A

aliasing

A rendering technique that assigns to pixels the color of the primitive being rendered, regardless of whether that primitive covers all of the pixel's area or only a portion of the pixel's area. This results in jagged edges, or jaggies.

alpha

A fourth color component typically used to control color blending. The alpha component is never displayed directly. By convention, OpenGL alpha corresponds to opacity rather than transparency, meaning an alpha value of 1.0 implies complete opacity, and an alpha value of 0.0 implies complete transparency.

animation

The generation of repeated renderings of a scene quickly enough, with smoothly changing viewpoint or object positions, so that the illusion of motion is achieved. OpenGL animation almost always uses double-buffering.

antialiasing

A rendering technique that assigns colors to pixels based on the fraction of the pixel area that is covered by the primitive being rendered. Antialiased rendering reduces or eliminates the jaggies that result from aliased rendering. See also jaggies, rendering.

application-specific clipping

Clipping of primitives against planes in eye coordinates. The planes are specified by the application using glClipPlane. See also eye coordinates.