## V

VBI
  Abbreviation for Vertical Blanking Interval.
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.
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 cuboid.
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 will be rendered.
VREF
  Acronym for vertical refresh. In a video stream, the VREF is active to signal that the display is to begin a new screen. See also, HREF.