -estimate.

Binary Space Partition

  1. (Mapping) The name given to the second stage of the map compile process. It primarily involves the subdivision of the player space within the map into Leaves and Portals. Often abbreviated as BSP. In ZHLT, this process is performed by the hlbsp.exe program.


  1. (Geometry) The process of performing a cut or division at any non-axial angle (i.e. an angle that is not a multiple of 90°).


  1. (Mapping) A specific type of Entity Keyvalue. Its value is an integer sum that can be used to represent the state of around 16 individual boolean values. To determine the value of this type of Keyvalue, the mapper should add up the individual values of the options he wishes to enable.

Bounding Box

  1. (Engine) A 3D rectangular cuboid that is used to enclose the total space occupied by an object.
  2. (Worldcraft) The coloured rectangular box that is used to describe the presence of a Point Based Entity.


  1. (Mapping) A primitive solid used to construct the map architecture with. Because of the nature of the map file format which is used to store Brushes, all Brushes:

Brush Based Entity

  1. (Engine) An Entity which makes use of Brushes to describe its physical presence within the map. Brush Based Entities can be thought of as Point Based Entities with Brushes attached, which can be manipulated (as a group) by the parent Point Based Entity for appropriate effects when the map is played.

Brush Model

  1. (Engine) A Brush Based Entity.


  1. (Worldcraft) A subtractive geometric building tool integrated into the Worldcraft/Valve Hammer Editor editor. It is accessible through:
    • the right click menu
    • the menu item Tools, Carve
    • the keyboard shortcut Shift+Ctrl+C
    • the carve toolbar button
Taken directly from the Worldcraft help file:


  1. (Engine) A single stream of audio. Each stream can only play one sound at a time. The engine uses several channels for separate purposes, all of which are mixed together into a single stream (by either a software or hardware mixer) before being sent to the audio hardware device.


  1. (Engine) A particular mode of operation for the Half-Life engine. In client mode, the engine connects to a game server and communicates with that server using a set protocol in order for Half-Life to play over the Internet or Network with other players.
  2. (Engine) A specific DLL in the Half-Life modification API. The client DLL file contains code that is specific to the client mode of engine operation and the modification itself. The client DLL communicates with the Server DLL though the Half-Life message API.
  3. (Half-Life) A player on a multiplayer game Server.

CLIP or Clip

  1. (Mapping) The name given to a special Texture that, when applied to all Sides of a Brush, is used to make a Clip Brush. It is included in the standard halflife.wad file.
  2. (Worldcraft) A tool that is used to split a Brush into two parts along a Clip Plane, or remove a section of Brush defined by a Clip Plane.

Clip Brush

  1. (Mapping) A Brush that has the CLIP Texture on all Sides. When the map is run though the Half-Life engine, the Brush blocks the player, but does not stop projectiles and is not visible.

Clip Plane

  1. (Worldcraft) A plane that is positioned in the 2D views by the mapper where he wishes the editor to perform the clip operation. By default, this is a bold white line.
  2. (Mapping) A Plane created by a Side of a Clip Brush.


  1. (Engine) A surface that is used to perform collision detection. In Half-Life, the map compile process assigns Clipnodes to the Surfaces in the map which it determines should behave solid when the map is run though the Half-Life engine.


  1. (Engine) A text based method of communication between the player and the Half-Life engine. If the console is enabled, it can be accessed in the game by pressing the tilde key (~).

Constructive Solid Geometry

  1. (Mapping) The name given to the first stage of the map compile process. This stage often involves basic compilation operations such as initial surface subdivisions, texdata heap validation and initial hull construction. Often abbreviated as CSG. In ZHLT, this process is performed by the hlcsg.exe program.


  1. (Geometry) A solid composed of 6 sides, 12 edges and 8 vertices. All six sides are square and are equal in all respects with exception to spatial orientation.


  1. (Engine) A closed source proprietary graphics library API provided by Microsoft and used by the Half-Life engine to render the Half-Life world if the "Direct3D" rendermode is chosen by the user.


