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# Graphics

Term Name Description

#### 13h

A mode of the VGA video card hardware that displays the screen in 320 x 200 pixels.

#### 2 1/2 D Graphics

Slang. Refers to games with 3D polygon sprites and backgrounds, yet which have gameplay restricted to a 2D style. Examples are Super Smash Brothers, Einhander and Kirby 64.

#### 2.5D

A buzzword used to describe raycasting engines, such as Doom or Duke Nuke Em. The maps were generally drawn as 2D bitmaps with height properties but when rendered gave the appearance of being 3D models.

#### 3D

The name of your third dimension for viewing things. The first two being width and height, the third being depth.

#### 3D Accelerator Card

A type of graphics card which helps a computer to process 3D graphics very quickly.

* Computers cannot actually do 'real' 3D imagery (well, none that you can buy without three major lottery wins and a Chair of Lucasian Mathematics at Cambridge University). We haven't invented the Star Trek-style Holosuite(tm) yet, so computers have to create a fake 3D which gets shown on a monitor or TV. Unfortunately, the conversion from 3D to 2D that has to be done requires a lot of mathematics. A 3D Accelerator card has specially-designed stuff on it which does a lot of the mathematics for the computer - leaving the computer to get on with more interesting work. Most 3D Accelerator cards now also accelerate the basic 2D stuff.

#### 6DOF

6 Degrees of Freedom. This refers to the ability to move in the X, Y and Z axis and also rotate around the X, Y, and Z axises.

#### AABB

AABB is an acronym for Axis-Alligned Bounding Box. Effectively it is a cuboid which is not rotated. All of its edges are parallel to the axes it is alligned to. AABBs can be defined using just two points, a maxium point and a minimum point. The rest of the box can be worked out from these two points. AABBs can be used for collision detection and scene culling (among other things).

#### Absolute Coordinate System

A coordinate system where all objects must be shown from the position of your viewpoint. Coordinates are all static and the Viewpoint (camera) moves through the preset coordinates.

#### Accumulation Buffer

A surface where multiple scenes can be added to before the surface is displayed.

#### ACT File

.ACT files are the actor files for Genesis3D - also referred to as models.

#### Affine Texture Mapping

The simplest form of texture mapping. The texture coordinates of a polygon are linearly interpolated across the polygon surface. This technique does not account for perspective and therefore produces swimming texture effects.

#### Affine Transformation

A combination of a set of linear transformations, usually stored in a single matrix. Affine transformations include rotation, scaling, translation and shear.

#### Albedo Texture

An albedo is a physical measure of a material's reflectivity, generally across the visible spectrum of light. An albedo texture simulates a surface albedo as opposed to explicitly defining a colour for it.

#### Aliasing

The effect produced when a complex image is put onto a display with a limited resolution. This effect is a product of downsampling. Examples include jagged looking lines in lower resolutions.

#### Alpha Blending

Assigning varying levels of translucency to graphical objects, allowing the creation of things such as glass, fog, and ghosts. This can be accomplished by using alpha channels, or other means.

#### Alpha buffer

A linked list of depth-sorted colors, typically representing each pixel in a z-buffer. The colors may either be added to the list in a pre-sorted order or the list may be able to sort them by itself. After all colors are added the list is used to create on resulting color by blending the containing colors from the back and forward using their alpha channel.

#### Alpha Channel

In 32-bit color, 24-bits are used for the color, and the extra 8-bits represent an alpha value, or alpha channel. This value is used to determine the pixel's translucency level.

#### Alpha Testing

A method for creating transparency by checking the alpha value of a given pixel.

#### Animation

The process of creating simulated motion or activity.

#### Anisotropic Filtering

The level past trilinear filtering, this uses samples from multiple Mip Maps to get the best approximation for a texture. Very heavy performance cost.

#### Anti-aliasing

This is the process that gets rid of the aliasing effect. A filtering process is normally used in the process that removes "jaggedness effect" produced by pixels.

#### antialias

Antialiasing refers to the process of adding additional pixels around the border of an object in order to blend it into it's background more smoothly, and to reduce the appearance of jagged edges. Typically, the colour used is the average of the surrounding background pixels and that of the object being antialiased, or an approximation of the average. This technique was invented by MIT's Media Lab.

#### Arc

A section of a circle that is measured in degrees or radians.

#### Artifacts

In graphics, persistent portions of images resulting from improper blitting operations.

#### Aspect Ratio

The aspect ratio of an image is the ratio of its width to its height. Aspect_Ratio = Width / Height See Pixel Ratio