1. A method of generating an image, comprising: generating a two-dimensional image by perspectively transforming a virtual three-dimensional space relative to a predetermined viewpoint at a given instant; determining a corresponding position to a representative point of a waterdrop on the two-dimensional image depending on a position at which the waterdrop exists in the virtual three-dimensional space or a position at which the waterdrop is to be displayed in a display image; determining a reference position on the two-dimensional image corresponding to a vertex or a configuration point which forms the waterdrop, by using reference information relative to the corresponding position to the representative point on the two-dimensional image, the reference information being previously determined for the vertex or the configuration point forming the waterdrop; and linking the determined reference position with the vertex or the configuration point forming the waterdrop and mapping at least a portion of the two-dimensional image onto the waterdrop to generate an image of the waterdrop at a given instant or in a frame proximate to the instant.