The roots of CGI lie in the first mechanical aids to drawing and painting. The earliest of these were developed to help solve a problem every artist has found to be sticky: perspective. Before the introduction of geometric perspective, the realistic depiction of nature was not one of the purposes of art. Instead, artists chose the size and position of objects in a picture by their relative importance to one another. A distant castle might appear to be larger than one in the foreground simply because it was considered more important.
» Ron Miller | io9.com