Computer Graphics  1

Point Depth
Every point in a single display is given a pair of x and y index which determines the position of the point on the screen and a  z-index which determines the depth of this point, for example, if two points have the same x and y index, then z-index of the two are compared and the one with a lower z-index will be displayed whereas the other one will not.
	For Example, In this Screen capture of the famous 3D Role playing game-- Final fantasy VIII. The guardian force is displayed on the screen in a two dimensional way. However, all points are calculated in 3D. In this picture, point A has the lowest z-depth followed by C then b. However, this does not seem to contribute much to graphic. But consider two points with the same X and Y coordinates, which point will be displayed? This is when z-depth comes into play, the point with the lowest z-depth will be displayed rather than the mix up of the two points.