V

VBI

Vertical blanking interval. In broadcast video, a small period of time that elapses between video frames, during which a display device refreshes its display for the next frame.

velocity

In music, the speed at which a MIDI key is pressed, roughly equivalent to the dynamic level at which the note is played in some instrumental timbres.

In 3-D sound, the speed at which a sound source or listener is considered to be moving for calculating Doppler shift.

vertex

A point in 3-D space.

video frame

A single image in a video stream, comprised of one odd field and one even field. See also field.

view space

See camera space.

view transformation

The application of a matrix to a model's vertices to change its orientation from world space to view space.

viewing frustum

A 3-D volume in a scene positioned relative to the viewport's camera. Objects within the frustum are visible. For perspective viewing, the viewing frustum is the volume of an imaginary pyramid that is between the front clipping plane and the back clipping plane. For orthographic viewing, the viewing frustum is cubic.

viewport

A rectangle that defines how a 3-D scene is rendered into a 2-D window. A viewport also defines an area on a device into which objects are rendered.

VREF

Vertical refresh. In a video stream, the VREF is active to signal that the display is to begin a new screen. See also HREF.