Computer Animation

The computer animation glossary is an attempt to assemble some of the more common terms a writer is likely to come across when working with computer animation. It's by no means an exhaustive list. If you don't find what you want here, try the computer graphics glossary.

Click an index letter below to jump to terms:

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #

additive colors: The additive colors are red, green, and blue. Adding these colors together creates white (all light reflects back to the eye).
Adobe: A family of programs used for electronic, web, and print publishing. Adobe produces great programs such as Photoshop, GoLive, and FrameMaker.
aliasing: Visual artifacts produced in graphics images that use pixels for display. One example of aliasing is jagged edges on curved lines.
alpha: A fourth color component in the RGB color model representing opacity. Alpha values can range from completely transparent to completely opaque.
alpha blending: Used to render polygons that are partially transparent based on the polygon's alpha value. Alpha blending is useful in rendering smoke, explosions, water or glass effects.
ambient light: A lighting model that creates a constant level of illumination on all surfaces, regardless of orientation.
angle of refraction: The angle at which light bends as it passes through a transparent or semi-transparent object. I've got a list of some refraction values on Hokum Home.
animated GIF: Solid-color motion graphic file format that doesn't include audio. It's best suited for small frame sizes, and ideal for use on the web.
Animation:Master: A budget-conscious modeling and animating software package produced by Hash Inc. that is as good as some more expensive packages.
animation path: An editable line that objects follow during the course of an animation.
anti-aliasing: Rendering techniques that reduce aliasing. It determines the color value of a pixel by averaging the color value of the pixels around it. This is usually based on some form of interpolation or oversampling.
ARB: Architecture Review Board. An independent consortium that governs OpenGL specifications, defines conformance tests and approves OpenGL enhancements. The board includes representatives from companies such as 3Dlabs, Compaq, Evans & Sutherland, Hewlett Packard, IBM, Intel, Intergraph, NVIDIA, Microsoft, and SGI.
Architecture Review Board: see ARB
aspect ratio: The ratio of width to height. NTSC aspect ratio is 4:3. Some motion picture sizes are 16:9.

back face cull: The process of removing surfaces in an image that are not facing the viewer.
bi-linear interpolation: A texture display mode used to minimize aliasing. It produces a single value by averaging the values of the four texels nearest the texture coordinate.
binary space partition: The process of pre-analyzing a scene so that the depth sorting has all been done. This only works for the static elements in the scene, such as the walls and other structural elements. The results of the sorting are stored in a database and merged with real time changes as the user interacts with the scene.
bitmap: An grid of pixels assigned a color and X and Y locations. Bitmap images are resolution dependant, unlike vector graphics (which are resolution independent). Bitmap graphics are also known as raster images.
blender: A freeware 3D graphics application developed by Blender.org as part of the open source movement.
BMP: Bitmap. A standard Windows uncompressed image format. It supports RGB, indexed-color, grayscale, and Bitmap color modes. It doesn't support alpha channels.
bones: Bones is jargon for an internal skeleton used for animating models. The model deforms based on the movement of the bones inside it.
B-spline curve: A mathematical representation of a curve that can be easily manipulated through control points.

camera: The viewpoint through which a scene is viewed.
cartesian coordinate system: Coordinate system used to define specific points in three-dimentional space. It's center is the origin, through which run the X, Y, and Z axes. A point is located within the coordinate system by specifying a value for each of these axes. The values can be positive and negative. A point is expressed as (X, Y, Z). The origin has a value of (0,0,0).
cel animation: Traditional form of animation. Images are drawn by hand, transferred to acetate, colored and photographed one frame at a time.
child object: The subordinate object in a hierarchical pair. Typically, you assign hierarchies to portions of a model, making one part of the model the parent. For instance, if you make a human model, and assign the torso as the parent object, the head, arms and legs of the model are the child objects. Similarly, in this example the hand would be the child of the lower arm, which is the child of the upper arm.
clamping: When dealing with textures, the process of repeating the last pixel encountered on the texture across the rest of the object.
clipping: The process of eliminating a portion of a geometric primitive that's outside the half-space defined by a clipping plane.
collision detection: The process whereby the boundaries of objects are detected by other objects in a scene. This prevents objects from passing through each other.
color depth: The number of bits per pixel used to define color. Different monitor systems and software can display colors in 1 bit (black and white), 4 bits (16 colors), 8 bits (256 colors), 16 bits (65,536 colors), 24 bits (16.4 million colors), and 32 bits ( 16.4 million colors with 256 levels of transparency).
color index: A single value that represents a color by name, rather than by value.
color map: A table showing index-to-RGB mapping that's accessed by display hardware. Each color index is read from a color buffer, converted to an RGB triple by lookup in the color map then sent to the monitor.
color model: Models used to describe and reproduce color.
culling: The process of eliminating a front or back face of a polygon so that it isn't drawn. This saves on render time.

