44 CHAPTER 2: All That Math Jazz^
he sketched the first mammoth on a cave wall. But it is actually quite easy to grasp, as
opposed to transformations.
There are two main kinds of projections at work here: perspective and parallel.
Perspective projection is the way we see the 3D world on our 2D retina. Perspective
views consist of vanishing points and foreshortening. Vanishing points are where all
parallel lines converge in the distance, providing the perception of depth (think of
railroad tracks heading toward the horizon). The result is that the closer something is,
the bigger it appears, and vice versa, as shown in Figure 2-7. The parallel variety, also
called orthographic projection, simply removes the effects of distance by effectively
setting the z component of each vertex to 0 ( the location of our viewing plane), as
shown in Figure 2-8.Figure 2-7. Perspective projectionFigure 2-8. Parallel projection