This glossary contains terms that are used specifically for the Apple implementation of OpenGL and a few terms that are common in graphics programming. For definitions of additional OpenGL terms, see OpenGL Programming Guide, by the OpenGL Architecture Review Board.
The Apple framework for using OpenGL graphics in Mac OS X applications written in the Carbon environment.
Graphics whose edges appear jagged; can be remedied by performing anti-aliasing operations.
In graphics, a technique used to smooth and soften the jagged (or aliased) edges that are sometimes apparent when graphical objects such as text, line art, and images are drawn.
The OpenGL Architecture Review Board, which is the group that oversees the OpenGL specification and extensions to it.
An operation that establishes a connection between two existing objects. Compare with bind.
An operation that creates a new object and then establishes a connection between that object and a rendering context.
A rectangular array of bits.
A rectangular array of pixels.
A block of memory dedicated to storing a specific kind of data, such as depth values, green color values, stencil index values, color index values, and so forth.
The Apple framework for using OpenGL graphics in Mac OS X applications (Cocoa or Carbon) that need low-level access to OpenGL.
An operation that identifies the area of drawing. Anything not in the clipping region is not drawn.
The coordinate system used for view-volume clipping. Clip coordinates are applied after applying the projection matrix and prior to perspective division.
A table of values used to map color indexes into actual color values.
A state that indicates whether a framebuffer object meets all the requirements for drawing.
A set of OpenGL state variables that affect how drawing is performed for a drawable object attached to that context. Also called a rendering context.
Eliminating parts of a scene that can't be seen by the observer.
The rendering context to which OpenGL routes commands issued by your application.
A matrix used by OpenGL to transform coordinates in one system to those of another system, such as the modelview matrix, the perspective matrix, and the texture matrix. GL shading language allows user-defined matrices.
In OpenGL, refers to the z coordinate and specifies how far a pixel lies from the observer.
A block of memory used to store a depth value for each pixel. The depth buffer is used to determine whether or not a pixel can be seen by the observer. Those that are hidden are typically removed.
A list of OpenGL commands that have an associated name and that are uploaded to the GPU, preprocessed, and then executed at a later time. Display lists are often used for computing-intensive commands.
The practice of using a front and back color buffer to achieve smooth animation. The back buffer is not displayed, but swapped with the front buffer.
In Mac OS X, an object allocated outside of OpenGL that can serve as an OpenGL framebuffer. A drawable object can be any of the following: a window, a view, a pixel buffer, offscreen memory, or a full-screen graphics device. See also framebuffer object
A feature of OpenGL that's not part of the OpenGL core API and therefore not guaranteed to be supported by every implementation of OpenGL. The naming conventions used for extensions indicate how widely accepted the extension is. The name of an extension supported only by a specific company includes an abbreviation of the company name. If more then one company adopts the extension, the extension name is changed to include EXT instead of a company abbreviation. If the OpenGL Architecture Review Board approves an extension, the extension name changes to include ARB instead of EXT or a company abbreviation.
The coordinate system with the observer at the origin. Eye coordinates are produced by the modelview matrix and passed to the projection matrix.
A token used by the GL_APPLE_fence extension to determine whether a given command has completed or not.
A process that modifies an image by combining pixels or texels.
An effect achieved by fading colors to a background color based on the distance from the observer. Fog provides depth cues to the observer.
The color and depth values for a single pixel; can also include texture coordinate values. A fragment is the result of rasterizing primitives.
The collection of buffers associated with a window or a rendering context.
The rendering destination for a framebuffer object.
An OpenGL extension that allows rendering to a destination other than the usual OpenGL buffers or destinations provided by the windowing system. A framebuffer object (FBO) contains state information for the OpenGL framebuffer and its set of images. A framebuffer object is similar to a drawable object, except that a drawable object is a window-system specific object whereas a framebuffer object is a window-agnostic object. The context that's bound to a framebuffer object can be bound to a window-system-provided drawable object for the purpose of displaying the content associated with the framebuffer object.
Defines the region of space that is seen by the observer and that is warped by perspective division.
A technique that takes multiple samples at a pixel and combines them with coverage values to arrive at a final fragment.
A function that changes color intensity values to correct for the nonlinear response of the eye or of a display.
Graphics library utilities.