depth-cueing: A rendering technique that assigns color based on distance from the viewpoint.
diffuse reflection: The scattering of light in all directions. This type of reflection occurs when an object has a matte surface.
Direct3D: Microsoft's standardized 3D programming interface.
dithering: Simulates unavailable colors using patterns that intersperse pixels from available colors. Dithered colors often look coarse and grainy.
double-buffering: A technique that divides the frame buffer into one back buffer and one front buffer. An application then displays completed frames in the front buffer while building a new frame in the back buffer. Once the new frame is built, it's jumped to the front buffer, and the back buffer begins building another new frame.
dpi: dots per inch. The display resolution of devices such as monitors or printers.
DXF: Drawing Exchange Format. A vector based format originated by AutoCAD that uses 256 colors. It's a popular choice for porting models between programs.

element: The faces that share vertices.
extrusion: Extending a 2D object into 3D space by adding a z plane.

face: One side of a polygon.
field rendering: A rendering technique that splits each frame into a single field when rendering to video. A standard NTSC video has approximately 60 fields per second.
FLA: Flash project. Flash is used to create vector-based animation, interactive Web sites, and even games. Flash is a Macromedia product.
flat shading: A basic shading technique that produces a faceted look. Each face of a polygon is assigned a normal. Color calculations are carried out based on the direction of the normal relative to the light source. Then, a single color is applied to each face.
FLM: Animation:Master's native file format. It can be opened with a standard "Targa" reader but requires special RealPixel decoding. The RealPixel format and sample decoding source code is available in the Animation:Master Software Development Kit.
fps: frames per second. The speed at which a computer renders each frame.
frame: In an NTSC video signal, one frame is 1/30 of a second. In a PAL video signal one frame equals 1/25 of a second.
frame buffer: The portion of video memory where pixel data is stored. Pixel data includes color information and may include other information such as z value.
frame rate: The rate at which a computer renders each frame of a 3D graphic.
front plane: The plane created by the x and y axes.

geometric primitives: A point, line or polygon.
geometry: The 3D structure of an object.
GIF: Graphics Interchange Format. A common file format used to display indexed-color graphics and images for HTML documents. It can display interlaced lines of an image as it downloads. It can also store multiple bitmaps in one file, producing animated GIFs. GIF 89a supports transparency.
GIMP: GNU Image Manipulation Program. A freeware graphics application developed and maintained by Gimp.org as part of the open source movement. It's features are as robust as for-profit applications, like Photoshop.
gouraud shading: A shading technique that applies a normal to each face of a polygon and smoothly interpolates the color transition between them. It's well suited for making round objects look smooth.
graphics acceleration: The technique of increasing graphics processing speed.
graphics engine: Software that generates interactive 2D and 3D graphics. Examples of graphics engines are Direct3D and OpenGL.
graphics library: A tool set for application programmers. It usually includes a defined set of primitives and function calls that enable the programmer to bypass many low-level programming tasks.
graphics pipeline: A sequence of operations that creates an image from user defined settings to final output. The pipeline determines how color information and geometric coordinates are processed in the hardware and software.
GZ: GIMP image file.

hidden surface removal: The process of hiding surfaces behind the surfaces that appear in front of them.
HSB: hue, saturation, brightness. Based on the human perception of color, the HSB model describes three fundamental characteristics of color.; Hue is the color reflected from or transmitted through an object, such as red, green or blue. It's measured as a location on the color wheel and is expressed as a degree between 0 and 360 on that wheel.; Saturation, also called chroma, is the strength or purity of the color. Saturation represents the amount of gray in proportion to the hue and is measured as a percentage from 0% (gray) to 100% (fully saturated).; Brightness is the relative lightness or darkness of the color, usually measured as a percentage from 0% (black) to 100% (white).

in-betweening: In animation, the process of adding frames between keyframes to produce smooth motion. Also known tweening.
immediate mode: A rendering mode in which the graphics system processes each drawing command as soon as it receives it.
index of refraction: The angle at which light bends as it passes through a material. I have a list of some common index of refraction values in my reference section.
interpolation: Literally: filling in the empty space between existing parts. Interpolation is used in graphics to describe the process of upscaling graphics. It's used in animation to describe the process of tweening. There are a number of different methods for interpolation.
inverse kinemetics: A technique used to produce realistic movement. In a parent/child hierarchy, moving one child object at the end of a chain automatically calculates the movements up through the parent object.