  1. (Mapping) A static image that is placed onto a brush surface using the infodecal entity. Often used for minor 2D surface detail such as bullet holes, blood, scorch marks, etc.


  1. (Geometry) A line in 3D space where two sides meet. At each end of this line is a vertex.


  1. (Engine) A block of memory space used by an entity. The Half-Life engine (which is primarily based on the Quake engine) has a limited number of Edicts that it may create and use.



  1. (Geometry) A general term for a facade or surface. Brush sides are also Brush Faces.


  1. (Half-Life) A kill generated on an online/network multiplayer game.
  2. (Geometry) A fragment.


  1. (Mapping) A condition where a map has no apparent lightmap, and is therefore displayed at maximum brightness when run through the Half-Life engine. This brightness is usually the result of a map compilation error in which the radiosity process failed to run to completion successfully, and no lightmap for the map was generated.


  1. (Engine) The lighting scale applied to the video output from the engine. Raising the gamma level usually results in a brighter, more luminous output at the expense of contrast. Lowering the gamma level usually results in a darker output with deeper tones.


  1. (Half-Life) Short for giblet. Especially, for Half-Life, in description of fragmented body parts.

Hall of Mirrors

  1. (Engine) The name given to a specific effect in the rendering engine, which resembles a Hall of Mirrors. The effect is caused by an absence of rendering information being sent to the renderer about a specific area in the frame, which is not updated, leaving the existing render data in place. Over successive frames, this old data builds up on itself to leave a pixel trail based effect. In Half-Life mapping, the effect is usually a sign of a greater problem within the map, such as a leak or a leaf portal saw into leaf compile error.


  1. (Mapping) The name of a specific texture which allows the creation of Hint brushes. This texture is included in the ZHLT series of compile tools in zhlt.wad.

Hint Brushes

  1. (Mapping) A brush textured only with HINT and SKIP textures. The brush is used to force the compile tools to generate additional BSP splits during the map compile process.


  1. (Worldcraft) A tool used to hollow a solid primitive into several smaller primitives. The tool is accessible via:
    • the right-click menu
    • the menu item Tools, Make Hollow
    • the keyboard shortcut Ctrl+H
From the Worldcraft help file:


  1. (Mapping) A set of surfaces generated by the compile tools during the map compile process. There are 4 hulls (stored in hullfiles mapname.p0 through mapname.p3) generated for any given map. The first hull (Hull 0) stores all of the visible surfaces in the map, while the remaining three (Hulls 1 to 3) contain clipnode information for the 3 basic hull sizes.


  1. (Mapping) A piece of information attached to an Entity. The keyvalue is composed of two components: A Key, which uniquely identifies the bit of data, and a Value, which contains the actual data for that specific key. The value is always dependant on the key, but the key is never dependant on the value.
An example of a keyvalue for an entity, such as a moving door, may be:
Key: Speed (units per second)
Value: 10

In programming, a pointer to a keyvalue data structure is often abbreviated as PKVD.


  1. (Gameplay) Used to describe the effects of high latency. These effects often include 'stuttered' or 'jerky' client movement, improper physics, apparent weapon fire inaccuracies, and other such anomalies.
  2. (Engine) Any sort of apparent sluggishness or slowdown in performance.


  1. (Engine) The amount of time (often measured in milliseconds) for a single packet of data to traverse from the Server to the Client and back to the Server again. High levels of latency (e.g. in the range of 300+ ms) indicate a slow or otherwise poor connection from the client to the server; low levels (e.g. lower than 100 ms) indicate the opposite.


  1. (Mapping) A 'chunk' of player space within the map which has been assigned surfaces.


  1. (Engine) A node on the end of the node tree in a Binary Space Partition file.


  1. (Mapping) A level design/construction error in the map which occurs when all Point Based Entities are not enclosed by world brushes. This condition is usually picked up in the BSP stage of the map compile process. Usual error messages include LEAK LEAK LEAK and Warning: === LEAK in hull [number] === depending on the compiler that you are using.


