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Semantic AudiovisuaL Entertainment
Reusable Objects

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Game and Game Development Terms

Actor
A 3D model to render. A hierarchy of nodes arranged in a tree structure with one root node, and each node having any number of children (See node - actor). Each node has some number of triangles attached which move and rotate as the node does. The model can therefore be controlled by just moving a few nodes, rather than having to move each triangle individually.
Animation Segment
A self contained portion of animation that represents a specific action an actor in the game can perform. For example you may have animation segments for "Walk", "Run", "Holster Weapon" or "Fall Down"
Asset Conditioning Pipeline
The sequence of processing steps required to convert a source asset such as a bitmap file or raw 3d mesh data into a format suitable for use by the game engine. Game engines require data in highly platform specific formats for maximum performance and memory efficiency rather than raw uncompressed source data. See Distributed Asset Conditioning Pipeline.
Asset Database
The database of all source bitmaps, sound files, meshes, text spreadsheets, binary files and world files that are required by the game. Ideally everything except the source code for the game will live in the asset database providing
Avatar
General term used to refer to the representation of the player's presence in the game. Usually this is the game object they have direct control over with their keyboard, mouse or game pad. For example in the well known Tomb Raider game the avatar is the Lara Croft character the player controls.
Axis-Aligned Bounding Box Tree
An AABB Tree is an efficient way of organising a complex collection of objects (e.g. triangles in a collision mesh) so that you can quickly find objects that are near a given location. You start at the top level of the tree and test each bounding box to see if it encompasses the area of space you are interested in. If it doesn't, then there's no need to test it's children because they are always within the parent. In the case of a collision mesh, each leaf node in the tree of bounding boxes has one triangle associated with it, so when you reach one of those you know you need to test that triangle.
Bloom
Lighting effect used to simulate the atmospheric effect of visual glows around very bright objects. For example strong sunlight shining through a window or reflecting off glossy or wet surfaces will often appear to 'glow' when looked at. Bloom is often used as a lower computation cost version of High Dynamic Range Rendering or on platforms that do not have the requisite hardware for full HDR.
Bone
A node in an actor hierarchy that has position, orientation and scale relative to it's parent. Bones are animated and used to influence nearby Vertices in a Skin.
Bounding Box
This is a box associated with an object in your world, which completely encompasses that object. You would use it to quickly decide that something else is not touching that object. This is because if a point does not lie inside the bounding box, it can't be touching the object.
Bounding Box (Axis-Aligned)
This is a bounding box whose x, y and z axes point along the axes of the world. It's much quicker to decide if a point is inside a box if you know the box is axis-aligned.
Bounding Sphere
This is a sphere associated with an object in your world, which completely encompasses that object. You would use this for exactly the same purpose as a bounding box. It's quicker to decide if a point is inside a sphere than a box (and arguably an axis aligned box too)
Cartoon Shading/Lighting
A method of lighting that makes an actor appear to have been cell-shaded with hard bands of illumination rather than the traditional computer generated smoothly graduated lighting.
Collision Detection
The whole process of working out which objects in your game world are touching, so that you can take appropriate action to force them apart. This prevents objects simply moving through each other.
Collision Detection (Broad phase)
The process of quickly and efficiently eliminating most pairs of objects in your world from the collision detection phase, because they are clearly nowhere near eachother. This saves spending time doing precise tests to see if they overlap. Generally you just use axis-aligned bounding boxes or spheres for this phase, because it's so much faster than testing the actual shapes of the object.
Collision Mesh
A Mesh of triangles used to physically represent an object in-game. Collision detection with that object is done by testing other objects against each triangle of the mesh. Various methods are available to avoid having to actually test every trangle (see Axis-Aligned? Bounding Box Tree Tree).
Console
Generic term referring to any games console, see also Target and Platform
Deployment
The act of gathering together all source assets required for a section of the game and processing them into platform specific binary files that can be used by the game engine (see Asset Conditioning Pipeline). Usually only source assets that have changed since the last deployment are re-processed to minimise the time taken.
Distributed Asset Conditioning Pipeline
An asset conditioning pipeline that runs simultaneously on multiple PCs to improve performance
Field of View
The field of view that the camera can see, usually described as an angle (e.g. 90 degrees). Often abbreivated to F.O.V. The horizontal and vertical field of view can be different, the ratio between them being the Aspect Ratio. High fields of view produce fish-eye type effects while low fields of view produce a zoomed in effect.
First Person Camera
A style of presentation where the view of the game world is shown as if the player were looking through their own eyes - objects or weapons carried by the player are typically shown coming on the bottom or sides of the screen as if they were being carried in their hands. See Third Person Camera
FPS
Acronym used when referring to "First Person Shooter" games.
Keyframe
A single frame of an animation where the artist has explicitly set the position, orientation and scale of an actor's mesh node or bone. Animations are constructed by setting keyframes at various times during the required animation duration. During animation playback the game engine will interpolate between the keyframes to provide smooth animation - as each keyframe uses up memory, the skill is in setting as few keyframes as possible while still obtaining a suitable quality of animation.