JPG (JPEG): Joint Photographic Experts Group. A commonly used graphics file format that uses lossy compression. It supports up to 24 bit color. Its small size makes it ideal for web graphics.

keyframe: In animation, a frame that marks the position of an object at a point in time. A series of keyframes show the object at key positions during the course of motion. In-between frames are then made to finish out the movement.

L*a*b* color model: Based on the model proposed by the Commission Internationale d'Eclairage (CIE) in 1931 as an international standard for color measurement. It's designed to be device independent; creating consistent color whatever the device (such as monitor, printer, computer, or scanner) used to create or output an image. L*a*b color consists of a luminance or lightness component (L) and two chromatic components: the a component (from green to red) and the b component (from blue to yellow).; In 1976, this model was refined and named CIE L*a*b.
lathing: Creating a 3D surface by rotating a 2D spline around an axis.
level of detail: A series of models representing the same object and containing increasing levels complexity and detail. The less detailed models are displayed when the viewer is far away. The more detailed models are displayed as the viewer gets closer.
lighting: The process of computing the color of a vertex based on current lights, material properties and lighting-model modes.
luminance: The perceived brightness of a surface.
l-system: Procedural techniques used to generate the illusion of growth in animation.
LWO: Lightwave Object. NewTek's Lightwave native file format.

Macromedia: A family of programs used for graphics and web development. They produce programs such as Dreamweaver and Flash. Macromedia purchased eHelp, makers of RoboHelp, in 2003.
mapping: Placing an image on or around an object so that the image is like the object's skin.
material: Computer generated colors and patterns applied to model surfaces independent of textures. Materials can contain transparency, specularity, reflectivity and other values.
metaballs: Shapes used to simulate the behavior of bone, muscle and tissue under the surface of a model.
MIP-mapping: Multum In Parvam map. Multiple textures of increasing size are used to represent a single texture. When the texture is used on a polygon, the size that most closely matches the size of the polygon is used. The process reduces rendering artifacts.
mixed mode: A combination of both immediate and retained mode rendering from within the same application.
model: A free-form, 3D object.
modeling: The process of creating freeform 3D objects.
moire': A shimmering 'interference' pattern produced when two geometrically regular patterns are superimposed.
morphing: The metamorphasis of one object into another object over time.
motion blur: A blurring effect that occurs in film and video when objects move quickly.
motion capture: The process of digitizing a motion and applying it to a model.
MOV: Movie. Apple's QuickTime movies.

MP3: Mpeg Layer 3. A type of audio compression that produces relatively small file sizes while maintaining high quality audio. It's difficult to tell the difference between a song recorded to an MP3 file and a song from a CD.
MPG (MPEG): Motion Picture Experts Group. A compressed video file format.
MRB: MultiResolution Bitmap. A bitmap that contains up to four versions of a picture, each created with a different resolution.

normal: A vector that defines the orientation of a plane or a vertex.
NTSC: National Television Standards Committee. Created the standards for American televisions. This acronym also refers to the standard formulated by the committee. This format has approximately 30 frames (60 fields) per second.
NURBS: Nonuniform Rational B-Spline. A type of spline used to create curved surfaces.

OpenGL: An open graphics API originally developed by SGI. It's used with many video adapters for many 3D applications, from games to high-end CAD.
overlay planes: Frame buffer memory that stores pixel data that is independent of the image buffer. This is often used for menus, window borders and other user interface images.

PAL: phase alternate line. A video format used in Europe and England. There are approximately 25 frames (50 fields) per second in this format.
PAL\M: The television standard used in Brazil.
palettized textures: A form of texture compression. It's used to reduce the size of a texture when the texture does not have many unique colors. 4-bit palletized textures can have 16 different colors. 8-bit palletized textures can have 256 different colors.
parenting: The process of assigning hierarchy to objects.
parent object: The dominate object in a hierarchical chain. Typically, you assign hierarchies to portions of a model, making one part of the model the parent and the other the child. For instance, if you make a human model, and assign the torso as the parent object, the head, arms and legs of the model are the child objects. Similarly, in this example the upper arm would be the parent of the lower arm, which would be the parent of the hand.
perspective correction: A technique that is used to give the proper illusion of depth when pictures are textures mapped onto polygons. Without perspective correction, warping occurs and the resulting image does not look realistic.
phong shading: A lighting model that accounts for the ambient, diffuse and specular reflections of light from a point on a surface.
PIXAR: The PIXAR format is designed specifically for exchanging files with PIXAR image computers. PIXAR workstations are designed for high-end graphics applications, such as those used for three-dimensional images and animation. The PIXAR format supports RGB and grayscale files with a single alpha channel.
pixel: picture element. The smallest element that can be independently assigned color.
PNG: Portable Network Graphics. Developed as a patent-free alternative to GIF, it's used for losslessly compressing and displaying images on the Internet. It supports 24-bit images and produces background transparency without jagged edges. It supports grayscale and RGB color modes with a single alpha channel, and Bitmap and indexed-color modes without alpha channels.
polygon: A near-planar surface bounded by edges specified by vertices.
primitive: A point, a line, a polygon, a bitmap or an image.
PSD: Photoshop native file format. It contains layer and transparency information.

