Optical reflection and refraction are expressed of an object extending through a water surface by rather light load processing without using any cut models prepared in advance. A photographing angle of a virtual camera for displaying the object OB is set. Virtual cameras A, B and C are generated for photographing reflected and refracted object. The image processing is executed by projecting texture value of transparent degree for each of media different from texture for other media. Parameters are defined concerning the virtual cameras A, B and C, in order to achieve a desired visual expression of an object extending through various media.