Graphics library.
Graphics library utilities toolkit, which is independent of the window system. In Mac OS X, GLUT is implemented on top of Cocoa.
An OpenGL extension that supports using OpenGL within a window provided by the X Window system.
A rectangular array of pixels.
The practice of OpenGL executing commands at the time an application issues them. To prevent commands from being issued immediately, an application can use a display list.
Arrays of dissimilar data that are grouped together, such as vertex data and texture coordinates. Interleaving can speed data retrieval.
A set of texture maps, provided at various resolutions, whose purpose is to minimize artifacts that can occur when a texture is applied to a geometric primitive whose onscreen resolution doesn't match the source texture map. Mipmapping derives from the latin phrase multum in parvo, which means "many things in a small place."
A 4 X 4 matrix used by OpenGL to transforms points, lines, polygons, and positions from object coordinates to eye coordinates.
A mutual exclusion object in a multithreaded application.
A methodology use to specify parametric curves and surfaces.
Converting pixel color components from a buffer into the format needed by an application.
See pixel buffer.
A picture element; the smallest element that the graphics hardware can display on the screen. A pixel is made up of all the bits at the location x, y, in all the bitplanes in the framebuffer.
A type of drawable object that allows the use of offscreen buffers as sources for OpenGL texturing. Pixel buffers, introduced in Mac OS X v10.3, allow hardware-accelerated rendering to a texture.
The number of bits per pixel in a pixel image.
A format used to store pixel data in memory. The format describes the pixel components (that is, red, blue, green, alpha), the number and order of components, and other relevant information, such as whether a pixel contains stencil and depth values.
The simplest elements in OpenGL—points, lines, polygons, bitmaps, and images.
A matrix that OpenGL uses to transform points, lines, polygons, and positions from eye coordinates to clip coordinates.
The process of converting vertex and pixel data to fragments, each of which corresponds to a pixel in the framebuffer.
A rendering destination for a 2D pixel image, used for generalized offscreen rendering, as defined in the OpenGL specification for the GL_EXT_framebuffer_object extension.
A combination of hardware and/or software that OpenGL uses to create an image from a view and a model. The hardware portion of a renderer is associated with a particular display device and supports specific capabilities, such as the ability to support a certain color depth or buffering mode. A renderer that uses only software is called a software renderer and is typically used as a fallback.
A container for state information.
The order of operations used by OpenGL to transform pixel and vertex data to an image in the framebuffer.
An operation that draws content directly to a texture target.
Red, green, blue, and alpha color components.
A program that computes surface properties.
A high-level language, accessible in C, used to produce advanced imaging effects. The Apple implementation of OpenGL supports ARB_shading_language_100.
Memory used specifically for stencil testing. A stencil test is typically used to identify masking regions, identify solid geometry that needs to be capped, and to overlap translucent polygons.
The internal representation of a single buffer that OpenGL actually draws to and reads from. For windowed drawable objects, this surface is what the Mac OS X window server uses to composite OpenGL content on the desktop.
A visual anomaly caused when part of the current frame overwrites previous frame data in the framebuffer before the current frame is fully rendered on the screen.
An operation that reduces a surface to a mesh of polygons or a curve to a sequence of lines.
A texture element used to specify the color to apply to a fragment.
Image data used to modify the color of rasterized fragments; can be one-, two-, three- dimensional or be a cube map.
The process of applying a texture to a primitive.
A 4 x 4 matrix that OpenGL uses to transform texture coordinates to the coordinates that are used for interpolation and texture lookup.
An opaque data structure used to store all data related to a texture. A texture object can include such things as an image, a mipmap, and texture parameters (width, height, internal format, resolution, wrapping modes, and so forth).
A three-dimensional point. A set of vertices specify the geometry of a shape. Vertices can have a number of additional attributes such as colors, and texture coordinates. See vertex array.
A data structure that stores a block of data that specifies such things as vertex coordinates, texture coordinates, surface normals, RGBA colors, color indices, and edge flags.
A combination of hardware, renderer, and pixel format that OpenGL selects as suitable for an imaging task. When the current virtual screen changes, the current renderer typically changes.
Last updated: 2009-08-28
Mac OS X Reference Library Graphics & Animation: 3D Drawing OpenGL Programming Guide for Mac OS X