Last Modified: 9^th April 2003

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. (Foo) The name of the term.
2. (popupid) See this article for more information on Collective Pop-ups.
3. Some terms may have multiple symbolic meanings. These are split up into seperate entries.
4. (Context) Indicates the context of the particular meaning. eg. Mapping, Programming, Geometry...
5. The definition itself.
6. A definition may also have relevant information available elsewhere. If you want to know more on a particular topic, then use these links provided.

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Note: The majority of this article is written by a single person. I have devoted a fair amount of effort to validatinng what is written here, but there are are possibly innacuracies present, even if it does benefit from the eagle eye verification of the collective editors. While I dont 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 innacuracies, please jump about and attract some attention, so the article may be ammended.

Index of Terms

Argument [popupid: argument]
1.	(Map Compilation) A commandline parameter passed to a particluar tool in order to modify a setting within that tool when it is executed. Usually, commandline parameters/arguments are handled by the copilation controller, but in the case of manual or batchfile compilations, the mapper must manually specify program arguments though the commandline. An example of an argument for the hlcsg.exe program in ZHLT is -estimate.
Binary Space Partition [popupid: bsp]
1.	(Mapping) The name given to the second stage of the map compile process. It primarily involves the subdvision of the player space within the map into Leafs and Portals. Often abbreviated as BSP. In ZHLT, this process is performed by the hlbsp.exe program.
Bevel [popupid: bevel]
1.	(Geometry) The process of performing a cut or division at any non-axial angle (ie. an angle that is not a multiple of 90?).
Bitfield [popupid: bitfield]
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 [popupid: 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.
Brush [popupid: brush]
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: Must be Convex. Cannot contain Coplanar faces. Must have all Vertexes within the Half-Life world grid limits of ?4096. See Also: Map File Format.
Brush Based Entity [popupid: bbe]
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. See Also: Brush Based Entity.
Carve [popupid: carve]
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 toolbar button Taken directly from the Worldcraft help file: In the editor, any solid can be used to carve a volume out of other solids. For example, you can place a solid within the room's wall and tell Hammer to subtract the solid from the wall -- effectively punching a hole right through the wall! This feature is not limited to using cubic shapes as a carving tool: any solid -- cylinders, cubes and wedges -- can be used to carve other solids. See Also: Carving Responsibly.
Channel [popupid: audio_channel]
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.
Client
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. See Also: How To Make A Mod.
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 [popupid: 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. See Also: Clip Brush.
Clipnode [popupid: clipnode]
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. Compare: Node.
Console [popupid: console]
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 [popupid: csg]
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.
Cube [popupid: cube]
1.	(Geometry) A solid composed of 6 sides, 12 edges and 8 vertexes. All six sides are square and are equal in all respects with exception to spatial orientation.
Direct3D
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. See Also: Direct3D homepage. Compare: OpenGL.
Decal [popupid: decal]
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 bulletholes, blood, scorch marks, etc. See Also: Half-Life Entity Guide: infodecal.
Edge [popupid: edge]
1.	(Geometry) A line in 3D space where two sides meet. At each end of this line is a vertex.
Edict [popupid: edict]
1.	(Engine) A block of memory space used by an entity. The Half-Life engine (which is primarly based on the Quake engine) has a limited number of Edicts that it may create and use.
Face
1.	(Geometry) A general term for a facade or Surface. Brush sides are also Brush Faces.
Frag
1.	(Half-Life) A kill generated on an online/network multiplayer game.
2.	(Geometry) A fragment.
Fullbright [popupid: fullbright]
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 sucessfully, and no lightmap for the map was generated.
Gamma
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 expese of contrast. Lowering the gamma level usually results in a darker output with deeper tones.
Gib
1.	(Half-Life) Short for giblet. Especially, for Half-Life, in description of fragmented body parts.
Hall of Mirrors [popupid: 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 sucessive 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.
HINT
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. See Also: Hint Brushes.
Hint Brushes [popupid: hint_brush]
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. See Also: Hint Brush Tutorial.
Hollow [popupid: hollow]
1.	(Worldcraft) A tool used to hollow a solid primitive into several smaller primitives. The tool is accecible via: the right-click menu the menu item Tools, Make Hollow the keyboard shortcut Ctrl+H From the Worldcraft help file: The hollow function allows you to take a block and hollow it. To hollow outward (ie: to make the block the inside area of the hollow cube), use a negative number for the wall thickness.
Hull [popupid: hull]
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 thru 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.
Keyvalue [popupid: keyvalue]
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.
Lag [popupid: lag]
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. See Also: Latency.
2.	(Engine) Any sort of apparent sluggishness or slowdown in performance.
Latency [popupid: latency]
1.	(Engine) The amount of time (often measured in miliseconds) for a single packet of data to traverse from the Server to the Client and back to the Server again. High levels of latency (eg. in the range of 300+ ms) indicate a slow or otherwise poor connection from the client to the server; low levels (eg. lower than 100 ms) incdicate the opposite. See Also: Ping. See Also: Lag.
Leaf [popupid: leaf]
1.	(Mapping) A 'chunk' of player space within the map which has been assigned surfaces. Compare: Leafnode.
Leafnode [popupid: leafnode]
1.	(Engine) A node on the end of the node tree in a Binary Space Partition file.
Leak [popupid: leak]
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 n === depending on the compiler that you are using. See Also: Leaks.
Model [popupid: model]
1.	(Engine) An object that is not constructed of brushes, but modelled triangles loaded from an .mdl file (a format that is proprietry 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.
Noclip [popupid: noclipping]
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.
Node
1.	(Engine) A branching of the BSP Tree.
NULL [popupid: null_texture]
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: The NULL texture is one that is removed from the map during compilation, so that it won't exist when you play the compiled .bsp file in Half-Life. You should be able to apply it to any entity or world brush within your map. The main point of this texture is to use it on faces that the player would under normal circumstances never see, so that those faces will not add to the w_poly count and lower the fps (frames per second) rate. See Also: ZHLT Custom Build.
OpenGL [popupid: opengl]
1.	(Engine) Short for Open Graphics Library, an opensource 3D graphics rendering API that the Half-Life engine uses in the OpenGL rendermode. Taken from the OpenGL website: OpenGL is a cross-platform standard for 3D rendering and 3D hardware acceleration. The software runtime library ships with all Windows, MacOS, Linux and Unix systems. OpenGL is the essential 3D library that lets you harness the power of hardware acceleration to thrust games into the realm of professional-quality rendering, texture-mapping and special effects. Almost all of the leading games (e.g. Quake III, Half-Life, MDK2, Baldurs Gate, Decent 3, Madden NFL 2001 etc.) require OpenGL for hardware acceleration. See Also: OpenGL homepage.
ORIGIN
1.	(Mapping) The name of the texture used when making an Origin Brush. See Also: Origin Brush.
Origin Brush [popupid: 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. See Also: Using ORIGIN for Rotating Entities.
Pantone
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 desginer needs a specific colour with little error margin. Compare: RGB. Compare: CMY.
Ping
1.	(Engine) Synonym for Latency. See Also: Latency.
Pitch [popupid: pitch]
1.	(Audio) A measure of the degree of highness or lowness in a particular sound.
2.	(Engine) A measurement of view elevation. See Also: Pitch Roll Yaw.
Plane [popupid: plane]
1.	(Geometry) A flat 2D surface that extends infinately in all directions along i