A friend was writing a flight simulator from scratch (using Foley and van Dam as reference for all the math involved). A classic perspective problem might be a runway.
Imagine a regularly spaced dashed line down the runway. If you get your 3D renderer to the stage that you can texture quads with a bitmap, it might seem like a simple thing to have a large rectangle for the runway, a bitmap with a dashed line down the center for the texture.
But the texture mapping will not be perspective (well, not without a lot of complicated math involved).
Foley and van Dam say — break the runway into a dozen or so "short" runways laid end to end (subdivide). The bitmap texture for each is just a single short stripe. Now because you have a bunch of these quads end to end, it is as if there is a longer runway and a series of dashed lines. And while each individual piece of the runway (with a single stripe), is not in itself truly perspective, each quad as it gets farther from you is nonetheless accounting for perspective — is smaller, more foreshortened.