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Game Development Dictionary


Graphics


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  Term Name Description

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).

Blender

An open-sourced 3D modeller released under the GPL. Blender was originally a commercial product, but was open-sourced when the parent company, Not a Number, folded. The Blender Foundation was formed by one of NaN's founders, with the intention of raising enough money to purchase the rights to make Blender open source, and met their goal within a matter of weeks. Blender is a powerful modeller, featuring built-in ray-trace renderer, NURBS curves and surfaces, Beziers curves and surfaces, powerful mesh modelling tools, meta-balls, skeletal animation and inverse kinematics, non-linear animation, sub-division surfaces, particle systems, etc... A Python interface allows for the creation of custom scripts for import/export, special effects, and so on. http://www.blender.org

HLSL

High-Level Shading Language. A C-like language developed by Microsoft for DirectX Graphics. Shader programs, such as vertex and pixel shaders, can be written and compiled in HLSL rather than the various hardware shader assembly languages. The resulting compiled can then be loaded onto modern graphics hardware that supports programmable shaders.

Palette

A collection of indexed colors.

Milkshape 3D

A popular 3D modelling package. It was originally made for modding games, and can export and import a wide variety of popular game formats. It supports textures and texture coordinate mapping very well, and has a nice SDK. The registered version is currently $25. http://www.swissquake.ch/chumbalum-soft/

Wings 3D

An increasingly popular free modeling utility. It has a very nice interface, and doesn't take much time to learn. It's good for both high and low polygon models, but is not particularly well suited for entire scenes or rooms. http://www.wings3d.com/

CG

nVidia's (relatively) simple shader language. It's currently one of the most commonly used shader languages, and it supports OpenGL and Direct3D even on non-nVidia cards. Toolkit and information can be found at www.developer.nvidia.com

Boolean Geometry

Named after mathematician George Boole Boolean geometry refers to combining multiple objects. Common operations include "unions" which combine two shapes and "difference" operations. Difference operations can be used to cut one shape out of another. 3d Studio Max and the game Red Faction for the Playstation II are good examples of how Boolean geometry can be used in practical applications.

Billboard

A 2D image rotated in 3D so that its normal follows the normal of the viewing direction. Another definition would be: A 2D image that is rendered on the same plane as the viewing camera in a 3D world.

Particle System

A particle system is a collection of entities, related or unrelated, that comply with a set of logical and physical rules. The components of a basic particle system are: an emitter, particles and particle modifiers. A particle is an entity that holds the necessary info about a particular particle in the system. The particle has different properties, or attributes, such as: velocity, position, size, affecting force, color, etc. The emitter is the object (usually not visible on screen) responsible for emitting the particles into the scene and giving them initial properties. Once these properties has been set, they can later be modified by the modifiers. The particles belonging to one particle system are usually associated with one texture. The texture is often applied to a rectangle that, in each game loop, is adjusted so that it always faces the camera, a technique known as billboarding. One visual effect can be made up by many particle systems, with different textures and characteristics. A burning fire, for example, could consist of one particle system for the flames, one for the smoke, and another one for emitting sparks.

GLAUX

The OpenGL Auxillary Library. A library including functions to load textures and do other common tasks. It is no longer supported or updated, but it is still used for many beginning OpenGL tutorials.

Morfit

A 3d engine developed in the late 1990s based on DirectX. Now known as 3d State. It has generated a large following of programmers and is praised for it's ease of use and compatability with many programming languages and compilers such as Microsoft Visual C++, Borland C++, Delphi, and Visual Basics. More information can be found at thier website at www.3dState.com.

Color Key

A value indicating the color to be used for transparent or translucent effects. For example, when using a hardware blitter, all the pixels of a rectangular area are blitted, except the value that was set as the color key; this creates nonrectangular sprites on a surface.

DirectGraphics

Introduced in DirectX 8; DirectGraphics combines both Direct3D and DirectDraw. (DirectDraw was removed after DirectX 7)

Interpolation

An approximation between two known values. In graphics, this is a process in which the software increases the resolution of an image by first filling the image with blank pixels and then coloring the blank ones based on the color values of its surrounding pixels.

RenderWare

Developed by Criterion Software Limited in 1993, RenderWare (RW) is a 3D "middleware" applications programming interface (API) graphics rendering engine that has become more popular since version 3 and the Playstation 2 video game console where it has been used in various games (most notably Grand Theft Auto 3), many of which have been ported to the PC.

Normal

A "vector" that points away from the face of an object at a right (90 degree) angle.

Clipping Plane

The Clipping Plane is a barrier to determine the loading and display points of 3d models and textures. The farther away the clipping pane from the main object, the further you can "see", but comes at a heavy performance cost.

Z-Fighting

The flickering distortion effect caused by two or more textures which overlap each other / are too close to each other / occupy simliar planes. It is called z-fighting because the multiple textures appear to be 'fighting' for dominance of the z-axis.

JPEG

This is an ISO standard by the Joint Photographic Experts Group. JPEGs work with color resolutions of up to millions of colors (also called 24 bit color). When you save an image as a JPEG, it gets compressed, making the file smaller. However, JPEG compression is lossy, so each time you save a JPEG, you lose some data and reduce image quality. When saving a JPEG, you can choose a compression level from low to high. Low compression gives you better quality but a larger file size. High compression gives you a smaller file - but less quality.

Machinima

Scripted (non-interactive) 3D animation comprised of pre-set camera motion, character motion and environment changes. Mostly used for cutscenes within a game in place of pre-rendered CGI animation or film. Typically uses a game's real-time 3D engine to depict a portion of the game story in a non-interactive cinematic representation. Gamasutra Article

GLUT

The OpenGL Utility Toolkit. This set of libraries provides a set of helper functions to OpenGL, including methods to abstract the windowing system (for cross-platform development), rendering "standard" 3D objects, etc. For more info, visit the GLUT homepage

Carmack's Reverse

Refers to a modification to Heidmann's original stenciled shadow volumes technique generally attributed to John Carmack, although others came up with the same modification at about the same time. Rather than incrementing and decrementing for the front and back faces (respectively) when the depth test passes, the method increments for back faces and decrements for front faces when the depth test fails. This prevents shadow volumes from being clipped by the near plan, but introduces the problem of them being clipped by the far plane.

You can find out more about the algorithm here.

FVF

Flexible Vertex Format.

shader

An assembly-like program which replaces part of the rendering pipeline with custom code. Shaders that affect vertices (vertex shaders) replace the normal transformation and lighting stage of the pipeline, while shaders that affect pixels (pixel shaders), work at the rasterization stage, affecting how the final screen color is determined. Shaders are supported in DirectX 8 and later, and in OpenGL through extensions (and as part of the proposed OpenGL 2.0 standard).


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