  1. (Engine) An object that is not constructed of brushes, but modelled triangles loaded from an .mdl file (a format that is propriety to Half-Life). Scientists and Apache Helicopters are examples of engine models. In general, the Half-Life engine can handle the render of models much better than it can of brush surfaces. (Note: in r_speeds readouts, the wpoly figure is a measure of brush surfaces, and epoly a measure of model triangles.)
  2. (Compile Tools) A Brush Based Entity. Not to be confused with the engine definition of a model, which is in all respects, totally different.


  1. (Engine) A Console command which is used to disable player clipping within the map. This has the effect of allowing the player to 'float' unobstructed anywhere within the map.


  1. (Engine) A branching of the BSP Tree.


  1. (Mapping) A texture used on surfaces within a map which the map designer does not wish to render when the map is played in the game. The texture is unique to the ZHLT Custom Build series of map compiling tools.
Taken from the instruction manual:


  1. (Engine) Short for Open Graphics Library, an open source 3D graphics rendering API that the Half-Life engine uses in the OpenGL rendermode.
Taken from the OpenGL website:


  1. (Mapping) The name of the texture used when making an Origin Brush.

Origin Brush

  1. (Mapping) A Brush which is used to describe the origin point of a Brush Based Entity. The Brush must have all Faces covered with the ORIGIN Texture found in the standard halflife.wad file. Each Brush Based Entity has a maximum of one Origin Brush. The center of the Origin Brush itself is used to mark the center of the Brush Based Entity.


  1. (Graphic) The name given to a particular colour model. Each colour has a code, relying on the output device to create the exact colour. Mostly used in Large scale printing projects where the designer needs a specific colour with little error margin.


  1. (Engine) Synonym for Latency.


  1. (Audio) A measure of the degree of highness or lowness in a particular sound.
  2. (Engine) A measurement of view elevation.


  1. (Geometry) A flat 2D surface that extends infinitely in all directions along its surface, and has a specific orientation within a 3D environment.

Point Based Entity

  1. (Engine) An Entity which makes use of a single point within the Half-Life universe to describe its physical presence within the map. These types of entities do not have any kind of brushes attached, and are often used for purposes or effects that do not involve the use of any brushes (such as logic control, insertion of models, rendering of sprites, etc).


  1. (Mapping) A file generated by the compile tools during the compile process which contains a set of points describing the path taken by the BSP process when it found a leak. The pointfile can be loaded by the Half-Life engine by typing pointfile into the console once the map has been loaded. The line of points is then typically followed by the mapper in-game until it passes though the hole in the map.


  1. (Geometry) Abbreviation for Polygon.


  1. (Engine) A triangle that is used in the composition of the visible Half-Life universe. The engine typically renders two types of polygons: epoly and wpoly.
  2. (Geometry) A flat shape on a single Plane that is bounded by Sides and Vertices.


  1. (Geometry) The generic name for any primitive solid that is composed of multiple polygons. Cubes, Cylinders and Pyramids are all Polyhedrons. A line is not a Polyhedron.


  1. (Compile Tools) A surface that describes the intersection of two Leaf boundaries (i.e. the slices of air that divide Leaves within the map). Portals are only used by the compile process for mathematical calculations, and are not written to the BSP file or used by the Half-Life engine.


  1. (Worldcraft) A prefabricated object. Prefabs are usually collections of brushes and/or entities that may be frequently used throughout a map (such as a chair or pop machine) stored in Worldcraft's Prefab Library, and can be inserted into any map at any particular point by the mapper.

QuArK / Quark

  1. (Mapping) An abbreviation of Quake Army Knife, a 3rd party mapping utility that supports Half-life maps.


  1. (Engine) The process of drawing the elements of the 3D world to the screen. The Half-Life world is rendered once every engine frame. This process is handled by the rendering API that is active (i.e. Software, OpenGL or Direct3D).


  1. (Geometry) A measure of rotational offset in the X axis.


  1. (Engine) A particular mode of operation for the Half-Life engine. In server mode, the engine hosts a game and accepts incoming connections from potential clients.
  2. (Engine) A specific DLL in the Half-Life modification API. The server DLL file contains code for functions of the game that cannot be influenced by any particular client.