GPU
Aconym standing for "Graphics Processing Unit" - the hardware chip that renders to the screen to produce the platforms graphics. Modern GPUs can render billions of triangles every second and can run complex Vertex Shaders and Pixel Shaders to produce cutting edge effects.
HDR
Acronym used for "High Dynamic Range" - usually with respect to rendering or lighting.
High Dynamic Range Rendering / Lighting
A method of rendering where illumination values in the scene can be much higher than the traditional range allowed by computer hardware and/or stored as fractional numbers instead of integers. By enabling much larger or fractional number to be used far greater fidelity is possible for dynamic brightness, contrast and bloom processes. For example the game camera can more accurately emulate the response of the human eye when looking at or moving from dark areas to light ones providing a more realistic experience for the player.
Leaf nodes
Leaf nodes are the nodes in a Tree which have no children, so they are at the bottom of the tree.
Light Map
A relatively low resolution texture that instead of storing the colour of a surface at each point stores the colour and intensity of light falling on the surface at each point. Light maps are generated off-line using a content creation tool of some sort, either proprietary or bespoke written by the game developer. Light maps provide a mechanism for storing lighting information at a higher spacial resolution than that offered by the geometry's vertices but suffer from various mapping problems, potentially high storage requirements and are hard to modify at runtime to reflect changes in the environment.
Massively Multiplayer Online Game
A game where hundreds or thousands of people can play together simultaneously over the internet. MMOGs are run on dedicated game servers operated by the game publishers and can usually deal with between one and twenty thousand simultaneous players in the same game. MMOGs take place in a persistant game world the player logs in to and out of as they see fit - players cannot usually be hurt, killed or lose accrued items while they are offline, but event continue to unfold in the virtual world as other players continue to play.
Mesh
A section of 3D geometry used in a game level for scenery, characters, etc. Usually made up of triangles. Meshes are frequently arranged into a hierarchy to form an Actor.
Middleware
Code libraries or tools bought in to assist in the development of a game to avoid the need to develop the technology internally. Middleware code libraries may for example be bought in to assist with Artificial Intelligence, online communication or to perform Physics calculations. Middleware tools may also be bought to aid in world construction or asset management. The relative financial sense in buying in technology rather than developing it internally depends on various factors including the cost of the product, the terms of it's license agreement, the size of the company buying it and the timeframe of the product for which it is being used.
MMOG
Acronym used to refer to a "Massively Multiplayer Online Game"
MMORPG
Acronym used to refer to a "Massively Multiplayer Online Role Playing Game"
MOG
Acronym used to refer to a "Multiplayer Online Game"
Motion Capture
A method of animation creation where cameras are used to capture the motion of a Human Being performing required actions. The data from the cameras is processed using advanced software to produce a sequence of keyframes the game engine can use to replay the movements of the Human on the virtual actor.
Multiplayer Online Game
Any game where multiple people can play together simultaneously over the internet. MOG's tend to support between two and thirty or so players with either dedicated game servers or using one of the players machines as the server.
Next-Gen
Catch-all term used when referring to games platforms that are currently in development or just recently released. Is also used when referring to games that are being developed for such hardware. The term tends to no longer be used once a platform has been available at retail for a couple of months.
Node
A generic term for an object, used when multiple objects of the same basic type are arranged in a Tree structure. Each node has a single parent, and can have children/siblings. For example each bounding box in an AABB Tree Collision mesh is a node.
Node - actor
A single node in an actor hierarchy (Tree) that has a position, scale and orientation relative to it's parent. A node can be a Mesh in which case it's vertices and triangles will be rendered using it's transform or it can be a Bone to influence a Skin.
Normal
A vector of length 1.0 that points perpendicular to the surface at that point. Normals are frequently used in computer graphics to calculate lighting.
Normal Map
A texture map that stores normal data (see Normal) rather than colours. Usually the X component of the normal vector at each point is stored in the Red channel of the texture map, the Y component of the normal is stored in the Green channel and the Z component is stored in the Blue channel. Normal Maps are used with Normal Mapping to give the illusion of surface detail where there is none.
Normal Mapping
A per-pixel lighting effect calculated using a Pixel Shader that takes as input a Normal Map. For each pixel being rendered, the Normal Mapping pixel shader calculates the lighting of the surface asif the surface was facing the direction stored in the normal map at that point rather than the direction it is actually facing. This gives the illusion that there is far more detail present on the surface than there actually is.
NURB
Non-Uniform Rational B-Spline(NURB) is a mathematical model that can be used to represent curves, or curved surfaces. NURB's are a generalisation of Bezier Splines, another mathematical model used for curve representation. A NURB is characteristed by the order of the NURB, a set of weighted control points and a knot vector. The weighted control points can be used to define the basic shape of the curve, with the knot vector specifying where and how each of the control points affects the final shape of the curve. For any distance along the curve, the order determines how many of the nearby control points will affect the position of the curve at that point, this has a direct bearing on the computational costs of evaluating the curve, as the degree of polynomial to be evaluated when calculating the position of a point on the curve is one less than the order.
