1. A three-dimensional model display program for displaying a three-dimensional model defined within a virtual three-dimensional space, the program causing a computer to execute the processes of: determining a line-of-sight vector indicative of a direction of viewing an inside of the virtual three-dimensional space from a viewpoint, in response to an operation input; determining a projection condition that two-point perspective projection is selected when the line-of-sight vector is close to a horizontal one, and a degree of influence of three-point perspective projection on two-point perspective projection increases with an increase in inclination of the line-of-sight vector with respect to a horizontal direction; generating an image by perspectively projecting the three-dimensional model according to the determined projection condition; and displaying the generated image.