1. An image generating program executed on an image processing device that comprises control means, storage means, and image display means, wherein a viewpoint, a movement path having a predetermined shape, and a plurality of moving objects that move on the movement path are arranged in a virtual three-dimensional space, and the moving objects present in a viewing frustum, which is a field-of-view range of the viewpoint, are drawn by being projected on a two-dimensional plane, the image generating program causing the control means to execute: a first step of calculating a area of the movement path present within a region based on a field-of-view region; a second step of determining whether or not the moving objects are to be generated based on the area; a third step, when a determination is made that the moving objects are to be generated, of storing in the storage means information of the moving objects to be generated; a fourth step of renewing positions of the moving objects present in the viewing frustum based on information of the plurality of moving objects stored in the storage means; and a fifth step of generating images of the plurality of moving objects.