In computer graphics we often need to be able to display a three-dimensional image in two dimensions and preserve the perspective appearance. If we walk on a straight road, it appears that the road narrows with the distance. This is the perspective effect and it is a result of mapping a three-dimensional image on a two-dimensional surface (i.e. a computer monitor, a screen, or the retina of the eye). This tutorial is not about stereoscopic view, which refers to a technique for enhancing the illusion of depth in an image by presenting two offset images separately to the left and right eye of the viewer.