Particle System
An algorithm that controls and renders from dozens to thousands of discrete particles usually used for special effects such as explosions or water. Typically each particle has a finite lifespan during the effect with properties such as velocity, direction, gravity and collision applied to it to produce the desired result. Each particle is rendered individually either as a small Sprite or a Streak to better represent it's movement over time.
Pixel (or Fragment) Shader
A program that can be uploaded to the graphics hardware to adjust or calculate the colour of a pixel/fragment. The Vertex Shaders will set the properties of the vertices of a triangle primitive, which then get interpolated across the surface of the triangle. These interpolate values are inputted into the pixel shader which then outputs a single colour depending on these values. Pixel Shaders can also fetch the values from a texture map. Pixel shaders can be used to do lighting or texture space calculations to generate a wide variety of effects including Normal Mapping
Platform
Generic term referring to the underlying hardware upon which the game is running. For example the PC is a platform, as is the Sony Playstation or the Microsoft Xbox. See also Console and Target.
Polygon
A set of coplanar points connected by lines. E.g. a triangle is a polygon with 3 points, Pentagon a polygon with 5 points. The points are known as vertices (see vertex), and the lines are edges.
Procedural generation
The process of creating content on the fly, as opposed to creating it before distribution.
Push Scroll
A technique for scrolling two dimensional game fields where the scrolling takes place only when the player is close to an edge of the screen and trying to move further towards that edge.
Real Time Strategy
A genre of games that let the player give commands to a large number of units that execute those actions in real time rather than in a turn-based basis. Usually set in a combat environment, such games normally also let the player gather resources of one or more types from the game world and use them to build structures for defense, offense, researching new unit types or to manufacture new units amongst other things. Often referred to with the acronym "RTS", most real time strategy games are published on the PC platform as controlling a large number of discrete units on a map is difficult without a mouse.
RPG
Acronym used when referring to "Role Playing Games"
Role Playing Game
A genre of game where the players character can evolve over the coarse of the game by improving existing or learning new skills and abilities. Players are normally awarded new abilities or Experience Points with which to purchase new abilities by completing quests, killing enemies or exploring new areas of the game. Role playing games are often referred to with the "RPG" acronym.
RTS
Acronym used when referring to "Real Time Strategy" games.
Shader
A program that can be uploaded to the graphics hardware to control the rendering of geometry. See Pixel Shader and Vertex Shader.
Skinning
The process of repositioning vertices during rendering by influencing them with a weighted average of the current positions of one or more Bones. A model will have a skeleton of such Bones over which the 'skin' of triangles is hung - by positioning the skin's vertices based upon the position of the bones a smoothly deforming seamless skin can be generated.
Sprite
A two dimensional rectangle of pixels that can be rendered at any position on the screen. By rendering a sequence of sprites in turn animation is produced. Before the advent of game hardware that could render polygons all computer game graphics were sprite based. Sprites are still used in 3D graphics, but instead of being of fixed size they are usually scaled and position to represent a point in space such as a particle in a Particle System
Stencil Shadows
A rendering effect that produces shadows from objects in the game by extruding their silhouette as seen from the lightsource to create a solid volume. All geometry in the scene that falls within this volume is darkened to simulate being in shadow.
Streaming
The process of loading data from disc in the background while the game is being played to allow a bigger play area than would otherwise be possible because of console memory limitations.
Target
Generic term referring to the type of hardware currently being run on or processed for. For example you would Deploy for the PC Target or compile the game for the Sony Playstation Target.
Texture
A bitmap image that is applied to the surface of a polygon or 3D model to add surface detail. Used to reduce the amount of detail required in the geometry. Whole or part of a textures may be mapped onto the surface, typically using a 3D modelling package or specialised application.
Third Person Camera
A style of presentation where the viewpoint is positioned behind and above the players Avatar so they can be seen on-screen. Third person cameras help remind the player who it is they are controlling but it is often difficult for the game to calculate an ideal position for the camera at all times without it going through walls or other solid environmental objects, resulting in frustration at times for the player when they can't see what they want to because the camera is poorly positioned.
Tree
A term widely used to describe a layout of objects (nodes) where you have one root node at the top of the tree, and that has one or more children. Each node in turn can have any number of children and so on. The nodes at the bottom of the tree (with no children) are called "Leaf nodes"
Vertex
One of the corner points which makes up a polygon. Usually expressed as an X, Y and Z coordinate in 3D space.
Vertex Buffer
A logical container for vertices in memory that allows them to be used more efficiently by the graphics hardware. Vertex buffers are "locked" for reading from or writing to then "unlocked" to allow the graphics hardware to use their contents.
Vertex Shader
A program that can be uploaded to the graphics hardware to adjust the position and properties of vertices before the triangles that use them are rendered. Example uses include Skinning and Cartoon Shading
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