Quicktime: A compressed video file format developed by Apple.

rasterize: The process of converting a projected point, line, polygon, or the pixels of a bitmap or image to fragments, each corresponding to a pixel in the framebuffer.
ray tracing: A shading model that takes into account the direct light sources, as well as all the reflected, refracted and transmitted light in a scene.
reflection: A surface characteristic used to determine color intensity in lighting models.
refresh rate: The number of times per second the display screen is scanned.
rendering: The process of producing images or pictures. Rendering techniques such as shading, light modeling or depth cueing are sometimes used to make an image look realistic.
resolution: For a CRT, the maximum number of displayable pixels in the horizontal and vertical directions. For a printer or plotter, the number of pixels per inch.
RGB (red, green, blue) color model: A color model. A large percentage of the visible spectrum can be represented by mixing red, green and blue (RGB) in various proportions and intensities. Where the colors overlap, they create cyan, magenta, and yellow. RGB colors are known as additive colors because they combine to form white. RGB colors are used for lighting, video and monitors. Hokum Home has a list of RGB color values that you can use.
rotation: A geometric transformation that causes points to be re-oriented about an axis.

saturation: The amount of color.
scaling: Changing the size of an object without changing its location or orientation.
SECAM: Sequential couleur a Memoire. The television standard for France and some Eastern European nations.
shading: The process of interpolating color within the interior of a polygon or between the vertices of a line during rasterization.
shading model: The algorithm used to create the intensity and color of the visible portions of a primitive.
side plane: The plane created by the y and z axes.
solids modeling: Computer graphics that require not only specifying the surface characteristics but also the inside volume characteristics of an object.
specular reflection: The type of reflection that occurs when light hits a shiny surface. It produces highlights on the object that are seen when the light rays from the light source reflect directly into the viewer's eyes.
spline: Mathematically derived curves.
spline-based modeling: Representing 3D objects as surfaces made up of splines.
surface modeling: A surface model is created when primitives are filled with color. A surface model has a skin on the outside but is hollow on the inside.
SWF: Flash Movie Player. Standard format used by Flash to create movies. Generally, you save work in the SWF format and then export your finished work to another file format, such as an animated GIF, MOV file or even an EXE file.

texel: A texture element. A texel is obtained from texture memory and represents the color or the texture to be applied to a corresponding fragment.
texture: A 2D bitmap image applied to 3D surfaces.
texture mapping: The process of applying a texture to 3D surfaces. It's used to add visual detail to 3D surfaces without increasing the geometry.
timeline: A scale measured in either frames or seconds.
top plane: The plane created by the x and z axes.
transformation: Translation, scaling, and rotation of a geometric object.
translation: The process of changing the position of an object without changing its shape, size or orientation.
triple buffering: Triple buffering is a technique of dividing the frame buffer into three areas: two drawing buffers and one display buffer.
tri-linear filtering: An extension of Bilinear filtering for better image quality. For tri-linear filtering, Bilinear Filtering is done twice, against two MIPmap levels. Tri-Linear Filtering eliminates "texture crawling" or "texture sparkles" on moving textured surfaces.
true color system: A 24-plane graphics subsystem which produces the complete range of 16.7 million available colors.
tweening: In animation, the process of adding frames between keyframes to produce smooth motion. It's also known in-betweening.

viewing coordinates: A coordinate system that defines the positions of objects relative to the location of a viewer or camera.

wireframe: The process of drawing a model by tracing features such as edges or contour lines without attempting to remove invisible or hidden parts, or to fill surfaces. The result is a model "frame."

x-axis: In a Cartesian plane, the horizontal axis running left and right. Positive values indicate a point to the right of the origin. Negative values indicate a point to the left of the origin.
x-coordinates: Values located on the x-axis.