  1. (Geometry) A surface that bounds a solid object.

SKIP or Skip

  1. (Mapping) The name of a particular texture that is used in the creation of a Hint Brush.


  1. (Mapping) The name of the texture used in a Sky Brush.

Sky Brush

  1. (Mapping) A special Brush that produces the effect of a distant sky in the map when played though Half-Life. Sky brushes are also Visblockers and under ZHLT will by default clip the player.

Software renderer

  1. (Engine) A 3D rendering mode used in the Half-Life engine. This particular mode is entirely dependant on the CPU to perform 3D rendering calculations. This means it does not benefit from the extra hardware resources a dedicated card can provide, which makes it much slower with minimal features.


  1. (Engine) A flat image that has a 3D position and size, but no spatial orientation. When placed in maps, it has the effect of a 2D image that always faces the player.


  1. (Mapping) The process of indirectly Triggering another Entity.


  1. (Mapping) An 8-bit image used to 'paint' brush surfaces in Half-Life maps in order to give them colour and appearance.

Texture Application Mode

  1. (Worldcraft) A specific mode of operation that allows the mapper to modify the texture settings of each individual Brush surface. In Worldcraft 3.3 and Valve Hammer Editor 3.4, the mapper is also provided with a set of automatic texture formatting tools, including automatic fit.

Texture Light

  1. (Mapping) A map lighting method which gives the impression that certain textures in the map emit light. The technique involves editing a configuration file to describe what textures emit what light, which is parsed by the radiosity process during map compilation, so that the map is lit accordingly.

Texture Lock

  1. (Worldcraft) A feature that maintains the visual orientation of a texture on a brush face when the brush is translated (moved) in the map. Worldcraft 3.3 and Valve Hammer Editor versions also maintain this during brush rotation. The feature can be toggled on and off by clicking the Texture Lock button on the toolbar.


  1. (Mapping) The process of directly targeting another entity.
  2. (Mapping) A set of conditions that when met, catalyses another event. e.g. When a player steps into the area of a trigger_once (meets the condition), the entity triggers whatever entity name is in its Target keyvalue (catalyses the other event).


  1. (Engine) The unit of measurement used in the Half-Life engine. The 3D universe is composed of 8192³ units in total, with the origin point at the center of the cube designated as point (0, 0, 0), and the buildable space extending in ±4096 units along each axis.


  1. (Geometry) The point of intersection of multiple Edges of a solid object, such as a Brush.


  1. (Mapping) Any Brush in the map that blocks the line of sight used by the Leaves. Most world brushes will act as a Visblocker by default, with exceptions to special cases (such as Hint Brushes, Clip Brushes, etc.).


  1. (Worldcraft) A group of editor placed objects that can be made visible or invisible in the editor. The group can also be assigned a particular colour and name. Often used to hide particular areas of the map while editing to avoid clutter and confusion to the mapper.

Visible Information Set

  1. (Compile Tools) The name of a process which involves the determination of visibility between Leaves in the BSP tree. The results of this are written to the BSP file in a Visiblity Matrix which is used by the engine when the map is run through Half-Life to determine which Leaves should be visible from any point in the map. In ZHLT, the name of the program that performs this process is hlvis.exe.


  1. (Mapping) The name given to the outside 'dark' region of the mapspace that is not occupied by Brushes and entities. Point Based Entities that are outside of the intended map building reigon are said to be in the Void, and will probably cause Leaks if not sealed properly.


  1. (Compile Tools) A set of points.


  1. (Mapping) The name given to Entity 0 in the map. This entity holds all of the Brushes that are not tied to other Brush Based Entities.


  1. (Geometry) A measure of rotational offset in the vertical (z) axis.
This article was originally published on Valve Editing Resource Collective (VERC).
The archived page is available here.
TWHL only publishes archived articles from defunct websites, or with permission. For more information on TWHL's archiving efforts, please visit the TWHL Archiving Project page.


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